HIV/AIDS denialism

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Electron micrograph of the human immunodeficiency virus. HIV/AIDS denialists dispute the existence of HIV or its role in causing AIDS.

HIV/AIDS denialism is the refusal to acknowledge that human immunodeficiency virus (HIV) causes acquired immune deficiency syndrome (AIDS), despite the conclusive evidence. Some of its proponents reject the existence of HIV, while others accept that HIV exists but argue that it is a harmless passenger virus and not the cause of AIDS. Insofar as they acknowledge AIDS as a real disease, they attribute it to some combination of sexual behavior, recreational drugs, malnutrition, poor sanitation, haemophilia, or the effects of the medications used to treat HIV infection (antiretrovirals).

The scientific consensus is that the evidence showing HIV to be the cause of AIDS is conclusive and that HIV/AIDS denialist claims are pseudoscience based on conspiracy theories, faulty reasoning, cherry picking, and misrepresentation of mainly outdated scientific data. With the rejection of these arguments by the scientific community, HIV/AIDS denialist material is now targeted at less scientifically sophisticated audiences and spread mainly through the Internet.

Despite its lack of scientific acceptance, HIV/AIDS denialism has had a significant political impact, especially in South Africa under the presidency of Thabo Mbeki. Scientists and physicians have raised alarm at the human cost of HIV/AIDS denialism, which discourages HIV-positive people from using proven treatments. Public health researchers have attributed 330,000 to 340,000 AIDS-related deaths, along with 171,000 other HIV infections and 35,000 infant HIV infections, to the South African government's former embrace of HIV/AIDS denialism. The interrupted use of antiretroviral treatments is also a major global concern as it potentially increases the likelihood of the emergence of antiretroviral-resistant strains of the virus.

History

A constellation of symptoms named "Gay-related immune deficiency" was noted in 1982. In 1983, a group of scientists and doctors at the Pasteur Institute in France, led by Luc Montagnier, discovered a new virus in a patient with signs and symptoms that often preceded AIDS. They named the virus lymphadenopathy-associated virus, or LAV, and sent samples to Robert Gallo's team in the United States. Their findings were peer reviewed and slated for publication in Science.

At a 23 April 1984 press conference in Washington, D.C., Margaret Heckler, Secretary of Health and Human Services, announced that Gallo and his co-workers had discovered a virus that was the "probable" cause of AIDS. This virus was initially named HTLV-III. In the same year, Casper Schmidt responded to Gallo's papers with "The Group-Fantasy Origins of AIDS", published in the Journal of Psychohistory. Schmidt posited that AIDS was not an actual disease, but rather an example of "epidemic hysteria", in which groups of people subconsciously act out social conflicts. Schmidt compared AIDS to documented cases of epidemic hysteria in the past which were mistakenly thought to be infectious. (Schmidt himself would later die of AIDS in 1994.)

In 1986, the viruses discovered by Montagnier and Gallo, found to be genetically indistinguishable, were renamed HIV.

In 1987, molecular biologist Peter Duesberg questioned the link between HIV and AIDS in the journal Cancer Research. Duesberg's publication coincided with the start of major public health campaigns and the development of zidovudine (AZT) as a treatment for HIV/AIDS.

In 1988, a panel of the Institute of Medicine of the U.S. National Academy of Sciences found that "the evidence that HIV causes AIDS is scientifically conclusive." That same year, Science published Blattner, Gallo, and Temin's "HIV causes AIDS", and Duesberg's "HIV is not the cause of AIDS". Also that same year, the Perth Group, a group of denialists based in Perth, Western Australia led by Eleni Papadopulos-Eleopulos, published in the non-peer-reviewed journal Medical Hypotheses their first article questioning aspects of HIV/AIDS research, arguing that there was "no compelling reason for preferring the viral hypothesis of AIDS to one based on the activity of oxidising agents."

In 1989, Duesberg exercised his right as a member of the National Academy of Sciences to bypass the peer review process and published his arguments in Proceedings of the National Academy of Sciences of the United States of America (PNAS) unreviewed. The editor of PNAS initially resisted, but ultimately allowed Duesberg to publish, saying, "If you wish to make these unsupported, vague, and prejudicial statements in print, so be it. But I cannot see how this would be convincing to any scientifically trained reader."

In 1990, the physiologist Robert Root-Bernstein published his first peer-reviewed article detailing his objections to the mainstream view of AIDS and HIV. In it, he questioned both the mainstream view and the "dissident" view as potentially inaccurate.

In 1991, The Group for the Scientific Reappraisal of the HIV-AIDS Hypothesis, comprising twelve scientists, doctors, and activists, submitted a short letter to various journals, but the letter was rejected.

In 1993, Nature published an editorial arguing that Duesberg had forfeited his right of reply by engaging in disingenuous rhetorical techniques and ignoring any evidence that conflicted with his claims. That same year, Papadopulos-Eleopulos and coauthors from the Perth Group alleged in the journal Nature Biotechnology (then edited by fellow denialist Harvey Bialy) that the Western blot test for HIV was not standardized, non-reproducible, and of unknown specificity due to a claimed lack of a "gold standard".

On 28 October 1994, Robert Willner, a physician whose medical license had been revoked for, among other things, treating an AIDS patient with ozone therapy, publicly jabbed his finger with blood he said was from an HIV-infected patient. Willner died in 1995 of a heart attack.

In 1995, The Group for the Scientific Reappraisal of the HIV-AIDS Hypothesis in 1991 published a letter in Science similar to the one they had attempted to publish in 1991. That same year, Continuum, a denialist group, placed an advertisement in the British gay and lesbian magazine The Pink Paper offering a £1,000 reward to "the first person finding one scientific paper establishing actual isolation of HIV", according to a set of seven steps they claimed to have been drawn up by the Pasteur Institute in 1973. The challenge was later dismissed by various scientists, including Duesberg, asserting that HIV undoubtedly exists. Stefan Lanka argued in the same year that HIV does not exist. Also that year, the National Institute of Allergy and Infectious Diseases released a report concluding that "abundant epidemiologic, virologic and immunologic data support the conclusion that infection with the human immunodeficiency virus (HIV) is the underlying cause of AIDS."

In 1996, the British Medical Journal published "Response: arguments contradict the "foreign protein-zidovudine" hypothesis" as a response to a petition by Duesberg: "In 1991 Duesberg challenged researchers… We and Darby et al. have provided that evidence". The paper argued that Duesberg was wrong regarding the cause of AIDS in haemophiliacs. In 1997, The Perth Group questioned the existence of HIV, and speculated that the production of antibodies recognizing HIV proteins can be caused by allogenic stimuli and autoimmune disorders. They continued to repeat this speculation through at least 2006.

In 1998, Joan Shenton published the book Positively False – Exposing the Myths Around HIV and AIDS, which promotes AIDS denialism. In the book, Shenton claims that AIDS is a conspiracy created by pharmaceutical companies to make money from selling antiretroviral drugs.

In 2006, Celia Farber, a journalist and prominent HIV/AIDS denialist, published an essay in the March issue of Harper's Magazine entitled "Out of Control: AIDS and the Corruption of Medical Science", in which she summarized a number of arguments for HIV/AIDS denialism and alleged incompetence, conspiracy, and fraud on the part of the medical community. Scientists and AIDS activists extensively criticized the article as inaccurate, misleading, and poorly fact-checked.

In 2007, members of the Perth Group testified at an appeals hearing for Andre Chad Parenzee, asserting that HIV could not be transmitted by heterosexual sex. The judge concluded, "I reject the evidence of Ms Papadopulos-Eleopulos and Dr Turner. I conclude… that they are not qualified to give expert opinions."

In 2009, a paper was published in the then non-peer-reviewed journal Medical Hypotheses by Duesberg and four other researchers which criticized a 2008 study by Chigwedere et al., which found that HIV/AIDS denialism in South Africa resulted in hundreds of thousands of preventable deaths from HIV/AIDS, because the government delayed the provision of antiretroviral drugs. The paper concluded that "the claims that HIV has caused huge losses of African lives are unconfirmed and that HIV is not sufficient or even necessary to cause the previously known diseases, now called AIDS in the presence of antibody against HIV." Later that year, the paper was withdrawn from the journal on the grounds of it having methodological flaws, and that it contained assertions "that could potentially be damaging to global public health". A revised version was later published in Italian Journal of Anatomy and Embryology.

US courts

In 1998, HIV/AIDS denialism and parental rights clashed with the medical establishment in court when Maine resident Valerie Emerson fought for the right to refuse to give AZT to her four-year-old son, Nikolas Emerson, after she witnessed the death of her daughter Tia, who died at the age of three in 1996. Her right to stop treatment was upheld by the court in light of "her unique experience." Nikolas Emerson died eight years later. The family refused to reveal whether the death was AIDS related.

South Africa

In 2000, South Africa's President Thabo Mbeki invited several HIV/AIDS denialists to join his Presidential AIDS Advisory Panel. A response named the Durban Declaration was issued affirming the scientific consensus that HIV causes AIDS:

"The declaration has been signed by over 5,000 people, including Nobel Prize winners, directors of leading research institutions, scientific academies and medical societies, notably the US National Academy of Sciences, the US Institute of Medicine, Max Planck institutes, the European Molecular Biology Organization, the Pasteur Institute in Paris, the Royal Society of London, the AIDS Society of India and the National Institute of Virology in South Africa. In addition, thousands of individual scientists and doctors have signed, including many from the countries bearing the greatest burden of the epidemic. Signatories are of MD, PhD level or equivalent, although scientists working for commercial companies were asked not to sign."

In 2008, University of Cape Town researcher Nicoli Nattrass, and later that year a group of Harvard scientists led by Zimbabwean physician Pride Chigwedere each independently estimated that Thabo Mbeki's denialist policies led to the early deaths of more than 330,000 South Africans. Barbara Hogan, the health minister appointed by Mbeki's successor, voiced shame over the studies' findings and stated: "The era of denialism is over completely in South Africa."

In 2009, Fraser McNeill wrote an article arguing that South Africa's reluctance to openly address HIV/AIDS resulted from social conventions that prevent people from talking about causes of death in certain situations, rather than from Mbeki's denialist views. Similarly, political scientist Anthony Butler has argued that "South African HIV/AIDS policy can be explained without appeals to leadership irrationality or wider cultural denialism."

In July 2016 Aaron Motsoaledi, the Health Minister of South Africa, wrote an article for the Centre for Health Journalism in which he criticised past South African leaders for their denialism, describing it as an "unlucky moment" in a country which has since become a leader in treatment and prevention.

Denialists' claims and scientific evidence

The term "HIV/AIDS denialism" denotes the rejection of the mainstream scientific view that AIDS is a medical condition that is brought about by HIV infection. The use of the term encompasses the denial of the existence of the virus (HIV denialism), the denial of the causation of AIDS by HIV (that is, the proposed link between the virus and the syndrome), and the denial of the effects on the human body that are ascribed to HIV (that is, the description and characterization of the virus). In a framework incorporating the second denial and/or the third, criticism of the current scientific view has variously been rested on the claim that HIV has not been adequately isolated, that HIV does not fulfill Koch's postulates, HIV testing is inaccurate, and/or that antibodies to HIV neutralize the virus and render it harmless. Suggested alternative causes of AIDS variously include recreational drugs, malnutrition, and the very antiretroviral drugs used to treat the syndrome.

Such claims have been examined extensively in the peer-reviewed medical and scientific literature; a scientific consensus has arisen that denialist claims have been convincingly disproved, and that HIV does indeed cause AIDS. In the cases cited by Duesberg where HIV "cannot be isolated", PCR or other techniques demonstrate the presence of the virus, and denialist claims of HIV test inaccuracy result from an incorrect or outdated understanding of how HIV antibody testing is performed and interpreted. Regarding Koch's postulates, New Scientist reported: "It is debatable how appropriate it is to focus on a set of principles devised for bacterial infections in a century when viruses had not yet been discovered. HIV does, however, meet Koch's postulates as long as they are not applied in a ridiculously stringent way". The author then demonstrated how each postulate has been met – the suspected cause is strongly associated with the disease, the suspected pathogen can be both isolated and spread outside the host, and when the suspected pathogen is transmitted to a new and uninfected host, that host develops the disease. The latter was proven in a number of tragic accidents, including an instance when multiple scientific technicians with no other known risk factors were exposed to concentrated HIV in a laboratory accident, and transmission by a dentist to patients, the majority of whom had no other known risk factor or source of exposure except the same dentist in common. In 2010, Chigwedere and Max Essex demonstrated in the medical journal AIDS and Behavior that HIV as the cause of AIDS fulfills both Koch's postulates and the Bradford Hill criteria for causality.

Early denialist arguments held that the HIV/AIDS paradigm was flawed because it had not led to effective treatments. However, the introduction of highly active antiretroviral therapy in the mid-1990s and dramatic improvements in survival of HIV/AIDS patients reversed this argument, as these treatments were based directly on anti-viral activity and the HIV/AIDS paradigm. The development of effective anti-AIDS therapies based on targeting of HIV has been a major factor in convincing some denialist scientists to accept the causative role of HIV in AIDS.

In a 2010 article on conspiracy theories in science, Ted Goertzel lists HIV/AIDS denialism as an example where scientific findings are being disputed on irrational grounds. He describes proponents as relying on rhetoric, appeal to fairness, and the right to a dissenting opinion rather than on evidence. They frequently invoke the meme of a "courageous independent scientist resisting orthodoxy", invoking the name of persecuted physicist and astronomer Galileo Galilei. Regarding this comparison, Goertzel states:

...being a dissenter from orthodoxy is not difficult; the hard part is actually having a better theory. Publishing dissenting theories is important when they are backed by plausible evidence, but this does not mean giving critics 'equal time' to dissent from every finding by a mainstream scientist.

— Goertzel, 2010

Denialist community

Denialists often use their critique of the link between HIV and AIDS to promote alternative medicine as a cure, and attempt to convince HIV-positive individuals to avoid ARV therapy in favour of vitamins, massage, yoga and other unproven treatments. Despite this promotion, denialists will often downplay any association with alternative therapies, and attempt to portray themselves as "dissidents". An article in the Skeptical Inquirer stated:

AIDS denialists [prefer] to characterize themselves as brave "dissidents" attempting to engage a hostile medical/industrial establishment in genuine scientific "debate." They complain that their attempts to raise questions and pose alternative hypotheses have been unjustly rejected or ignored at the cost of scientific progress itself...Given their resistance to all evidence to the contrary, today's AIDS dissidents are more aptly referred to as AIDS denialists.

Several scientists have been associated with HIV/AIDS denialism, although they have not themselves studied AIDS or HIV. One of the most famous and influential is Duesberg, professor of molecular and cell biology at the University of California, Berkeley, who since 1987 has disputed that the scientific evidence shows that HIV causes AIDS. Other scientists associated with HIV/AIDS denialism include biochemists David Rasnick and Harvey Bialy. Kary Mullis, who was awarded a Nobel Prize for his role in the development of the polymerase chain reaction, has expressed sympathy for denialist theories. Biologist Lynn Margulis argued that "there's no evidence that HIV is an infectious virus" and that AIDS symptoms "overlap...completely" with those of syphilis. Pathologist Étienne de Harven also expressed sympathy for HIV/AIDS denial.

Additional notable HIV/AIDS denialists include Australian academic ethicist Hiram Caton, the late mathematician Serge Lang, former college administrator Henry Bauer, journalist Celia Farber, American talk radio host and author on alternative and complementary medicine and nutrition Gary Null, and the late activist Christine Maggiore, who encouraged HIV-positive mothers to forgo anti-HIV treatment and whose 3-year-old daughter died of complications of untreated AIDS. Nate Mendel, bassist with the rock band Foo Fighters, expressed support for HIV/AIDS denialist ideas and organized a benefit concert in January 2000 for Maggiore's organization Alive & Well AIDS Alternatives. Organizations of HIV/AIDS denialists include the Perth Group, composed of several Australian hospital workers, and the Immunity Resource Foundation.

HIV/AIDS denialism has received some support from political conservatives in the United States. Duesberg's work has been published in Policy Review, a journal once published by The Heritage Foundation but later acquired by the Hoover Institution, and by Regnery Publishing. Regnery published Duesberg's Inventing the AIDS Virus in 1996, and journalist Tom Bethell's The Politically Incorrect Guide to Science, in which he endorses HIV/AIDS denialism, in 2005. Law professor Phillip E. Johnson has accused the Centers for Disease Control of "fraud" in relation to HIV/AIDS. Describing the political aspects of the HIV/AIDS denialism movement, Sociology professor Steven Epstein wrote in Impure Science that "... the appeal of Duesberg's views to conservatives—certainly including those with little sympathy for the gay movement—cannot be denied." The blog LewRockwell.com has also published articles supportive of HIV/AIDS denialism.

In a follow-up article in Skeptical Inquirer, Nattrass overviewed the prominent members of the HIV/AIDS denialist community and discussed the reasons of the intractable staying power of HIV/AIDS denialism in spite of scientific and medical consensus supported by over two decades of evidence. She observed that despite being a disparate group of people with very different background and professions, the HIV/AIDS denialists self-organize to fill four important roles:

• "Hero scientists" to provide scientific legitimacy: Most notably Duesberg who plays the central role of HIV/AIDS denialism from the beginning. Others include David Rasnick, Étienne de Harven, and Kary Mullis whose Nobel Prize makes him symbolically important.
• "Cultropreneurs" to offer fake cures in place of antiretroviral therapy: Matthias Rath, Gary Null, Michael Ellner, and Roberto Giraldo all promote alternative medicine and remedies with a dose of conspiracy theories in the form of books, healing products, radio shows and counseling services.
• HIV-positive "living icons" to provide proof of concept by appearing to live healthily without antiretroviral therapy: Christine Maggiore was and still is the most important icon in the HIV/AIDS denialist movement despite the fact that she died of AIDS related complications in 2008.
• "Praise singers": sympathetic journalists and filmmakers who publicize the movement with uncritical and favorable opinion. They include journalists Celia Farber, Liam Scheff and Neville Hodgkinson; filmmakers Brent Leung and Robert Leppo.

Some of them had overlapping roles as board members of Rethinking AIDS and Alive and Well AIDS Alternatives, were involved in the film House of Numbers, The Other Side of AIDS or on Thabo Mbeki's AIDS Advisory Panel. Nattrass argued that HIV/AIDS denialism gains social traction through powerful community-building effects where these four organized characters form "a symbiotic connection between AIDS denialism and alternative healing modalities" and they are "facilitated by a shared conspiratorial stance toward HIV science".

Former denialists

Several of the few prominent scientists who once voiced doubts about HIV/AIDS have since changed their views and accepted the fact that HIV plays a role in causing AIDS, in response to an accumulation of newer studies and data. Root-Bernstein, author of Rethinking AIDS: The Tragic Cost of Premature Consensus and formerly a critic of the causative role of HIV in AIDS, has since distanced himself from the HIV/AIDS denialist movement, saying, "Both the camp that says HIV is a pussycat and the people who claim AIDS is all HIV are wrong...The denialists make claims that are clearly inconsistent with existing studies."

Joseph Sonnabend, who until the late 1990s regarded the issue of AIDS causation as unresolved, has reconsidered in light of the success of newer antiretroviral drugs, stating, "The evidence now strongly supports a role for HIV… Drugs that can save your life can also under different circumstances kill you. This is a distinction that denialists do not seem to understand." Sonnabend has also criticized HIV/AIDS denialists for falsely implying that he supports their position, saying:

Some individuals who believe that HIV plays no role at all in AIDS have implied that I support their misguided views on AIDS causation by including inappropriate references to me in their literature and on their web sites. Before HIV was discovered and its association with AIDS established, I held the entirely appropriate view that the cause of AIDS was then unknown. I have successfully treated hundreds of AIDS patients with antiretroviral medications, and have no doubt that HIV plays a necessary role in this disease.

A former denialist wrote in the Journal of Medical Ethics in 2004:

The group [of denialists] regularly points to a substantial number of scientists supportive of its agenda to re-evaluate the HIV/AIDS hypothesis. Some of those members still listed are people who have been dead for a number of years. While it is correct that these people supported the objective of a scientific re-evaluation of the HIV/AIDS link when they were alive, it is clearly difficult to ascertain what these people would have made of the scientific developments and the accumulation of evidence for HIV as the crucial causative agent in AIDS, which has occurred in the years after their deaths.

Death of HIV-positive denialists

In 2007, aidstruth.org, a website run by HIV researchers to counter denialist claims, published a partial list of HIV/AIDS denialists who had died of AIDS-related causes. For example, the editors of the magazine Continuum consistently denied the existence of HIV/AIDS. The magazine shut down after both editors died of AIDS-related causes. In each case, the HIV/AIDS denialist community attributed the deaths to unknown causes, secret drug use, or stress rather than HIV/AIDS. Similarly, several HIV-positive former dissidents have reported being ostracized by the AIDS-denialist community after they developed AIDS and decided to pursue effective antiretroviral treatment.

In 2008, activist Christine Maggiore died at the age of 52 while under a doctor's care for pneumonia. Maggiore, mother of two children, had founded an organisation to help other HIV-positive mothers avoid taking antiretroviral drugs that reduce the risk of HIV transmission from mother to child. After her three-year-old daughter died of AIDS-related pneumonia in 2005, Maggiore continued to believe that HIV is not the cause of AIDS, and she and her husband Robin Scovill sued Los Angeles County and others on behalf of their daughter's estate, for allegedly violating Eliza Scovill's civil rights by releasing an autopsy report that listed her cause of death as AIDS-related pneumonia. The litigants settled out of court, with the county paying Scovill $15,000 in March 2009, with no admission of wrongdoing. The Los Angeles coroner's ruling that Eliza Scovill died of AIDS remains the official verdict.

Local community group denialism

Australia: In 2009 representing the then Australian Vaccination-Skeptics Network, President Meryl Dorey signed a petition claiming that "the AIDS industry and the media" had tricked the public and the media into believing that HIV causes AIDS.

Canada: The Alberta Reappraising AIDS Society created the petition in March 2000 and has reportedly since attracted "2,951 doubters" representing groups and individuals. Signatories reportedly deny "that Aids is heterosexually transmitted".

Impact beyond the scientific community

AIDS-denialist claims have failed to attract support in the scientific community, where the evidence for the causative role of HIV in AIDS is considered conclusive. However, the movement has had a significant impact in the political sphere, culminating with former South African President Thabo Mbeki's embrace of AIDS-denialist claims. The resulting governmental refusal to provide effective anti-HIV treatment in South Africa has been blamed for hundreds of thousands of premature AIDS-related deaths in South Africa.

North America and Europe

Skepticism about HIV being the cause of AIDS began almost immediately after the discovery of HIV was announced. One of the earliest prominent skeptics was the journalist John Lauritsen, who argued in his writings for the New York Native that amyl nitrite poppers played a role in AIDS, and that the Centers for Disease Control and Prevention had used statistical methods that concealed this. Lauritsen's The AIDS War was published in 1993.

Scientific literature

The publication of Duesberg's first AIDS paper in 1987 provided visibility for denialist claims. Shortly afterwards, the journal Science reported that Duesberg's remarks had won him "a large amount of media attention, particularly in the gay press where he is something of a hero." However, Duesberg's support in the gay community diminished as he made a series of statements perceived as homophobic; in an interview with The Village Voice in 1988, Duesberg stated his belief that the AIDS epidemic was "caused by a lifestyle that was criminal twenty years ago."

In the following few years, others became skeptical of the HIV theory as researchers initially failed to produce an effective treatment or vaccine for AIDS. Journalists such as Neville Hodgkinson and Celia Farber regularly promoted denialist ideas in the American and British media; several television documentaries were also produced to increase awareness of the alternative viewpoint. In 1992–1993, The Sunday Times, where Hodgkinson served as scientific editor, ran a series of articles arguing that the AIDS epidemic in Africa was a myth. These articles stressed Duesberg's claims and argued that antiviral therapy was ineffective, HIV testing unreliable, and that AIDS was not a threat to heterosexuals. The Sunday Times coverage was heavily criticized as slanted, misleading, and potentially dangerous; the scientific journal Nature took the unusual step of printing a 1993 editorial calling the paper's coverage of HIV/AIDS "seriously mistaken, and probably disastrous."

Finding difficulty in publishing his arguments in the scientific literature, Duesberg exercised his right as a member of the National Academy of Sciences to publish in Proceedings of the National Academy of Sciences of the United States of America (PNAS) without going through the peer review process. However, Duesberg's paper raised a "red flag" at the journal and was submitted by the editor for non-binding review. All of the reviewers found major flaws in Duesberg's paper; the reviewer specifically chosen by Duesberg noted the presence of "misleading arguments", "nonlogical statements", "misrepresentations", and political overtones. Ultimately, the editor of PNAS acquiesced to publication, writing to Duesberg: "If you wish to make these unsupported, vague, and prejudicial statements in print, so be it. But I cannot see how this would be convincing to any scientifically trained reader."

HIV/AIDS denialists often resort to special pleading to support their assertion, arguing for different causes of AIDS in different locations and subpopulations. In North America, AIDS is blamed on the health effects of unprotected anal sex and poppers on homosexual men, an argument which does not account for AIDS in drug-free heterosexual women who deny participating in anal sex. In this case, HIV/AIDS denialists claim the women are having anal sex but refuse to disclose it. In haemophiliac North American children who contracted HIV from blood transfusions, the haemophilia itself or its treatment is claimed to cause AIDS. In Africa, AIDS is blamed on poor nutrition and sanitation due to poverty. For wealthy populations in South Africa with adequate nutrition and sanitation, it is claimed that the antiretroviral drugs used to treat AIDS cause the condition. In each case, the most parsimonious explanation and uniting factor – HIV positive status – is ignored, as are the thousands of studies that converge on the common conclusion that AIDS is caused by HIV infection.

Haemophilia is considered the best test of the HIV-AIDS hypothesis by both denialists and AIDS researchers. While Duesberg claims AIDS in haemophiliacs is caused by contaminated clotting factors and HIV is a harmless passenger virus, this result is contradicted by large studies on haemophiliac patients who received contaminated blood. A comparison of groups receiving high, medium and low levels of contaminated clotting factors found the death rates differed significantly depending on HIV status. Of 396 HIV positive haemophiliacs followed between 1985 and 1993, 153 died. The comparative figure for the HIV negative group was one out of 66, despite comparable doses of contaminated clotting factors. A comparison of individuals receiving blood donations also supports the results; in 1994 there were 6888 individuals with AIDS who had their HIV infection traced to blood transfusions. Since the introduction of HIV testing, the number of individuals whose AIDS status can be traced to blood transfusions was only 29 (as of 1994).

Lay press and on the Internet

With the introduction of highly active antiretroviral therapy (HAART) in 1996–1997, the survival and general health of people with HIV improved significantly. The positive response to treatment with anti-HIV medication cemented the scientific acceptance of the HIV/AIDS paradigm, and led several prominent HIV/AIDS denialists to accept the causative role of HIV. Finding their arguments increasingly discredited by the scientific community, denialists took their message to the popular press. A former denialist wrote:

Scientists among the HIV dissidents used their academic credentials and academic affiliations to generate interest, sympathy, and allegiances in lay audiences. They were not professionally troubled about recruiting lay people—who were clearly unable to evaluate the scientific validity or otherwise of their views—to their cause.

In addition to elements of the popular and alternative press, AIDS denialist ideas are propagated largely via the Internet.

A 2007 article in PLoS Medicine noted:

Because these denialist assertions are made in books and on the Internet rather than in the scientific literature, many scientists are either unaware of the existence of organized denial groups, or believe they can safely ignore them as the discredited fringe. And indeed, most of the HIV deniers' arguments were answered long ago by scientists. However, many members of the general public do not have the scientific background to critique the assertions put forth by these groups, and not only accept them but continue to propagate them.

Lay opinion and AIDS-related behaviors

AIDS activists have expressed concern that denialist arguments about HIV's harmlessness may be responsible for an upsurge in HIV infections. Denialist claims continue to exert a significant influence in some communities; a survey conducted at minority gay pride events in four American cities in 2005 found that 33% of attendees doubted that HIV caused AIDS. Similarly, a 2010 survey of 343 people living with HIV/AIDS found that one in five of them thought that there was no proof that HIV caused AIDS, and that HIV treatments did more harm than good. According to Stephen Thomas, director of the University of Pittsburgh Center for Minority Health, "people are focusing on the wrong thing. They're focusing on conspiracies rather than protecting themselves, rather than getting tested and seeking out appropriate care and treatment." African Americans are exceptionally likely to believe that HIV does not cause AIDS, partly because they sometimes perceive the role of HIV in the disease as part of a racist agenda. A 2012 survey of young adults in Cape Town, South Africa found that belief in AIDS denialism was strongly related to an increased probability of engaging in unsafe sex.

South Africa

HIV/AIDS denialist claims have had a major political, social, and public health impact in South Africa. The government of then President Thabo Mbeki was sympathetic to the views of HIV/AIDS denialists, with critics charging that denialist influence was responsible for the slow and ineffective governmental response to the country's massive AIDS epidemic.

Independent studies have arrived at almost identical estimates of the human costs of HIV/AIDS denialism in South Africa. According to a paper written by researchers from the Harvard School of Public Health, between 2000 and 2005, more than 330,000 deaths and an estimated 35,000 infant HIV infections occurred "because of a failure to accept the use of available [antiretroviral drugs] to prevent and treat HIV/AIDS in a timely manner." Nicoli Nattrass of the University of Cape Town estimates that 343,000 excess AIDS-related deaths and 171,000 infections resulted from the Mbeki administration's policies, an outcome she refers to in the words of Peter Mandelson as "genocide by sloth".

Durban Declaration

In 2000, when the International AIDS Conference was held in Durban, Mbeki convened a Presidential Advisory Panel containing a number of HIV/AIDS denialists, including Duesberg and David Rasnick. The Advisory Panel meetings were closed to the general press; an invited reporter from the Village Voice wrote that Rasnick advocated that HIV testing be legally banned and denied that he had seen "any evidence" of an AIDS catastrophe in South Africa, while Duesberg "gave a presentation so removed from African medical reality that it left several local doctors shaking their heads."

In his address to the International AIDS Conference, Mbeki reiterated his view that HIV was not wholly responsible for AIDS, leading hundreds of delegates to walk out on his speech. Mbeki also sent a letter to a number of world leaders likening the mainstream AIDS research community to supporters of the apartheid regime. The tone and content of Mbeki's letter led diplomats in the U.S. to initially question whether it was a hoax.

AIDS scientists and activists were dismayed at the president's behavior and responded with the Durban Declaration, a document affirming that HIV causes AIDS, signed by over 5,000 scientists and physicians.

Criticism of governmental response

The former South African health minister Manto Tshabalala-Msimang also attracted heavy criticism, as she often promoted nutritional remedies such as garlic, lemons, beetroot and olive oil, to people suffering from AIDS, while emphasizing possible toxicities of antiretroviral drugs, which she has referred to as "poison". The South African Medical Association has accused Tshabalala-Msimang of "confusing a vulnerable public". In September 2006, a group of over 80 scientists and academics called for "the immediate removal of Dr. Tshabalala-Msimang as minister of health and for an end to the disastrous, pseudoscientific policies that have characterized the South African government's response to HIV/AIDS." In December 2006, deputy health minister Nozizwe Madlala-Routledge described "denial at the very highest levels" over AIDS.

Former South African president Thabo Mbeki's government was widely criticized for delaying the rollout of programs to provide antiretroviral drugs to people with advanced HIV disease and to HIV-positive pregnant women. The national treatment program began only after the Treatment Action Campaign (TAC) brought a legal case against Government ministers, claiming they were responsible for the deaths of 600 HIV-positive people a day who could not access medication. South Africa was one of the last countries in the region to begin such a treatment program, and roll-out has been much slower than planned.

At the XVI International AIDS Conference, Stephen Lewis, UN special envoy for AIDS in Africa, attacked Mbeki's government for its slow response to the AIDS epidemic and reliance on denialist claims:

It [South Africa] is the only country in Africa … whose government is still obtuse, dilatory and negligent about rolling out treatment… It is the only country in Africa whose government continues to promote theories more worthy of a lunatic fringe than of a concerned and compassionate state.

In 2002, Mbeki requested that HIV/AIDS denialists no longer use his name in their literature and stop signing documents with "Member of President Mbeki's AIDS Advisory Panel". This coincided with the South African government's statement accompanying its 2002 AIDS campaign, that "...in conducting this campaign, government's starting point is based on the premise that HIV causes AIDS". Nonetheless, Mbeki himself continued to promote and defend AIDS-denialist claims. His loyalists attacked former President Nelson Mandela in 2002 when Mandela questioned the government's AIDS policy, and Mbeki attacked Malegapuru William Makgoba, one of South Africa's leading scientists, as a racist defender of "Western science" for opposing HIV/AIDS denialism.

In early 2005, former South African President Nelson Mandela announced that his son had died of complications of AIDS. Mandela's public announcement was seen as both an effort to combat the stigma associated with AIDS, and as a "political statement designed to… force the President [Mbeki] out of his denial."

Post-Mbeki government in South Africa

In 2008, Mbeki was ousted from power and replaced as President of South Africa by Kgalema Motlanthe. On Motlanthe's first day in office, he removed Manto Tshabalala-Msimang, the controversial health minister who had promoted AIDS-denialist claims and recommended garlic, beetroot, and lemon juice as treatments for AIDS. Barbara Hogan, newly appointed as health minister, voiced shame at the Mbeki government's embrace of HIV/AIDS denialism and vowed a new course, stating: "The era of denialism is over completely in South Africa."

Food irradiation

From Wikipedia, the free encyclopedia

https://en.wikipedia.org/wiki/Food_irradiation 

 

Cobalt-60 irradiation facility is used to test irradiation as a tool to ensure food safety.

 

The international Radura logo, used to show a food has been treated with ionizing radiation.

 

A portable, trailer-mounted food irradiation machine, circa 1968

Food irradiation is the process of exposing food and food packaging to ionizing radiation, such as from gamma rays, x-rays, or electron beams, without direct contact to the food product. When ionizing radiation passes through a food product, some energy is absorbed by some chemical bonds. Some bonds rupture and produce free radicals which are highly reactive and unstable. They instantaneously rejoin with neighboring compounds and the results are called radiolytic compounds. Food irradiation is used to improve food safety by extending product shelf life (preservation), reducing the risk of foodborne illness, delaying or eliminating sprouting or ripening, by sterilization of foods, and as a means of controlling insects and invasive pests. Food irradiation extends the shelf life of irradiated foods by effectively destroying organisms responsible for spoilage and foodborne illness and inhibiting sprouting. Consumer perception of foods treated with irradiation is more negative than those processed by other means. The U.S. Food and Drug Administration (FDA), the World Health Organization (WHO), the Centers for Disease Control and Prevention (CDC), and U.S. Department of Agriculture (USDA) have performed studies that confirm irradiation to be safe. In order for a food to be irradiated in the US, the FDA will still require that the specific food be thoroughly tested for irradiation safety.

Food irradiation is permitted in over 60 countries, and about 500,000 metric tons of food are processed annually worldwide. The regulations for how food is to be irradiated, as well as the foods allowed to be irradiated, vary greatly from country to country. In Austria, Germany, and many other countries of the European Union only dried herbs, spices, and seasonings can be processed with irradiation and only at a specific dose, while in Brazil all foods are allowed at any dose.

Uses

Irradiation is used to reduce or eliminate pests and the risk of food-borne illnesses as well as prevent or slow spoilage and plant maturation or sprouting. Depending on the dose, some or all of the organisms, microorganisms, bacteria, and viruses present are destroyed, slowed, or rendered incapable of reproduction. When targeting bacteria, most foods are irradiated to significantly reduce the number of active microbes, not to sterilize all microbes in the product. Irradiation cannot return spoiled or over-ripe food to a fresh state. If this food was processed by irradiation, further spoilage would cease and ripening would slow, yet the irradiation would not destroy the toxins or repair the texture, color, or taste of the food.

Irradiation slows the speed at which enzymes change the food. By reducing or removing spoilage organisms and slowing ripening and sprouting (e.g. potato, onion, and garlic) irradiation is used to reduce the amount of food that goes bad between harvest and final use. Shelf-stable products are created by irradiating foods in sealed packages, as irradiation reduces chance of spoilage, the packaging prevents re-contamination of the final product. Foods that can tolerate the higher doses of radiation required to do so can be sterilized. This is useful for people at high risk of infection in hospitals as well as situations where proper food storage is not feasible, such as rations for astronauts.

Pests such as insects have been transported to new habitats through the trade in fresh produce and significantly affected agricultural production and the environment once they established themselves. To reduce this threat and enable trade across quarantine boundaries, food is irradiated using a technique called phytosanitary irradiation. Phytosanitary irradiation sterilizes the pests preventing breeding by treating the produce with low doses of irradiation (less than 1000 Gy). The higher doses required to destroy pests are not used due to either affecting the look or taste, or cannot be tolerated by fresh produce.

Process

Efficiency illustration of the different radiation technologies (electron beam, X-ray, gamma rays)

The target material is exposed to a radiation source that is separated from the target material. The radiation source supplies energetic particles or waves. As these waves/particles enter the target material they collide with other particles. The higher the likelihood of these collisions over a distance are, the lower the penetration depth of the irradiation process is as the energy is more quickly depleted. Around the sites of these collisions chemical bonds are broken, creating short lived radicals (e.g. the hydroxyl radical, the hydrogen atom and solvated electrons). These radicals cause further chemical changes by bonding with and or stripping particles from nearby molecules. When collisions occur in cells, cell division is often suppressed, halting or slowing the processes that cause the food to mature. When the process damages DNA or RNA, effective reproduction becomes unlikely halting the population growth of viruses and organisms. The distribution of the dose of radiation varies from the food surface and the interior as it is absorbed as it moves through food and depends on the energy and density of the food and the type of radiation used.

This leaves a product with qualities (sensory and chemical) that are more similar to unprocessed food than any preservation method that can achieve a similar degree of preservation.

Irradiated food does not become radioactive; only radiation sources that are incapable of causing significant induced radioactivity are used for food irradiation. Radioactivity is the ability of an atom to emit energetic particles. When particles hit the target materials, they may free other highly energetic particles. When the nucleus is not modified this ends shortly after the end of the exposure, much like objects stop reflecting light when the source is turned off and warm objects emit heat until they cool down but do not continue to produce their own heat. To modify a material so that it keeps emitting radiation (induce radiation) the atomic cores (nucleus) of the atoms in the target material must be modified by colliding with particles above a specific energy threshold. Particles below this energy can never be strong enough to modify the nucleus of the targeted atom in the food, regardless of how many particles hit the target material, and radioactivity can not be induced without modifying the nucleus. Food irradiators using radioactive materials (gamma irradiation) or electron beams as sources produce radiation at a precise energies making it impossible to induce any amount of radiation. Food irradiatiors using x-rays produce radiation at a wider power spectrum, a small portion of this radiation is above the threshold for inducing radiation, therefore is impossible for food irradiators to induce radiation above the background level (above the normal level of radiation) in a product.

Dosimetry

The radiation absorbed dose is the amount energy absorbed per unit weight of the target material. Dose is used because, when the same substance is given the same dose, similar changes are observed in the target material(Gy or J/kg). Dosimeters are used to measure dose, and are small components that, when exposed to ionizing radiation, change measurable physical attributes to a degree that can be correlated to the dose received. Measuring dose (dosimetry) involves exposing one or more dosimeters along with the target material.

For purposes of legislation doses are divided into low (up to 1 kGy), medium (1 kGy to 10 kGy), and high-dose applications (above 10 kGy). High-dose applications are above those currently permitted in the US for commercial food items by the FDA and other regulators around the world. Though these doses are approved for non commercial applications, such as sterilizing frozen meat for NASA astronauts (doses of 44 kGy) and food for hospital patients.

The ratio of the maximum dose permitted at the outer edge (D_max) to the minimum limit to achieve processing conditions (D_min) determines the uniformity of dose distribution. This ratio determines how uniform the irradiation process is.

Applications of food irradiation

	Application	Dose (kGy)
Low dose (up to 1 kGy)	Inhibit sprouting (potatoes, onions, yams, garlic)	0.06 - 0.2
	Delay in ripening (strawberries, potatoes)	0.5 - 1.0
	Prevent insect infestation (grains, cereals, coffee beans, spices, dried nuts, dried fruits, dried fish, mangoes, papayas)	0.15 - 1.0
	Parasite control and inactivation (tape worm, trichina)	0.3 - 1.0
Medium dose (1 kGy to 10 kGy)	Extend shelf-life of raw and fresh fish, seafood, fresh produce	1.0 - 5.5
	Extend shelf-life of refrigerated and frozen meat products	4.5 - 7.0
	Reduce risk of pathogenic and spoilage microbes (meat, seafood, spices, and poultry)	1.0 - 7.0
	Increased juice yield, reduction in cooking time of dried vegetables	3.0 - 7.0
High dose (above 10 kGy)	Enzymes (dehydrated)	10.0
	Sterilization of spices, dry vegetable seasonings	30.0 max
	Sterilization of packaging material	10.0 - 25.0
	Sterilization of foods (NASA and hospitals)	44.0

Chemical changes

As ionising radiation passes through food, it creates a trail of chemical transformations due to radiolysis effects. Irradiation does not make foods radioactive, change food chemistry, compromise nutrient contents, or change the taste, texture, or appearance of food . However, the Organic consumers organisation disputes that taste and nutritional value are not harmed by food irradiation.

Food quality

Assessed rigorously over several decades, irradiation in commercial amounts to treat food has no negative impact on the sensory qualities and nutrient content of foods, the only new contrary evidence was indicated in publications on leukoencephalomyelopathy in cats which have been fed mainly or exclusively with highly irradiated feed.

Research on minimally processed vegetables

Watercress (Nasturtium officinale) is a rapidly growing aquatic or semi aquatic perennial plant. Because chemical agents do not provide efficient microbial reductions, watercress has been tested with gamma irradiation treatment in order to improve both safety and the shelf life of the product. It is traditionally used on horticultural products to prevent sprouting and post-packaging contamination, delay post-harvest ripening, maturation and senescence.

Public Perceptions

Some who advocate against food irradiation argue the long term health effects & safety of irradiated food cannot be scientifically proven, despite hundreds of animal feeding studies of irradiated food performed since 1950. Endpoints include subchronic and chronic changes in metabolism, histopathology, function of most organs, reproductive effects, growth, teratogenicity, and mutagenicity.

Industrial process

Up to the point where the food is processed by irradiation, the food is processed in the same way as all other food.

Packaging

For some forms of treatment, packaging is used to ensure the food stuffs never come in contact with radioactive substances and prevent re-contamination of the final product. Food processors and manufacturers today struggle with using affordable, efficient packaging materials for irradiation based processing. The implementation of irradiation on prepackaged foods has been found to impact foods by inducing specific chemical alterations to the food packaging material that migrates into the food. Cross-linking in various plastics can lead to physical and chemical modifications that can increase the overall molecular weight. On the other hand, chain scission is fragmentation of polymer chains that leads to a molecular weight reduction.

Treatment

To treat the food, it is exposed to a radioactive source for a set period of time to achieve a desired dose. Radiation may be emitted by a radioactive substance, or by X-ray and electron beam accelerators. Special precautions are taken to ensure the food stuffs never come in contact with the radioactive substances and that the personnel and the environment are protected from exposure radiation. Irradiation treatments are typically classified by dose (high, medium, and low), but are sometimes classified by the effects of the treatment (radappertization, radicidation and radurization). Food irradiation is sometimes referred to as "cold pasteurization" or "electronic pasteurization" because ionizing the food does not heat the food to high temperatures during the process, and the effect is similar to heat pasteurization. The term "cold pasteurization" is controversial because the term may be used to disguise the fact the food has been irradiated and pasteurization and irradiation are fundamentally different processes.

Gamma irradiation

Gamma irradiation is produced from the radioisotopes cobalt-60 and caesium-137, which are derived by neutron bombardment of cobalt-59 and as a nuclear source by-product, respectively. Cobalt-60 is the most common source of gamma rays for food irradiation in commercial scale facilities as it is water insoluble and hence has little risk of environmental contamination by leakage into the water systems. As for transportation of the radiation source, cobalt-60 is transported in special trucks that prevent release of radiation and meet standards mentioned in the Regulations for Safe Transport of Radioactive Materials of the International Atomic Energy Act. The special trucks must meet high safety standards and pass extensive tests to be approved to ship radiation sources. Conversely, caesium-137, is water-soluble and poses a risk of environmental contamination. Insufficient quantities are available for large scale commercial use. An incident where water-soluble caesium-137 leaked into the source storage pool requiring NRC intervention has led to near elimination of this radioisotope.

Cobalt 60 stored in Gamma Irradiation machine

Gamma irradiation is widely used due to its high penetration depth and dose uniformity, allowing for large-scale applications with high through puts. Additionally, gamma irradiation is significantly less expensive than using an X-ray source. In most designs, the radioisotope, contained in stainless steel pencils, is stored in a water-filled storage pool which absorbs the radiation energy when not in use. For treatment, the source is lifted out of the storage tank, and product contained in totes is passed around the pencils to achieve required processing.

Treatment costs vary as a function of dose and facility usage. A pallet or tote is typically exposed for several minutes to hours depending on dose. Low-dose applications such as disinfestation of fruit range between US$0.01/lbs and US$0.08/lbs while higher-dose applications can cost as much as US$0.20/lbs.

Electron beam

Treatment of electron beams is created as a result of high energy electrons in an accelerator that generates electrons accelerated to 99% the speed of light. This system uses electrical energy and can be powered on and off. The high power correlates with a higher throughput and lower unit cost, but electron beams have low dose uniformity and a penetration depth of centimeters. Therefore, electron beam treatment works for products that have low thickness.

Irradiated Guava: Spring Valley Fruits, Mexico

X-ray

X-rays are produced by bombardment of dense target material with high energy accelerated electrons (this process is known as bremsstrahlung-conversion), giving rise to a continuous energy spectrum. Heavy metals, such as tantalum and tungsten, are used because of their high atomic numbers and high melting temperatures.Tantalum is usually preferred versus tungsten for industrial, large-area, high-power targets because it is more workable than tungsten and has a higher threshold energy for induced reactions. Like electron beams, x-rays do not require the use of radioactive materials and can be turned off when not in use. X-rays have high penetration depths and high dose uniformity but they are a very expensive source of irradiation as only 8% of the incident energy is converted into X-rays.

UV-C

UV-C does not penetrate as deeply as other methods. As such, its direct antimicrobial effect is limited to the surface only. Its DNA damage effect produces cyclobutane-type pyrimidine dimers. Besides the direct effects, UV-C also induces resistance even against pathogens not yet inoculated. Some of this induced resistance is understood, being the result of temporary inactivation of self-degradation enzymes like polygalacturonase and increased expression of enzymes associated with cell wall repair.

Cost

Irradiation is a capital-intensive technology requiring a substantial initial investment, ranging from $1 million to $5 million. In the case of large research or contract irradiation facilities, major capital costs include a radiation source, hardware (irradiator, totes and conveyors, control systems, and other auxiliary equipment), land (1 to 1.5 acres), radiation shield, and warehouse. Operating costs include salaries (for fixed and variable labor), utilities, maintenance, taxes/insurance, cobalt-60 replenishment, general utilities, and miscellaneous operating costs. Perishable food items, like fruits, vegetables and meats would still require to be handled in the cold chain, so all other supply chain costs remain the same. Food manufacturers have not embraced food irradiation because the market does not support the increased price of irradiated foods, and because of potential consumer backlash due to irradiated foods.

The cost of food irradiation is influenced by dose requirements, the food's tolerance of radiation, handling conditions, i.e., packaging and stacking requirements, construction costs, financing arrangements, and other variables particular to the situation.

State of the industry

Irradiation has been approved by many countries. For example, in the U.S. and Canada, food irradiation has existed for decades. Food irradiation is used commercially and volumes are in general increasing at a slow rate, even in the European Union where all member countries allow the irradiation of dried herbs spices and vegetable seasonings, but only a few allow other foods to be sold as irradiated.

Although there are some consumers who choose not to purchase irradiated food, a sufficient market has existed for retailers to have continuously stocked irradiated products for years. When labeled irradiated food is offered for retail sale, consumers buy it and re-purchase it, indicating a market for irradiated foods, although there is a continuing need for consumer education.

Food scientists have concluded that any fresh or frozen food undergoing irradiation at specified doses is safe to consume, with some 60 countries using irradiation to maintain quality in their food supply.

Standards and regulations

The Codex Alimentarius represents the global standard for irradiation of food, in particular under the WTO-agreement. Regardless of treatment source, all processing facilities must adhere to safety standards set by the International Atomic Energy Agency (IAEA), Codex Code of Practice for the Radiation Processing of Food, Nuclear Regulatory Commission (NRC), and the International Organization for Standardization (ISO). More specifically, ISO 14470 and ISO 9001 provide in-depth information regarding safety in irradiation facilities.

All commercial irradiation facilities contain safety systems which are designed to prevent exposure of personnel to radiation. The radiation source is constantly shielded by water, concrete, or metal. Irradiation facilities are designed with overlapping layers of protection, interlocks, and safeguards to prevent accidental radiation exposure. Additionally, "melt-downs" do not occur in facilities because the radiation source gives off radiation and decay heat; however, the heat is not sufficient to melt any material.

Labeling

The Radura symbol, as required by U.S. Food and Drug Administration regulations to show a food has been treated with ionizing radiation.

The provisions of the Codex Alimentarius are that any "first generation" product must be labeled "irradiated" as any product derived directly from an irradiated raw material; for ingredients the provision is that even the last molecule of an irradiated ingredient must be listed with the ingredients even in cases where the unirradiated ingredient does not appear on the label. The RADURA-logo is optional; several countries use a graphical version that differs from the Codex-version. The suggested rules for labeling is published at CODEX-STAN – 1 (2005), and includes the usage of the Radura symbol for all products that contain irradiated foods. The Radura symbol is not a designator of quality. The amount of pathogens remaining is based upon dose and the original content and the dose applied can vary on a product by product basis.

The European Union follows the Codex's provision to label irradiated ingredients down to the last molecule of irradiated food. The European Union does not provide for the use of the Radura logo and relies exclusively on labeling by the appropriate phrases in the respective languages of the Member States. The European Union enforces its irradiation labeling laws by requiring its member countries to perform tests on a cross section of food items in the market-place and to report to the European Commission. The results are published annually on EUR-Lex.

The US defines irradiated foods as foods in which the irradiation causes a material change in the food, or a material change in the consequences that may result from the use of the food. Therefore, food that is processed as an ingredient by a restaurant or food processor is exempt from the labeling requirement in the US. All irradiated foods must include a prominent Radura symbol followed in addition to the statement "treated with irradiation" or "treated by irradiation. Bulk foods must be individually labeled with the symbol and statement or, alternatively, the Radura and statement should be located next to the sale container.

Packaging

Under section 409 of the Federal Food, Drug, and Cosmetic Act, irradiation of prepackaged foods requires premarket approval for not only the irradiation source for a specific food but also for the food packaging material. Approved packaging materials include various plastic films, yet does not cover a variety of polymers and adhesive based materials that have been found to meet specific standards. The lack of packaging material approval limits manufacturers production and expansion of irradiated prepackaged foods.

Approved materials by FDA for Irradiation according to 21 CFR 179.45:

Material	Paper (kraft)	Paper (glassine)	Paperboard	Cellophane (coated)	Polyolefin film	Polyestyrene film	Nylon-6	Vegetable Parchment	Nylon 11
Irradiation (kGy)	.05	10	10	10	10	10	10	60	60

Food safety

In 2003, the Codex Alimentarius removed any upper dose limit for food irradiation as well as clearances for specific foods, declaring that all are safe to irradiate. Countries such as Pakistan and Brazil have adopted the Codex without any reservation or restriction.

Standards that describe calibration and operation for radiation dosimetry, as well as procedures to relate the measured dose to the effects achieved and to report and document such results, are maintained by the American Society for Testing and Materials (ASTM international) and are also available as ISO/ASTM standards.

All of the rules involved in processing food are applied to all foods before they are irradiated.

United States

The U.S. Food and Drug Administration (FDA) is the agency responsible for regulation of radiation sources in the United States. Irradiation, as defined by the FDA is a "food additive" as opposed to a food process and therefore falls under the food additive regulations. Each food approved for irradiation has specific guidelines in terms of minimum and maximum dosage as determined safe by the FDA. Packaging materials containing the food processed by irradiation must also undergo approval. The United States Department of Agriculture (USDA) amends these rules for use with meat, poultry, and fresh fruit.

The United States Department of Agriculture (USDA) has approved the use of low-level irradiation as an alternative treatment to pesticides for fruits and vegetables that are considered hosts to a number of insect pests, including fruit flies and seed weevils. Under bilateral agreements that allows less-developed countries to earn income through food exports agreements are made to allow them to irradiate fruits and vegetables at low doses to kill insects, so that the food can avoid quarantine.

The U.S. Food and Drug Administration and the U.S. Department of Agriculture have approved irradiation of the following foods and purposes:

• Packaged refrigerated or frozen red meat — to control pathogens (E. Coli O157:H7 and Salmonella) and to extend shelf life
• Packaged poultry — control pathogens (Salmonella and Camplylobacter)
• Fresh fruits, vegetables, and grains — to control insects and inhibit growth, ripening and sprouting
• Pork — to control trichinosis
• Herbs, spices and vegetable seasonings — to control insects and microorganisms
• Dry or dehydrated enzyme preparations — to control insects and microorganisms
• White potatoes — to inhibit sprout development
• Wheat and wheat flour — to control insects
• Loose or bagged fresh iceberg lettuce and spinach
• Crustaceans (lobster, shrimp, and crab)
• Shellfish (oysters, clams, mussels, and scallops)

European Union

European law stipulates that all member countries must allow the sale of irradiated dried aromatic herbs, spices and vegetable seasonings. However, these Directives allow Member States to maintain previous clearances food categories the EC's Scientific Committee on Food (SCF) had previously approved (the approval body is now the European Food Safety Authority). Presently, Belgium, Czech Republic, France, Italy, Netherlands, Poland, and the United Kingdom allow the sale of many different types of irradiated foods. Before individual items in an approved class can be added to the approved list, studies into the toxicology of each of such food and for each of the proposed dose ranges are requested. It also states that irradiation shall not be used "as a substitute for hygiene or health practices or good manufacturing or agricultural practice". These Directives only control food irradiation for food retail and their conditions and controls are not applicable to the irradiation of food for patients requiring sterile diets. In 2021 the most common food items irradiated were frog legs at 65.1%, poultry 20.6% and dried aromatic herbs, spices and vegetables seasoning.

Because of the Single Market of the EU any food, even if irradiated, must be allowed to be marketed in any other Member State even if a general ban of food irradiation prevails, under the condition that the food has been irradiated legally in the state of origin.

Furthermore, imports into the EC are possible from third countries if the irradiation facility had been inspected and approved by the EC and the treatment is legal within the EC or some Member state.

Nuclear safety and security

Interlocks and safeguards are mandated to minimize this risk. There have been radiation-related accidents, deaths, and injury at such facilities, many of them caused by operators overriding the safety related interlocks. In a radiation processing facility, radiation specific concerns are supervised by special authorities, while "Ordinary" occupational safety regulations are handled much like other businesses.

The safety of irradiation facilities is regulated by the United Nations International Atomic Energy Agency and monitored by the different national Nuclear Regulatory Commissions. The regulators enforce a safety culture that mandates that all incidents that occur are documented and thoroughly analyzed to determine the cause and improvement potential. Such incidents are studied by personnel at multiple facilities, and improvements are mandated to retrofit existing facilities and future design.

In the US the Nuclear Regulatory Commission (NRC) regulates the safety of the processing facility, and the United States Department of Transportation (DOT) regulates the safe transport of the radioactive sources.

Historical timeline

• 1895 Wilhelm Conrad Röntgen discovers X-rays ("bremsstrahlung", from German for radiation produced by deceleration)
• 1896 Antoine Henri Becquerel discovers natural radioactivity; Minck proposes the therapeutic use
• 1904 Samuel Prescott describes the bactericide effects Massachusetts Institute of Technology (MIT)
• 1906 Appleby & Banks: UK patent to use radioactive isotopes to irradiate particulate food in a flowing bed
• 1918 Gillett: U.S. Patent to use X-rays for the preservation of food
• 1921 Schwartz describes the elimination of Trichinella from food
• 1930 Wuest: French patent on food irradiation
• 1943 MIT becomes active in the field of food preservation for the U.S. Army
• 1951 U.S. Atomic Energy Commission begins to co-ordinate national research activities
• 1958 World first commercial food irradiation (spices) at Stuttgart, Germany
• 1970 Establishment of the International Food Irradiation Project (IFIP), headquarters at the Federal Research Centre for Food Preservation, Karlsruhe, Germany
• 1980 FAO/IAEA/WHO Joint Expert Committee on Food Irradiation recommends the clearance generally up to 10 kGy "overall average dose"
• 1981/1983 End of IFIP after reaching its goals
• 1983 Codex Alimentarius General Standard for Irradiated Foods: any food at a maximum "overall average dose" of 10 kGy
• 1984 International Consultative Group on Food Irradiation (ICGFI) becomes the successor of IFIP
• 1998 The European Union's Scientific Committee on Food (SCF) voted in favour of eight categories of irradiation applications
• 1997 FAO/IAEA/WHO Joint Study Group on High-Dose Irradiation recommends to lift any upper dose limit
• 1999 The European Union adopts Directives 1999/2/EC (framework Directive) and 1999/3/EC (implementing Directive) limiting irradiation a positive list whose sole content is one of the eight categories approved by the SCF, but allowing the individual states to give clearances for any food previously approved by the SCF.
• 2000 Germany leads a veto on a measure to provide a final draft for the positive list.
• 2003 Codex Alimentarius General Standard for Irradiated Foods: no longer any upper dose limit
• 2003 The SCF adopts a "revised opinion" that recommends against the cancellation of the upper dose limit.
• 2004 ICGFI ends
• 2011 The successor to the SCF, European Food Safety Authority (EFSA), reexamines the SCF's list and makes further recommendations for inclusion.

 

Pasteurization

From Wikipedia, the free encyclopedia

https://en.wikipedia.org/wiki/Pasteurization 

Pasteurized milk in Japan

 

A Chicago Department of Health poster explains home pasteurization to mothers

Pasteurization or pasteurisation is a process in which packaged and non-packaged foods (such as milk and fruit juice) are treated with mild heat, usually to less than 100 °C (212 °F), to eliminate pathogens and extend shelf life. The process is intended to destroy or deactivate organisms and enzymes that contribute to spoilage or risk of disease, including vegetative bacteria, but not bacterial spores.

The process was named after the French microbiologist, Louis Pasteur, whose research in the 1860s demonstrated that thermal processing would deactivate unwanted microorganisms in wine. Spoilage enzymes are also inactivated during pasteurization. Today, pasteurization is used widely in the dairy industry and other food processing industries to achieve food preservation and food safety.

By the year 1999, most liquid products were heat treated in a continuous system where heat can be applied using a plate heat exchanger or the direct or indirect use of hot water and steam. Due to the mild heat, there are minor changes to the nutritional quality and sensory characteristics of the treated foods. Pascalization or high pressure processing (HPP) and pulsed electric field (PEF) are non-thermal processes that are also used to pasteurize foods.

History

Louis Pasteur's pasteurization experiment illustrates the fact that the spoilage of liquid was caused by particles in the air rather than the air itself. These experiments were important pieces of evidence supporting the idea of the germ theory of disease.

The process of heating wine for preservation purposes has been known in China since AD 1117, and was documented in Japan in the diary Tamonin-nikki, written by a series of monks between 1478 and 1618.

Much later, in 1768, research performed by Italian priest and scientist Lazzaro Spallanzani proved a product could be made "sterile" after thermal processing. Spallanzani boiled meat broth for one hour, sealed the container immediately after boiling, and noticed that the broth did not spoil and was free from microorganisms. In 1795, a Parisian chef and confectioner named Nicolas Appert began experimenting with ways to preserve foodstuffs, succeeding with soups, vegetables, juices, dairy products, jellies, jams, and syrups. He placed the food in glass jars, sealed them with cork and sealing wax and placed them in boiling water. In that same year, the French military offered a cash prize of 12,000 francs for a new method to preserve food. After some 14 or 15 years of experimenting, Appert submitted his invention and won the prize in January 1810. Later that year, Appert published L'Art de conserver les substances animales et végétales ("The Art of Preserving Animal and Vegetable Substances"). This was the first cookbook of its kind on modern food preservation methods.

La Maison Appert (English: The House of Appert), in the town of Massy, near Paris, became the first food-bottling factory in the world, preserving a variety of foods in sealed bottles. Appert's method was to fill thick, large-mouthed glass bottles with produce of every description, ranging from beef and fowl to eggs, milk and prepared dishes. He left air space at the top of the bottle, and the cork would then be sealed firmly in the jar by using a vise. The bottle was then wrapped in canvas to protect it while it was dunked into boiling water and then boiled for as much time as Appert deemed appropriate for cooking the contents thoroughly. Appert patented his method, sometimes called appertisation in his honor.

Appert's method was so simple and workable that it quickly became widespread. In 1810, British inventor and merchant Peter Durand, also of French origin, patented his own method, but this time in a tin can, so creating the modern-day process of canning foods. In 1812, Englishmen Bryan Donkin and John Hall purchased both patents and began producing preserves. Just a decade later, Appert's method of canning had made its way to America. Tin can production was not common until the beginning of the 20th century, partly because a hammer and chisel were needed to open cans until the invention of a can opener by Robert Yeates in 1855.

A less aggressive method was developed by French chemist Louis Pasteur during an 1864 summer holiday in Arbois. To remedy the frequent acidity of the local aged wines, he found out experimentally that it is sufficient to heat a young wine to only about 50–60 °C (122–140 °F) for a short time to kill the microbes, and that the wine could subsequently be aged without sacrificing the final quality. In honour of Pasteur, this process is known as "pasteurization". Pasteurization was originally used as a way of preventing wine and beer from souring, and it would be many years before milk was pasteurized. In the United States in the 1870s, before milk was regulated, it was common for milk to contain substances intended to mask spoilage.

Milk

180 kilograms (400 lb) of milk in a cheese vat

Milk is an excellent medium for microbial growth, and when it is stored at ambient temperature bacteria and other pathogens soon proliferate. The US Centers for Disease Control (CDC) says improperly handled raw milk is responsible for nearly three times more hospitalizations than any other food-borne disease source, making it one of the world's most dangerous food products. Diseases prevented by pasteurization can include tuberculosis, brucellosis, diphtheria, scarlet fever, and Q-fever; it also kills the harmful bacteria Salmonella, Listeria, Yersinia, Campylobacter, Staphylococcus aureus, and Escherichia coli O157:H7, among others.

Prior to industrialization, dairy cows were kept in urban areas to limit the time between milk production and consumption, hence the risk of disease transmission via raw milk was reduced. As urban densities increased and supply chains lengthened to the distance from country to city, raw milk (often days old) became recognized as a source of disease. For example, between 1912 and 1937, some 65,000 people died of tuberculosis contracted from consuming milk in England and Wales alone. Because tuberculosis has a long incubation period in humans, it was difficult to link unpasteurized milk consumption with the disease. In 1892, chemist Ernst Lederle experimentally inoculated milk from tuberculosis-diseased cows into guinea pigs, which caused them to develop the disease. In 1910, Lederle, then in the role of Commissioner of Health, introduced mandatory pasteurization of milk in New York City.

Developed countries adopted milk pasteurization to prevent such disease and loss of life, and as a result milk is now considered a safer food. A traditional form of pasteurization by scalding and straining of cream to increase the keeping qualities of butter was practiced in Great Britain in the 18th century and was introduced to Boston in the British Colonies by 1773, although it was not widely practiced in the United States for the next 20 years. Pasteurization of milk was suggested by Franz von Soxhlet in 1886. In the early 20th century, Milton Joseph Rosenau established the standards – i.e. low-temperature, slow heating at 60 °C (140 °F) for 20 minutes – for the pasteurization of milk while at the United States Marine Hospital Service, notably in his publication of The Milk Question (1912). States in the U.S. soon began enacting mandatory dairy pasteurization laws, with the first in 1947, and in 1973 the U.S. federal government required pasteurization of milk used in any interstate commerce.

The shelf life of refrigerated pasteurized milk is greater than that of raw milk. For example, high-temperature, short-time (HTST) pasteurized milk typically has a refrigerated shelf life of two to three weeks, whereas ultra-pasteurized milk can last much longer, sometimes two to three months. When ultra-heat treatment (UHT) is combined with sterile handling and container technology (such as aseptic packaging), it can even be stored non-refrigerated for up to 9 months.

According to the Centers for Disease Control, between 1998 and 2011, 79% of dairy-related disease outbreaks in the United States were due to raw milk or cheese products. They report 148 outbreaks and 2,384 illnesses (with 284 requiring hospitalization), as well as two deaths due to raw milk or cheese products during the same time period.

Medical equipment

Medical equipment, notably respiratory and anesthesia equipment, is often disinfected using hot water, as an alternative to chemical disinfection. The temperature is raised to 70 °C (158 °F) for 30 minutes.

Pasteurization process

General overview of the pasteurization process. The milk starts at the left and enters the piping with functioning enzymes that, when heat-treated, become denatured and stop the enzymes from functioning. This helps to stop pathogen growth by stopping the functionality of the cell. The cooling process helps stop the milk from undergoing the Maillard reaction and caramelization. The pasteurization process also has the ability to heat the cells to the point that they burst from pressure build-up.

Pasteurization is a mild heat treatment of liquid foods (both packaged and unpackaged) where products are typically heated to below 100 °C. The heat treatment and cooling process are designed to inhibit a phase change of the product. The acidity of the food determines the parameters (time and temperature) of the heat treatment as well as the duration of shelf life. Parameters also take into account nutritional and sensory qualities that are sensitive to heat.

In acidic foods (pH <4.6), such as fruit juice and beer, the heat treatments are designed to inactivate enzymes (pectin methylesterase and polygalacturonase in fruit juices) and destroy spoilage microbes (yeast and lactobacillus). Due to the low pH of acidic foods, pathogens are unable to grow. The shelf-life is thereby extended several weeks. In less acidic foods (pH >4.6), such as milk and liquid eggs, the heat treatments are designed to destroy pathogens and spoilage organisms (yeast and molds). Not all spoilage organisms are destroyed under pasteurization parameters, thus subsequent refrigeration is necessary.

Equipment

Food can be pasteurized in two ways: either before or after being packaged into containers. When food is packaged in glass, hot water is used to lower the risk of thermal shock. Plastics and metals are also used to package foods, and these are generally pasteurized with steam or hot water since the risk of thermal shock is low.

Most liquid foods are pasteurized using continuous systems that have a heating zone, hold tube, and cooling zone, after which the product is filled into the package. Plate heat exchangers are used for low-viscosity products such as animal milks, nut milks and juices. A plate heat exchanger is composed of many thin vertical stainless steel plates which separate the liquid from the heating or cooling medium. Scraped surface heat exchangers contain an inner rotating shaft in the tube, and serve to scrape highly viscous material which might accumulate on the wall of the tube.

Shell or tube heat exchangers are designed for the pasteurization of foods that are non-Newtonian fluids, such as dairy products, tomato ketchup and baby foods. A tube heat exchanger is made up of concentric stainless steel tubes. Food passes through the inner tube while the heating/cooling medium is circulated through the outer or inner tube.

The benefits of using a heat exchanger to pasteurize non-packaged foods versus pasteurizing foods in containers are:

• Heat exchangers provide uniform treatment, and there is greater flexibility with regards to the products which can be pasteurized on these plates
• The process is more energy-efficient compared to pasteurizing foods in packaged containers
• Greater throughput

After being heated in a heat exchanger, the product flows through a hold tube for a set period of time to achieve the required treatment. If pasteurization temperature or time is not achieved, a flow diversion valve is utilized to divert under-processed product back to the raw product tank. If the product is adequately processed, it is cooled in a heat exchanger, then filled.

High-temperature short-time (HTST) pasteurization, such as that used for milk (71.5 °C (160.7 °F) for 15 seconds) ensures safety of milk and provides a refrigerated shelf life of approximately two weeks. In ultra-high-temperature (UHT) pasteurization, milk is pasteurized at 135 °C (275 °F) for 1–2 seconds, which provides the same level of safety, but along with the packaging, extends shelf life to three months under refrigeration.

Verification

Direct microbiological techniques are the ultimate measurement of pathogen contamination, but these are costly and time-consuming, which means that products have a reduced shelf-life by the time pasteurization is verified.

As a result of the unsuitability of microbiological techniques, milk pasteurization efficacy is typically monitored by checking for the presence of alkaline phosphatase, which is denatured by pasteurization. Destruction of alkaline phosphatase ensures the destruction of common milk pathogens. Therefore, the presence of alkaline phosphatase is an ideal indicator of pasteurization efficacy. For liquid eggs, the effectiveness of the heat treatment is measured by the residual activity of α-amylase.

Efficacy against pathogenic bacteria

During the early 20th century, there was no robust knowledge of what time and temperature combinations would inactivate pathogenic bacteria in milk, and so a number of different pasteurization standards were in use. By 1943, both HTST pasteurization conditions of 72 °C (162 °F) for 15 seconds, as well as batch pasteurization conditions of 63 °C (145 °F) for 30 minutes, were confirmed by studies of the complete thermal death (as best as could be measured at that time) for a range of pathogenic bacteria in milk. Complete inactivation of Coxiella burnetii (which was thought at the time to cause Q fever by oral ingestion of infected milk) as well as of Mycobacterium tuberculosis (which causes tuberculosis) were later demonstrated. For all practical purposes, these conditions were adequate for destroying almost all yeasts, molds, and common spoilage bacteria and also for ensuring adequate destruction of common pathogenic, heat-resistant organisms. However, the microbiological techniques used until the 1960s did not allow for the actual reduction of bacteria to be enumerated. Demonstration of the extent of inactivation of pathogenic bacteria by milk pasteurization came from a study of surviving bacteria in milk that was heat-treated after being deliberately spiked with high levels of the most heat-resistant strains of the most significant milk-borne pathogens.

The mean log₁₀ reductions and temperatures of inactivation of the major milk-borne pathogens during a 15-second treatment are:

• Staphylococcus aureus > 6.7 at 66.5 °C (151.7 °F)
• Yersinia enterocolitica > 6.8 at 62.5 °C (144.5 °F)
• pathogenic Escherichia coli > 6.8 at 65 °C (149 °F)
• Cronobacter sakazakii > 6.7 at 67.5 °C (153.5 °F)
• Listeria monocytogenes > 6.9 at 65.5 °C (149.9 °F)
• Salmonella ser. Typhimurium > 6.9 at 61.5 °C (142.7 °F)

(A log₁₀ reduction between 6 and 7 means that 1 bacterium out of 1 million (10⁶) to 10 million (10⁷) bacteria survive the treatment.)

The Codex Alimentarius Code of Hygienic Practice for Milk notes that milk pasteurization is designed to achieve at least a 5 log₁₀ reduction of Coxiella burnetii. The Code also notes that: "The minimum pasteurization conditions are those having bactericidal effects equivalent to heating every particle of the milk to 72 °C for 15 seconds (continuous flow pasteurization) or 63 °C for 30 minutes (batch pasteurization)” and that "To ensure that each particle is sufficiently heated, the milk flow in heat exchangers should be turbulent, i.e. the Reynolds number should be sufficiently high". The point about turbulent flow is important because simplistic laboratory studies of heat inactivation that use test tubes, without flow, will have less bacterial inactivation than larger-scale experiments that seek to replicate conditions of commercial pasteurization.

As a precaution, modern HTST pasteurization processes must be designed with flow-rate restriction as well as divert valves which ensure that the milk is heated evenly and that no part of the milk is subject to a shorter time or a lower temperature. It is common for the temperatures to exceed 72 °C by 1.5 °C or 2 °C.

Double pasteurization

Since pasteurization is not sterilization, and does not kill spores, a second "double" pasteurization will extend the shelf life by killing spores that have germinated.

The acceptance of double pasteurization vary by jurisdiction. In places where it is allowed, an initial pasteurization usually happens when the milk was collected at the farm, so that it does not spoil before processing. Many countries disallow such milk to be simply labelled as "pasturized", so thermization, a lower-temperature process, is used instead.

Effects on nutritional and sensory characteristics of foods

Because of its mild heat treatment, pasteurization increases the shelf-life by a few days or weeks. However, this mild heat also means there are only minor changes to heat-labile vitamins in the foods.

Milk

According to a systematic review and meta-analysis, it was found that pasteurization appeared to reduce concentrations of vitamins B12 and E, but it also increased concentrations of vitamin A. Apart from meta-analysis, it is not possible to draw conclusions about the effect of pasteurization on vitamins A, B12, and E based merely on consultation of the vast literature available. Milk is not an important source of vitamins B12 or E in the North American diet, so the effects of pasteurization on the adult daily intake of these vitamins is negligible. However, milk is considered an important source of vitamin A, and because pasteurization appears to increase vitamin A concentrations in milk, the effect of milk heat treatment on this vitamin is a not a major public health concern. Results of meta-analyses reveal that pasteurization of milk leads to a significant decrease in vitamin C and folate, but milk is also not an important source of these vitamins. A significant decrease in vitamin B2 concentrations was found after pasteurization. Vitamin B2 is typically found in bovine milk at concentrations of 1.83 mg/liter. Because the recommended daily intake for adults is 1.1 mg/day, milk consumption greatly contributes to the recommended daily intake of this vitamin. With the exception of B2, pasteurization does not appear to be a concern in diminishing the nutritive value of milk because milk is often not a primary source of these studied vitamins in the North American diet.

Sensory effects

Pasteurization also has a small but measurable effect on the sensory attributes of the foods that are processed. In fruit juices, pasteurization may result in loss of volatile aroma compounds. Fruit juice products undergo a deaeration process prior to pasteurization that may be responsible for this loss. Deaeration also minimizes the loss of nutrients like vitamin C. To prevent the decrease in quality resulting from the loss in volatile compounds, volatile recovery, though costly, can be utilized to produce higher-quality juice products.

In regards to color, the pasteurization process does not have much effect on pigments such as chlorophylls, anthocyanins and carotenoids in plants and animal tissues. In fruit juices, polyphenol oxidase (PPO) is the main enzyme responsible for causing browning and color changes. However, this enzyme is deactivated in the deaeration step prior to pasteurization with the removal of oxygen.

In milk, the color difference between pasteurized and raw milk is related to the homogenization step that takes place prior to pasteurization. Before pasteurization milk is homogenized to emulsify its fat and water-soluble components, which results in the pasteurized milk having a whiter appearance compared to raw milk. For vegetable products, color degradation is dependent on the temperature conditions and the duration of heating.

Pasteurization may result in some textural loss as a result of enzymatic and non-enzymatic transformations in the structure of pectin if the processing temperatures are too high as a result. However, with mild heat treatment pasteurization, tissue softening in the vegetables that causes textural loss is not of concern as long as the temperature does not get above 80 °C (176 °F).

Novel pasteurization methods

Other thermal and non-thermal processes have been developed to pasteurize foods as a way of reducing the effects on nutritional and sensory characteristics of foods and preventing degradation of heat-labile nutrients. Pascalization or high pressure processing (HPP) and pulsed electric field (PEF) are examples of these non-thermal pasteurization methods that are currently commercially utilized.

Microwave volumetric heating (MVH) is the newest available pasteurization technology. It uses microwaves to heat liquids, suspensions, or semi-solids in a continuous flow. Because MVH delivers energy evenly and deeply into the whole body of a flowing product, it allows for gentler and shorter heating, so that almost all heat-sensitive substances in the milk are preserved.

Low Temperature, Short Time (LTST) is a patented method that implies spraying droplets in a chamber heated below the usual pasteurization temperatures. It takes several thousandth of a second to treat liquid products, so the method is also known as the millisecond technology (MST). It significantly extends the shelf life of products (50+ days) when combined with HTST without damaging the nutrients or flavor. LTST has been commercial since 2019.

Products that are commonly pasteurized

• Beer
• Canned food
• Dairy products
• Eggs
• Milk
• Juices
• Low alcoholic beverages
• Syrups
• Vinegar
• Water
• Wines