The Right Chemistry: Playing it safe with pasteurized milk



The pasteurization of milk has been one of the most successful public health measures of all time, and a big improvement over boracic acid.

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Isabella Beeton certainly did not intend to harm children. But a casual remark in her wildly popular 1861 book Mrs. Beeton’s Book of Household Management about boracic acid purifying milk was responsible for many children getting sick and even dying from drinking milk contaminated with bovine tuberculosis bacteria.

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With the advent of the Industrial Revolution, and the growth of cities in Victorian England, urban dairies could not keep up with the demand for milk. Unfortunately, transportation from farms in those pre-refrigeration, pre-pasteurization days allowed time for various microbes in the milk to multiply. Some of these microbes produce enzymes that convert the lactose and proteins in milk into smelly, foul-tasting compounds, and farmers had somehow discovered a work-around. Adding “boracic acid,” a mixture of sodium borate (borax) and its acidified derivative, boric acid, countered the milk’s unpleasant smell and off-taste. Mrs. Beeton was aware of this, and assured her readers that boracic acid was harmless, and recommended that they could even preserve their milk longer by adding some themselves. Bad idea!

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Boron compounds are not harmless. Indeed, an article in 1887 in The Lancet, the prime medical journal at the time, claimed that “even small quantities of boracic acid are capable of exerting a distinctly injurious action on the human organism.” This, however, was not the major problem. While boracic acid retarded the growth of microbes that caused the unpleasant sensory properties, it did not prevent the growth of disease-causing organisms. The longer the milk was kept, and boracic acid allowed for that, the more time the tuberculosis bacteria had to multiply. Infection of Victorian children with bovine tuberculosis was common, and many deaths could have been spared had boracic acid not contributed to the illusion of safety.

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Milk was killing children on this side of the pond as well. Here, the problem wasn’t the masking of spoiled milk with boracic acid, it was contaminated milk from cows kept in filthy conditions and fed brewery waste “swill.” New York, like London, had become a huge, bustling city with an ever-increasing demand for milk to feed infants. Distilleries in the city produced large amounts of alcoholic mash left over from making whiskey, something that did not go unnoticed by milk producers. Dairies sprang up around distilleries where cows were fed the “swill.” To maximize profits, the animals were squeezed into narrow stalls where they were covered with flies and wallowed in their own excrement. No wonder they became so sick they could hardly stand. Even the milk they produced looked sickly. To alter its bluish colour, plaster of Paris and molasses were added and flour was used as a thickener. A New York Times editorial in 1858 described “swill milk” as “bluish-white compound of true milk, pus and dirty water,” produced by “running distillery slops through the udders of dying cows and over the unwashed hands of milkers.” The Times estimated that every year some 8,000 infants died from drinking swill milk.

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Now, let’s hop back to Europe, where in 1856 Louis Pasteur, then Professor of Chemistry at the University of Lille, was investigating why wine sometimes turns sour. Looking through a microscope, he noted the presence of bacteria that he then determined were capable of converting alcohol into acetic acid. These bacteria, Pasteur found, could be inactivated by heat. This inactivation became known as “pasteurization.” Pasteur was not the first to note that beverages or foods could be preserved with heat. Some 40 years earlier, Nicholas Appert had shown that boiling food in a glass jar which was then sealed prevented the contents from spoiling. Pasteur’s contribution was working out conditions that allowed for heating at a lower temperature for a shorter time to preserve texture and flavour. He did not work with milk. It was Franz von Soxhlet, a German agricultural chemist who first suggested in 1886 that milk sold to the public be “pasteurized.”

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Back across the ocean once more. Nathan Straus, who as a young boy had emigrated from Germany to America, grew up to become the wealthy co-owner of Macy’s department store. He became interested in milk when he learned that a cow on a farm he owned had died of tuberculosis despite appearing to be healthy. Could milk from such cows be entering the marketplace and make children sick?

Upon learning von Soxhlet’s suggestion to “pasteurize” milk, Straus became a passionate advocate. In 1893 he built the Nathan Straus Pasteurized Milk Laboratory and set up stations in poor areas of New York to give away milk, eventually establishing 297 milk stations in 36 cities, all at his own expense. Nathan Straus is estimated to have directly saved the lives of close to half a million children!

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Straus was a great philanthropist, writing in his will that “what you give for the cause of charity in health is gold, what you give in sickness is silver, and what you give in death is lead.” He had a long healthy life, gave away millions, built shelters for the homeless, distributed food and coal to the poor, founded a health centre in Jerusalem which he said was to be for all the inhabitants of the country, irrespective of race, creed or colour. The Israeli city of Netanya is named after him.

The pasteurization of milk has been one of the most successful public health measures of all time, but has not escaped criticism. Advocates of drinking “raw milk” claim that pasteurization destroys vital nutrients in milk and that there is no problem with drinking raw milk from healthy cows. Farmers who produce raw milk, they say, are better at taking care of their cows than “factory farmers.”

I would rather play it safe and stick to pasteurized milk. As for borax? Belongs in the washing machine, not in milk.

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Joe Schwarcz is director of McGill University’s Office for Science & Society ( He hosts The Dr. Joe Show on CJAD Radio 800 AM every Sunday from 3 to 4 p.m.

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