conclusively proved to promote healthy skeletal growth. Dairy products clearly were the richest known source of both. From World War I on, public nutrition-education programs would urgently implore mothers to feed milk to children by the quart.
Two major worries continued to dog “Nature’s Perfect Food” as a continuous country-to-city pipeline materialized. The lesser was adulteration, which was very widespread but seldom involved anything more dangerous than a little adroitly administered water and whiting or plaster of Paris testifying to the premiums that fresh or theoretically fresh milk commanded. Milk-borne epidemics remained a more serious concern.
Public understanding of contagions had improved greatly with the work of the microbiologistsLouis Pasteur andRobert Koch. During the last third of the nineteenth century the milk industry used such discoveries to advance factory-scale production of relatively—though far from completely—safe milk. Sterile bottling techniques on plant production lines became feasible at the same time as tuberculin testing on dairy cows (now known to be a vector for tuberculosis) and bacterial counts of milk samples under a microscope. These factors would have been tremendously important in any era. But modern technology was about to usher in others—refrigeration andpasteurization—destined to make milk in the industrialized West even more firmly identified with the sweet, full-lactose milk that non-Westerners had trouble digesting.
The earlier successes in getting milk from country to city had not solved theproblem of temperature. Many bacteria, including the lactic-acid kinds that make milk go sour, can be kept in check if the milk is thoroughly chilled. Railway cars refrigerated with blocks of ice helped push back the geographical limits of milk collection and distribution after the Civil War, and by the early twentieth century mechanically refrigerated tank cars were starting to take over. Milk was already being chilled at bottling plants, and the consumers who bought it often kept it in home iceboxes until use.
The weak link here was the farm, where the milk emerged from cows (normal body temperature about 100°F) into the ambient temperature of the barn. When dairying was more of a home enterprise, many households had had springhouses for keeping things cold, but now farmers had little choice but to put the results of morning and evening milking into cans and head for the milk train. Depending on the season and the length of the journey from farm to plant, any resident bacteria might or might not have had opportunity to multiply. Thus despite many gains in understanding, milk-borne diseases were still enough of a reality at the end of the nineteenth century to spur a long, ultimately successful milk-pasteurization campaign whose most famous exponent was the New York department-store magnateNathan Straus.
The pasteurization process that became most common after about 1900 involved running the milk into a vat, heating it beyond the tolerance of nearly any microorganism, and maintaining a certain temperature for some period of time to kill bacteria as uniformly as possible. There were competing ideas about the ideal conditions, but eventually most dairy plants opted for a temperature of about 145°F and a heating period of thirty minutes, followed by prompt chilling. Between 1900 and 1920 pasteurization, usually by this formula, became mandatory in most parts of the country.
But that wasn’t the end of the pasteurization story. In the 1930s many plants began switching to another method involving not separate batches but a continuous pipe feed of milk—“high-temperature/short-time,” or HTST, pasteurization. This requires a pasteurizing temperature of 161°F maintained for fifteen seconds (not minutes) and nearly instantaneous cooling to 40°F. Since about 1970, the even more drastic continuous-feed “ultrahigh-temperature” pasteurization—UHT or
Two major worries continued to dog “Nature’s Perfect Food” as a continuous country-to-city pipeline materialized. The lesser was adulteration, which was very widespread but seldom involved anything more dangerous than a little adroitly administered water and whiting or plaster of Paris testifying to the premiums that fresh or theoretically fresh milk commanded. Milk-borne epidemics remained a more serious concern.
Public understanding of contagions had improved greatly with the work of the microbiologistsLouis Pasteur andRobert Koch. During the last third of the nineteenth century the milk industry used such discoveries to advance factory-scale production of relatively—though far from completely—safe milk. Sterile bottling techniques on plant production lines became feasible at the same time as tuberculin testing on dairy cows (now known to be a vector for tuberculosis) and bacterial counts of milk samples under a microscope. These factors would have been tremendously important in any era. But modern technology was about to usher in others—refrigeration andpasteurization—destined to make milk in the industrialized West even more firmly identified with the sweet, full-lactose milk that non-Westerners had trouble digesting.
The earlier successes in getting milk from country to city had not solved theproblem of temperature. Many bacteria, including the lactic-acid kinds that make milk go sour, can be kept in check if the milk is thoroughly chilled. Railway cars refrigerated with blocks of ice helped push back the geographical limits of milk collection and distribution after the Civil War, and by the early twentieth century mechanically refrigerated tank cars were starting to take over. Milk was already being chilled at bottling plants, and the consumers who bought it often kept it in home iceboxes until use.
The weak link here was the farm, where the milk emerged from cows (normal body temperature about 100°F) into the ambient temperature of the barn. When dairying was more of a home enterprise, many households had had springhouses for keeping things cold, but now farmers had little choice but to put the results of morning and evening milking into cans and head for the milk train. Depending on the season and the length of the journey from farm to plant, any resident bacteria might or might not have had opportunity to multiply. Thus despite many gains in understanding, milk-borne diseases were still enough of a reality at the end of the nineteenth century to spur a long, ultimately successful milk-pasteurization campaign whose most famous exponent was the New York department-store magnateNathan Straus.
The pasteurization process that became most common after about 1900 involved running the milk into a vat, heating it beyond the tolerance of nearly any microorganism, and maintaining a certain temperature for some period of time to kill bacteria as uniformly as possible. There were competing ideas about the ideal conditions, but eventually most dairy plants opted for a temperature of about 145°F and a heating period of thirty minutes, followed by prompt chilling. Between 1900 and 1920 pasteurization, usually by this formula, became mandatory in most parts of the country.
But that wasn’t the end of the pasteurization story. In the 1930s many plants began switching to another method involving not separate batches but a continuous pipe feed of milk—“high-temperature/short-time,” or HTST, pasteurization. This requires a pasteurizing temperature of 161°F maintained for fifteen seconds (not minutes) and nearly instantaneous cooling to 40°F. Since about 1970, the even more drastic continuous-feed “ultrahigh-temperature” pasteurization—UHT or
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