Low-fat and skim milk is frequently deficient in two important vitamins, according to a recent study by UC Davis researchers.
The survey discovered that levels of vitamins A and D fluctuated significantly below and above the amounts set by state and federal regulations for fortified milk.
John C. Bruhn, a food technologist with the UC Davis Cooperative Extension, directed the project that found milk's vitamin levels were as much as 24% below state-mandated levels. The problem was caused by inadequate manufacturing practices in many of the 12 Northern California dairy plants surveyed, the report stated.
The study, requested by the dairy industry, was prompted by the advent of a more accurate technique for monitoring vitamin content in milk. The discovery that the nutritional content of milk fluctated from one firm to another was initially made by state and federal regulators, according to Bruhn.
Milk is nutritionally fortified by machines that pump vitamins into the fluid. The enhancement can also be done manually. In those plants surveyed by the researchers, the vitamin pumps were not operating correctly but the deficiency went undetected because of antiquated measuring devices.
As a result, milk samples that were laboratory tested with the more accurate methods showed a wide variance in vitamins A and D levels. While some tested at 24% below required levels, others were found to exceed the state requirements by 160%.
Vitamin A must be added whenever fat is removed from milk because the nutrient is otherwise lost in the process. Vitamin D fortification is optional for manufacturers. But the addition was required in the past because sufficient amounts of the nutrient were found effective in preventing rickets, a childhood disease that was a problem earlier in this century.
Vitamin irregularities in milk may be a widespread problem, according to Antoine A. Franke, a UC Davis research associate. Studies done in other parts of the country, namely in Connecticut and New York, found similar results, he said.
The variances in vitamin content are of little consequence to consumers, however, because milk drinkers are likely to consume the recommended vitamin levels from other foods or from more nutrient-balanced milk.
At the same time, the firms producing vitamin-deficient milk may face state regulatory violations as well as risk losing consumer confidence in their products. Those firms found to be out of compliance were not named in the report.
"This study provides a background for the industry to point out where improved quality control is necessary, and that is part of the mission of the extension service: helping industry do a better job," said Franke. "The equipment was there to do the job but someone forgot to turn the valve."
The data was released earlier this month at the American Dairy Science Assn.'s annual meeting. Since the study's results have become known, many of the state's dairies have corrected the problems, according to Bruhn.
"When a company is outside the required nutrient levels then they're not legal," he said. "They are now trying with dilligence to put into the milk what's on the label."
Troublesome Bacteria--A federal survey designed to detect the presence of salmonella in cattle herds found that one in 12 animals contains the harmful bacteria. The discovery that 8% of the animals leaving feedlots for slaughter are contaminated was made in tests conducted by U.S. Department of Agriculture scientists, according to Nutrition Week.
Although troublesome, the rate for salmonella in beef is far below that being found in the nation's poultry. As many as 40% of the chickens entering retail channels in this country are believed to be infected with salmonella bacteria. Poultry products are also suspected as one of the leading causes of food-related salmonellosis cases in this country.
Salmonellosis can cause nausea, vomiting, fever and diarrhea. The infection can be fatal in those with compromised immune systems such as infants, the elderly, pregnant women and those with underlying illnesses such as cancer or AIDs.
The USDA study, conducted in both 1987 and 1988, tested cattle for salmonella at several stages of the livestock process. The animals were sampled for the presence of the pathogen at four points during the life cycle: as calves, at the auction barn, before entering the feedlot and upon departing the feedlot for slaughter.
"Test results indicated that the percentage of cattle with positive blood or fecal samples increased from 0% of the calves to 8% of the animals leaving the feedlot," Nutrition Week reported.
The study's authors, however, said that the infection does not necessarily occur while the cattle are at the feedlot. More likely, the cows become infected as a result of stress induced during the marketing system, such as in transport or sudden changes in diet.
Under Scrutiny--Beef will also receive federal scrutiny for possible contamination during the coming school year, according to a meat industry trade publication.
The USDA's Agricultural Marketing Service has announced that it will survey microbial levels in ground beef served as part of the 1989-90 school lunch program, reports Lean Trimmings, published by the Western States Meat Assn.
The study's objective is to determine how bacteria levels affect the quality and storage life of the meat while it is frozen. The study will randomly monitor for spoilage and to determine whether the agency's guidelines in this area need to be changed, according to the newsletter.
However, the survey follows by just a year a Minnesota outbreak where hamburgers, contaminated with E. coli, caused severe illness in about a dozen school children. Similar illnesses are also being reported from states in the Pacific Northwest.