Squeezing the fat out of milk

A new cattle-feed supplement that dramatically boosts the content of unsaturated fatty acids over saturated fats in cows' milk has been developed by researchers at the University of California, Davis. The additive, based on naturally occurring proteins, promises to improve significantly the healthfulness of milk and provide dairy-food processors with the ability to modify various food qualities, such as the spreadability of butter and the flavor of cheese.

Dairy products and meats long have been known to contain high levels of saturated fats which have been implicated in contributing to a higher risk of cardiovascular disease and high cholesterol in humans. There has been a great deal of interest during the past 30 years in improving food quality by reducing fat content.

Cows commonly eat a variety of plant-based feeds, including hay, corn, cotton seed, and almond hulls, all containing varying amounts of vegetable oils. These are naturally high in unsaturated fats, and one would expect cows' milk to contain more unsaturated than saturated fats. Somewhere between mouth and milk, however, the unsaturated fats found in the feed are transformed into saturated ones. Scientists discovered years ago that microorganisms that live in the rumen--the largest of four compartments in the cow's stomach--are the culprits responsible for converting the fats.

During the 1970s, efforts were made to protect the unsaturated fats against modification by mixing chemical additives with the feed. Those supplements, though, included toxic substances such as formaldehyde, which were not permitted in the U.S. and some other countries. In the 1980s, scientists attempted to prevent modification of unsaturated fats by mixing in soaplike formulations with the cattle feed, a technique that had limited success.

Unlike the earlier methods, the supplement devised by Cal-Davis relies on proteins that occur naturally in milk and other foods, without using any synthetic substances. During feeding trials, the supplement was mixed with the cows' normal feed. Within less than three days, they recorded as much as an 800% increase in the proportion of specific unsaturated fatty acids, such as linolenic acid, in the cows' milk. In addition, this same protein-based, rumen-protected supplement could be used as an efficient system for delivering bioactive compounds and medicines to cows and other livestock.

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