Dietary influence of conjugated linoleic acid content of milk and consumer acceptability of milk and cheese naturally enriched with conjugated linoleic acid

摘要

Influence of diet on conjugated linoleic (CLA) acid content of milk and consumer acceptability of milk and cheese naturally enriched with CLA were studied in a series of experiments. Cows grazing perennial ryegrass pasture had 3 to 3.5 times the milk fat CLA content (P < 0.01) of cows fed total mixed rations (TMR). There was no increase (P > 0.05) in milk fat CLA content for cows grazing on pasture supplemented with linoleic acid through full fat extruded soybeans, a grain mix containing 75% full fat extruded soybeans or an equivalent amount of soy oil compared with unsupplemented cows.;Commercial dairies that grazed cows during summer and supplemented with grain mix produced ≥60% milk fat CLA content on a year-round basis than the dairy that fed 10% of dry matter as fresh cut grass. Milk fat CLA content during summer was 2-times that of winter. It varied from 0.27 to 1.35% and from 0.16 to 2.22% for bulk tank and individual cow samples, respectively, with a majority of cows (89%) ranging between 0.3 and 1.0%. Variation in milk fat CLA content was larger in summer than in winter and in dairies that grazed cows during summer compared with dairies that either did not graze or grazed only 1/3 of the cows. Supply of CLA was highest from June through September and lowest from February through April.;When cows were turned out to pasture from a TMR diet, it took 23 d to establish the highest concentration of CLA in milk fat (2.53%), which was 5.5 times of the original CLA concentration (0.45%), whereas only 4 d were needed to bring it back to the original level once the cows were withdrawn from pasture and fed a similar TMR diet.;Processing of CLA enriched milk into cheddar cheese did not alter the CLA content of cheese fat. Consumer acceptability of milk and cheese naturally enriched with CLA was similar to milk and cheese containing low levels of CLA and none of the specific flavors investigated were perceived to a degree that could be considered objectionable.