EFFECT OF FEED ON FLAVOR IN DAIRY FOODS

Cattle diets that are low in lipids produce a hard milk fat high in the cheesy-flavored endogenous fatty acids and the precursors of the blue-cheese-flavored methyl ketones and of the coconut-peachy-flavored delta-lactones. The reverse is true for high lipid diets. Diets that induce a propionate metabolism in the rumen cause the formation of the sweet, raspberry - flavored gamma-dodecanolactone from dietary oleic acid and of the sweet, raspberry-flavored gamma-dodec-cis-6-enolactone from dietary linoleic acid. Lush pastures produce a richly colored milk fat and introduce phytol, dihydrophytol, phytenes, and phytadienes, and probably their lower homologues, into the milk fat. A protein-free synthetic diet lowers the animal-flavored indole and skatole, eliminates 2-enals (C3 to C12), and increases branched-chain and odd carbon-numbered delta-lactones and branched-chain and odd carbon-numbered fatty acids in the milk fat. Milk from pasture-fed cows is less susceptible to oxidation than milk from cows on dry feed. Most cows will produce spontaneously lipolyzing milk if their plane of nutrition is sufficiently low; milk from well-fed herds is seldom susceptible to spontaneous lipolysis. Poor quality silage and various weeds produce off-flavors in the milk due to direct transfer of off-flavors, to the breakdown products of weed components, or to the effect of components of the weeds on the biochemistry of the cow.