Cow's milk – favourite drink of many children and adults – sometimes gains bitterish smack. Generally the reason of bitterness is in the sterns received by a cow; but quality and structure of forages – not the only factors affecting taste of drink. Both a boiled, and raw milk can turn rancid.
The taste of cow's milk depends first of all on with what fed an animal. The bitter smack and a smell of radish can appear at white drink in the spring, at a herd pasture on meadows where a large number of a charlock, wild radish, a winter cress grows. Milk tastes bitter and gets a garlic (onions) smell if in a fresh grass or in hay only several small stalks of wild garlic or onions got to a cow. And if fennel, caraway seeds, a camomile odorous are a part of hay, fennel, milk becomes not bitter, but unpleasant at the use – these rezkopakhnushchy plants transfer it the specific smell and taste. When feeding to a cow of mouldy products (a silo, straw, hay) the product of its lactation gets a stale smell and bitterish smack. An organoleptical properties of milk (taste and a smell) change for the worse and when keeping an animal in insanitary conditions: in the dirty, not aired stall when the udder of a cow isn't washed before milking. The bitter taste appears at old milch milk – at the end of the lactation period (on the ninth or tenth month) when the cow already brought up a calf and is ready to start (to new conception). Bitterness in this case is explained by splitting of milk fat already in an udder under the influence of the lipase enzyme which strongly is allocated during this period. Milk fat, breaking up, forms acids with a bitter taste and an unpleasant odor. Process of splitting of milk fat can be caused not only by action of a lipase, but also strong agitation of milk in a can, a tank or other capacity. Therefore when transporting a dairy products on long distances it is necessary to be careful. Also the turned sour boiled milk can turn rancid, unlike not boiled (from it at turning sour curdled milk turns out). It is explained by the fact that in the course of turning sour two species of bacteria participate: lactic and butyric acid. At heat treatment the lactic bacteria perish, and butyric acid survive. As a result of their activity the turned sour milk also becomes bitter. One more reason of dairy bitterness – a disease of a cow and treatment by her medicamentous means. If the animal received medicines, from it it is possible to eat milk not earlier, than in 3-4 days after the end of treatment.