Fresh milk has a mild, pleasing and slightly sweet and rich flavor. The sweet flavor is contributed by the milk sugar and the richness by the fat. On the other hand milk which has been produced under less than ideal conditions or which has been abused during handling may have acquired or developed and undesirable flavor.
Consumer acceptance of milk, and particularly the acceptance by children, is greatly affected by flavor. Therefore, it is important that producers and others associated with the dairy industry have full knowledge of the farm factors which have an adverse effect on milk flavor. Following are common flavor defects encountered in raw milk, the contributing factors and procedures which should be practiced to prevent off-flavors and preserve the delicate flavor of fresh milk.
The milk tastes unnaturally sweet, aromatic or bitter. Flavor may be similar to cabbage, turnips, and other vegetables or it may suggest wild onions, ragweed, bitterweed, peppergrass, buckhorn, wild dog fennel and other weeds. Feed flavors may be detected by the sense of smell and may disappear rapidly from the mouth, leaving no aftertaste. "Weedy" milk may have a strong odor and leave an aftertaste in the mouth.
Strong-flavored feedstuff consumed prior to milking and/or breathing the odors of feedstuff such as sweet clover, alfalfa or soybean silage produces milk which has feed or weed flavors. Normal quantities of concentrate feeds such as wheat bran, rolled barley, dried beet pulp, coconut meal, soybean meal, cottonseed meal and wet brewer's grains given at milking time do not influence milk flavor. However, when concentrates are fed in quantities of seven pounds or more one to two hours before milking, milk with a slight feed flavor and aftertaste may result. Table 1 shows the relationship between various feeds and the flavor of milk.
It has been commonly thought that silage and other feed flavors are caused largely by milk absorbing the odors in the milking area. This view is erroneous. Feed flavor results from ingestion of strong feeds by the cow rather than from the milk absorbing the flavor after it has been drawn. However, milk may absorb odors of some fruits, vegetables, chemicals and other volatile materials.
Table 1: The relationship of various feeds to the flavor of milk.
|Feed||Amount fed (lbs)||Time fed before milking (hrs)||Effect on milk flavor|
|Alfalfa - green hay||5||2||Strong feed flavor|
|Alfalfa - silage||5||1||Slight feed flavor|
|Alfalfa - silage||20||1||Strong feed flavor|
|Alfalfa - pasture||--||6||Very slight feed flavor|
|Barley||5||1||Very slight feed flavor|
|Beets - pulp||3-4||1||No off-flavor detected|
|Beets - tops||20||1||Strong feed flavor, reduced by aeration|
|Cabbage||14||1||Strong feed flavor, reduced by aeration|
|Carrots||30||1||Very slight feed flavor|
|Citrus pulp||3-4||1||No off-flavor detected|
|Citrus pulp||5||1||Slight feed flavor|
|Clover - hay||5||1||Slight feed flavor|
|Clover - hay||10||1||Very strong feed flavor, reduced by aeration|
|Clover - pasture||--||2||No off-flavor detected|
|Corn - green||25||1||No off-flavor detected|
|Corn - silage||1||1||Definite feed flavor|
|Corn - silage||free choice||5||Slight feed flavor|
|Cottonseed - meal||--||1||No off-flavor detected to very slight|
|Cowpeas||15||1||Very slight feed flavor|
|Grass||--||5||Definite feed flavor|
|Oats||30||1||Very slight feed flavor|
|Pumpkin||30||1||No off-flavor detected|
|Rye - green||30||1||Slight feed flavor|
|Soybean - silage||5||1||Feed flavor|
|Soybean - green||30||1||Slight improved flavor|
|Tankage||50||1||No off-flavor detected|
|Turnip||15||1||Strong feed flavor|
The milk has a rather unpleasant, distinct odor and flavor which resembles the odor of a poorly cleaned and ventilated barn. An unclean aftertaste persists in the mouth.
This objectionable flavor results when cows inhale the odors of a damp, unclean, poorly ventilated barn and dirty cows are milked with improperly cleaned and sanitized milk-handling equipment. The general health of the cow(s) may also be a contributing factor.
The milk has a sharp, unclean, astringent taste that persists in the mouth. Rancid milk is often bitter or soapy and has an odor resembling spoiled nut meats when the flavor is intense.
Milkfat is practically flavorless. Rancid flavor develops when the fat globules in raw milk are disrupted and the milkfat is exposed. The enzyme, lipase, will react with the fat and produce highly flavored free fatty acids. Excessive agitation of warm milk in the presence of air, which causes foaming, and temperature fluctuation such as cooling milk to 50°F or below, warming it to about 86°F and then cooling it again are conditions which aid rancid flavor developmeet. The off-flavor is encountered most frequently in winter milk when cows are on dry feed and in milk from cows in late lactation. Milk from individual cows varies markedly in susceptibility to become rancid.
The milk has a tallowy, metallic or cardboard like off-flavor. The off-flavor may be detected by smell but it is better identified by taste. Oxidized flavor is most prevalent during late winter and early spring after cows have been on a dry ration for a prolonged period.
Contamination of milk with copper, iron, rust, chlorine, exposure to sunlight and excessive incorporation of air are factors known to contribute to the development of oxidized flavor. The milk from some cows becomes oxidized spontaneously.
The milk has a malty or grapenutlike flavor.
Malty flavor results from bacterial growth. Contamination may be from improperly washed or sanitized milking machines and other milk handling equipment, dirty pulsators and air hoses, the cow's teats and the environment. Bacterial growth occurs when milk is cooled slowly and improperly, for example, due to under-sized or malfunctioning equipment.
The milk has an unpleasant, disagreeable odor and an acid or sour taste.
High acid flavor, like malty, results when milk is heavily contaminated with bacteria and the bacteria is permitted to grow.
See control measures for malty flavor.
Foreign flavor includes a variety of sensations. The term is generally used to describe the flavor of milk which has absorbed or been contaminated with chemicals.
Cows may have consumed or inhaled fumes from foreign materials, or a foreign material may have directly contaminated the milk. Common sources of contaminatin include medications, disinfectants, sanitizers, fly sprays, gasoline and other petroleum products, and many other materials and compounds commonly used on the farm.
Dairymen who need help in identifying the source or cause of off-flavors in their milk may contact their fieldman or the Department of Food Science and Nutrition, Ohio State University, for assistance.
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This page was last updated on November 16, 2002