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Factors Affecting the Flavor of Milk

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.

Feed or Weed Flavor

Distinguishing Characteristics:

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.

Contributing Factors:

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.

Control Measures:

• Take cows off pastures of grass, sweet clover, alfalfa and other strong-flavored feeds or weeds two to four hours before milking.
• Delay feeding of silage, alfalfa hay and other strong-flavored feedstuffs until milking is completed.
• Remove feed not eaten from mangers and feed bunks.
• Keep loaded silage carts out of the milking area until milking is completed.
• Control weed growth in pastures by pasture renovation or by the use of proper herbicides and allow only dry cows and heifers to graze weedy pastures.
• Avoid feeding vegetable crops such as cabbage or turnips.
• In the spring, pasture cows only a few hours each day at the outset to permit a gradual change from winter to spring feed.
• Provide adequate ventilation in the barn and milking area to prevent the accumulation of strong feed odors.

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.

Unclean Cowy-Barney Flavor

Distinguishing Characteristics:

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.

Contributing Factors:

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.

Control Measures:

• House and milk cows in clean, dry, well ventilated buildings.
• Keep cows clean and wash and dry udders and teats immediately before milking.
• Use clean, properly sanitized milking equipment.
• Avoid contamination of milk with manure and other dirt.
• Identify cows with ketosis or acetonemia and exclude their milk from the milk supply. Cows afflicted with ketosis and acetonemia should be treated by a veterinarian and kept isolated. The urine from such cows emits an offensive odor which is transmitted to the milk when inhaled by healthy cows.

Rancid Flavor

Distinguishing Characteristics:

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.

Contributing Factors:

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.

Control Measures:

• Select high producing cows and milk rapidly.
• Eliminate as much air as possible from pipelines during milking and periodically check the milking system for leaky fittings.
• Eliminate risers in pipelines where practical, keep the number and height of risers to a minimum, and maintain as high a rate of milk in the presence of air, which causes foaming, and adequate cooling for raw milk and maintain the bulk tank in good working order to insure that milk is cooled rapidly and that the blend temperature does not exceed 50°F when warm milk is added to cold.
• Do not freeze raw milk nor hold it at excessively low temperatures (below 35°F).
• Avoid excessive agitation of milk in centrifugal pumps by proper maintenance of the controls which cause the pump to run only when the pump chamber is full.
• Dry off cows when production drops to 20 pounds per day, or when cows are within six weeks of freshening.
• Feed green succulent feeds when available.
• Cull those cows whose milk is subject to spontaneous rancid flavor development.

Oxidized Flavor

Distinguishing Characteristics:

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.

Contributing Factors:

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.

Control Measures:

• Use only milk handling equipment with milk contact surfaces constructed of stainless steel, glass, plastic, or rubber. Avoid milk handling equipment constructed of copper-bearing metals such as brass, nickel, "white metal," and poorly tinned or rusty cans, strainers and pails.
• Use water free of copper and iron for cleaning milk contact surfaces.
• Maintain cows in a good state of nutrition.
• Feed green, succulent feeds containing Vitamin E. In many instances oxidized flavor development may be inhibited by feeding cows, in the concentrate, one to two grams of alpha-tocopherol acetate, a stable form of Vitamin E, per cow per day.
• Protect milk in transparent pipelines and receiving jars from sunlight and strong artificial light.
• Avoid excessive agitation and foaming of raw milk.
• Completely drain chlorine sanitizing solutions from all lines and equipment before use.
• Identify and cull cows producing milk susceptible to spontaneous oxidized flavor development.

Malty Flavor

Distinguishing Characteristics:

The milk has a malty or grapenutlike flavor.

Contributing Factors:

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.

Control Measures:

• Clean all milk-handling equipment after each use.
• Select the proper cleaning compound based on prevailing water conditions and use according to the manufacturer's recommendations.
• Acidify the rinse water, where water is hard, to prevent the formation of waterstone (white film) on equipment.
• Sanitize all milk contact surfaces of milking machines and milk-handling equipment just prior to milking.
• Protect milk from contamination with soil, bedding and other extraneous material.
• Have a properly engineered refrigeration system which will cool the total herd output to 40°F or below within two hours after milking during the season of maximum production. The cooling system must also be of such capacity that the temperature of the milk does not exceed 50°F when milk is added at subsequent milkings.
• Have the refrigeration system serviced regularly to assure adequate cooling and continuous operation.
• Avoid delays in milk shipment and prolonged holding of raw milk even at low temperature.

High Acid Flavor

Distinguishing Characteristics:

The milk has an unpleasant, disagreeable odor and an acid or sour taste.

Contributing Factors:

High acid flavor, like malty, results when milk is heavily contaminated with bacteria and the bacteria is permitted to grow.

Control Measures:

See control measures for malty flavor.

Foreign Flavor

Distinguishing Characteristics:

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.

Contributing Factors:

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.

Control Measures:

• Keep foreign materials away from or out of the milk.
• Prevent cows from consuming and inhaling the odor from foreign materials.
• Use medications, insecticides, disinfectants and similar materials with caution and according to directions.

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.

Related web pages:

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Commercial suppliers:

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Electronic mailing lists:

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Suggested references:

If you are interested in any of the titles below, click on the title and it will take you to Amazon.com for ordering. Click on the icon at the left for more information.

• Dairy Development in Sub-Saharan Africa : A Study of Issues and Options (World Bank Technical Paper, Africa Technical Department Series, No 135) - by Michael J. Walshe - Publication Date: March 1991 - List: $7.95 + $1.35 special surcharge
• Milk Quotas : European Community and United Kingdom Law - by Michael Cardwell - Publication Date: July, 1996 - List: $82.00
• The Family Cow - by Dirk. Van Loon - Publication Date: August, 1983 - List: $14.95
• The Behaviour of Cattle - by J. L. Albright, Clive Wendell Arave, C.A.B. International - Publication Date: October 1997 - List: $90.00

Periodicals:

• None identified.

This page was last updated on November 16, 2002