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Identifying Milk Quality

For complete information of milk identification from Cornell University of Agriculture and Life Science

Cause – associated with late lactation or mastitic cows (check for Staphylococcus Aureus count in lab results).  If you think mastitis is the culprit, test the milk and identify the type so you can treat it.

Basic taste sensation. No odor. Generally easily detected. Clean mouth-feel.


Cause - free fatty acids (e.g., butyric acid) released from milkfat by natural or microbial enzymes (lipase). In raw milk it’s associated with excessive agitation, temperature abuse or cow factors (e.g., poor health and/or nutrition). Pasteurization destroys natural enzyme (lipase), but spoilage microorganism may have similar enzymes that cause rancidity. Uncleanness  generally due to growth of spoilage microorganisms in milk or on excessively dirty equipment. Can occur due to milk absorbing odors from dirty coolers or environment

Pungent odor when extreme. Taste soapy, unclean, bitter, blue cheese-like or “baby vomit.” Provolone cheese has a rancid flavor profile. Pronounced lingering aftertaste. Mouth fails to clean up after expectorated. Sensitivity varies.  Suggestive of mustiness, putrid, “dirty dish-rag” or other “unclean” flavors.

Rancid or Unclean

Cause – Growth of Lactococcus lactis var. maltigenes (or possibly other organisms) due to poor refrigeration. May be followed by “acid” or “unclean” flavors.

Malt-like aroma or taste (like malted milk or Grape-Nuts®). May be similar to feed or cooked odors, but is considered a severe defect as microbial spoilage. Milk often is acid as well.


Cause - Usually due to age, staleness, residual milk enzymes or initial stage of microbial spoilage (e.g., psychrotrophic bacterial off-flavors such as unclean, bitter and rancid).

 Lacks fine, pleasing flavor. Mild off-flavor that lacks specific characteristic to make identification Freshness easy. May be “stale” or less sweet (e.g., “flat”). Generally not intense enough to fail product.

Lack of Freshness

Cause - Contamination of milk with foreign substance. May be direct contamination of the milk (e.g., udder ointment/chemical sanitizers, phenols/chlorine); may be transmitted through the cow or absorbed during raw storage or through retail packages in plant, store or home refrigerators.

 Foreign May have odor and/or flavor that is not commonly associated with milk. Often “chemical” in nature. Depends on causative agent; sanitizers, detergents, exhaust fumes, cow medications, citrus fruits, etc. Chloro-phenol compounds may give “medicinal” or “bandage-like” flavor.

Foreign Taste (Synthetic/Chemicals)

Cause - cows consume particular feed or inhale feedy odors prior to milking; transmitted to the milk. Feeding should be done after milking when practical, barns should be well ventilated.

 Feed Odor & flavor is characteristic of associated feed; silage, hay, grassy, etc. Can be slightly sweet, generally not unpleasant, although could be unclean when strong or feed quality is poor. Most feed flavors clear up readily after milk is discharged from mouth. Common, though most often slight.

Feed Smell

Cause – growth of psychrotrophic spoilage bacteria, especially certain psychrotrophic Pseudomonas species or some of the spore-forming organisms (e.g., Bacillus, Paenibacillus). (Better cleaning practices on cow and equipment.)

Odor and flavor is usually pronounced, similar (not exact) to pineapple, apple or strawberry. Fermented fruit (fruity); may have more of a sauerkraut or vinegar-like odor or flavor (fermented).


Cause – enzymatic breakdown (microbial or milk enzymes) of milk proteins to short bitter peptides due to bacteria in the milk – (clean your equipment and dry your udders thoroughly)  Certain weeds ingested by cows may also cause bitterness although this is rare.

Basic taste sensation. Pure bitter has no odor. Taste sensation is detected on the tongue after expectoration (delayed) and tends to persist.


Cause – Udders not clean/dry;  absorbed, transmitted odor/flavor due to cow inhaling barn odors associated with poor ventilation and unclean barn conditions/dirty bedding. Similar defect may be due to ketosis in cows, but with more of a medicinal or chemical after taste.

Unpleasant odor and taste of a poorly maintained barn or unpleasant feed. May be perceived as “unclean.” “Cowy” or “cow’s-breath” may present a similar defect but generally with an unpleasant medicinal or chemical (i.e., acetone) aftertaste.


Cause - Growth of lactic acid producing organisms such as Lactococcus lactis, due to poor refrigeration, especially when temperatures exceed 70°F (21°C). “Malty” milks may be acid also.

Basic taste sensation. Sour, tart, may cause tingling sensation on tongue. “Cultured milk” or “sour” odor may be present.


It is easy to differentiate between clean raw pure milk and anything otherwise. If there is something off with your milk and you want to determine the culprit then look for these clues to single out a prognosis.    

Every few months we test our food supplies and release the lab results to the public to verify our food content is kept at a certain standard. Transparency of lab tests is something thing this company would like to achieve and set a standard for as a consumer deserve to know every bit that they and their famalies are consuming. Sometimes our results will vary from time to time and adjustments will be made to achieve a constant standard.

For complete information of milk identification from Cornell University of Agriculture and Life Science check the pdf here