Introduction:
Flavor of the milk and milk products may be divided into two groups i.e.
- Natural flavors that is desirable and
- Off flavors or those that are not typical of the products and that usually but not always are undesirable flavors.
Flavor of milk
- Milk is both sweet and salty.
- Good quality milk should have a pleasantly sweet and clean flavor with no distinct aftertaste.
- To prevent flavor/odor defects in milk, proper milk handling procedures from the farm to the consumer are essential.
The flavor defects of milk can be divided into 3 categories:
a) Absorbed:
- Feedy, barny, cowy, weedy, unclean, lacks freshness, stale, refrigerator/cooler odors.
- On the farm, off-flavors can be absorbed through the cow and/or during farm storage (i.e. feedy, barny, cowy).
- Pasteurized milk can absorb flavors during refrigeration storage, especially in paperboard or low barrier cartons.
b) Bacterial:
- Acid, bitter, malty, lacks freshness, unclean, fruity/fermented, putrid and rancid.
- Bacterial off-flavors result from the growth of bacteria that are present in milk due to poor sanitation and/or milk handling practices.
- The bacteria responsible for spoiling refrigerated milks are psychrotrophic in nature (they grow at temperatures < 45°F/7.2°C).
c) Chemical:
- Cowy (ketosis), rancid, oxidized, sunlight, foreign, astringent, medicinal, flat and salty.
- Chemical defects can occur in both raw and pasteurized milk.
- Abusive handling of raw milk may result in a rancid flavor from the action of the naturally occurring lipase enzyme, which breaks down butterfat to fatty acids (i.e. butyric acid perceived as “rancid”).
- Oxidized flavors can be induced by heavy metals, particularly copper, or by exposure to sunlight and fluorescent lights.
- Other chemical or foreign off-flavors can occur due to contamination with or absorption of cleaning chemicals, sanitizers, medicines, or other substances.
The common flavor defects in milk, their causes and prevention are as follows:
|
Flavor defects |
Causes |
Prevention |
|
Barney Flavor |
1. Improper ventilation of milking barn. 2. Milk not properly covered during production. |
1. There should be provision of proper ventilation in milking barn. 2. Milk should be properly covered during production. |
|
Bitter taste or Bitter flavor |
1. Intake of bitter weeds by milch animals 2. Using late lactation. |
1. It is desirable to prevent cows from eating bitter weeds for a period of three to five hours before milking. 2. Use normal lactation. |
|
Cooked flavor |
Over heating of milk. |
Avoid over heating of milk. |
|
Absorbed/foreign flavors |
Addition or absorption of foreign smelling substances in milk. |
Avoid contact of milk with foreign smelling substances. |
|
High-acid /sour |
Excessive lactic acid development (Due to considerable growth of lactic acid producing micro-organism) |
Store milk at 5 0 C (40 0 F) or below (to check bacterial growth and acid development). |
|
Malty |
Growth of streptococcus lactic var malt genes microorganisms in milk. |
Store milk at 5 0 C below to check bacterial growth. |
|
Rancid flavor (Hydrolytic rancidity) |
Fat hydrolysis due to lipase action. |
Inactive lipase by proper pasteurization of milk |
|
Oxidized, oily, Metallic, tallowy |
Fat oxidization due to direct contact of milk with copper or iron, exposure of milk to light, etc. |
1. Tin milk-holding vessels properly; or use aluminum alloy/stainless steel as milk- contact surfaces. 2. De-aerate/ vacuumizes pasteurized milk. |
|
Salty |
Milk of animals suffering from mastitis or far advanced in lactation. |
Avoid mastitis or late lactation milk. |
|
Weedy |
Intake of milk-tainting weeds |
1. Eradicate milk-tainting weeds. 2. Vacuum pasteurization of milk. |