a. Milk Lipase. The indigeneous lipase of milk can produce a significant lipolysis in cheese made of raw milk (Table 6). Pasteurization of the milk at 72 °C for 15 sec inactivates about 95% of the milk lipase.
b. Rennet and Starter Bacteria. Standard rennet does not contain lipase and the starter cultures of lactic acid bacteria do not produce enzymes that can liberate fatty acids from milk triglycerides.
Consequently there will be only slight lipolytic activity in cheese made of good-quality pasteurized milk.
Table 6 Examples of Typical Acid Degree Values for Cheese Fat
Cheese Acid degreea (BDI)
Nonhydrolyzed milk fat 0.5-0.8
Flavor threshold value for milk 1.2
Semihard cheese from raw milk, ripened 6 months 3-5
Semihard cheese, made of pasteurized milk of good quality, 1-2 ripened 6 months
Semihard cheese, made of pasteurized milk with 500,000 3-5
psychrotropic bacteria per mL before pasteurization, ripened 6 months
Blue-veined cheese (Mycella) made of raw milk, ripened 3 months 10-20
Blue-veined cheese (Danablu) made of raw homogenized milk, 30-50 ripened 3 months a mL 1 N alkali per 100 g fat. Source: Ref. 16.
c. Added Enzyme Preparations. Traditional rennet paste, made by macerating stomachs plus pregastric region of lambs or kid goats, contains pregastric lipases with high specificity for the liberation of short chain fatty acid, which in cheese can contribute to a piquant flavor (e.g., Provolone and Feta) (18).
d. Lipases from Psychrotropic Bacteria. In raw milk, psychrotropic, gramnegative bacteria may produce lipases (and proteases). These bacteria are killed by pasteurization, but their enzymes may persist (19). If the milk is high in psychotropic bacteria before pasteurization, thermo-resistant bacterial lipases can split fat during ripening. Concomitantly, an unclean flavor may develop, due to thermoduric protein degrading enzymes from the psychrotropic bacteria.
e. Lipases from Surface Microflora. Bacteria and yeasts in the smear on surface-ripened cheesescan hydrolyze fat on the surface, and the liberated fatty acids can diffuse into the cheese (20) and contribute to the flavor, in combination with ammonia and other low-molecular-weight compounds from degraded proteins of the surface smear.
f. Mold Lipases. The molds of blue-veined and white-mold cheeses produce very active lipases. However, in Camembert, for example, the contribution of free fatty acids to the flavor is reduced because of the dissociation of the acids at the high final pH.
Was this article helpful?