Standardization of Cheesemilk Composition
The casein concentration in the cheesemilk is a determining factor of coagulation and notably of gel firmness. Increasing the casein content by adding MF or UF retentates is a valuable and effective method for correcting cooled milk: 10% addition of a UF retentate (generally, 9% to 12% in protein) gives a firmer gel and may reduce curd dust losses into the whey by nearly 20%.
Standardization of casein content by means of MF (membrane pore size 0.1 pm) changes the ratio of casein to whey protein, originating in a permeate-containing native whey protein suitable to be more efficiently used for whey products. Standardization of protein content by UF does not change the ratio between the milk proteins. Membrane processing is performed on skim milk and concentrate is mixed with cream to obtain the expected ratio of casein to fat.
The degree of protein milk concentration by MF/UF processing may vary by a large extent (volume reduction factor of milk from 1.2 to about 5 to 6 times), depending on the amount of whey to be drained from the curd, according to the cheesemaking technology.
Whole protein enrichment of cheesemilk by UF is now widely used in many countries, and the presence of UF equipment in a cheese plant is becoming as typical as that of a cream separator.
A special mention should be made to the MMV process that has completely modified the traditional way of converting milk to cheese, using the differential concentration of fat and protein on the milk itself instead of draining whey from the cheese curd. The process, involving UF or MF equipement, pushes the concentration until obtaining a protein and fat level similar to the one existing in the drained curd, obtaining a product named liquid precheese (Maubois et al., 1969). Despite its numerous advantages in terms of yield, plant efficiency, and rennet saving, the MMV process took almost 10 years to be applied industrially on large scale, probably because it cannot be simply applied to the existing technology but requires some adjustments taking into account a modified situation concerning the buffering capacity, rheology, rennet coagulation, and aqueous phase of liquid precheese. A number of cheese varieties are now industrially produced all over the world by using UF and MF according to their specific recipes. In the case of lactic curd cheese, such as Quarg, cream cheese, fromages frais, and also mascarpone the use of UF has replaced in many plants filtration clothes or centrifugal separators (Mistry and Maubois, 2004).