Milk Proteine Concentrate

It is easy to appreciate the evolution that has taken place with the traditional glass of milk when we consider the vast array of dairy products available today. Thanks to new technological advancements in the isolation/extraction of milk components, milk can now be "eaten," rehydrated, sliced and even spread. A complete, rich, complex and multifunctional food, milk gives life-sustaining nourishment to newborns babies. This is due in large part to the suspended protein factions, saline, emulsified fat, vitamins and other dissolved matter contained in the aqueous Whey material found in milk.

Ultrafiltration is the preferred method employed to extract milk proteins used in the manufacture of milk protein concentrate (MPC). This concentration process uses varying degrees of pressure to force the liquid matter through a porous membrane. The holes in the membrane are so small (2 to 20 nanometers) that only water, minerals and organic molecules can pass through; the larger-sized proteins are trapped and collected from the membrane. These concentrated milk proteins are then carefully subjected to evaporation and then spray drying. The resulting dry powder is highly sought after for both its nutritional and functional properties, which serve to enhance many finished food products.

Technological factors that influence the quality of MPC are as follows:

• Quality of raw milk and operating parameters during heat treatment (pasteurization);
• Degree of protein concentration (ultrafiltration and diafiltration, lactose washing, used for MPC 65 or greater); (Note: Figures/numbers indicate protein percentage in MPC)
• Operating parameters when removing water (evaporation and spray drying);
• Storage conditions of final product (T_max = 20oC, hermetic packaging).

The quality of raw milk used to manufacture MPC must meet rigorous standards in terms of composition and microbiological characteristics.Fresh milk is collected according to stringent health and safety regulations and must be free of colostrum and foreign substances such as chemical products or antibiotics. A low somatic-cell content (100-200 000 per cm3) is desirable and helps toavoid a decreased flowduring the ultrafiltration process. Milk fat solids are separated from the nonfat milk solids, after which the liquid nonfat material is pasteurized for the first time and is then concentrated by ultrafiltration until the desired protein content is achieved. The dried material is then subjected to a second pasteurization treatment to ensure a clean, innocuous concentrate.

MPC must be free from Salmonella, Staphylococcus aureus, Escherichia coli and other coliforms. MPC-75 must not contain more than 10 000 colony-forming units (CFU) per gram, in terms of total bacteria count, and a maximum count of 50 CFU/g for yeast and mold. The number of microorganisms capable of developing spores under aerobic conditions must not exceed 500CFU/g. Microorganisms capable of sporing under anaerobic conditions must not exceed 700 CFU/g.

Milk proteins are divided into two general classes: caseins and serum proteins.

Caseins are made up of three components (alpha (Α), beta (Β) and kappa (Κ)) and exist in colloidal suspension (micelle) whose diameter varies between 30 and 300 nanometers. Unlike caseins, serum proteins are soluble molecules that appear in the aqueous phase of milk. They are composed of four main components: Α-lactalbumin, Β-lactoglobulin, seric bovine serum albumen and proteose-peptone. During cheesemaking, caseins are used to form the curd while the serum proteins are found in the aqueous whey (the by-product of cheesemaking).

Although no official federal standards of identity have been developed to address the moisture content in MPC, the current standard applied in the case of commercially dried milk powders (CFR 21, moisture 4%, max) is applied to MPC.

The ever-increasing appeal of using MPCs as a food ingredient is easily explained by the fact that the original structure and amino acid content of dairy proteins have remained intact during the separation and concentration processes. Consequently, by resorting to exclusively physical processes, the properties of native proteins are preserved and the following functional aspects can be exploited for specific purposes of use: