Milk contains, among other things, fats, proteins (casein and a variety of other proteins such as .beta.-lactoglobulin, .alpha.-lactalbumin, serum albumin, and immunoglobulins), salts, sugar (lactose), and various vitamins (such as vitamins A, C, and D, along with some B vitamins) and minerals (primarily calcium and phosphorus). The composition of milk varies with the species, breed, feed, and condition of the animal from which the milk is obtained. Commercially produced milk commonly undergoes pasteurization to mitigate bacterial growth and homogenization to improve fat dispersion stability. Whey is the watery part of milk that separates from the curds, as in the process of making cheese. As such, whey contains all of the milk components except for calcium caseinate and most of the milk fat.
In the commercial processing of milk products (such as skim milk and whey), it is desirable in certain instances to remove as much fat as possible from the milk products. In addition, since many of the components of milk products have separate commercial value independent of the milk products as a whole, it is desirable to be able to recover such components (particularly proteins) from the milk products. For example, a wide variety of whey proteins are used as functional and nutritional ingredients in bakery products, pasta, confections, beverages, meats, and the like.
Conventional milk processing heretofore has involved the use of mechanical separation (centrifugation), evaporation/cystallization, steam injection, electrodialysis, reverse osmosis, ultrafiltration, gel filtration, diafiltration, and/or ion exchange chromatography. For example, whey typically is subjected to mechanical separation (e.g., centrifuged) to remove fat, condensed via evaporation to increase solids content, and then spray dried or used for lactose crystallization. After desludging, the residual concentrate is dried, which yields whey powder containing about 11-14% protein (which usually is denatured, particularly during the evaporation/condensation step). The whey powder can be subjected to electrodialysis to remove ash and thereby prepare demineralized whey powder. Alternatively, the whey powder can be subjected to reverse osmosis to remove water, thereby obtaining whey powder containing about 12-15% protein. Such a whey powder can be subjected to ultrafiltration or gel filtration to remove further ash and lactose and thereby obtain a whey protein concentrate containing about 30-50% protein, which, in turn, can be subjected to diafiltration or ion exchange chromatography to remove yet more ash and lactose so as to obtain whey protein concentrates containing about 50-90% protein.
Such conventional processing involves many disadvantages, including long processing times, high costs, and poor or inconsistent component fractionations. Thus, there is a need for improved methods of treating milk products, particularly to more efficiently remove fat and to allow for the more efficient recovery of protein fractions therefrom. The present invention provides such treatment methods for milk products (particularly whey products). These and other advantages of the present invention, as well as additional inventive features, will be apparent from the description of the invention provided herein.