In the history of milk production, a reoccurring problem for dairy farmers has been the capacity of producing more milk than can be utilized. This problem is complicated by the limited shelf life of milk. In the early 1900s, farmers dealt with this issue by fractionating milk into cream and skim milk. The cream was then churned into butter, and the buttermilk produced was used in baking. The skim milk was fermented into cottage cheese, and the whey produced was fed to farm animals. Consequently, fractionation of milk into its various components and creation of milk-based ingredients is not a new concept.
Obviously, the issue of milk utilization is different today than it was in the early 1900s. As an example, in the U.S., milk production has climbed from 115 billion pounds in 1975 to over 170 billion pounds today. This increase in milk production has been largely driven by a steady increase in milk production per cow. On average, since 1960 milk production has increased by 273 pounds per cow per year.
It is interesting to note that in the last 10 years cow numbers have remained fairly constant at approximately 9.1 million. If cow numbers continue to remain constant, we can expect to have an additional 2.5 billion pounds of milk (9.1 million cows x 273 pounds milk per cow) produced each year.
The U.S. population grows at a rate of approximately three million per year. This increase in the U.S. population will partially compensate for the expected increases in milk production. However, in order to find an outlet for the expected increases in milk production we will need to increase the U.S. consumption of dairy products and expand our export market for dairy products. In my opinion, fractionation of milk into ingredients targeted for export markets is one of the keys to expanding the utilization of U.S. milk.
To be successful in producing milk products for the export market, the U.S. industry needs to identify components of milk that are the most valuable and determine how these components can be economically isolated. The major components of milk include water (88 percent), lactose (4.8 percent), fat (3.5 percent), protein (3.2 percent) and minerals (0.7 percent).
Of these components, protein is considered to be the most valuable. Currently, the world demand for dairy protein exceeds the world supply of dairy protein, and the U.S. will have an opportunity to expand its milk production if economical systems for fractionation of milk protein are available.
The protein present in milk consists of two major fractions called casein and whey protein. Currently, these two classes of milk protein are produced from milk during cheese manufacture. However, in the future these two classes of protein will be fractionated from milk in a filtration-based process. Filtration is performed by passing milk through a semi-permeable membrane that fractionates milk into two components called retentate and permeate. Permeate is the material that passes through the membrane, whereas retentate is the material retained by the membrane.
There are various types of filtration that can be utilized and examples include ultrafiltration, microfiltration, nanofiltration and reverse osmosis. All of these filtration techniques use a semi-permeable membrane and differ only in the pore size of the membrane. The pore size of the membrane determines what material in milk passes through the membrane. As an example, casein and whey protein can be separated from each other using microfiltration.
There is no doubt milk fractionation will be critical in the development of new products and ingredients that drive the demand for dairy products. The question for the U.S. dairy industry is: Will we identify components of milk that are valuable and determine how these components can be economically isolated so we can compete in a global market? It is my opinion fractionation of milk proteins using filtration is the key to this endeavor. PD
—From 2nd Annual I-29 Dairy Conference Proceedings
