Milk proteins have long been a valuable part of the milk supply and have taken on increased importance in recent years.
As milk processing continues to evolve and more uses for milk proteins are discovered, there are also increasing export opportunities for U.S. milk products, and much of this is related to the high-quality proteins found in milk.
First, we should review the major proteins that are in milk. Cow’s milk averages about 3.1 percent true protein in the U.S. with 80 percent of the protein being caseins and 20 percent being serum (whey) proteins. There are four primary caseins in cow’s milk which are A1, A2, beta and kappa caseins.
Some of the common serum or whey proteins are alpha-lactalbumin and beta-lactoglobulin. During cheese production, the caseins precipitate and remain in the cheese and the whey proteins are separated out in the liquid whey fraction.
Milk filtration technology provides a means of separating proteins and other components of milk into various fractions for use in a myriad of product applications. When milk passes through filters (membranes), the portion of the milk that passes through the filter is referred to as permeate or filtrate and the fluid that is rejected by the membrane is the retentate or concentrate.
Through the processes of microfiltration (small pore-size filters) or ultrafiltration (extremely small pore-size filters), milk is separated into various fractions depending upon needs. After the filtration process takes place, the concentrates are then spray-dried to make powders which can be shipped anywhere in the world for use in product applications.
Some of the common ultrafiltration (UF) protein products on the market are milk protein concentrates (MPC) which are produced by concentrating the proteins in skim milk, and whey protein concentrates (WPC) which concentrates the proteins in whey.
Both of these products have reduced levels of lactose and soluble minerals and can be concentrated to various protein levels depending upon manufacturing needs.
Microfiltration (MF) of skim milk separates milk casein (micellar casein) and soluble proteins by directly filtering skim milk instead of making cheese. The soluble proteins are similar to whey proteins from cheese-making but do contain the flavors from the cheese-making.
MPCs are complete milk proteins, containing both casein and whey proteins in the same or similar ratio as milk. MPC typically contains from 42 to 85 percent protein, so as the protein content increases, more lactose is removed. There is a further concentration of MPC to produce a powder that is 90 percent or more protein that is referred to as milk protein isolate (MPI).
MPCs have traditionally been used in various cheese, yogurt and food applications, but with higher protein MPCs now available, the uses for MPC are growing. Lower protein MPCs (42-50 percent protein) are used in the manufacture of some types of cheese, yogurts and soup applications.
Higher protein MPCs (70-plus percent protein) and micellar casein concentrates are used in the manufacture of beverages, medical foods and protein bars, among other uses. Micellar casein concentrates are very heat-stable and are ideal for shelf-stable unrefrigerated beverages.
Milk soluble proteins are clear in solution and are stable at low pH, making them ideal for protein fortification of clear fruit-flavored beverages. U.S. production of MPCs has grown steadily over the last 10 years to meet growing market demand, and much of this is due to the use of higher-protein MPCs.
WPCs contain only whey proteins and can vary in protein content from 34 to 80 percent depending upon the product application. Similar to MPCs, when WPC is concentrated to 90 percent or greater protein, it is referred to as whey protein isolate (WPI).
WPCs can be used as an ingredient in calf milk replacers. Human application for lower-protein WPC (35 percent protein) include a replacement for skim milk powder, in yogurts, bakery mixes, dietetic foods, infant foods and confections.
Higher-protein WPC (50-plus percent protein) is used in nutritional drinks, soups, bakery products, meat, dietetic products, low-fat products and protein-fortified beverages. The use of WPCs in sports and nutrition drinks and protein bars has exploded in recent years.
Further fractionation of milk proteins creates ingredients that can be used across other product applications. Future applications of milk proteins can be divided into three different categories: technology-oriented applications, nutrition-oriented applications and other uses.
Future technology-oriented uses of milk proteins would include:
- Clear protein-fortified “non-dairy” beverages with low pH stability. Examples of this are protein-fortified water and protein-fortified juices. These can be made by producing milk-soluble protein concentrate that is clear as opposed to WPC, which has a milky appearance.
- Replacement of chemical emulsifiers in foods with protein-based emulsifiers, thus creating a “clean” product label on foods which would eliminate many of the chemicals that appear on food product labels.
- Providing flavor-neutral protein fortification of health snacks and nutrition bars.
- Products with high heat stability in high-protein shelf-stable beverages, such as sports nutrition drinks and meal replacement products.
- Products with cold gelation properties of individual protein isolates for use in foods, such as beta-lactoglobulin.
Future nutrition-oriented uses of milk proteins would include:
- Isolation of glycomacropeptide from cheese whey (phenylalanine-free dietary protein) for individuals with phenylketonuria.
- Production of bioactive peptides by hydrolysis of specific milk proteins. Examples would be angiotensin converting enzyme (ACE) inhibitory activity to help control high blood pressure, opioid-like activity for pain relief, anti-thrombotic (blood clotting) activity and cholesterol-reducing activity.
- Milks with different “naturally occurring” protein structures, such as A2 milk.
- Isolating alpha-lactalbumin for use in infant formulas that better match human milk.
Future other uses for milk proteins would include:
- Antimicrobial activity, such as isolating lactoferrin from whey proteins for healing infections.
- Anticariogenic activity, again isolating lactoferrin or producing milk protein hydrolysates for the prevention of tooth decay.
The future of milk proteins is indeed bright as demonstrated by the growth in higher-protein powders containing less lactose. Milk proteins have very diverse uses in many products.
With the increased focus on nutritional products such as protein bars, weight management foods, protein-fortified beverages, infant foods, foods for seniors and nutritional supplements, the demand for milk proteins will continue to increase. PD
David Barbano is a professor of food science and director of Northeast Dairy Foods Research Center at Cornell University.