It is well established that milk is a natural beverage packed with nutrients such as protein, fat, lactose, vitamins, and minerals. Over time, the improved understanding of milk components coupled with the advancements in process technology (spray drying, membrane separation, etc.) gave the dairy industry the capability to manufacture several value-added dairy ingredients that can enhance the functional and nutritional quality of many food formulations to meet consumer demand.

Milk protein concentrates/isolates

Milk protein concentrates (MPCs) are specialty high-purity dairy ingredients (with a casein-to-whey protein ratio as that is similar to milk) that have a protein content ranging from 40% to 90% (weight by weight). If the protein concentration in the MPC is above 85%, it is referred to as milk protein isolate (MPI). 

MPCs are typically manufactured by ultrafiltration of skim milk — often coupled with diafiltration to remove lactose and minerals — followed by further concentration using nanofiltration or evaporation before spray drying. 

Protein quality

Milk protein is considered a “complete protein” because it contains all the nine essential amino acids in balanced proportion for building protein in the body. In 2013, The United Nation’s Food and Agriculture Organization recommended the adoption of the Digestible Indispensable Amino Acid Score (DIAAS) as the new method of protein quality measure to replace the Protein Digestibility Corrected Amino Acid Score (PDCAAS) because of shortcomings in the PDCASS. 

The DIAAS score of MPCs is 1.18 and stands out compared to several plant protein isolates. This simply means MPC is the best source of bioavailable amino acids and makes it unique for crucial pediatric and geriatric nutrition formulations apart from several other food applications. 

Another advantage of MPCs over several other proteins is the flavor. A milky flavor that comes from MPCs is always desired, unlike the off-flavors that some other proteins can bring into the food formulation. 

Functional properties

It is important to test any ingredient for its performance attributes so one can select the right ingredient for a food application. The significant functional properties of MPCs are solubility, emulsification, gelation, water binding, and viscosity. 

Solubility — the most critical functional property of MPCs — is the ability of the dairy ingredient to dissolve in water and to remain dissolved in solution. A good-quality protein can be fully hydrated using a high-speed mixer at a suitable temperature and time combination. 

Dairy proteins function as a good emulsifiers because they have both hydrophilic and hydrophobic areas and can be used as clean-label ingredients. Because of these hydrophilic areas, MPCs exhibit superior water-holding ability and help in building the viscosity of the solutions. Likewise, MPCs can form stable gels by acidification. 

Applications of MPCs, MPIs

Because of their superior nutritional quality, clean flavor, and excellent functional properties, MPCs are increasingly the preferred dairy protein ingredient compared to several other protein sources. Mainly, MPCs are now single-stop solutions to increase the protein load in many food formulations, including nutrition bars, ready-to-drink (RTD) beverages, ready-to-mix powders, yogurt, and ice cream.

The use of MPCs in ice cream could improve foaming, melting, and retention properties. And in yogurt, MPCs can be used to improve the gel strength and viscosity. 

The heat stability and solubility of MPCs are two important functional properties that help in increasing the protein load in RTD beverages. The water-holding capacity of MPCs helps in retaining the softness of nutritional bars. MPCs/MPIs can also be used in cheese manufacturing to improve the yield.