The milk protein and enzyme symposium chaired by Dr. Rafael Jimenez-Flores of California Polytechnic State University conducted, as a part of the ADSA joint annual meeting, consisted of sessions by world-renowned researchers in the field of milk biochemistry.
A number of native enzymes populate milk along with the other major components like proteins, fat and carbohydrates. Dr. Don Otter of AgResearch Limited, New Zealand, stated, “Many of the enzymes in milk are not there by accident”. Many of these enzymes are in very low concentrations in milk but have very specific functions including protection of calf digestive system and promotion of better digestion and absorption of milk. According to Otter, there are also enzymes that are spilled over from the blood of the cow in the udder during milk synthesis. All of these enzymes can have desirable and deleterious effects on milk and milk products. The enzymes in bovine milk are different from human milk and are tailored for the needs for the respective species. The concentration and the presence of enzymes in milk depend on the age of cows, environmental conditions, diet, parity and other physiological factors. Some of the native enzymes in milk are alkaline phosphatase, lactoperoxidase, lysozyme, lipase, proteinase, cathepsin D etc. Many processing technologies including heat treatment destroy many of these enzymes in milk.
Modulating the different enzyme content in milk can be used as an effective method to improve the functionality of different components in milk. Dr. Richard Ipsen of the University of Copenhagen, Denmark, elaborated about the use of phospholipases to modify the properties of phospholipids in milk. Phospholipids are major constituents of milk fat globule membrane. Phospholipases were utilized in his study to hydrolyze phospholipids and improve their ability to complex with other proteins. This also improves the water holding capacity of these proteins which can then be utilized to increase the yield of products like yogurt and cheese.
Other researchers Dr. Michael Gänzle of the University of Alberta, Canada, and Dr. Ulrich Kulozik of Technische Universität München, Germany, emphasized the use of enzyme synthesis of oligosaccharides and modifying proteins and peptides using transglutaminase enzyme. Oligosaccharides in milk have been shown to protect the gut against enteropathogenic bacteria. They compete as an alternate receptor for E. coli adsorption and enable them to be flushed out of the gut without adhesion. Such oligosaccharides can be synthesized by enzymes from lactose and glucose. The modifications of milk proteins especially caseins have shown improvement in gelling and foaming properties in milk products. This further benefits the utilization of these modified proteins and peptides as ingredients in many food products.
Overall, a number of enzymes are natively present in milk and perform a number of functions. These enzymes can be utilized in many ways to manipulate different components in milk and improve the product characteristics in milk and other food products. They can also add greatly to the profitability of utilizing dairy ingredients and thus boost the dairy industry.
Maneesha. S. Mohan is a PhD student at the Food Sci. and Tech. dept., The Univ. of Tennessee, Knoxville. She is also the current ADSA Graduate Student Division– Dairy Foods Director (2013-2014).