Applications for Functional and Environmental Purposes
Use of Transglutaminase
Transglutaminase (TG) has recently become of great interest to food scientists for its ability in strengthening the structure of protein gels. TG catalyzes the post-translational modification of proteins by transamidation of available glutamine residues by the formation of covalent cross-links between glutamine and lysine residues (Ozrenk, 2006). Addition of transglutaminase to milk induces cross-linking of caseins and whey proteins that improves the strength of milk gels: Jaros et al. (2010) have recently reviewed the use of TG in the dairy field. Practical applications are the increase of techno-functional properties of yogurt by increment of viscosity values and decline in syneresis (Sanli, 2011), and preparation of whey proteins gels (Gauche et al., 2010 LWT).
Hydrolysis of Milk Proteins
Controlled enzymatic hydrolysis of milk proteins can improve some functional properties of dairy ingredients or give rise to functional molecules. Digestion of casein and whey proteins by tripsin and chymotripsin strongly enhance solubility, foaming, and emulsification capacity of milk protein concentrates (Banach et al., 2013). An innovative application is the enzymatic production of bioactive peptides, such as ACE- inhibitory and casein-phospho peptides, which are encrypted within milk proteins. Increasing the presence of these compounds in dairy products is one of the most attractive challenges—the goal can be pursued by controlled hydrolysis by gastrointestinal enzymes or enzymes derived from microorganisms or plants. Even though some commercial developments already exist, many issues must be resolved to reach a full expression of the potential of bioactive peptides in the dairy industry (Gobbetti et al., 2002). Targeted enzymatic hydrolysis of whey proteins is a well-known method to reduce allergenicity, which is mainly identified in specific sequences of aminoacids in P-lactoglobulin, in milk-based products. Digestion of whey protein concentrate with bacterial proteases, such as alkaline subtilisin from Bacillus licheniformis, and purification by ultrafiltration is a modern way to obtain hydrolysates with antigenicity reduction of about 100 folds with respect to the native protein (Guadix et al., 2005).