Maryam Moslehishad - Department of Food Science and Technology, Safadasht Branch, Islamic Azad University, Tehran, Iran

Background and Aim : Modification of food proteins with enzymes is an attractive way for improving the functional and nutritional properties of these proteins. Chemical modification is not desirable for food applications because of the harsh reaction condition, non-specificity, and difficulties of removing residual reagent from the final products, but enzymatic modification has some advantages such as fast reaction rates, mild condition, high specificity, and the possibility of production in large quantities. Methods : Enzymatic modification of milk proteins increases the number of bioactive peptides with biological activity such as antimicrobial properties. These peptides can be released in three ways (a) Enzymatic hydrolysis by digestive enzymes (b) Fermentation of milk with starter cultures (c) Through the action of proteolytic enzymes derived from microorganisms or plants. Results : These bioactive peptides reveal multifunctional properties such as antihypertensive, antioxidative, antimicrobial, immunomodulating, antithrombotic, and opioid or mineral-binding activities. Antimicrobial peptides have been derived from the cleavage of lactoferrin with pepsin. The resulting peptide had better antimicrobial activity than the undigested lactoferrin due to its smaller size which accessed the microbial surface sites. Lactoferricin, a peptide derived from lactoferrin by pepsin digestion, has been shown to display antimicrobial activity against microorganisms including Bacillus, Escherichia coli, Klebsiella, Listeria, Proteus, Pseudomonas, Salmonella, Streptococcus, and Candida. An αS۲-casein fragment (۱۶۵–۲۰۳), named casocidin-I, containing a high proportion of basic amino acids was also found to be an antibacterial agent which can inhibit the growth of E. coli and Staphylococcus arnosus. αs۱-casein f(۱-۲۳), isracidin, obtained from chymosin hydrolysis has been shown to protect mice against Staphylococcus aureus and Candida albicans. Whey protein hydrolyzate obtained by pepsin–trypsin treatment inhibited growth of E. coli. Conclusion : The use of enzymes to improve the functional and nutritional properties of milk proteins is developing rapidly, but additional research is necessary for commercially successful application.

Milk Protein; Bioactive Peptide; Antimicrobial Activity; Enzyme