C: Food Chemistry Aminopeptidase from Streptomyces gedanensis as a useful Tool for Protein Hydrolysate Preparations with Improved Functional Properties Raji Rahulan, Kiran S. Dhar, K. Madhavan Nampoothiri, and Ashok Pandey Abstract: The aim of the present study was to evaluate the efficiency of amino peptidase (AP) from Streptomyces gedanensis to produce protein hydrolysates (PHs) with better antioxidant, nutritional, and functional properties and to compare it with the PHs produced by commercial protease. Three proteins, soy, casein, and wheat protein were employed to produce their hydrolysates by applying 2% (w/w) AP at optimal conditions of pH 8.5 and temperature 55 ◦ C. The results disclosed that the degree of hydrolysis ranges from 15.93 to 20.68% after 6 h showed better antioxidant activity and functional properties such as solubility, foaming properties, and water holding capacity than the commercial protease treated hydrolysates. AP treated PHs were enriched in Glu followed by Leu, Tyr, Lys, Phe, Asp, Met, His, Ile, Ala, and Val. Therefore, S. gedanensis AP would be an attractive microbial AP with high potential for the preparation of PHs which could offer industrial applications especially in the realm of producing food formulations as food additives in medicine and sport. Keywords: amino peptidase, anti oxidant activity, nutritional property, protease, DPPH radical scavenging activity Practical Application: AP from S. gedanensis was found to be the most effective enzyme to produce PHs with good antioxidant, nutritional, and functional properties. The antioxidant and essential amino acids of AP treated PHs unveiled that this amino peptidase could give credence to eliminate the bitter taste by hydrolysis of peptides and could offer interesting possibilities for industrial applications, including debittering of protein hydrolysates. The findings could be useful in the food industry especially in the realm of producing food formulations requiring high protein supplements. Introduction Proteins are essential food components because they are source of amino acids needed for growth and maintenance and provide functional properties to foods. Proteins can be modified by treat- ment with proteolytic enzymes, thus, the functional properties and nutrition value of proteins could be improved by enzymatic hydrolysis (Yu and others 2007), which can generate polypeptides and free amino acids (Quist and others 2009). Protein hydrolyzates can be used as emulsifying agents in a number of applications such as salad dressings, ice cream, coffee whitener, spreads, and emulsi- fied meat products like sausages or luncheon meat. However, the enzymatic treatment of various food proteins often results in bitter taste due to the formation of low molecular weight peptides com- posed mainly of hydrophobic amino acids. Amino peptidases (AP) are exopeptidases that selectively release N-terminal amino acid residues from polypeptides and proteins. Moreover, these enzymes from various sources can be used successfully to debitter pro- tein hydrolyzates. A number of commercial microbial APs have been in use for preparation of protein hydrolysates (PHs) lacking bitter taste (Monod and others 2008). The utilization of pro- MS 20120085 Submitted 1/16/2012, Accepted 4/24/2012. Authors are with Biotechnology Division, National Ins. for Interdisciplinary Science and Technol- ogy, CSIR, Trivandrum-695 019, India. Direct inquiries to author Nampoothiri (E-mail: madhavan85@hotmail.com). teins or their hydrolysates for food and/or cosmetic applications not only presents additional advantages over other antioxidants but also confers nutritional and functional properties (Moure and others 2006). As a proteolytic enzyme with broad specificity and strong hy- drolysis capability, Alcalase has been used for hydrolyzing vegetable proteins (Cui and others 2009). Through cleaving peptide linkage, enzymatic hydrolysis can decrease the molecular weight and en- hance the functional properties of proteins (Klompong and others 2007). Furthermore, it can also facilitate the dissolution of proteins from plant material by breaking the linkage between proteins and other components. The special structure of proteins and covalent linkage to other components make the proteins difficult to hy- drolyze. Therefore, it is of significance to find a way to efficiently hydrolyze the protein sources. The present study was undertaken in order to investigate the extent of hydrolysis of different pro- teins, soybean, casein, and wheat proteins, by S. gedanensis AP and to evaluate the antioxidative activity, amino acid profile and functional properties of the above PHs and to compare it with Aspergillus oryzae proteases treated PHs. Materials and Methods L-para-nitroanilide, O-phthaldialdehyde (OPA), 2, 4, 6 tri-nitro benzene sulphonic acid (TNBS), 2-diphenyl-1-picryhydrazyl (DPPH), amino acid standards, and hemoglobin were obtained from Sigma–Aldrich, Inc. (St. Louis, Mo., USA). The prote- olytic enzymes used were protease from A. oryzae (St. Louis) and C  2012 Institute of Food Technologists R  doi: 10.1111/j.1750-3841.2012.02773.x Vol. 77, Nr. 7, 2012  Journal of Food Science C791 Further reproduction without permission is prohibited