40-3 |
Effect of proteinase inhibitors and microbial transglutaminase on gelation of lizardfish surimi |
J. YONGSAWATDIGUL, Institute of Agricultural Technology, Suranaree Univ. of Technology, School of Food Technology, 111 University Ave., Nakhon Ratchasima, 30000, Thailand, P. Piyadhamviboon, Food Technology, Suranaree University of Tech., 111 University Ave., Nakhon Ratchasima, 30000, Thailand, and A. Worratao, Thailand. Lizardfish (Saurida spp.) is one of the main species used to produce surimi in Thailand and Southeast Asia. However, the fish muscle contains high endogenous proteolytic activity, resulting in poor gel-forming ability. Inhibition of proteolysis can be achieved using food grade enzyme inhibitors. Microbial transglutaminase (MTGase) could also be applied to improve textural properties of surimi. Therefore, the effective means to minimize proteolysis and maximize gel strength must be sought. The objectives of this study were to characterize the autolytic activity of lizardfish surimi. In addition, to study the effect of proteinase inhibitors; egg white powder (EW) and whey protein concentrate (WPC), and microbial transglutaminase (MTGase) on proteolysis and textural properties of lizardfish surimi. Autolytic activities of mince and surimi as a function of pH, temperature, and NaCl were determined. Specific inhibitors, such as leupeptine, E-64, EDTA, soybean trypsin inhibitors, and etc. were used to identify the responsible proteinase(s). Degradation and cross-linking of myosin were monitored using SDS-PAGE. Textural properties of surimi gels were measured using a 5-mm spherical probe. Microstructure of gel was evaluated using scanning electron microscopy (SEM). Optimum autolytic activity of mince fish and surimi was at 65°C, pH 6-8. Serine proteinase(s) responsible for the proteolysis appeared to be a myofibril-bound proteinase(s). Degree inhibition increased with added concentration of EW and WPC. Addition of 2% EW with pre-incubation at 25°C increased breaking force of surimi gel. However, retention of myosin heavy chain was minimal. Gel strength significantly increased when 0.6 units/g surimi of MTGase was added and pre-incubated at 25°C. At 4-40°C, oligopeptides content decreased as added MTGase content increased from 0 to 1.2 units/g surimi. MTGase provided a fine gel network structure. Gel quality of lizardfish surimi can be improved by addition of 2% EW or 0.6 units/g surimi of MTGase in conjuction with pre-incubation at 25°C.
Session 40, Aquatic Food Products: Surimi and proteins
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