Original article Evaluation of red bean protein (Vigna angularis) isolate on rheological properties of pork myofibrillar protein gels induced by microbial transglutaminase

Summary The effects of 1% red bean protein isolate (RBPI) on the gel properties of myofibrillar protein (MP) invarious levels of microbial transglutaminase (MTG: 0%, 0.1%, 0.5%, & 1%) were evaluated. The cook-ing yield (CY) of the MP gels decreased with increasing MTG level, while the addition of RBPI improvedthe CY of the MP gels. Gel strength (GS) was also improved when RBPI was incorporated into the MPgels containing higher than 0.5% of MTG. The addition of MTG and RBPI was slightly changed theendothermic peak temperatures. Scanning electron microscopy (SEM) showed that the three-dimensionalstructure of MP with RBPI alone or in combined with MTG was compacted as compared to the control.Based on the results, RBPI could be functioned as a substrate for MTG (0.5–1.0%) and a water binderof meat protein gel mediated by MTG.Keywords Microbial transglutaminase, myofibrillar protein gels, red bean protein isolate, rheological properties. Introduction Microbial transglutaminase (MTG) catalyses the forma-tion of cross-links between food protein substrates byintermolecular interactions of glutamine and lysine (Nioet al., 1986; Motoki & Seguro, 1998), as affected byreaction conditions such as temperature and time as wellas their concentrations (Sakamoto et al., 1994; Hwanget al., 2008; Hong & Chin, 2010a). The addition ofMTG improves the textural properties of meat and meatproducts through the formation of isopeptide bonds(Ahhmed et al., 2009; Hong & Chin, 2010b). Recently,research has been performed to improve the functionaland textural properties of sodium reduced meat andmeat products utilising the reaction induced by the addi-tion of MTG in meat systems (Lee & Chin, 2011).Myofibrillar proteins (MP) are salt soluble proteinswhich can be induced to form gels via heating. Themain role of MP is to improve the elasticity and cohe-siveness in comminuted and restructured meat prod-ucts (Ramirez-Suarez et al., 2005). The gelling andfunctional properties of MP could be changed accord-ing to the processing conditions (e.g. pH, salt concen-tration, temperature and functional ingredients)(Doerscher et al., 2003; Ramirez-Suarez & Xiong,2003; Chin et al., 2009a,b).Red bean [Vigna angularis] (RB; adzuki bean or pat)protein is one of the nonoil legume seed proteinswhich contains plentiful amounts of essential aminoacids (Meng & Ma, 2002). Meng & Ma (2002)reported that RB has more lysine content than soyaprotein (Hwang et al., 2005), which has high emulsionstability and solubility in a wide range of pH (Meng M Jang & Chin, 2011). However, there islack of research examining the efficacy of red beanapplied in meat systems and influence on the rheologi-cal properties of meat protein induced by MTG. Thus,the objective of this study was to evaluate the effectsof red bean protein isolate (RBPI) implemented at 1%on the rheological properties of MP gels in the pres-ence of various levels of MTG (0%, 0.1%, 0.5% and1%).