Effects of high amylose corn starch and microbial transglutaminase on the textural and microstructural properties of wheat flour composite gels at high temperatures.

Textural and microstructural properties of composite gels (CGs), along with wheat flour and high amylose corn starch (Hylon VII) mixed with microbial transglutaminase (MTGase) at different levels and temperatures were investigated. The results showed by increasing Hylon starch content, the firmness increased and adhesiveness decreased. Indeed, high level of amylose and cross-linking formed by MTGase enhanced the gel elasticity and reduced adhesiveness. Moreover, MTGase had more effect on the firmness and provided more cross-linked intermolecular gel structures at high temperatures. By adding MTGase to the CG, the lowest peak viscosity and final viscosity were found for 15% of Hylon starch. As the more Hylon content in the CG, the more water solubility index was particularly obtained at high temperature. Scanning electron microscopy (SEM) results showed that MTGase and Hylon starch addition enhanced the structure. The differences in SEM of CG were reflected the pasting properties of the gels. Consequently, MTGase treated gels can withstand high temperature as well as maintain the overall structure of the samples gels. Therefore, the increment of Hylon to the CG gels supplied tighter, stronger, and denser protein network which were formed by MTGase cross-linking within the network of starch and proteins.

PRACTICAL APPLICATIONS: Although, transglutaminase was practically used in the production of noodles and pasta in Japan, but there is little academic and industrial knowledge concerning its utilization in the pasta or noodles. Moreover, long shelf-life noodle/pasta products have become popular in the Japanese market and in the emergency conditions like as floods or earthquake, but they can be stored for at least 5 months by applying heat treatment at 95C. Here, high amylose corn starch as a resistant starch, wheat flour, and microbial transglutaminase (MTGase) were selected as the main components in the composite gel (CG) systems to elucidate the effects of MTGase and Hylon on the texture, microstructure, and pasting behavior of CGs at high temperatures to produce long-life noodle/pasta products (about 2 years) through retort processing.