Effect of washing treatment and microbial transglutaminase on the gelling properties of blue crab (Callinectes sapidus) proteins

Improving of Gelling Capacity of Cooked Crab Meat Proteins

Cooked crab meat subjected to a cutting process can aggregate again, forming weak gels. The objective of this work was to determine the effect of two mixing methods, combined with the addition of the microbial enzyme TGase (MTGase) on the mechanical and functional properties of gels from washed or unwashed blue crab (Callinectes sapidus) meat. Live crabs were obtained from Laguna Madre, Tamaulipas, Mexico, and cooked at 120°C for 20 min before hand-picking the meat from the shell. Cooked meat was processed by mixing and cut at temperatures of 25 or 60°C, without (control) or 0.5% of MTGase. Then cooked at 90°C for 15 min. Changes in texture profile analysis, percentage of extractable water, and color were evaluated. The mixing method at 60°C allowed increasing the textural properties of the gels, and the addition of MTGase significantly improved the mechanical properties. The results allowed stablishing a viable technique to obtain restructured gels from cooked crab meat with no need to extract the soluble compounds responsible for their distinctive odor and taste which often affect the mechanical properties.

Effect of microbial transglutaminase cross-linking on the quality characteristics and potential allergenicity of tofu

Microbial transglutaminase (MTGase) has been developed as a new tofu coagulant in recent years due to its good hydrophilicity, high catalytic activity, and strong thermal stability. This study aimed to investigate the effect of MTGase on the physicochemical properties and immunoreactivity of tofu relative to conventional coagulants [brine and glucono-δ-lactone (GDL)]. Structural changes of the MTGase cross-linked soymilk protein were characterized by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), circular dichroism (CD) spectroscopy, ultraviolet (UV) absorption spectroscopy, and fluorescence spectroscopy. The IgE-binding capacity of MTGase cross-linked proteins was tested by enzyme-linked immunosorbent assay (ELISA). The physicochemical properties, quality characteristics, and surface microstructures of five different types of tofu were determined by the Kjeldahl nitrogen method, texture analysis, and scanning electron microscopy (SEM). The digestibility of tofu was evaluated in vitro by simulated gastrointestinal (GIS) digestion. A cell sensitization experiment was performed in vitro to evaluate the capability of tofu digestion products to induce the release of bioactive mediators from human basophil leukemia (KU812) cells. Results indicated that MTGase significantly changed the advanced structure of the soymilk protein. Compared with tofu without MTGase, the composite coagulant tofu containing MTGase exhibited better quality. MTGase improved the water-holding capacity (WHC) of the internal mesh structure and increased the yield of tofu. The digestion products of the composite coagulant tofu, especially the GDL plus MTGase tofu, induced KU812 cells to release fewer bioactive mediators compared with those of MTGase-free tofu. MTGase can not only improve the quality of conventional coagulant tofu but also reduce the potential allergenicity of tofu to a certain extent.