Addition of microbial transglutaminase and protease inhibitors to improve gel properties of frozen squid muscle

Thermal gelation profiles of batters from newly frozen and long-term (five months) frozen squid with added protease inhibitors, microbial transglutaminase (MTG) or a combination of the two, revealed notable differences as a consequence of frozen storage, attributed in part to decreased autolytic activity in the muscle. Puncture and compression-relaxation tests in gels revealed that the incorporation of protease inhibitors in addition to MTG considerably improved gel elasticity; however, MTG alone produced higher breaking deformation than in other samples. SDS-PAGE showed a higher prevalence of covalent cross-linking in gels containing MTG, where MHC and paramyosin were mainly involved. The combination of protease inhibitors and MTG produced the hardest gels, which achieved the maximum score in the folding test.