Transglutaminase effects on gelation capacity of thermally induced beef protein gels

Transglutaminase (TG) is an enzyme that catalyzes an acyl-transfer reaction between the gamma-carboxyamide group of peptide or protein-bound glutaminyl residues, and primary amines. TG action on protein molecules, causes a cross-linking and polymerizing effect of these latter, through epsilon-(gamma-glutamyl)lysine bonds. This TG-mediated protein cross-linking creates drastic physical changes in protein-rich foods. This research objective, was to evaluate the microbial transglutaminase (MTGase) effect on beef gel texture. Time and incubation temperature, enzyme concentration, and Chilean jack mackerel (Trachurus murphyi) surimi addition effects, were studied. Beef gel quality, was assessed by measuring gel strength and cooking yield. Additionally, SDS-PAGE electrophoresis and epsilon-(gamma-glutamyl)lysine bond analysis by HPLC were carried out on the gels. MTGase addition, significantly increased gel strength. The optimal attributes were observed at 60 degrees C after 2 h and 0.5% w/w of MTGase, with a gel strength 88% higher than the control-gel. Jack mackerel surimi and MTGase incorporation in beef gels, significantly increased gel strength and cooking yield. SDS-PAGE analysis revealed that the myosin heavy chain (MHC) content decreased and that the cross-linked protein amount, apparently increased with time and MTGase addition. Proteolysis was also observed. epsilon-(gamma-Glutamyl)lysine bond production also increased as a function of incubation time and MTGase concentration. These results, suggest that it is possible to improve mechanical properties of beef gels by adding MTGase and jack mackerel surimi, thus increasing their potential utilization in minced based products. (c) 2005 Elsevier Ltd. All rights reserved.