ε-(γ-Glutamyl)lysine Crosslink Distribution in Foods as Determined by Improved Method

Quantitative analysis of ε-(γ-glutamyl)lysine crosslink in 127 foods was achieved with a, preliminary separation by reverse phase-HPLC before o-phthalaldehyde derivatization to remove interfering peaks. ε-(γ-Glutamyl)lysine was detected in 96 foods and its contents ranged from 0.2 to 135 μmol/lOOg protein. High levels were found in fish paste products, processed fish, shellfish, meats and soybeans, and raw poultry organs. For fish and meats, the level of ε-(γ-glutamyl)lysine in processed foods and fish paste was relatively higher than that in raw materials. The improved procedure could be applied for screening materials with transglutaminase activities.     

Gel Strength Enhancement by Addition of Microbial Transglutaminase during Onshore Surimi Manufacture

Surimi from Alaska pollock flesh was manufactured onshore with Microbial transglutaminase (MTGase). Effect of MTGase was investigated by evaluating breaking strength and deformation of gels from MTGase-treated surimi with and without setting at 30°C. Quantitative analysis of ε-(γ-glutamyl)lysine (GL) crosslink was also carried out to monitor the MTGase reaction. In set gels, breaking strength and GL crosslink increased, and myosin heavy chain decreased correspondingly with MTGase concentration. These changes were smaller in gels prepared without setting. Results suggest that surimi gel could be improved through the formation of GL crosslinks by added MTGase in surimi.     

Microbial Transglutaminase and ε-(γ-Glutamyl)lysine Crosslink Effects on Elastic Properties of Kamaboko Gels

Kamaboko gels from Alaska pollock surimi (SA? and 2nd? grades) were prepared by setting at 10 or 45°C with Microbial transglutaminase (MTGase) and its effect on gel properties was investigated. At 10 and 45°C, gels from 2nd? grade surimi paste showed increases in breaking strength, without decline in deformation. Gel from SA? graded surimi paste showed an increase in breaking strength with no changes in deformation in 45°C setting, up to 0.03% MTGase. Crosslinking of myosin heavy chains through ε-(γ-glutamyl)lysine bonds was observed and a possible correlation was shown between ε-(γ-glutamyl)lysine content and gel strength (breaking strength X strain). ε-(γ-Glutamyl)lysine content up to 3 μmol/100g or MTGase 0.03% or higher improved gel properties.