Unaided efficient transglutaminase cross-linking of whey proteins strongly impacts the formation and structure of protein alginate particles

There is a dogma within whey protein modification, which dictates the necessity of pretreatment to enzymatic cross-linking of 13-lactoglobulin (13-Lg). Here microbial transglutaminase (MTG) cross-linked whey proteins and 13-Lg effectively in 50 mM NaHCO3, pH 8.5, without pretreatment. Cross-linked 13-Lg spanned 18 to >240 kDa, where 6 of 9 glutamines reacted with 8 of 15 lysines. The initial isopeptide bond formation caused loss of 13-Lg native structure with t1/2 = 3 h, while the polymerization occurred with t1/2 = 10 h. Further, cross-linking effects on protein carbohydrate interaction have been overlooked, leaving a gap in understanding of these complex food matrices. Complexation with alginate showed that 13-Lg cross-linking decreased onset of particle formation, hydrodynamic diameter, stoichiometry (13-Lg/alginate) and dissociation constant. The complexation was favored at higher temperatures (40 degrees C), suggesting that hydrophobic interactions were important. Thus, 13-Lg was cross -linked without pretreatment and the resulting polymers gave rise to altered complexation with alginate.

Automated summary

This study challenges the dogma of pretreatment in whey protein modification by showing that enzymatic cross-linking of whey proteins and 13-lactoglobulin can be achieved without pretreatment. The cross-linked proteins had altered structure and showed different complexation behavior with alginate.