Property changes of caseinate in response to its dityrosine formation induced by horseradish peroxidase, glucose oxidase and d ‐glucose

BACKGROUND A ternary system containing horseradish peroxidase (HRP), glucose oxidase and d ‐glucose using one‐ or two‐step treatment was evidently able to cross‐link proteins via dityrosine formation and thus was assessed for its possible impact on several properties of a protein ingredient caseinate. RESULTS HRP, glucose oxidase and d ‐glucose were used at 200 U, 6 U and 0.05 mmol g −1 protein to treat caseinate by one‐ and two‐step methods, producing two cross‐linked caseinates named CLCN‐I and CLCN‐II, respectively. In response to the conducted cross‐linking, both CLCN‐I and CLCN‐II gained slightly reduced dispersibility at pH 5–10, enlarged hydrodynamic radius (particle size distribution, 266.37 and 258.33 versus 226.67 nm) and negative zeta‐potential (−26.60 and −22.27 versus −14.30 mV) in dispersions, increased water‐binding (3.70 and 3.09 versus 2.68 kg kg −1 protein), decreased oil‐binding (1.75 and 2.74 versus 2.87 kg kg −1 protein) and emulsifying activity (76.2 and 82.3 versus 94.3 m 2 g −1 protein), increased emulsion stability (84.3% and 82.5% versus 78.6%), and enhanced thermal stability with lower mass loss (58.5% and 59.6% versus 64.3%) or higher decomposition temperatures (331.2 °C and 328.7 °C versus 327.6 °C) upon heating at 105–450 °C. In addition, CLCN‐I and CLCN‐II had decreased gelling temperatures and shortened gelling times when forming acid‐induced gels, and the gels were endowed with increased values in four textural indices and finer microstructure. Moreover, CLCN‐I with a higher cross‐linking extent showed greater property changes than CLCN‐II. CONCLUSION This ternary system could be used in caseinate cross‐linking to improve properties such as aggregation, emulsification, gelation and thermal stability. © 2020 Society of Chemical Industry