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

Abstract

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. 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 m2 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. 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.