Milk casein modification in response to dual oxidative enzymatic system

Abstract

Enzymatic cross-linking of proteins refers to the formation of intra-and inter-molecular cross-links by biocatalysts. Thus, the purpose of present work was to evaluate whether the dual oxidative enzymatic systems could be used for enhancing the functional properties of casein in order to use it as a texture improver. The results showed that peroxidase in the crude extract of moringa (Moringa oleifera) leaves exhibits 1342.19 specific activity (U/mg protein), while at 20% saturation of ammonium sulfate had specific activity of 1617.14 (U/mg protein) within 14.03% yield and 1.21 purification fold. Also, oxidative cross-linked casein clearly had higher relative di-tyrosine intensity than control casein. The control casein had the smallest particle size (272.121 µm) but other samples possessed enlarged particle size ~392.48-1294.60 µm which confirmed with the electrophoretic profile using SDS-PAGE. Moreover, the acid curd contains cross-linked casein had greater viscosity and lower syneresis than control. The total amino acids (TAA), essential amino acids (EAA), and TAA/EAA ratio of acid curd with enzymatic cross-linked casein were higher than control curd. Protein efficiency ratio and biological value of both CMII and CMIII treatments were higher than control curd. Also, CMIII treatment had the highest chemical score of valine, histidine, isoleucine, and leucine; while control acid curd had the highest chemical score of threonine only. It could be concluded that dual oxidative enzymatic system improved the functional properties of casein which could be used as texture improver without any negative impact on the nutritional value of such product.