Functional and structural properties of gum arabic complexes with casein and hydrolyzed casein achieved by Maillard reaction

Abstract

In this study, casein was extracted from milk and hydrolyzed with pepsin at three different enzyme/substrate ratios (0.1:100, 0.15:100, and 0.2:100). Three molar ratios of casein or hydrolyzed caseing/gum Arabic (GA) (1:1, 1:2, and 2:1) were exposed to Millard reaction using wet heating method at 80 °C, 6 h. The conjugation of biopolymers through Millard reaction was verified by Fourier Transform Infrared (FT-IR), high performance size exclusion chromatography (HPSEC) and fluorescence spectrophotometry methods. Higher molecular weight was observed after the reaction experiment. Moreover, FT-IR spectrum showed changes in amide 1 and 2 bands and fluorescence spectrophotometry showed reduction of intrinsic fluorescence intensity. Maillard reaction got faster by increasing the degree of hydrolyzation and GA/hydrolyzed casein ratio. Conjugates with higher ratios of GA/casein showed more stable particle size distribution against freeze-thawing process. Increasing the degree of hydrolyzation did not affect significantly on particle size distribution of conjugates. Functional properties of conjugated biopolymers including solubility, emulsifying and foaming properties were promoted compared to casein and casein/GA mixture. Also, hydrolyzed casein-GA showed better emulsifying and foaming ability but less foaming stability than non-hydrolyzed samples.