Hydrolyzed rice glutelin as plant-based emulsifier to reduce tween in emulsion facing process stresses and its application in coconut milk

Abstract

The demand for natural plant–based emulsifier to reduce synthetic emulsifier is attractive to the food industry. The low emulsifying property of native rice glutelin (RG) can be improved by trypsin hydrolysis due to the partial unfolding of intact protein. The solubility and surface hydrophobicity of hydrolyzed RG at degree of hydrolysis (DH) 2.0 (HRG2) (89.48%, 7461.97) were much higher than RG (9.85%, 249.50). HRG2 was substituted for Tween 60 (Tw) in emulsion at ratio 100 : 0, 75 : 25, 50 : 50, 25 : 75, and 0 : 100. The selected 75 : 25 ratio emulsion was subjected to environmental stresses (pH, ionic strength, and temperature). The interfacial pressure of HRG2 and HRG2–Tw was in an increasing trend even after 3 h indicated the presence of HRG2 in the adsorbed interface. After amplitude sweep, the interface formed by HRG2 showed higher elastic modulus (Ed’) indicated a stiffer interface than HRG2–Tw. HRG2–Tw emulsion showed smaller mean droplet size with less concentration dependence than HRG2– and Tw–emulsion. HRG2–Tw–emulsion was precipitated at pI but was stable at pH > 6 and was stabilized under ionic strength similarly to Tw–emulsion. The pasteurized coconut milk with Tw (1%) had the lowest creaming index, followed by HRG2 (1%) and HRG2–Tw (1%) after 7 days which indicated the possibility to replace or reduce the use of synthetic surfactant in coconut milk.