Effect of pH on formation of starch complexes with lauric acid and β-lactoglobulin

The aim of present study was to investigate the effect of pH on interactions between macro constituents of foods using wheat starch (WS), lauric acid (LA) and beta-lactoglobulin (beta LG) in a model system. Results from the Rapid Visco Analyzer (RVA) showed that viscosity peaks appeared during the cooling stage and that their intensity increased gradually from 105 to 5565 cP with increasing pH in the WS-LA binary system. With the WS-LA-beta LG ternary system, the cooling viscosity peaks occurred throughout the pH range, and the change in intensity (from 1111 to 3688 cP) was not as evident as in binary systems. Results from differential scanning calorimetry (DSC), X-ray diffraction (XRD) and Raman spectroscopy showed that higher pH promoted the formation of both WS-LA binary and WS-LA-beta LG ternary complexes, attributed to greater solubility of LA and higher leaching of amylose. The limited effect of pH variation on the formation of ternary complexes compared with binary complexes is proposed to be due to the pH buffering effect of beta LG.