Fabrication, characterization and emulsifying properties of potato starch/soy protein complexes in acidic conditions

Starch and proteins can be assembled into binary complexes with functional attributes that combine the desirable facets of each individual component. In this study, the formation of gelatinized potato starch (GPS)/soy protein (SP) complexes was investigated by turbidimetric analysis in acidic conditions. The optimum conditions for complexation included a pH of 3.5 and a GPS/SP mixed ratio of 4:1 (w/w). Differential scanning calorimetry (DSC), fourier transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD) were used to characterize the formed complexes. DSC data revealed that the endothermic peak temperature of gelatinized potato starch was increased due to the interaction between these two polymers. FTIR analysis showed that the complexes were mainly formed between the phosphate group of GPS and the amino groups of SPs. XRD results indicated that new structures were formed through electrostatic attraction. Moreover, the stability of emulsions stabilized by GPS/SP complexes at acidic pH were evaluated. We found that GPS/SP complexes formed at pH values lower than 3.0 displayed better emulsifying stability. Findings from this study will help in understanding the nature of interactions between potato starch and soy proteins and so as to design new food materials for nutraceutical and biomaterial applications.