Starch controls brittleness in emulsion-gels stabilized by pea flour. (October 2022) - Sridharan, Simha
Abstract: Pea proteins are widely studied as emulsifying and gelling agents in soft food materials. However, their extraction process consumes energy and often focuses only on protein purity. To reduce extraction-related energy consumption, unpurified pea protein-starch mixtures could be used directly as functional ingredients. Such mixtures provide additional advantages due to their binary role, such as using proteins as emulsifiers and starch as a gelling agent. Therefore, we investigated the heat-induced gelation of emulsions (30 or 50% oil), stabilized by pea flour (PF) containing 20 wt% protein and 50 wt% starch. To understand the effect of starch on gelation, starch was removed from pea flour by filtration. Heat-induced gelation behavior of the pea protein mixture (PPM) stabilized emulsions was investigated and compared with PF emulsions. Both the PF and PPM stabilized emulsions gelled upon temperature treatment, monitored by oscillatory shear rheology. At pH 7, starch (in PF) contributed to a higher G' (2000Pa) compared with the emulsions without starch (PPM:∼1000 Pa). Whereas, at pH 3, the presence of starch did not contribute to a higher G′ in the emulsions. The presence of starch at both pH values affected the microstructure of the emulsion gels. The PF emulsions after heating were more brittle upon applying strain compared to the PPM emulsions. The brittle nature of the emulsions containing starch was most likely due to the starch gel's disruption of the oil droplet network. Our results provide insight into emulsion gelation when using a native pea protein-starch mixture. Our study demonstrates that depending on the pH conditions, native protein blends could have better gelling functionality. Graphical abstract: Image 1 Highlights: Pea protein emulsion-gels at pH 3 form firmer emulsion-gels than at pH 7. Aggregation of oil droplets causes an increase in gel strength upon heating. Starch gelatinization increases emulsion elasticity only at pH 7, not at pH 3. Presence of starch results in the breakdown of emulsions at lower strains (brittle).