Influence of Extrusion on Emulsifying Properties of Soybean Proteins and Pectin Mixtures Modelled by Response Surface Methodology

A simplex-centroid design was applied to the model emulsifying activity index（EAI），average droplet size（D［4，3］）and creaming inhibition（CI%）of the mixtures.The objective was to apply response surface methodology to estimate the emulsifying capacity and stability of mixtures containing isolated and textured soybean proteins combined with pectin and to evaluate if extrusion process affects these interfacial properties.Results showed that all models were significant and able to explain more than 86% of the variation.The high predictive capacity of the models was also confirmed.The mean values for EAI，D［4，3］and CI% observed in all assays were（0.173±0.015）nm，（19.2±1.0）μm and 53.3%±2.6%，respectively.No synergism was observed between the three compounds.This result could be attributed to the low soybean protein solubility at pH 6.2（＜35%）.Pectin was the most important variable for improving all responses.The emulsifying capacity of the mixture increased 41% after extrusion.Pectin could substitute or improve the emulsifying properties of soybean proteins and that the extrusion brought additional advantage to interfacial properties of this combination.