Impact of pH on the Physicochemical, Structural, and Techno-Functional Properties of Sesame Protein Isolate

Abstract

Sesame protein isolate (SPI) is a highly nutritious plant protein distinguished by its essential amino acid profile. This study investigates the influence of pH on SPI's physicochemical, structural, and techno-functional properties, highlighting its potential as a sustainable protein source for various food applications. Our findings revealed that SPI had a protein content of 90.60% and a protein extraction yield of 77.2%. The density is measured at 0.72 g/mL, with a critical compressibility index of 19.22, indicating excellent flowability for weaning foods. Notably, the ζ-potential shifts from +39 mV at pH 3.0 to 0 at the isoelectric point (pI, 5–5.5) and becomes negative at higher pH levels. We observed a direct correlation between solubility, fluorescence intensity, and functional characteristics of SPI, with peak solubility and functional properties at acidic and alkaline pH levels and lowest values at the pI. Structural analyses confirmed the relationship between electrical charge, hydrophobicity, and functional attributes, with the highest surface hydrophobicity observed at pH 2.0. In conclusion, our findings underscore the critical role of pH in modulating the physicochemical properties of sesame protein isolate, enhancing its applicability in food formulations. SPI demonstrates significant potential as a versatile ingredient in the functional food product development.