The effect of organic acids on high-moisture extrusion of soy protein isolate: Comparison between monocarboxylic acid and polycarboxylic acids

Abstract

This study aimed to explore the potential of organic acids to promote formation of fibrils in plant-based meat analogs during extrusion, as acids were able to induce formation of amyloid-fibrils from protein molecules. Specifically, the effects of acetic acid, tartaric acid, and citric acid with various concentrations (0.05, 0.10, 0.20, and 0.30 mol/kg protein) on the structure and properties of the soy protein isolate (SPI)-based meat analogs from extrusion were investigated. Tartaric acid and citric acid improved the fibrous degree of the meat analogs with the optimal concentration of 0.20 mol/kg SPI, while acetic acid did not have a significant effect. Besides, it was found that citric acid led to a higher fibrous degree than tartaric acid, which might be due to that citric acid was more effective in cross-linking than tartaric acid. Moreover, adding organic acids promoted degradation of SPI, enhancing the flexibility of SPI molecules during extrusion. This, facilitated the rearrangement of protein molecules and the formation of fibrils in meat analogs. Although acetic acid also promoted the hydrolysis of SPI, it hindered the unfolding of SPI during heating and was not able to induce cross-linking of SPI molecules. As a result, acetic acid had no significant impact on the fibrous degree of meat analogs. In conclusion, citric acid and tartaric acid were promising and cost-effective additives to promote production of plant protein-based meat analogs.