Effects of Cysteine on Physicochemical Properties of High-Moisture Extrudates Prepared from Plant Protein

The effects of cysteine addition (0%, 0.05%, 0.10%, 0.15%, 0.20%, 0.25%) on the physicochemical properties of plant-based extrudates by high-moisture extrusion were investigated. The texturization degree, rheological properties, hardness, springiness and chewiness of the extrudates significantly improved with the addition of cysteine (<0.15%). Analysis of the microstructure showed that the addition of cysteine (<0.15%) improved the formation of the fiber structure in the extrudates. Cysteine (<0.15%) promoted the formation of new disulfide bonds and non-covalent bonds by changing the disulfide bonds of protein molecules and enhanced the cross-linking degree between proteins. However, the excessive addition of cysteine (>0.15%) had a negative impact on the formation of fiber structure. Analysis of secondary structure suggested that the ordered beta-sheet structures gradually converted to the disordered beta-turn and random coil structures with the addition of cysteine (>0.15%). In addition, analysis of odor properties with the addition of cysteine using an electronic nose showed the difference in volatile components of the extrudates mainly existed in halides, hydrocarbons, sulfides and amines. On the whole, the addition of cysteine could improve the quality of plant-based extrudates.

Automated summary

This study investigated the effects of cysteine addition on the physicochemical properties of plant-based extrudates. The results showed that the addition of cysteine (<0.15%) significantly improved the texturization degree, rheological properties, hardness, springiness and chewiness of the extrudates, and enhanced the formation of fiber structure. However, excessive addition of cysteine (>0.15%) had a negative impact on the fiber structure and secondary structure. Analysis of odor properties showed that the volatile components of the extrudates were mainly affected by cysteine addition.