Effects of moisture content and processing temperature on the strength and orientation regulation of fibrous structures in meat analogues

Abstract

The fibrous structure is one of the most important qualities in meat analogues. This study aimed to regulate the fibrous structure (including strength and orientation) of extruded yeast protein isolate (YPI) meat analogues by controlling the moisture content and processing temperature. Therefore, high-moisture extruded YPI with different moisture contents (55%, 60%, and 65%) and processing temperatures (160, 170, and 180 °C) was produced, and its fibrous properties and protein structures were analyzed. The results suggested that the angle (between the orientation of fibrous structures and the extrusion direction) was reduced and the strength of fibrous structures was enhanced in samples as the processing temperature increased at the same moisture content. The fibrous degree was >1.60 at a processing temperature of 180 °C, corresponding to a rich fibrous structure. The ordered secondary structures accounted for 73.41 ± 0.35% at 55% moisture content and 180 °C processing temperature, which was higher than that at 65% moisture content and 160 °C processing temperature (P < 0.05). Therefore, ordered secondary structures could be conducive to the fibrous structures in extrudates. Moreover, increasing the processing temperature resulted in more exposures of –SH groups and tryptophan residues; meanwhile it enhanced the formation of S–S bonds.