Structural changes of flaxseed protein modified by fermentation and the gel properties and swallowing characteristics of its composite system with mung bean starch

The fermentation modification of plant-based proteins has attracted extensive attention recently. This study was to investigate the effect of fermentation on molecular structures of flaxseed protein (FP), and evaluate the gel properties and swallowing characteristics of the composite gel composed of mung bean starch (MBS) and fermented FP (FFP). After 10 h of fermentation, the content of free amino acids in FFP increased ∼14.3 times over that of the unfermented FP, while the proportion of small peptides increased by ∼37.2%. Fermentation reduced the α-helical conformation in FFP. After heating, FFP was easier to cross-link with MBS to form strengthened composite gel network with denser and larger pores as well as thicker pore wall, in which the maximum gel hardness increased by 2.6 times. MBS-FFP composite gels also exhibited increase in viscoelastic moduli, cohesiveness, thermal stability, and water-holding capacity (WHC) than the control gel. The WHC was increased from 63.4% to 92.3% when composite gel contained 10 h fermented FP. Furthermore, international dysphagia diet standardization initiative (IDDSI) tests indicated that all MBS-FFP composite gels could be categorized as level 7 dysphagia food. These findings provide new insights into the structural nature and potential application of plant protein-based fermentation-induced gel systems.