Dysphagia food: Impact of soy protein isolate (SPI) addition on textural, physicochemical and microstructural properties of peach complex gels

In this study, dysphagia-friendly diets were prepared based on the interaction between polysaccharides from peach, namely Meirui (MR), Yangshan (YS) and Cons758 (Cons), and soy protein isolate (SPI). MR-alcohol insoluble residues (AIR) and YS-AIR were low methoxylated polymers, while Cons-AIR was high methoxylated polymer. According to the international dysphagia diet standardization initiative, YS-SPI and MR-SPI could be qualified as level 5-minced/moist dysphagia diets. Following SPI addition, the apparent viscosity, G′ and G′′ of peach pulp-SPI complexes were significantly increased. At the shear rate of 10 s-1, corresponding to oral processing, MR-SPI performed the highest apparent viscosity (35.2 Pa·s), followed by YS-SPI (33.5 Pa·s). Additionally, the SPI-treated strategy pronounced improved the hardness, springiness, adhesiveness and chewiness of complexes. Both YS-SPI and Cons-SPI showed the reduced particle size, alongside the uniform distribution, owing to the strong hydrogen bonding and electrostatic interaction between peach pulp substances and SPI, which was confirmed by FT-IR result. The biggest ζ-potential value (-23.55 mV) was found in YS-SPI. Meanwhile, compared with peach pulps, the highest increase ratio (87.94%) of water holding capacity was depicted in MR-SPI. LF-NMR analysis revealed immobilized water was dominant in peach pulp-SPI. The results suggested that MR was promising for the optimal choice to form gel food for people with swallowing problems.