Multiscale structures, physicochemical properties, and in vitro digestibility of oat starch complexes co-gelatinized with jicama non-starch polysaccharides

The wide applications of natural starches in industries often encounter problems such as easy syneresis, pH sensitivity, and heating instability. The influences of an addition of 10% (w/w) jicama non-starch polysaccharides (PEP-3P & PEP-6P) with different molecular structures on the multiscale structure, gelatinization properties, and in vitro digestibility of gelatinized oat starch (OS) were investigated. Compared to OS, the swelling power, solubility, short-range ordered structure, crystalline shape, and apparent viscosities did not show significant differences. The contents of amylose leaching, proportions of amorphous area, thermal resistance, and gel strength increased to some extents, but contents of rapidly digestible starch (RDS) decreased after PEPs were added. Moreover, PEP-3P and PEP-6P with different chemical components and molecular weights performed differently in two main aspects. Firstly, the swelling power and solubility were markedly different between OS/PEP-3P and OS/PEP-6P. Secondly, the in vitro digestible behaviours of OS/PEPs showed different patterns as the contents of RDS, slowly digestible starch (SDS), and resistant starch (RS) were different. Based on the above results, the inhibition effects on digestibility of PEPs were probably attributed to the enhancement of starch gels during and after gelatinization. Molecular structures of PEPs did affect the functional properties when PEPs were combined with OS. These findings may provide more fundamental information about interactions between non-starch polysaccharides and starch.