Characterization of Physicochemical Properties of Collagen Peptide-Sweet Potato Starch Complex System

In order to investigate the effect of collagen peptide on the gel properties of sweet potato starch, the present study was carried out to characterize the pasting, thermodynamics, texture, microstructure, rheological properties, gel size and relative crystallinity of the collagen peptide-sweet potato starch composite system by using Brabender's viscosity determination, differential scanning calorimetry analysis, full texture test, scanning electron microscopy observation, rheological characterization, particle size and X-ray diffraction. The results showed that the addition of collagen peptide significantly reduced the paste-forming viscosity and regrowth value of starch (P<0.05), and when 9% collagen peptide was added, the peak viscosity and regrowth value of sweet potato starch gel were reduced by 31.35% and 34.25%, respectively. In addition, the addition of collagen peptides made the three-dimensional network structure of starch gels dense and the pore walls thicker. This addition also significantly reduced the hardness of the starch gel (P<0.05), which had a better taste. Compared to the control, the addition of collagen peptide reduced the gelatinization enthalpy of the gel system, indicating that collagen peptide disrupted the ordered internal structure of the starch gel and damaged the crystalline structure of the starch. The relative crystallinity of X-ray diffraction suggestted that the physical barrier formed by the incorporation of collagen peptides under hydrothermal conditions exacerbated the disruption of this crystalline structure. The results of rheological analysis showed that the hardness and apparent viscosity of the composite system gradually decreased with the increase of collagen peptide addition concentration, leading to the difficulty of starch gel formation, indicating that the addition of collagen peptide inhibited the formation of starch gel, and the protein peptide impeded the order rearrangement of the straight-chain starch, which further slowed down the short-term regrowth of the starch gel. Collagen peptides can be used as suitable additives to sweet potato starch-based foods and can improve the rheological properties and eating quality of sweet potato starch gels.