Improving the cross‐linking degree of oxidized potato starch via addition of nanocrystalline cellulose

Abstract

Nanocrystalline cellulose (NCC) has attracted considerable interest in the starch modification field due to its biodegradability, renewability, and high biocompatibility. Here, oxidized potato starch was cross‐linked with sodium hexametaphosphate ((NaPO3)6) at different temperatures, pH values, and (NaPO3)6 and NCC concentrations. The bound phosphorus content and the substitution degree of the oxidized cross‐linked potato starch were measured to analyze the effect of NCC on the cross‐linking reaction. The structure of the oxidized cross‐linked potato starch was further analyzed using Fourier transform infrared (FT‐IR) spectroscopy, X‐ray diffraction (XRD), scanning electron microscopy (SEM), and thermogravimetric (TG) analysis. The results showed that when (NaPO3)6 cross‐linked the starch, the addition of NCC promoted the cross‐linking reaction in the oxidized potato starch. In comparison to the native starch, the thermal stability of the oxidized cross‐linked starch was increased. Additionally, the cross‐linking reaction occurred mainly in the non‐crystalline region of the potato starch and only partly in the crystalline region due to degree of crystallinity decreasing. The optimum conditions for the oxidized potato starch cross‐linking reaction were 1.0 wt.% (NaPO3)6 and 5.0 wt.% NCC at 50°C and a pH of 10.5. Under these conditions, the bound phosphorus content of the potato starch increased by 4.87% compared to the same conditions without NCC addition. In summary, NCC is a good additive to improve the cross‐linking degree of oxidized potato starch.