Optimised preparation and characterisation of lotus root starch oxidised with sodium hypochlorite (NaOCl) using response surface methodology

In this paper, response surface methodology (RSM) was used to study the optimised process conditions of lotus root starches modified by treatment with sodium hypochlorite (NaOCl). Based on the Box-Behnken design, quadratic models were developed to correlate the reaction variables. Analysis of variance (ANOVA) revealed that the active chlorine content was the most significant variable for the response. Under the experimental conditions in this paper, the calculated carboxyl content (CNCOOH) of obtained samples was approximately 0.98% ± 0.02% (n = 5). The spectra of Fourier transform infrared (FTIR) spectroscopy displayed that the formation of carboxyl groups successfully occurred on the oxidised lotus root starches. Scanning electron microscope (SEM) analysis showed that the oxidised lotus root starch (CNCOOH, 0.98%) granules were mostly spherical in shape and their surfaces were slightly rougher than those of native lotus root starch. This work may contribute to providing technical support and theoretical guidance for the production of oxidised lotus root starches using NaOCl as an oxidising agent.