Preparation and characterization of rice starch citrates by superheated steam: A new strategy of producing resistant starch

In this study, starch citrates were synthesized by superheated steam (SS) treatment without changing the granule structure of starch. The degree of substitution (DS) of starch citrates prepared in present study was ranged from 0.015 to 0.064. Fourier transform infrared spectroscopy confirmed that citric acid (CA) and starch were successfully esterified with an absorption peak appeared at 1735 cm- 1. In vitro digestion results revealed that the content of resistant starch (RS) was significantly increased by citric acid esterification, which was attributed to the cross-linked structure of starch and the inhibition of gelatinization and swelling. According to the physicochemical properties analysis, the pasting temperature of rice starch citrates were significantly increased by citric acid treatment, while the swelling power and gelatinization enthalpy were significantly decreased and the shortand long-range molecular order of the starch was disrupted after the esterification reaction. These results indicated that it is a feasible method to synthesize starch citrate by superheated steam to increase resistant starch, and it could be used as an alternative approach for preparing starch citrate to conventional hot air treatment.

Automated summary

The study successfully synthesized starch citrates by superheated steam treatment, maintaining the granule structure of starch. Esterification with citric acid increased resistant starch content, changed physicochemical properties of rice starch, and disrupted molecular order. This method shows potential as an alternative approach for producing starch citrate compared to conventional hot air treatment.