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The edible quality of starch paste formed by direct dispersion in boiling water is crucial to the design and production of instant starch-based products. In the present study, the kudzu powder was complexed with different chain-length fatty acids to improve its instant properties. The formation of V6-type kudzu powder-fatty acid complexes was initially characterized. Then, the impact of different chain-length fatty acids on instant properties of kudzu powder was characterized by measuring agglomeration rate and viscoelasticity. The agglomeration rate was decreased from 42.31% (native kudzu powder) to 0.08% (kudzu powder-myristic acid complex). Moreover, the viscoelasticity of the kudzu powder complexed with fatty acids (except for stearic acid) was stronger than that of native kudzu powder. These improvements were related to the formation of kudzu powder-fatty acid complexes with high thermal stability existed on the surface of complexed kudzu powder and extending the time for water to enter into complexed kudzu powder. Thus, all of kudzu powder could absorb sufficient water to avoid aggregating together that was involved into the formation of kudzu paste. This research had important implication for the preparation of instant starchy products that could be directly dispersed in hot water with high edible quality. • The instant properties of kudzu powder was improved by complexing with fatty acid. • Crystallinity and complexing index decreased with increasing fatty acid chain length. • The complexes with V-type crystalline enhanced thermal properties of kudzu powder. • The formed complexes decreased the agglomeration rate and maintained the viscosity. • The formed complexes extended time for water to penetrate into kudzu powder. [ABSTRACT FROM AUTHOR]

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 short- and 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. • A superheated steam technology was adopted to synthesize starch citrates. • The starch citrates were maintaining the granule structure of starch. • The resistant starch content was increased by the formation of starch citrates. • The esterified and cross-linked structure was formed in starch citrates. • The inhibition of gelatinization and swelling was found in starch citrates. [ABSTRACT FROM AUTHOR]