Evaluating the digestion-resistant properties of rice variety with low AC and medium eGI via an in vitro continuous digestion model

Description

Currently, the digestion resistance of lowamylose (AC) rice varieties with lower estimated glycemic index (eGI) remains unclear. This study used intact cooked rice grains (solid) as the research material and examined the morphological and digestive characteristics of lowAC rice with different eGI during in vitro digestion at both macroscopic and microscopic levels. Results showed that DG2, a lowAC highRS variety, had an eGI of 60.98, significantly lower than the other three low AC-low RS varieties which were high eGI. Additionally, DG2 has the highest polysaccharide molecular weight at 1.26×105 kDa, which is also significantly higher than the three‘s . All varieties exhibited biphasic digestion, but DG2 showed the slowest rate in the rapid phase and the most gradual change in the slow phase. After small intestinal digestion, DG2 had the highest residual starch (17.20%) with more intact granules and stronger resistance. Microscopic observation revealed that DG2's gastric residues contained the most numerous and largest green starch aggregates, while intestinal residues contained the highest amounts of starch, proteins, and starchprotein complexes. XRD indicated that DG2 had the highest crystallinity in both stomach and intestine. Mechanistically, extensive hydrolysis of A and B1 chains and their recombination with B3 chains shifted the crystalline type from Vtype to V+Btype, forming crystalline starch with enhanced digestion resistance. This study for the first time elucidates the digestion-resistant properties and structural changes of low AC-medium eGI rice, providing a basis for developing functional varieties.

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Institutions

• Yunnan Agricultural University

  Yunnan, Kunming

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