Effects of color protection and enzymatic hydrolysis on the microstructure, digestibility, solubility and swelling degree of chestnut flour

Chestnuts, despite their nutritional value, pose challenges in starch processing, digestion, and absorption. This study employed various color-fixing formulations and processing methods to simulate the <i>in vitro</i> digestion of both untreated and enzymatically hydrolyzed chestnut flour. Changes in starch properties, digestion characteristics, and estimated glycemic index (eGI) were analyzed to understand how enzymatic hydrolysis affects chestnut flour properties. The results showed that the browning of chestnut flour was the least when the mass ratio of vitamin C, citric acid, and EDTA-Na₂ was 9:1:0.3. Following treatment with pullulanase and glucoamylase, the content of rapidly digestible starch decreased to 10 %, while the content of slowly digestible starch and resistant starch increased to 62 % and 27 %, respectively. The eGI value of chestnut flour after enzymatic hydrolysis increased to 61.85-65.14, the hydrolysis rate was 78.37 %-89.20 %, the water holding capacity was 5.3-8.6, the solubility was 51.33 %-58.33 %, and the swelling degree decreased to 2.21-3.33 mL/g.