Abstract: The aim in this work was to explore the digestion characteristics of breads with added konjac glucomannan, guar gum or oat β-glucan by using a simulated gastrointestinal digestion model. The digestive characteristics were evaluated in terms of estimate glycemic index (eGI), estimate glycemic load (eGL), starch hydrolysis rate, and the contents of rapidly digestible, slowly digestible and resistant starch, in comparison to bread without added polysaccharides and white bread. Moreover, in vitro simulated intestinal fermentation of the digested product of each polysaccharide-supplemented bread was carried out by the fecal bacteria from normal people or the fecal bacteria from diabetic patients in order to observe the changes in pH and sugar consumption with inulin as the positive control. The results showed that the eGI values of the bread without added polysaccharide and the breads with added konjac glucomannan, guar gum and oat β-glucan were 53.24, 52.41, 52.84 and 52.71, respectively, and the eGL values were 9.79, 9.16, 9.00 and 8.76, respectively. In addition to having eGL values significantly lower than that of the bread without added polysaccharides (P < 0.05), the three polysaccharide-supplemented breads exhibited lower starch hydrolysis rate and higher resistant starch content as compared to white bread. During fermentation, the pH of the normal and diabetic groups decreased gradually, and a large quantity of non-digestible sugars in the digested products were consumed by the intestinal bacteria, with sugar consumption rates above 72%, significantly higher than that observed for inulin. Collectively, it can be concluded that the three breads with added polysaccharides are low GI, low GL foods, which are helpful to maintain the stability of postprandial blood sugar and are suitable for diabetic people to consume within a certain range.

Key words: estimate glycemic index; in vitro simulated gastrointestinal digestion; large intestinal fermentation