The microstructure of the food matrix influences the in vitro digestibility of starch. Almost no or a very small percentage of glucose formation is formed during simulated gastric digestion of starch and starch based foods. Majority of the starch hydrolysis occurs under simulated small intestinal conditions. Addition of guar gum to the starch matrix reduces the hydrolysis (%) of starch to a considerable extent. Microstructure of navy beans also plays an important role during in vitro gastrointestinal digestion of starch in cooked navy beans. The cooked whole navy beans show significantly lower levels of hydrolysis than navy bean flour and starch, which is attributed to the restrictions imposed by the intact cotyledon cell walls towards the gelatinization of starch during cooking and the entry of intestinal enzymes during in vitro digestion of whole navy beans. The starch in cooked potatoes is hydrolyzed in a similar manner to that of pure starch. However, the starch hydrolysis (%) values in cooked potatoes stay slightly lower than pure starch throughout the small intestinal digestion in vitro. This new knowledge about food microstructure and its effect on starch digestion will help in the manufacturing of novel foods with controlled starch digestibility. This research may also help in the development of low calorie foods matching the modern day life style and new foods with low glycemic index for diabetic and obese populations.