Effect of Thermal Processing of Wheat and Barley Dietary Fibers on the Bioavailability of Carbohydrates

Cereal grains are major sources of dietary fiber (DF), an important component of food and an important contributor to human health. Based on their water solubility DF are classified as soluble dietary fiber (SDF) and insoluble dietary fiber (IDF). The physical and physiological properties of dietary fibers are of commercial and nutritional importance. Food processing is mostly based on heating. Heat treatment alters the properties of plant cell wall and modifies the composition and solubility of fibers. The experiments had in view the effect of dry heat treatment (in forced air oven, and microwave oven) on the bioavailability of carbohydrates. The research investigated the dynamics of released glucose (RG) from heat treated whole wheat and barley flour, during in vitro gastric and intestinal digestion. RG after 240 minutes of intestinal digestion revealed a higher digestibility of carbohydrates in wheat samples heated at 150°C for 10 and 15 minutes and in barley samples heated for 5 minutes. When the heating time of the barley samples was longer, the digestibility of carbohydrates decreased due to the formation of higher starch resistant to amylase action. Carbohydrates digestibility of wheat samples exposed to microwaves was lower compared with untreated samples. We observed a moderate increase in carbohydrate digestibility in barley samples after microwave exposure for 30 and 60 seconds. The digestibility decreased after 90 seconds of microwave exposure, due to accelerated Maillard reactions and increase in the proportion of resistant starch.