Effect of Thermal Processing of Dietary Fibers on the Bioavailability of Proteins from Wheat and Barley Flour

Changes in particle size, solubility and chemical structure of different fiber components can cause changes in the bioavailability of some nutrients. Numerous studies have shown a reduction in apparent digestion of proteins in the gastrointestinal tract caused by direct and indirect processes. Endogenous nitrogen losses are due to increased secretion of digestive juices and increased desquamation in the presence of dietary fiber. Food fibers reduce digestion of food and endogenous proteins. Food processing can improve the bioavailability of proteins. Reduction of thermally latent antinutritional factors, such as trypsin inhibitors, phytates and polyphenols, as well as partial denaturation of proteins by heat treatment contributes to their digestibility. Protein quality in processed foods decreases primarily due to reduced lysine bioavailability. Experiments revealed an increase in protein digestibility (PD) in whole wheat flour heated samples in a forced air oven at 150°C over 0-10 minutes: 31.8% at time 0, 43.73% at 5 minutes and 48.43% at 10 minutes of heating. When heating for 15 minutes, digestibility decreased to near the unprocessed sample value (33.8%). PD in wheat samples exposed to microwave for 30, 60 and 90 seconds increased throughout the entire time period, with a maximum of 45.06% when exposed for 90 seconds. PD increased moderately in whole barley flour samples heated at 150°C, from 27.46% for the unprocessed sample to a maximum of 33.47% for the 5 minutes heated sample. PD in barley samples exposed to microwave was higher than in the unprocessed sample, with a maximum of 36.34% for 30 seconds exposure.