Green extraction of dietary fiber concentrate from pearl millet bran and evaluation of its microstructural and functional properties

Pearl millet bran is an underutilized by-product of millet with great potential in the food processing industries due to its dietary profile. The dietary fiber extraction from pearl millet bran could be valued approach for utilization of waste with commercial feasibility at the industrial scale. To overcome the disadvantages of conventional techniques, green techniques like ultrasonication might be effective in terms of shorter duration of time and less consumption of solvent, increasing the extraction yield of dietary fiber. In present study, comparative analysis of different green techniques (enzyme-assisted extraction, ultrasound-assisted extraction, microwave-assisted extraction, ultrasound-assisted enzyme extraction, and microwave-assisted enzyme extraction) for extraction of dietary fiber concentrate from pearl millet bran was investigated and microstructural and functional properties using ultrasound-assisted enzymatic extraction were studied. The ultrasound treatment combined with enzymatic extraction at amplitude (35%), temperature (50 degrees C) and liquid to solid ratio (40:1) after treatment time (10 min) resulted the highest extraction yield (78.8 %, w/w) of total dietary fiber obtained from pearl millet bran. SEM images showed the significant effect of ultrasound-assisted enzymatic treatment on extracted dietary fiber. The dietary fiber from the pearl millet bran possesses good water holding capacity (4.04 g/g and 3.04 g/g) and oil holding capacity (5.33 g/g and 2.42 g/g). The results indicated that pearl millet bran contains a substantial amount of dietary fiber that could be utilized for the preparation of functional food products.