Study on the effect of stepwise decreasing microwave power drying (SDMPD) of moth bean sprouts on its quality

Abstract

AbstractVigna aconitifolia (Jacq.), locally known as moth bean, is a drought‐resistant pulse crop and grown in arid and semi‐arid areas of India. Green pods and grains, in cooked or sprouted form, are a mostly consumable part of the plant as they are rich in protein. Sprouting increases the bioavailability of protein by 30%, but bacterial contamination is high in sprouts due to its high initial moisture content that creates a problem for its storage. Hence, to rectify the said problem, drying the sprouts up to storable moisture level can be the best solution. The microwave drying was investigated for drying of sprouted moth beans. The microwave drying of sprouted moth beans using single microwave power was not suitable for drying, as the burning of the product takes place before reaching desired moisture content while dried at a microwave power of 900, 720, 540, and 360 W. During the drying at a microwave power of 180 W, it took about an hour for drying. However, during this drying, by the time it reaches moisture content at around 57.89 kg per 100 kg dm, the product shows browning. Therefore, a new technique was employed for drying sprouted moth beans, that is, Stepwise Decreasing Microwave Power Drying (SDMPD). The sprouts were dried at each microwave power level, in decreasing order for a particular time at each respective microwave power, to reduce the browning effect thus protecting the product from burning. The sprouted moth beans were dried in 19 min using SDMPD. The rehydration ratio was found to be 1.96. The moisture content of resultant dried sprouted moth beans was found to be 4.95 kg per 100 kg dm with a minimum color change (∆e*) of 10.46, which was found to be reduced up to 6.84 after rehydration, indicating the improved color.