Effect of processing on storage stability of millet flour: A review

Grains are an important source of many nutrients and minerals and because of the phytochemicals they contain, they help to maintain optimum health. Millets, a category of small-seeded grasses, widely cultivated around the world as cereal crops, are one of the oldest grains known to mankind. These are extremely nutritious and are proven to play a pivotal role in preventing and curing several health issues. However, millet flour has poor shelf life due to its high fat content as well as lipase activity which causes rapid development of rancidity and bitterness. Its keeping quality greatly depends on different pre-treatments applied and storage conditions. In the present review, the effect of various processes/treatments like mechanical processing, thermal treatments, fermentation, germination, addition of preservatives, and some novel techniques like gamma irradiation, microwave processing, infrared heating, high-pressure processing, pulsed light processing, and ultrasound processing on storage stability and other nutritional properties of different millet flour was reviewed. Their principle of action, advantages, and disadvantages have also been highlighted. All the technologies emphasized in this review have proven to augment the shelf life of millet flour. However, traditional processes are accompanied by changes in nutritional and functional properties, which necessitate the need for alternatives. Novel thermal and non-thermal techniques were found to cause both microbial decontamination and enzyme inactivation, although their application is limited as far as millet flour is concerned. These techniques are yet to be explored as millets are regaining popularity and have become part of the staple diet of many health-conscious consumers.