Characterization of biochemical indicators and metabolites linked with rancidity and browning of pearl millet flour during storage

Pearl millet is a nutrient-rich and drought tolerant crop with high production potential under changing climatic conditions. Despite the nutritional and climatic advantage, the rancidity and browning of pearl millet flour during storage is the major limitation to consumer acceptance. In the present study, four diverse pearl millet genotypes (Dhanshakti, MPMH 17, WGI-100 and Pusa purple) were analyzed for total lipid content, primary and secondary oxidation products, total phenolic content, C-glycosyl flavone (C-GF’s) content and their related enzyme activities. It was observed that the lipid content in pearl millet vary between 5 and 7.2% with higher composition of linoleic acid (34.3 to 42.5%). The activity of the lipoxygenase enzyme leads to the formation of primary (hydroperoxides) and secondary oxidation products (aldehydes and ketones), and is therefore responsible for the development of rancidity. A positive correlation was observed between polyphenol oxidase and peroxidase activity with total phenolic content (TPC), involved in flour browning. In addition, a higher C-GF’s content was associated with a darker color and off odor of the flour. Therefore, the higher content of linoleic acid, C-GF’s, TPC, and enzyme activities make the pearl millet flour unsuitable for human consumption after 10 days of storage. This study provides insight into the selection of pearl millet traits for the development of new variety with improved shelf life and better health benefits.