Hydrothermal infra-red (HT-IR): the most effective technology for enhancing the shelf-life of pearl millet flour without compromising with the nutrient density and flour quality

Abstract

Pearl millet, considered as nutri-cereal, has better nutritional composition and quality, as compared to other cereals. Though, it is less popular due to low shelf-life of the flour. Here, we characterize the rancid behavior of three diverse genotypes of pearl millet—WGI-100 (White), Purple, and fortified Dhanshakti (complete grains and decorticated) using different quality determinants linked with shelf-life. Starch, amylose, resistant and non-resistant starch content was observed maximum in Dhanshakti, whereas amylopectin was observed maximum in cv. purple. The activities of carbohydrate degrading enzyme (α-/β-Amylases) were observed maximum on 6th days after milling (DAM) in cv. Dhanshakti. Phytic acid and micronutrients (Fe and Zn) were observed more stabilized in flour during storage. We observed gradual decrease in the storage proteins and total lipid with increase in DAM due to oxidation. Evaluation of physicochemical treatments [salt (1%), lime (1%, grains soaked for overnight), hydrothermal-infrared (HT-IR, grains steamed for 5 min followed by quick drying using IR bulbs with wavelength of 0.7–2.0 µm), kilning (live steam, quick heating), near infra-red (NIR, short wave for 5 min) and air tight aluminum pouches (50 µm thickness)] showed HT-IR to be most effective treatment in arresting the lipid hydrolysis by denaturating/aggregating the rancidity causing enzymes (lipase and lipoxygenase). We observed Dhanshakti to be better in flour quality and nutrient density, as compared to other cvs. HT-IR was observed to be most cost-effective and promising technology in enhancing the shelf-life of pearl millet flour.