Roasting-Assisted Extrusion Efficiently Inhibits Lipolytic Enzymes and Degrades Antinutritional Factors in Pearl Millet (Pennisetum glaucum).

Abstract

The study investigated the inhibition of lipolytic enzymes and reduction of antinutritional factors in pearl millet flour through roasting-assisted extrusion. Pearl millet was roasted at three different temperatures (120, 140, and 160°C) and time intervals (2.5, 5, and 10 min) and then extruded under previously optimized conditions of 140°C, screw speed of 150 rpm, and moisture content of 30%. The optimized roasting conditions of 140°C for 10 min showed reduction below detectable limits of phytic acid and 97.11% reduction in tannins while simultaneously inhibiting lipase and lipoxygenase by 90.30% and 94.06%, respectively. The optimally roasted flour so obtained was evaluated for thermal properties, structural properties, morphology, and crystallinity. Roasting-assisted extrusion not only significantly inhibited lipolytic enzymes but also improved physicochemical properties of the flour like color (9.45), expansion index (1.55), bulk density (1.41 g/cm3) as well as functional properties such as water absorption index (4.13 g/g), water solubility (4.7 g/g), foaming capacity (11%) and stability (12.22%), emulsion capacity (4.67%) and stability (29.31%). These findings suggest optimized roasting-assisted extrusion to be an effective approach for enhancing the functional quality and extending the shelf life of pearl millet flour, thereby increasing its potential application in food product development. PRACTICAL APPLICATIONS: The lipolytic enzymes, mainly lipase and lipoxygenase found in pearl millet, affect its shelf life by producing free fatty acids that contribute to off-flavors and bitter taste during storage. Moreover, anti-nutritional factors such as trypsin inhibitors, condensed tannins, and phytic acid are detrimental to digestibility. Although thermal processing like extrusion is a commercially viable approach to reduce these factors to some extent, complete inhibition of these factors remains a constraint at b