Inactivation of enzyme activity in pearl millet flour using atmospheric cold plasma and steam treatments: Kinetics and impact on its antinutritional and compositional properties

Pearl millet flour (PMF) has a well-balanced protein content with fat, gluten-free, and low glycemic index, making it a substitute diet for diabetes and celiac disease. However, PMF spoils quickly due to enzymatic rancidity, thus limiting its shelf life, and anti-nutrient factors, such as tannins and phytic acid, also limit its usage. This study aims to inactivate quality deteriorating enzymes, viz. lipase, lipoxygenase, polyphenol oxidase (PPO), and peroxidase (POD) by using cold plasma (5–25 kV; 2–10 min). Cold plasma treatment at 25 kV/8 min, led to 95.9 kat/hkat, 99.2 kat/hkat, 94.8 kat/hkat, and 100 kat/hkat inactivation of lipase, lipoxygenase, peroxidase, and PPO activity, respectively. Cold plasma-induced enzyme inactivation followed n th-order kinetics, such as 1.55, 1.35, 1.15, and 1.05 for lipase, peroxidase, lipoxygenase, and PPO, respectively. Steam treatment at 100 °C/4 min inactivated lipase, lipoxygenase, peroxidase, and PPO by 97.9, 98.8, 97.6, and 100 kat/hkat, respectively. The PMF showed 24.0 g/hg and 19.5 g/hg reduction in phytic acid and 77.7 g/hg and 16.9 g/hg reduction of tannin content at 25 kV/8 min of cold plasma treatment and steam treatment at 100 °C/5 min, respectively. Color, particle size, and proximate composition remained unaffected; a reduction in secondary oxidation products and minor modifications in the secondary structure of the protein were observed in both treatments. Additionally, cold plasma treatment enhanced the functional properties of the PMF. Cold plasma as an alternative to thermal treatment to inactivate enzymes and antinutrients while preserving compositional attributes of PMF. • Cold plasma (25 kV/8 min) reduced >94 % lipase & POD activity in pearl millet flour. • Steam treatment (100 °C/4 min) led to >94 % lipase and POD inactivation in the flour. • Enzyme inactivation followed n th order kinetics ( n > 1) during cold plasma exposure. • Cold plasma exposure reduced 24 % phytates and 77 % tannins in the flour. • Neither treatment impacted the color, particle size, or composition of the flour.