| Abstract |
The postharvest loss of onions during storage is extremely significant, and it has become a global challenge. In this study, the impact of drying conditions (temperature and time) on the physicochemical, antioxidant, and functional properties of red and yellow onion powder was evaluated. Fresh onions of two varieties (red and yellow) were sliced, dried using a hot air oven drier at 40, 50, and 60 °C for 12, 24, and 36 h, and ground into powder. The obtained powders were analyzed for their physicochemical and functional properties, including total soluble solids, pH, titratable acidity, ascorbic acid, and color. The antioxidant properties were determined using total phenolic content (TPC), total flavonoid content (TFC), and DPPH scavenging activity assays. Additionally, the hydration properties such as bulk density, shrinkage ratio, water activity, water holding capacity and moisture content of the powders were evaluated. Finally, to assess the economic feasibility of different drying conditions, the energy requirements and costs were also evaluated. Both drying conditions and variety had significant effects on evaluated parameters. The maximum TPC, TFC, and antioxidant activity for red onion powder was found at drying condition of 70 °C for 36 h, with values of 44.36 mg GAE/g dry matter, 12.75 mg QE/g dry matter, and 67.35%. However, in terms of the best compromise between onion powder quality and energy consumption, drying at 60 °C for a drying time of 30 h appears to be the optimal condition. This investigation might help to address the growing demand for good quality, nutritional, and healthy dried onion powder among consumers and the food industry.
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