Effect of different drying methods on drying kinetics, modeling, energy‐economic, texture profile, color, and antioxidant of lotus rhizomes ( Nelumbo nucifera )

Abstract

The study was conducted on lotus rhizomes to find the kinetics of drying and ultrasound-assisted extraction process of antioxidant, energy-economic, quality parameters, and phytochemicals, under different drying processes. Midlli et al. model was found the best-fitted drying model with a low SSerror (0.0145–0.0088), RMSE (0.02 to 0.005), and highest R2 (0.999 to 0.992) value. The energy consumption cost (1518.33 Rs) is high in tray dryers and low in microwave dryers (28.68 Rs). The vacuum-dried lotus rhizomes had a high content of total phenolics of 78.364 mg/g, flavonoids of 10.819 mg/g (dm) content, DPPH of 74.621 μmol/g, ABTS of 104.36 μmol/g, and FRAP of 108.312 μmol/g. Low hardness (12.642 N), resilience (0.468), and high whiteness (61.158) were observed in freeze-dried rhizomes. Microwave and vacuum drying were showing a short time drying process with better energy economy as well as higher antioxidant content, but quality parameters are best for a freeze-drying product. Novelty impact statement The use of waste parts of plants as a source of functional food requires intensive study. Lotus rhizomes are edible and can have a vast range of applications in the food and pharmaceutical industries. The novelty of this study is that it explores different drying methods of lotus rhizomes and makes a comparative analysis of these methods based on their costs and effects. In addition, it also discusses the extraction of both free and bound phenolic compounds. The extraction of bound phenolic compounds increases the antioxidant content of the samples. Physicochemical properties (texture and color) of lotus rhizomes are also discussed in detail.