Drying of ginger slices—Evaluation of quality attributes, energy consumption, and kinetics study

摘要

Ginger slices were dried with Freeze drier (FD), relative humidity convective drier (RHCD), infrared drier (IR), and microwave drier (MD) at a temperature of 60 degrees C. The influence of the drying techniques on total phenolic content (TPC), total flavonoid content (TFC), antioxidant activities, ABTS (2,2-azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid), DPPH (1,1-diphenyl-2-picrylhydrazyl), FRAP (Ferric reducing antioxidant power capacity), and CUPRAC (Cupric ion reducing capacity), rehydration ratio (RR), color, enzyme inactivation (polyphenol oxidase, PPO and peroxidase, POD), energy consumption rate (ECR), microstructure, volatile compounds (aroma profile), and drying kinetics were assessed. The results showed that FD-ginger slices retained the highest antioxidant properties, ABTS (51.88 mgTE/g db), CUPRAC (95.51 mgTE/g db), DPPH (132.95 mgTE/g db), and FRAP (95.32 mgTE/g db), TPC (118.70 mg GAE/g db) and TFC (98.94 mg CE/g db), preserved microstructure and higher volatile compounds compared RHCD, IR, and MD. The RHCD-ginger slices attained the highest RR (3.6), lowest ECR (7.88 kWh/kg), lowest PPO (17%), and POD (22%) residual activity with preserved color properties than FD, IR, and MD. RHCD also enhanced the drying kinetics and lessened the drying time compared to FD, IR, and MD. Page model best fitted the experimental results of drying kinetics (R-2 > 0.99). Practical application One of the world's most consumed and used spices is ginger and due to its high moisture content, drying is normally used for its preservation. Therefore, to attain dried ginger of better quality, an effective, safe, efficient drier that can preserve product quality and reduce processing time, as well as energy consumption, is required for commercial purposes as a poor selection can have an adverse effect on the product quality. The outcome of the current investigation will offer a better understanding of various drying techniques and also provide more information on the selection of the best drying technique for drying ginger.