Abstract:
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 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 (R2 > 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.
