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The objective of this study was to investigate the effect of maturity at harvest and drying temperature on antioxidant activity and physiochemical properties in ginger (Zingiber officinale). The effects of two different maturities of harvest, 6 months and 9 months were examined. The contents of carbohydrate and fiber values increased in the 9 month sample. The 9-month sample was higher in total phenolic contents (8.64 mg Tannin/g), DPPH (85.33% inhibition), ABTS (10.57 mgTrolox/g) and FRAP (3.45 mgTrolox/g) than the younger 6-month sample. In essential oil constituents, the 9-month sample contained higher amounts of geranial (28.31%), neral (15.29%), β-phellandrene (13.32%), campene (7.77%) and α–zingiberene (6.17%) in comparison to the 6-month samples. 6-gingerol was found to be the most pungent bioactive compounds in fresh ginger. The 9-month sample contained the highest level of 6-gingerol (24.36±0.56 mg/g). Therefore, the ginger harvested at 9 months was selected the study of different drying temperatures. Drying times and temperatures to achieve moisture content below 10% were 510, 394 and 308 minutes at 40°C, 50°C and 60°C, respectively. Drying temperature at 60°C proved to be the best condition as it achieved the highest total phenolic (20.77 mg tannin/g), DPPH (91.35%), ABTS (55.94 mgTrolox/g) and FRAP (10.61 mgTrolox/g). Ginger contains 45 volatile compounds, the highest main compounds being α-zingiberene (18.28%), α-farnesene (10.73%) and geranial (12.42%). The content of 6-gingerol was also found to be the highest in the sample dried at 60°C (12.57±0.05 mg/g).
Keywords: Zingiber officinale, ginger, maturity, antioxidant, volatile compounds, drying
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