The effects of type and time of thermal processing on ginger (Zingiber officinale Roscoe) rhizome antioxidant compounds and its quality

The type of thermal processing either roasting or boiling gave an effect on the antioxidant quality of ginger (Zingiber officinale Ross) rhizome extracts.It was found that 6 minutes of either roasting or boiling gave the best effect of its antioxidant activity. This condition was shown by the free radical activity of extract of roasted samples: 84.21 ± 0.18% and 83.59 ± 0.52% for the boiled one. The total phenolic content of roasted samples was 29.94 ± 0.15 mg/g and for boiled samples was 30.87 ± 0.26%, whilst its gingerol content of roasted samples was 19.84 ± 0.19 mg/g and 20.78 ± 0.14 mg/g for boiled samples. The results of GC-MS analysis showed that methyl ester (0,17%), 9-octadecenoic (0.32%), nortrachelogenin (0.30%) were the compounds of antioxidant agent. It is interesting to note that zingerone compound total area increased from 5.68% to 6.32%. The FTIR analysis showed that C-O-C antisym strecht vibration at 1270.04 cm^-¹ wave was found for methyl ester compound and OH stretch H-bonded at 2870.84 and 2982.71 cm^-¹ wave were found for 9-octadecenoic compound.