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Processing Effects on Phytochemical Content and Antioxidative Potential of Ginger Zingiber officale

Ginger, Zingiber officinale Roscoe, is widely cultivated in tropical and subtropical countries where it is mainly used as food spice and for medicinal purposes. In the foods and beverages industry, ginger is used as an additive for its aroma and pungency. The chemical composition of fresh ginger varies with varieties or cultivar, the location for which the ginger is cultivated [3], extraction methods and the processing methods.

Ginger is rich in antioxidants and phytochemicals with anti-inflammatory, antimicrobial and anticancer properties. However, there are limited studies on the antioxidant and scavenging power of processed ginger. The objectives of this study were to determine the effects that processing has on the total phenolic and flavanoid content of ginger and its antioxidant potential using 1,1-Diphenyl-2-picrylhydrazyl (DPPH), Radical-Scavenging Activity and Ferric Reducing Antioxidant Power (FRAP). Fresh ginger (FG) was used as a control with oven drying (OD) sun drying (SD) and freeze drying (FD) as processing methods.

This study observed that selected processing methods resulted in significant (P < 0.05) differences in total phenol and flavonoid contents, as well as the free radical scavenging activity and ferric reducing antioxidant power. The highest total phenolic content was observed in freeze dried ginger (FD) (1021.15 mg GAE/100g) and the lowest was observed in fresh ginger (FG) extracts (514.02 mg GAE/100g). At the lowest concentration (12.5 mg/ml), inhibition of DPPH by FG was 9.25 which was the lowest of all ginger extracts. FD and SD ginger exhibited the greatest effect in DPPH inhibition at the lowest concentration (12.5 mg/ml). The highest FRAP was observed in SD (35.28 ± 0.69 mmol Fe [II]/mg) and the lowest observed in OD extracts (27.78 ± 0.63 mmol Fe [II]/mg).

According to the results in this experiment, total phenols in the processed ginger were higher compared to the unprocessed ginger. Freeze dried ginger had the highest phenolic and flavonoids compared to other processed ginger (OD and SD). Similar results was seen where FD had showed higher potency in ferric reducing antioxidant power and percentage DPPH inhibition. However, at concentration of 50 mg/ml processed and fresh ginger had the same DPPH inhibition percentage. At higher concentration (100 mg/ml), FG was a better free radical scavenger compared to the processed ginger.

Article by R. Offei-Oknye, et al, from USA.

Full access: http://t.cn/EtfeFv0
Image by Stephen Buchan, from Flickr-cc.

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