Effect of processing methods on the polyphenol and antioxidant activity of Zingiber officinale and Hedychium coronarium ginger species.

Abstract

Ginger has been used as a condiment and for the treatment of ailments such as coughs and Flus and recently for COVID 19. However, there are limited studies on the bioactive molecules and antioxidant activity of processed ginger. The objectives of this study were to determine the effect that processing and preparation methods have on the polyphenol and antioxidant activity of the two ginger varieties, Z. officinale and H. coronarium in Uganda. Ginger is utilized in various forms that include powder, oil or the fresh form. Preparation can be by boiling with hot water or adding the ginger to already boiled hot water for some minutes before consumption. Qualitative analysis of methanol extracts from the two species indicated presence of flavonoids, anthocyanins, phenolic acids and terpenoids in both Z. officinale and H. coronarium. Total flavonoid content was determined using the Aluminium chloride colorimetric method while the antioxidant activity was determined using the DPPH method and the results analyzed using excel software and mean. The samples that were boiled for 10 minutes had higher flavonoid content (61mg-73.5mg per 100ml) and antioxidant activity (29.9%-63.17%) compared to the ginger samples that were added in hot water. The dried powder samples also had more flavonoid content than fresh samples in the range of 57.5mg-73.5mg for Z. officinale and 48.5mg-65mg per 100ml of solvent in H. coronarium. In conclusion, the powdered ginger variety boiled for sometime may be the best source of flavonoids and antioxidant activity