Abstract
Zingiber officinale (Zingiberaceae) is a common spice and a medicine widely cultivated in tropical and subtropical climate around the globe, which contains both precious polyphenols and terpenes in its extracts. The ubiquity of ginger in a variety of foods encouraged the authors to assess the influence of thermal processing and digestion of the plant material on its antioxidant capacity. The obtained results of DPPH assay showed marked differences in the antioxidant potential of the processed samples, in comparison with fresh ginger rhizomes. Autoclave and microwave heating procedures were found to evoke the mildest decomposition of the antioxidants and increase the antioxidant capacity of the plant (from IC50 of 210±10 for a fresh rhizome to ca 160±16 μg/mL for the former, and to 150±18 for the latter technique), whereas frying and boiling for different durations significantly deteriorated the antiradical potential up to IC50 = 940±36 μg/mL. Mouth and stomach digestion decreased the antioxidant potential of the extracts even to ca. 1000±47 μg/mL. A protective role of saliva towards the antioxidant compounds against hydrochloric acid and pepsin activities has been proven. A marked deterioration in antioxidant capacity in digested rhizomes may shed new light on the actual absorption of consumed polyphenols with food products.