Influence of drying and roasting temperatures and humidity on the content of polyphenols and flavonoids, antioxidant activity, and quality of ginger tea

Ginger tea is a popular drink in Asian countries and has many health benefits. However, its production process is complicated as it requires the product to retain biologically active compounds and sensory criteria. The purpose of the research was to determine the heat treatment regime in the drying stage, the moisture content after drying, the roasting temperature, and the appropriate product moisture content to preserve the polyphenol content, antioxidant activity, flavonoid content, and quality of ginger tea products. The research results showed that when ginger was dried at 60 % moisture content, then roasted at 140 degrees C to 8 % product moisture content, good results were achieved in maintaining the polyphenol content (9.85 +/- 0.18 mg GAE/g dw), antioxidant activity (27.02 +/- 0.17 mu mol TE/g dw), flavonoid content (25.51 +/- 0.18 mg QE/100 g dw), water activity (0.48 +/- 0.01) and the quality of ginger tea. The optimal experimental conditions obtained can be easily applied to the ginger tea production process on a larger scale in the future.