The results of the present study show that careful management of culture conditions can produce a dark tea high in theabrownins. Furthermore, high-theabrownins instant dark tea could serve as a source of bioactive products and be used in functional foods as an ingredient imparting antioxidant properties and the ability to inhibit pancreatic lipase and α-glucosidase. © 2017 Society of Chemical Industry.

In this study, green tea extracts was used as material to produce a kind of instant dark tea by Eurotium cristatum via submerged fermentation. Response surface methodology was implemented with desirability function approach for optimization of fermentation parameters of instant dark tea product. The effects of inoculum size (6-12%), liquid-solid ratio (10-20 mL/g) and fermentation time (132-204 h) on mycelia dry weight, redness and turbidity of fermented tea infusion were investigated. The optimum condition was as follows: inoculum size of 9.35%, liquid-solid ratio of 14.50 mL/g and fermentation time of 169.00 h. At this optimum point, mycelia dry weight, redness and turbidity of fermented tea infusion was 0.579 g/100 mL, 41.35 and 76.96 nephelometric turbidity units, respectively. Inoculated E. cristatum by submerged fermentation changed the content of main bioactive compounds in tea extracts. The tea extracts formed the unique dark tea taste, aroma and color. PRACTICAL APPLICATIONUsing waste green tea leaves as raw materials, we developed a new strategy based on submerged fermentation to process instant dark tea product by Eurotium cristatum. A dark tea infusion was achieved with good taste, aroma and color at very short time and in mild manufacturing conditions compared with traditional solid state fermentation technology. Fermentation of tea extracts by E. cristatum could combine the function of tea and E. cristatum and develop a new product with more health benefits. The submerged fermentation method increases the process efficiency to achieve similar product quality, which will be a breakthrough for instant dark tea industry.

IDT exerted better anti-obesity effects than PET in HFD-fed mice, as evidenced by reduced BW and regulated obesity-related factors. IDT also showed inhibitory effect on pancreatic lipase in vitro.

In this study, submerged fermentation mode for preparing instant dark tea production was developed through utilizing industrial low grade green tea as raw material and as fermentation microbe starter. The fermentation parameters (inoculum size, liquid-solid ratio and rotation speed) were optimized by using Box-Behnken design and response surface methodology (RSM) with desirability function, the theabrownins content, redness and turbidity value as responses. The optimal conditions were set as follow: inoculum size of 5.3% (), liquid-solid ratio of 27.78 mL/g, and rotation speed of 182 r/min. The optimized conditions model showed a good correlation between the predicted and experimental values. Further, the optimum product of instant dark was achieved in a 3-L laboratory fermenter, and the main parameters of product were theabrownins content of 140.92 g/kg and redness value of 40.78 and turbidity of 90.98 NTU. Sensory evaluation showed that the instant dark tea infusion approached mellow mouthfeel, an aroma of mint and a good overall acceptance.