High‐theabrownins instant dark tea product by Aspergillus niger via submerged fermentation: α‐glucosidase and pancreatic lipase inhibition and antioxidant activity

Abstract BACKGROUND Theabrownins ( TB ) are bioactive components that are usually extracted from Chinese dark tea, in which they are present at low concentrations. The present study aimed to produce an instant dark tea high in theabrownins via submerged fermentation by the fungus Aspergillus niger . Three fermentation parameters that affect theabrownins content (i.e. inoculum size, liquid–solid ratio and rotation speed) were optimized using response surface methodology. RESULT Optimum fermentation conditions were modeled to be an inoculum of 5.40% (v/v), a liquid–solid ratio of 27.45 mL g −1 and a rotation speed of 184 rpm and were predicted to yield 292.99 g kg −1 TB . Under these experimentally conditions, the TB content of the instant dark tea was 291.93 g kg −1 . The antioxidant capacity and α ‐glucosidase and pancreatic lipase inhibitory activities of the high‐ TB instant black tea were higher than four other typical instant dark tea products. CONCLUSION 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