Abstract:The effects of grape pomace on the flavor profile of Pu-erh tea fermented by Aspergillus tubingensis in liquid-state fermentation were investigated. A blended system of sun-dried green tea leaves and instant grape pomace powder was applied, fermentation parameters were optimized through single-factor experiments and the response surface methodology. The dynamic changes of key physicochemical indices including pH, color difference, total carbohydrates, proteins, total polyphenols, and theabrownins during optimal fermentation conditions were systematically examined. The optimal parameters were determined as follows: 0.03 g·g-1 instant grape pomace powder, solid-to-liquid ratio of 1 g to 30 mL, fermentation duration of 144 h, and spore inoculation concentration of 1×10? CFU/mL. Under optimal conditions, after 144 h fermentation: The tea infusion pH increased from 4.66 to 5.73; Theabrownin content rose from 1.89 g·L?1 to 5.40 g·L?1, and protein content increased from 0.06 g·L?1 to 0.10 g·L?1, both showing an upward trend. In contrast, total polyphenol content decreased from 6.10 g·L?1 to 2.76 g·L?1, and total carbohydrate content declined from 1.78 g·L?1 to 0.96 g·L?1, both showing a downward trend. The L* value of the tea infusion declined, while the a* and b* values increased, resulting in a darker, redder hue. These findings offer a theoretical basis for the efficient development of flavor-enhanced, grape pomace-blended Pu-erh tea using liquid-state fermentation.
