Optimization of Submerged Fermentation Parameters for Instant Dark Tea Production by E urotium cristatum

Abstract

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.

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

“…A, C). A smaller LSR again resulted in exponential growth of the microorganism but not enough enzyme production and secretion into the broth, whereas a higher LSR led to nutrient shortfalls that limited metabolite production …”

“…However, the amount of low‐grade green tea and crop waste (trimmed leaves, tea dust and mature leaves) produced is even greater. These low‐grade green tea and waste products can be used as inexpensive raw materials for the production of fermented dark tea . Mature tea leaves can be fermented into dark tea after inoculation of microorganisms and culture via solid‐state fermentation .…”

“…These low-grade green tea and waste products can be used as inexpensive raw materials for the production of fermented dark tea. 11 Mature tea leaves can be fermented into dark tea after inoculation of microorganisms and culture via solid-state fermentation. 12, 13 There is increasing interest in attmepting to inoculate microorganisms into green tea matrixes and using SF to prepare dark tea.…”

“…16,17 Instant dark teas are made by drying the infusions of dark tea that had been processed via solid-state fermentation. Lu et al 11 reported a new method of producing instant dark tea (Fu-brick) from green tea leaves processed by the fungus Eurotium cristatum using SF.…”

Amount of Eurotium sp. in Chinese Liupao tea and its relationship with tea quality

“…are associated with the physical and chemical properties of dark tea and its quality. Research has shown that using raw tea to process instant dark tea products with Eurotium cristatum results in good taste, aroma and colour (Lu et al ). In the existing standards for dark tea, the quality of dark tea is judged through sensory evaluation.…”