Abstract
Tannase is widely used in tea beverage processing because of its ability to catalyze the hydrolysis of hydrolysable tannins or gallic acid esters and effectively improve the quality of tea extracts through enzymatic extraction. A new thermophilic tannase was cloned from Aspergillus niger FJ0118 and characterized. The tannase exhibited an optimal reaction temperature of 80 °C and retained 89.6% of the initial activity after incubation at 60 °C for 2 h. The enzymatic extraction of green tea at high temperature (70 °C) for a short time (40 min) was devised on the basis of the superior thermal stability of tannase. The enzymatic reaction significantly increased the total polyphenol content of green tea extract from 137 g·kg−1 to 291 g·kg−1. The enzymatic reaction effectively degraded the ester catechins into non-ester catechins compared with the water extraction method. Results suggested that the thermally stable tannase exhibited potential applications in the enzymatic extraction of green tea beverage.
Highlights
Green tea is receiving considerable interest as a distinctively flavored beverage because of its antioxidant, anticarcinogenic, and antimutagenic properties [1,2] and is consumed in most Asian countries, especially in China and Japan
The tannase gene was amplified by polymerase chain reaction (PCR) from A. niger FJ0118 genome in accordance with the sequence information of tannase (XM_001401772)
Conclusions rAntan1, a novel thermostable tannase, was cloned from A. niger FJ0118, and its enzymatic properties were characterized. This tannase exhibited a t1/2 of 5.4 h and 30 min at 60 ◦ C and 70 ◦ C, respectively, suggesting its remarkable thermal stability
Summary
Green tea is receiving considerable interest as a distinctively flavored beverage because of its antioxidant, anticarcinogenic, and antimutagenic properties [1,2] and is consumed in most Asian countries, especially in China and Japan. Green tea contains higher amounts of polyphenols than oolong and black teas [3]. About 75–80% of tea polyphenols are found in 30% of the soluble ingredients of tea [2,4], and tea extract products differ because of extraction methods and conditions. Attempts have been made to improve the extractability of polyphenols and the clarity of tea by using pectinase and tannase for enzymatic extraction. Treatment with tannase alone can maximally improve the quality of black tea because of the high amounts of polyphenols in extracted solids [5]. Various cell wall-digesting enzymes have been used during green tea extraction to improve its quality in terms of aroma, flavor, taste, cold water solubility, and extraction yield [6]. Enzymatic extraction can only be performed at low temperatures (30–40 ◦ C) at prolonged treatment
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