Hui Ni, Feng Chen, Ze Dong Jiang, Ming Ying Cai, Yuan Fan Yang,An Feng Xiao, Hui Nong Cai
A tannase that was prepared from Aspergillus niger by a solid-state fermentation on tea byproducts was investigated to transform the catechins in tea infusion. The tannase could effectively hydrolyze epigallocatechin gallate (EGCG), gallocatechin gallate (GCG) and epicatechin gallate (ECG) of tea infusion, which showed pH values ranged from 4.8 to 5.3 during the tannase treatment. The enzyme was active and stable within pH 3.0–7.0 and 4–60 °C. The enzyme had Kms of 14.89 mmol/L, 16.13 mmol/L and 3.57 mmol/L for EGCG, GCG and ECG, respectively in pure solutions. However, the hydrolysis of individual EGCG, GCG and ECG in the tea infusion showed different kinetic parameters from those in pure solutions. The transformation of EGCG was the dominant reaction in tea infusion. After the tannase treatment, tea infusion was detected to have significant increases in the clarity and activities for scavenging 2, 2′-azino-bis (3-ethylbenzothiazoline-6-sulfonate) (ABTS)
Gallic acid (GA), gallocatechin (GC), epigallocatechin (EGC),epigallocatechin gallate (EGCG), epicatechin (EC), gallocatechin gallate (GCG), epicatechingallate (ECG) and digallate (DG) were bought from Chengdu Biopurify Phytochemicals Ltd. ..