Effects Of Enzyme Treatment On The Quality Of Green Tea Extract

Steamed green tea was taken to study the effect of tannase and proteinase on the taste and lightness of green tea extract. The suitable parameter of tannase applying to green tea extract was discussed;the difference of enzymolysis effects by different proteinase (papain, bromelain, neutral proteinase, proteinase M and umamizyme) was analyzed;a suitable proteinase for hydrolyzing tea protein and its optimal technologic parameter were selected. A preliminary extracting method of tea ptotein was discussed. The results were as follows:1. The composition of catachin changed greatly when green tea extract was treated by tannase. The content of EGCG and ECG decreased with the increase of tannase concentration and the enzymolysis time;whereas the content of ECG , EC and GA rised. Tannase separated gallic acid from estered catachin, preventing caffein's combination with it, which results the improvement of the lightness and the decline of pH.2. The taste of tea extract became less bitter when the much bitterer EGCG and ECG was hydrolyzed by tannase. Adding 0.05%(w/v)tannase to green tea infusion which was extracted for 10 minutes at 90℃ with ratio of tea to water 1:50 and then mixing for 30 minutes could create bitterless good taste and clear tea drinks.3. There was a big difference of enzymolysis effects on tea protein among proteinases derived from different materials. Within 0.01%~0.05% (w/v) proteinase concentration, papain, bromelain, neutral proteinase, proteinase M and umamizyme could improve the amino acids separately by 10.96%~26.64%,10.8%~35.05%, 15.35% -32.24%, 19.73%~56.50% and 21.08%~66.53% after processed for 1,5h. The hydrolyzing effects of proteinase produced by microorganism on insoluble tea protein was better than that of papain and bromelain which were derived from plant, especially umamizyme. Papain had high haze-activity to combine with teapolyphenols and had a slight effect on soluble protein in tea infusion. Umamizyme showed high ability to hydrolyze soluble protein in tea insusion and no haze-activity within the designed concentration.4. The optimized application parameter was obtained through single factor and orthogonal test: ratio of tea to water 1:50, extracting at 90 °C for lOmin;enzyme concentration 0.05%(w/v), temperature 50°C for 5h. The content of amino acides treated with umamizyme was twice as control. Tea polyphenols and caffeine increased by 3.23% and 10.36%. Ratio of tea polyphenols to amino acides decreased significantly compared with control so that the tea extract tasted fresh, pure and mild.5. Composition of protein in finished tea was analyzed quantificationally by the method of successive extraction using different solvent (water,2 % NaCl, 70 % ethanol, 0.2%NaOH). The extracting sequence, number of extracting times, total extracting time and yield were as follows: albumin,5 times, HOmin, 1.04%;globulin, 4 times,90 min, 0.81%;prolamine, 3 times, 70 min,0.26%;glutelin, 6 times,130 min;4.23 % 0 The total yield extracted was 6.34%,which was 24.93% of the tea protein. There was still a large quantity of protein can not be extracted by the above mentioned solvent.