| Due to the effects of processing conditions and environmental factors, The tea can easily damp moldy during the processing and storage, affecting the quality of tea. Irradiation technology as a novel food sterilization method can not only ensure the health and safety of tea, but also leaching out contains ingredients sufficient and improve product quality.In this paper, three kinds dark tea (Fuzhuan tea, Xiangjian tea and Qianliang tea) were irradiated of different doses by 60Co-y irradiation treatmen, and studied the effect of irradiation on the contents of dry matte, tea extract, tea polyphenol, catechin, total free amino acid, theanine, caffeine, theophylline, theobromine and microbial. The main results were as follows:1. Effect of physicochemical and microbiological indexes of Fuzhuan tea by irradiation treatment. In the range of 0～10kGy irradiation dose, The the Fuzhuan tea dry matter content, water extracts, caffeine and theophylline had no significant effects by irradiation; Total free amino acids showed an increasing trend when the radiation dose in the range of 0～2kGy,2kGy reaching maximum 3.01%, increased by 22.86% compared with non-irradiated sample; The theanine increased within 0-4kGy,4kGy reached the maximum 0.027%, increased by 17.39%; Tea polyphenols reduced decreased to in varying different degrees after irradiation, when the dose of 6kGy its reached the minimum value 8.92%,15.92% lower than non-irradiated sample. The total catechins of Fuzhuan tea was 3.937%, the content of EGCG up to 1.736%, accounting for 44.09% of total Fuzhuan tea catechins; content of DL-C was as low as 0.056%, only accounting for 1.42% of total catechins. When the irradiation dose was 2kGy, total catechins reached to the maximum 4.082%, increased by 3.68% compared with the control group. The The contents of theobromine varied different at different irradiation dose,6kGy reached the lowest value 0.016%, decreased by 20.00%. TheThe total bacterias and mould-yeasts were 7.6X 102CFU/gand 2.1×105CFU/g, respectivelymainly microorganisms of Fuzhuan tea was mold, Escherichia coli was negative; 4kGy irradiation dose treatment, the The total bacterias and mould-yeasts reduced to 1.7×101CFU/gand 5.8×102CFU/g, respectively,97.76% of bacteria and 99.7% of the mould-yeasts of Fuzhuan tea were killed.2. Effect of physicochemical and microbiological indexes of Xiangjian tea by irradiation treatment. In the range of 0-1 OkGy irradiation dose, the Xiangjian tea dry matter content, water extracts, caffeine and theophylline had no significant effects by irradiation; Total free amino acids increased significantly when the radiation dose in the range of 0-4kGy, and then reduced,8kGy reaching maximum 4.78%, increased by 6.46% compared with non-irradiated sample; The theanine increased within 0-2kGy,2kGy reached the maximum 0.258%, increased by 1.18% compared with control group, along with the irradiation dose increase, theanine showed a downward trend; Tea polyphenols changed diffenent after irradiation,4kGy increased to the maximum 14.05%, increased by 1.01%. The total catechins of Xiangjian tea was 5.114%, the content of EGCG up to 2.352%, accounting for 45.99% of total Xiangjian tea catechins; content of DL-C was as. low as 0.104%, only accounting for 2.03% of total catechins. When the irradiation dose was 2 kGy, total catechins reached to the minimum 5.096%,6kGy reached the maximum 5.238%. The contents of theobromine decreased significantly to the minimum value 0.224% when the radiation dose in the range of 0-4kGy, lOkGy increased to the maximum0.274%, increased by 10.39% compared with non-irradiated sample. E. coli were negative, the total bacterias and mould-yeasts were 4.0 X 103CFU/gand 4.8×103CFU/g, respectively, in non-irradiated Xiangjian tea,2 kGy irradiation dose treatment, the The total bacterias and mould-yeasts reduced to 2.8×102CFU/gand 7.5×102CFU/g,93.00% bacteria and 84.38% mould-yeasts of Xiangjian tea were killed.3. Effect of physicochemical and microbiological indexes of Qianliang tea by irradiation treatment. In the range of 0～10kGy irradiation dose, the Qianliang tea dry matter content, water extracts, caffeine and theophylline had no significant effects by irradiation; Total free amino acids increased significantly when the radiation dose in the range of 0～4kGy,4kGy reached the maximum 2.05%, increased by 39.46% compared with non-irradiated sample; The theanine increased within 0～2kGy,2kGy reached the maximum 0.012%, increased by 33.33% compared with control group; Tea polyphenols reduced to varying degrees within 0～8kGy,8kGy reached the minimum 4.93%, decreased by 33.33% compared with control group. The total catechins of Qianliang tea was 1.683%, the content of EGCG up to 0.728%, accounting for 43.26% of total Qianliang tea catechins; content of DL-C was as low as 0.054%, only accounting for 3.21% of total catechins. Total catechins increased when the irradiation dose within 0-4kGy,4kGy reached the maximum2.050%, increased by 21.81%. E. coli were negative, the total bacterias and mould-yeasts were 5.4×103CFU/gand 1.3×102CFU/g, respectively, in non-irradiated Qianliang tea, 2kGy irradiation dose treatment, the the total bacterias and mould-yeasts can be controlled within 103CFU/g when the radiation dose reached 6kGy, the total number of bacterials and mould-yeasts less than lOCFU/g, and coliform were negative of Qiangliang tea. |
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