The Research On Relationship Of Fluoride With Quality Chemistry And Microbiology Of Tea

Tea plant is known as a. fluorine accumulator. The fluoride contents of tea bushes are 100-1000 times higher than usual plants. Being as a special element in tea bushes, the function of fluoride during the tea processing and the tea quality evaluation remained unknown. 1. The relationship between fluoride and the tea quality gradesThe analysis of 16 samples from 7 provinces showed that the fluoride (F) contents of the young, mature, old and fallen leaves were 163 ± 80 mg/kg, 803±325 mg/kg, 1242 ± 591 mg/kg and 1358 ±675 mg/kg, respectively. The increasing rate was 1.1 to 3.0 between the two adjoining leaves of the young shoot. It showed that the F contents were closely related with the maturity of tea leaves. It was discovered as the first time that the F contents also showed significant relations with the levels of tea polyphenols and amino acids in the fresh leaves.The F contents of the made teas (total 102 samples) indicated that green tea, black tea and white tea had low F levels, while dark tea has high level, and flower tea is in the middle. These results are in good coincidence with the maturity degree of the green leaves. Relationship between F content and the tea quality was investigated with four tea categories: green tea, black tea, jasmine tea and oolong tea. High quality teas are usually made of buds and young leaves, and had low levels of F. A significant negative linear relationship was observed between F content and tea quality grades. The coefficient is 0.90, slightly higher than that of polyphenols or amino acids to the maturity. The results suggest that F content could be used as a quality potential indicator during tea quality evaluation. 2. The influence of fluoride during brick tea processingBrick tea is welcomed in the border area, with very high application value. The quality of Fuzhuan tea is mainly influenced by the development of 'Golden flower fungus'(GFF). This study is based on Fuzhuan tea, from which the GFF was separated. Several experiments were carried on to find out the influences of temperature change, pH change, different culture on the growth of GFF and the influence of change of single component in culture on the spore-producing ability of separated strains. Based on the basic physiological and biochemicalcharacters of the fungus, the separated strain is identified as Eurotium cristatum (Raper & Fennell) Mallon & Cain. This study made some preparation for the future research, and made it possible to improve the quality of Fuzhuan tea.After the identification and the evaluation of the physiological and biochemical characters, the function of GFF in the processing of Fuzhuan tea was analyzed. When E. cristatum isolated from the Fuzhuan tea was inoculated to the material of Fuzhuan tea, the levels and proportions of solubility and aroma components in the tea material were significantly changed and the flavor became better.During the processing of the Fuzhuan tea, GFF grows in the high fluoride level environment. It is suggested that GFF is compatible with the environment. The cultivation of GFF in the cultures with differents fluoride level showed that fluoride of low level (under 270mg/l) would accelerate the growth of this fungus while the increase of the fluoride level (270mg/l~500mg/l) the acceleration would disappear, and the growth would be inhibited under higher level of fluoride. The cultivation of GFF and other microorganisms from the Fuzhuan tea in different cultures showed that the characters of GFF were similar with other fungi, such as the consumption of the carbon and nitrogen sources. However, the growth of each microorganisms was significant different under the high osmotic pressure and high fluoride level. The bacteria were almost totally inhibited and the most of the fungi could not grow at the fluoride level of 136mg/kg, while the GFF grew well even in the fluoride level of 272 mg/1. From these results, it is suggested that a certain level of fluoride in the tea will not only accelerate the growth of GFF but also make it as the do...