青砖茶原料采收方式与嫩度对茶叶氟含量及品质的影响

目的 建立青砖茶原料采收新技术,有效降低氟含量。方法 选择三个不同地点的茶园对比分析青砖茶采收方式对氟含量的影响以及通过感官和理化分析不同嫩度原料加工青砖茶的品质差异。结果 在传统采收方式下,三个试验茶厂7月和11月每轮次茶叶氟含量平均都在600mg/kg以上。新的采收方式将传统的采收两轮改为四轮。随着采收轮次的增加(即采收时期的推移),茶叶氟含量呈现上升趋势,新采收方式的茶叶氟含量显著低于传统方式22-51%。枝梢部位对含氟量有极显著差异。随着嫩度的下降,氟含量呈先升后降的趋势,以红茎后段的含量最高,绿茎的含量最低。青砖茶感官品质分析表明,随着嫩度的下降,外形调匀度、汤色黄色度下降；带灰白色茎梗的原料加工的成品茶粗老气味较重,滋味较淡薄。这一结果说明,青砖茶原料并非越老越好。理化分析表明,随着嫩度的下降,水浸出物、茶多酚及其氧化产物、氨基酸、可溶性糖含量呈降低趋势,说明利用太老的原料加工青砖茶时不仅品质低下,而且氟含量超标。结论 青砖茶原料宜控制在一定成熟度范围,以成熟绿茎枝叶为宜,生产上可以采取增加采割轮次、缩短生长期、提高采割嫩度的技术措施来有效降低茶叶中的氟含量。

Effects of different harvesting methods and tenderness of fresh leaf on fluorine content and quality of Qingzhuan tea

Objective To explore the effects of raw material harvesting methods and tenderness on fluorine content and quality of Qingzhuan tea, and explore new technology of raw material harvesting for effectively reducing the fluorine content of Qingzhuan tea. Methods Three tea gardens in different locations were selected to compare and analyze the influence of the harvesting methods on the fluorine content, and the quality difference of Qingzhuan tea processed with different-tenderness fresh leaf through sensory evaluation and physicochemical index detection analysis. Results Through the traditional harvesting method, the fluorine content of tea processed in each round of the 3 experimental tea factories in July and November was more than 600 mg/kg on average. The traditional 2 harvesting rounds were changed into 4 rounds as a new harvesting method. With the increase of harvesting cycles (namely the time of harvest), the fluorine content of tea exhibited an downward trend, and the fluorine content of tea in the new harvesting mode was significantly lower than that in the traditional mode by 22%?51%. There was a very significant difference in fluorine content of different parts of treetops. With the decrease of tenderness, the fluorine content showed a trend of increasing first and then decreasing, with the highest content in the rear segment of red stem and the lowest content in green stem. The sensory quality analysis of Qingzhuan tea showed that the appearance uniformity and the yellow degree of soup color decreased with the decrease of tenderness; the tea processed from raw materials with gray-white stems had a heavy grassy smell and a thin taste, indicating that the raw material of Qingzhuan tea was not as old as possible. Physical and chemical analysis showed that the content of water extract, tea polyphenols and their oxidation products, amino acids and soluble sugar decreased with the decrease of tenderness, which indicated that the quality of Qingzhuan tea processed with too old raw materials was not only poor, but also the fluorine content exceeded the standard. Conclusion The raw materials of Qingzhuan tea should be controlled within a certain maturity range, and the branches and leaves with mature green stems are appropriate. In production, technical measures including increasing the number of picking rounds, shortening the growth period, and improving the picking tenderness can be taken to effectively reduce the fluorine content in tea.