加工过程对茶叶铅和铜污染的影响

Effect of Processing on the Pb and Cu Pollution of Tea

研究了初制加工对茶叶铅和铜污染的影响。结果表明,茶叶加工是铅和铜污染的重要途径之一,但污染的程度因工序、作业方式和机具的金属组分不同而异。初制加工的各个工序都有可能使茶叶铅和铜含量提高,其中铜增幅最大的工序是揉捻,铅增幅最大的工序是摊放;随着揉捻压力增大、时间延长,茶叶铜和铅含量逐渐提高。由于加工方式,特别是揉捻的时间和压力不同,导致不同茶类有明显的区别,烘青和炒青的污染程度较重,红碎茶和工夫红茶次之,龙井茶几乎没有污染。茶叶加工过程中铅和铜污染的来源不同,铜主要来自铜质揉捻机,该工序污染的铜约占茶叶加工铜污染总量的90%以上;铅的污染则主要来自尘土,其次是揉捻机中的铅,摊放在不清洁的地上会导致茶叶铅含量成倍提高。因此,保持加工场所的清洁卫生和调整揉捻机揉筒和揉盘的金属组成是降低茶叶加工过程中铅和铜污染的有效途径。另外,对初制加工的茶叶,清除其中的黄片和茶末对于降低茶叶铅含量也具有重要的作用。

The effect of processing on the Pb and Cu pollution of tea was studied in this paper. Results showed that tea processing was one of the main pollution sources of Pb and Cu. The extent of pollution was varied with the working procedure, machine and its metal composing. Almost every working procedure, including fresh leaves spreading out or withering, deenzyming, roiling or cutting, fermentation and drying could increase the Pb and Cu concentrations of tea. However, roiling and spreading out were the most important procedures resulting in Cu and Pb pollution, respectively. With the increase of rolling pressure and time, the Cu and Pb concentrations steadily increased. Due to different procedures, especially the roiling pressure and time, the Cu and Pb concentrations of made teas were different, oven dried and roast green tea were the highest, followed by CTC （Crushing, Tearing, Curling） and Orthodox black tea, almost no change in Longjing tea processing. The pollution sources were quite different between Cu and Pb. Cu pollution was mainly from roiling machine and the Cu content of the machine. Cu pollution from rolling procedure accounted for 90% of total one. Pb pollution was mainly due to dust, which came from unclean ground and air in the workshop. Therefore, keeping clean in workshop and regulating the metal constitution of rolling machine could reduce the Pb and Cu pollution during tea processing. In addition, clearing the mature leaves and tea dust away after tea primary processing also could decrease the Pb concentration of tea.