Sampling Inspection And Analysis Of Lead Content In Tea Products

The quality safety of tea is not only an important part of food quality and safety,but also a hot topic in the current tea industry and tea science research in China.Effectively controlling and reducing the content of toxic heavy metal and preventing excessive tea are key points to protect the quality and safety of tea. Nowadays,tea Pb pollution and excessive levels of it have become common hazard factors for the quality and safety of tea.Commercial tea products lie on the terminal of tea industry chain;its level of lead content is directly related to consumers’safety and health.Thus this paper systematic studies the lead content in commercial tea products for mastering the lead content in commercial tea and objectively and accurately assessing the level of contamination of the commercial tea for the feedback of problems in tea production. What is more, we will reveal lead contamination in tea security risks, then control the lead content of commercial tea, protect the quality of tea and the health of consumers, establish a regulatory system about the lead content in commercial tea, as well as guiding the tea industry health and realizing sustainable development.Based on the determination and test for the measuring method about tea lead content, we made a sample system testing on lead content of the commercial tea. Statistically analyze the overall situation of lead content in commercial tea, and separately analyze how different types, packages,levels and other factors influencing the lead content of commercial tea. Finally, draw a conclusion about how to control lead content of commercial tea.The specific main results are as follows:(1) Dry ashing-graphite furnace atomic absorption spectrometry studies the lead content in tea to assess the condition of the detection technology. The results showed:The method had strong maneuverability, high precision and good accuracy. Lead ion concentrated in 0.1-1.0μg/mL,appearing good linear relationship. The standard working curve equation was:y=0.0203x-0.000489, R2=0.9991; a detection limit was 0.36 ng/ mL, equivalent of tea (sample volume of 2.000g) lead content of 0.0018mg/kg; recoveries were high (87.77%-101.83%); the precision of atomic absorption instrument and experimental methods were also high (RSD values of 0.27% to 1.51%), experimental data measured was accurate and reliable.(2)The results of continuous sampling of lead content from 2012 to 2014 showed that the overall lead content in commercial tea products was in line with national standards, lower than the maximum limit(MRL)prescribed in the standard.Lead detection rate of commercial tea during the three years was between 98.72%-99.74%, ranging from 0.50mg /kg to 7.90mg/kg, the median values were 1.60mg/kg,2.00mg/kg and 1.90mg/kg, the average values were 1.84mg/kg,2.21mg/kg and 2.27mg/kg, the pass rates were all greater than 96%. Among the 2402 tea samples in the tree years, more than 50%tea samples distributed in lower range,lower than 2.0mg/kg, which only exceeded 1.49%.(3) Due to the differences in the choices of tea materials, different tea samples had different lead content,ranging from 0.50 mg/kg to 6,00 mg/kg. The median value and average value of lead content in black tea were relatively high (greater than 2 mg/kg), followed by black tea, oolong tea, tea category, scented tea and green tea (F= 644.35> F0.01 (6,13)= 4.62, p<0.01). Yellow tea was relatively low. The lead content of green tea, yellow tea, oolong tea, black tea and scented tea was generally distributed in the rang (constituent ratio greater than 55%) lower than 2.0mg/kg, and was not exceeded (GB lower than 5 mg/kg);most tea samples in black tea were distributed in the 2-5 mg/kg (constituent ratio greater than 93%), exceeding the rate of 3.99%. Studies have shown that the type of tea is one of the main factors influencing lead content tea.(4)Different packaging materials and forms can significantly affect the level of lead content in tea samples. Boxed and canned packaging were better than bulk and bagged packing; boxed (composition ratio of 95.24%) and canned (composition ratio of 65.85%) lead content of tea were distributed in lower than 2.0mg/kg; and the median and mean values of lead content of boxed and canned tea samples were significantly lower than that of bulk and bagged tea samples. Studies have shown that lead-free packaging materials are of high security.High grade packaging general used for high-grade tea, its quality and safety is better than ordinary packaging for the middle and low level tea.(5)Lead levels of different grades of tea are significantly different, from 0.50mg/kg to 4.80 mg/kg.The lead content of tea sample with higher general level was relatively low, from 0.50 mg/kg to 3.22 mg/kg. Results showed that the extent of lead contamination of Super Mao feng tea was relatively lower than a class of Maofeng tea; the lead content of Super Mao feng Tea was distributed in lower than 2.0mg/kg (composition ratio 87.04%), and the median (1.54 mg/kg) and average (1.61 mg/kg)value of lead content were significantly lower than a class of Maofeng tea.