The Detection Of Nitrite In Tea

People are more and more attention on food quulity and safety. The main factors affected food quality and safety are chemical factors, physical factors and biological factors. Nitrite is carcinogenic, and excessive consumption of nitrite would occur poison incidents. Therefore, Nitrite is also concerned about the vast number of consumers of food quality and safety factors. At present, tea contain nitrite has not yet been reported. The article used spectrophotometry to research tea nitrite content. The principle of Gris Reagent_colorimetry used the sample by precipitation of proteins, fat removed, nitrite with the amino acid diazotization under acidic condition, and forming purple dye with dinitroaniline coupling .finally quantitative standards. The main findings are as follows:1. Used food nitrite and nitrate determination method (GB/T 5009.33-2003) in tea nitrite. The application of tea inspection found that the former tea after filtrate is yellow-green, plus reagent after not showing the characteristics of color, Color interference effects, impact absorption and lower recovery rates, thus affecting the results. Therefore, Food nitrite and nitrate determination method (GB/T 5009.33-2003) can not be used for tea Mr nitrite determination.2. The tea nitrite detection method is initially established. The mothod is in 70℃temperature for 30 min after the extraction, Used basic lead-acid saturated solution of filtrate decolor filtrate further increases in 0.1 ml of sulfuric acid solution (4.5mol /L),that can remove some basic lead acetate, solution can be maintained in the acidic conditions of color. Sulfanilic acid solution and hydrochloric acid 2 -1 -Naphthodiamide Color Solution are more than the color stability in 120 minutes. This method recovery is 72.90% - 86.53%, the coefficient of variation is 4.6%. The detection limit is 0 .06mg/kg.The method is fast, accurate, and the economic conditions of the equipment, low, simple operation, apply to the tea nitrite content of the determination.(3) Application of this method to 112 tea samples were determined, the results showed : The kinds of Teas has devidently defference of nitrite content. Harmless green tea nitrite content is in average of 4.04 mg/kg; Green Food green tea is 2.97mg/kg; Organic food green tea is 2.25mg/kg. From the average,the pollution-free food tea is higher the nitrite content of green food and organic food green tea, with partial N fertilizer, as a future possibility standand to distinguish between pollution-free, green food, Organic food tea determine indicators. Gunpowder nitrite content was 0.86～5.15 mg/kg in between,and the average was 3.21mg/kg Mee tea nitrite content was in the 2.97～8.28 mg/kg between,average of 4.78 mg/kg. The brick Tea nitrite content was in 0.32～5.10mg/kg and the average was 2.59 mg/kg. Oolong Tea nitrite content was in 0.85～8.55mg/kg between, average of 4.57 mg/kg. Pu'er tea was in the range of 086～610 mg/kg, the average value of 3.09 mg/kg.