关键词: 茶叶, 掺杂, 蔗糖, DNS, 测定

Abstract: A method for the determination of sucrose in tea was established. The tea was soaked in hot water, potassium ferrocyanide and zinc acetate were precipitated to remove interferences such as protein, hydrolyzed by hydrochioric acid,developed by 3,5-dinitrosalicylic acid （DNS）, and compared with spectrophotometer color determination. The results show that, take about 5 g of tea leaves, add 50 mL of tertiary water, place in a 45 ℃ water bath, shake and extract for 1 hour, take the tea soup, centrifuge at 3 000 r/min for 3 minutes, filter the tea soup, dilute the volume to 100 mL, measure the total sugar and reducing sugar by DNS method, and calculate the sucrose content by the minusing. In 5 g of tea, when 10 mg and 50 mg of sucrose were added, the recoveries were 117.60% and 91.22%, respectively. The relative standard deviation of 5 samples of the same tea was 2.47%, and the detection limit of the method was less than 2 mg/g. In the test of 20 tea samples, the artificially added sucrose can be clearly distinguished from normal tea samples. The method has good sensitivity and reproducibility, low operation requirements, and practical application value.

Key words: tea, doped, sucrose, DNS, determination