Determination of Sucrose, Glucose and Fructose Levels in Low Grown Black Tea Using High Performance Liquid Chromatography Technique
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Date
2020
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Uva Wellassa University of Sri Lanka
Abstract
No extraneous matters are allowed to add during tea manufacture. Nevertheless, some of
the manufacturers add sugar to withered tea leaves to develop better appearance in black
tea. Sugar adulteration adversely affects the reputation of Ceylon Black Tea. As stipulated
by the Tea Research Institute of Sri Lanka, maximum permissible levels of fructose,
glucose, and sucrose for low grown black teas are 25 mg/g, 20 mg/g, and 35 mg/g
respectively. The present study was conducted to determine whether the black tea
manufactured in the low country in Sri Lanka was adulterated with sugar. Sample
collection was done according to stratified random sampling keeping administrative
districts; Galle, Matara, and Rathnapura as strata. Sixty-three black tea samples (Dust 1
grade) were collected during three consecutive weeks. Coldwater extracts of samples
were prepared and their sugar levels were determined using a High-Performance Liquid
Chromatograph fixed with a Zorbax NH2 column and a RI detector. The mobile phase
comprised of 75% Acetonitrile and 25% de-ionized water. The average fructose, glucose,
and sucrose contents of low grown tea were 6.3±2.7, 6.1±3.1, and 7.3±5.5 mg/g
respectively. Fructose, glucose, and sucrose contents of all tea samples collected from
Matara and Rathnapura districts were below the maximum permissible limits. Further,
fructose and sucrose contents of Galle district’s black tea samples were also below the
maximum permissible limits. The highest fructose, glucose, and sucrose contents were
detected from the Rathnapura district’s black tea samples. It can be concluded that Matara
and Rathnapura Districts’ black tea samples comply with the stipulated maximum
permissible levels of fructose, glucose, and sucrose whereas Galle District’s black tea
samples comply with the maximum permissible levels of fructose and sucrose.
Keywords: Black tea, Fructose, Glucose, Sucrose, Adulteration
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Export Agriculture, Food Science, Food Technology, Food Science & Technology, Tea Technology