Adulteration and quality of black tea in Sri Lankan market

Abstract

Adulteration of tea is becoming a severe issue in the Sri Lankan tea industry. Black tea is adulterated with sugar, glucose, sodium bicarbonate and ferrous sulphate to improve its colour and sand, iron fillings and leather flakes like physical adulterants to improve its bulk. Ceylon tea is reputed for its quality and purity. The present study examined the adulteration and the consumer preference for black tea available in the Sri Lankan market. Twenty-nine tea samples of grades BOP, BOPF and dust were collected as packed and loose forms from the local market. They were assessed for sugar and colour adulteration with the Phenol-sulphuric method and water column method. The presence of iron fillings, leather flakes and sand adulterants were assessed by shaking a magnet, flaming to feel the odour and shaking tea in water to detect sediments, respectively. Sensory evaluation was conducted with 30 untrained panellists separately for BOP, BOPF and dust tea samples. Data were analyzed using Minitab software. Absorbance values were analyzed using ANOVA, while sensory data and colour adulteration data were subjected to the Friedman test. Out of 29 tea samples tested, 83% showed an apparent colour change with normal water, confirming the colour adulteration in tea. Varying colour intensities illustrate the different levels of colour adulteration. The absorbance values of the Phenol- sulphuric method were significantly different (p<0.05) among samples. Among the tea samples tested, 7% were adulterated with sugar. None of the tea samples was identified as adulterated with iron fillings, leather flakes or sand. Sensory evaluation scored varying consumer preferences for different tea brands for their external and brewed characters. The present study attempts to alert the public on possible adulteration in black tea available in the local market and to ratify simple techniques to detect adulterated tea to safeguard the consumers from adverse health risks associated with consuming such tea.