Determination of Selective Chemical Quality Parameters of Commercial Tea Blends

Abstract

Tea (Camellia sinensis L.) is the second most widely consumed popular non-alcoholic beverage in the world for centuries due to its sensory attributes and health promoting effects. About 3x10 kg of various teas is consumed every year as a whole (Lu et al., 2004). Commercially, tea is used in blends combining several grades originated from different elevations and agro-climatic conditions. Those are distributed around the country through the auction and other meansunder different estate marks. This study was an effort to add more information on chemical quality of commercial tea blends by evaluating selected chemical quality parameters and comparing those with selected parallel products available in Australian market under different brands.

Methodology

The current study was carried out at Ceylon Tea Services PLC (CTS), Paliyagoda. Laboratory analysis was done at SLAB accredited chemical laboratory of Food Technology Department at CTS. Thirteen types of company standard green tea and black tea blends were evaluated.Total polyphenol content, caffeine content, moisture content of tea blends and pH, total soluble solid content, colour intensity of the brew were measured for 8 black tea blends 2 local green tea blends and 3 imported green tea blends. Chemical quality parameters were compared with 5 different tea brands under 5 different product categories. Five competitor samples (Twinings, Woolworth, Lipton, Abeya and Madura) which represent the leading brands in international tea market were compared with selective tea standards using chemical quality parameters. Those different tea blends which were used to produce different teas were considered as treatments. Total polyphenol content was determined according to the International Organization for Standardization method (ISO) 14502-1. Caffeine determination was based on Jenway Bibby Scientific (Application note: A09-010A). Moisture content (loss in mass at 103 °C) was determined on a portion of test sample in accordance with ISO 1572:1980 for leaf tea. The value for total soluble solids (TSS) of brew was measured using a refractometer(Atago, Japan) at 20°C (Borse et al., 2012).The color intensity of the tea brew was measured using a spectrophotometer at 450 nm (Halligudi et al., 2012). pH value of tea brew was measured using a pH meter (Cyberscan, Japan) at 25 C (Halligudi et al., 2012).Data were analyzed using the statistical procedure of one way analysis of variance (ANOVA) at 5 % level of significance and mean comparison was done using Tukey test at 95 % confidence interval using Minitab 16 statistical software.