A study was undertaken to determine the physiological and biochemical changes in tea leaves and made tea due to the attack of red spider mites on tea. The study was conducted at Bangladesh Tea Research Institute (BTRI), Srimangal, Moulvibazar and the laboratory of Department of Food Engineering and Tea Technology, Shahjalal University of Science and Technology (SUST), Sylhet, Bangladesh, during the period of January-December, 2013.
Sample collection: The pluckable green leaves from the tea bushes comprising of "Two leaves and a bud" were collected from BTRI main farm (D2 section) where the section was planted with red spider mite susceptible clone BT2. The experimental plots were divided into four categories such as T1: Fresh leaves (no mites per leaf), T2: Low infested leaves (<10 mites per leaf), T3: Medium infested leaves (10-20 mites per leaf) and T4: Highly infested leaves (>20 mites per leaf) and considered them as treatments. The categorization was made according to the number of mites in the infested leaves. Each treatment was replicated thrice. Besides, the mature fresh and infested leaves from selected bushes were also collected for the analysis of chlorophyll a, b and carotenoid contents.
Laboratory analysis: Physiological parameters i.e., chlorophyll contents, carotenoids, polyphenols, catechins and reducing sugar in green leaves of tea and biochemical parameters i.e., theaflavin, thearubigin, highly polymerized substances, total liquor colour, lipids, caffeine, total ash, water extract, dry matter content and moisture content in made tea were analyzed with standard methods in the laboratory of the Department of Food Engineering and Tea Technology, SUST.
Organoleptic test: Made tea samples prepared from different categories of mite infested shoots were forwarded to a professional tea taster for assessment of taint as positive or negative and for organoleptic test. All observations were replicated thrice. Leaf infusion, liquor colour, briskness, strength and creaming down parameters were considered for organoleptic test and standard score was as >34 being Excellent (E), 32-34 being Above Average (AA), 30-32 being Average (A) and <30 being Below Average (BA) out of 50.
Statistical analysis: The experimental data were statistically analyzed by Randomized Complete Block Design (factorial RCBD) using MSTAT statistical software in a microcomputer. The results were expressed as Mean±SE and data were statistically analyzed by one-way ANOVA, with the level of significance set at p<0.05. The mean values adjusted by Duncan’s Multiple Range Test (DMRT).