Optimisation of process parameters for preparation of flavoured instant green tea

Abstract

Tea is the second most popular drink in the world after water. Tea can be classified into three major categories: unfermented green tea, partially fermented oolong tea, and fermented black tea. Green tea contains more catechins, than black tea and oolong tea. So it is included in the group of beverages with functional properties. Green tea consumption helps in preventing cardiovascular diseases, cancer, diabetes and obesity. Nowadays, demand is increasing for instant tea, decaffeinated tea and flavoured tea. The use of instant tea powder will reduce the preparation time to a large extent and saves energy as well. Due to these reasons efforts were under taken for optimisation of process parameters for preparation of flavoured instant green tea. Production of flavoured instant green tea mainly includes three steps, extraction, flavour addition and drying. Extraction was performed and optimised conditions were 1:47 leaf-water ratio, 30 min extraction time and 52°C extraction temperature. Extract obtained with optimised condition was subjected to spray drying and optimised condition were 174°C inlet temperature, 2.7% MD and 671 ml.h -1 feed rate to produce instant green tea. Further flavouring was carried out with two spices (ginger and cardamom) and one herb (tulsi) of different concentration and spray dried at optimised spray drying condition. The best combination selected after sensory evaluation are G2 (4% ginger extract), C6 (3 g of cardamom with 30 min of soaking) and H3 (3:10 tulsi to green tea ratio, 30 min extraction time). The best samples were packed in PET, ALF and LDPE and kept for storage studies at room temperature. Predicted shelf-life period of instant flavoured green tea powder packaged in ALF, PET and LDPE based on moisture gain was found to be 210, 152 and 92 days, respectively. Among the six tested sorption models, the GAB model described the best fit to the experimental data with higher R 2 value and lowest SSE and RMSE. The HPLC analysis for catechin fraction of instant flavoured green tea indicates that, flavour addition will not affect the green tea catechins. The heat utilization efficiency of spray dryer for spray drying of green tea extract under non adiabatic condition was 18.18% and under adiabatic condition was 89.4%. The total cost of production for 1 kg of instant green tea was Rs. 3590/-, ginger flavoured instant green tea was Rs. 3683/-, cardamom flavoured instant green tea was 4025/- and tulsi flavoured instant green tea was Rs. 3631/- and benefit cost ratio was 1.40:1, 1.63:1, 1.49:1 and 1.65:1, respectively.