Evaluation of spray drying performance of banaba (Lagerstroemia speciosa (L.) Pers.) leaf extract for instant tea

The study was conducted to establish the spray drying performance of banaba leaf extract for instant tea using the Regression Surface Methodology. The effect of the process parameters such as air inlet temperature (100, 120 and 140 deg C), pump speed (7,000, 10,000 and 13,000 rpm) and decoction ratio (1:3, 1:5 and 1:7, banaba leaf to water) on the response variables, namely: drying capacity, product moisture content and recovery rate, were evaluated. The experimental test consisted of 15 runs using the Box-Behnken design. Pump speed and decoction ratio significantly affected drying capacity while the recovery rate and product moisture content were affected by pump speed and inlet temperature, respectively. Moreover, response surface analysis showed that models for drying capacity and moisture content were statistically adequate. The optimal processing condition is 22 deg C, 10,000 rpm and 17.5 (1:5.7, banaba to water) decoction ratio yielding to a drying capacity of 15.16 g/min and 6.84 percent moisture content, dry basis. Upon validation, it was found that the predictive model for the drying capacity is accurate and precise and better product moisture content was obtained. It was also evident that there was no difference as to the over-all effect of process parameters on treatments 9 and 10 for the rehydration characteristics and organoleptic test. The thermal energy loss from the system during the spray drying process was 1,208.57 kJ/hr. Calculated using the mass and energy balance equations. The spray dried banaba powder has shown significant anti-diabetic activity when tested on alloxan-induced diabetic mice at the dosage rate of 250- mg/100 g body weight. Hence, spray drying can be used in the production of banaba powder at specified optimum processing condition.