Solid-Liquid Extraction Kinetics of Total Phenolic Compounds (TPC) from Red Dates

Abstract

Red dates are one of the most famous herbal plants in making traditional Chinese medicine. They contain large amount of bioactive compounds. The objectives of this research were to optimise the crude extract yield and total phenolic compounds (TPC) yield from red dates using response surface methodology (RSM) and model the extraction kinetics of TPC yield from red dates. Date fruits were dried in an oven under temperatures 50°C, 60°C, 70°C and 80°C until a constant weight was obtained. The optimum drying temperature was 60°C as it gave the highest crude extract yield and TPC yield. Besides that, single factor experiments were used to determine the optimum range of four extraction parameters which were: liquid-solid ratio (10-30 ml/g); ultrasonic power (70-90%); extraction temperature (50-70°C); and extraction time (40-60min). The optimum range of the four parameters were further optimised using the Box-Behken Design (BBD) of RSM. The extraction conditions that gave the highest crude extract yield and TPC yield were chosen. The optimum value for liquid-solid ratio, ultrasonic power, extraction temperature and extraction time were 30ml/g, 70%, 60°C and 60 min respectively. The two equations generated from RSM were reliable and can be used to predict the crude extract yield and TPC yield. The higher the extraction temperature, liquid-solid ratio, and extraction time and lower ultrasonic power, the higher the crude extract and TPC yield. Finally, the results of TPC yield versus time based on the optimum extraction parameters from RSM optimisation were fitted into three extraction kinetic models (Peleg’s model, Page’s model and Ponomaryov’s model). It was found that the most suitable kinetic model to represent the extraction process of TPC from red dates was Page’s model due to its coefficient of determination (R2) was the closest to unity, 0.9663 while its root mean square error (RMSE) was the closest to zero, 0.001534.