Influence of Different Drying Techniques on Drying Characteristics and Quality Aspects of Pink Lotus (Nelumbo nucifera) Flowers

The present study investigated the effect of different drying methods on the drying kinetics and antioxidant activity of pink lotus flowers to identify the suitable drying models describe the dehydration as well as drying conditions giving minimum loss of antioxidant compounds and antioxidant properties of product. Samples were dried by freeze drying (FD), oven drying (OD) at 40, 50 and 60oC, microwave drying (MWD) with the powers of 140, 420 and 700 W. Drying kinetics from OD and MWD were analyzed mathematically and the dehydration data was statistically analyzed to obtain best fit among all available models basing on coefficient of determinations (R2), reduced chi-square (?2) and root mean square error (RMSE). The dried lotus flowers were analyzed total polyphenol contents (TPC), total flavonoid contents (TFC) and antioxidant activity (AA). It was found that the Midilli et al. model is the most appropriate model for drying behavior of samples by both OD and MWD. The activation energies of drying were 56.29 kJ/mol and 6.48 W/g for OD and MWD, respectively. FD was found to be the best method to give the highest antioxidant activity for lotus flowers and the next one was the OD at 50oC.