Investigating the Effects of Different Drying Methods on the Drying Kinetics and Proximate Composition of Zobo Calyces

Abstract

Hibiscus sabdarrifa are cultivated and consumed as tea, whereas other hibiscus varieties are planted for the fibers they produce. Hibiscus sabdariffa known as roselle, is one of the underexploited food crops with nutritional and food industry processing potential. Thus, this study was undertaken to determine the effects of different drying methods (sun, solar and oven drying) and drying kinetics on the proximate composition of dried calyx (Proximate and Mineral composition) using AOAC Standard. The data obtained from this study was statistically analyzed using Tukey HSD (Tukey Honest Significant Difference). The values of the model constant and other Statistical parameters for moisture ratio were obtained. The two-term exponential model had the highest R² and the lowest x² and RMSE value. The model constants, the R², x² and RMSE for each model were obtained. The page model had the highest R² and lowest x² and RMSE and was selected as the best fit model for describing the drying kinetics zobo calyces in an oven dryer while Logarithmic model and Wang and Sing Model was selected for modeling of zobo calyces in sun and solar dryer respectively. The experimental and predicted moisture ratio values are very close to the each other given the R² value and the straight-line graph when the predicted moisture ratio is plotted against the experimental moisture ratio. Sample dried with oven dryer gave the highest carotenoid and vitamin C content compared to other drying methods. Therefore, oven dryer is recommended for drying of zobo calyces as compared to sun and solar dryer.