Effects of Different Osmotic Pre-Treatments on the Drying Characteristics, Modeling and Physicochemical Properties of Momordica charantia L. Slices

A significant vegetable in the Cucurbitaceae family, the bitter gourd (Momordica charantia L.) is widely recognized for its beneficial health properties, including anti-diabetic, anti-carcinogenic, anti-inflammatory, anti-ulcer, antiviral activities. With a total of three Brix values (50, 60, and 70) and three different dipping times (10, 20, and 30 h), the goal of the current study was to identify the proper sugar and grape molasses solutions (pekmez) and dipping times for osmotic pre-treatments of bitter gourd samples to make it sweet and widely consumed. In the present study, mathematical modeling of drying processes, moisture content and water activity, total color changes, total phenolic content-antioxidant activity, and carotenoid contents were assessed. As a result of 13 different mathematical modeling tests, “Diffusion Approach”, “Logarithmic” and “Midilli et al.” models were the best models, giving the highest R2 and lowest X2-RMSE values. There were samples that were dipped at 50 °Brix grape molasses, which decreased below the 10% wet basis (w.b.) limit in the shortest time with 180 min, in a 10 h dipping time. The samples were dipped in 60 °Brix sugar, which fell below the same limit in the shortest time with 135 and 165 min, respectively, at 20 and 30 h dipping times. The highest total phenolic and carotenoid contents were found in 30 h dipping time in 60 °Brix grape molasses with 8296.87 mg/kg and 10 h dipping time in 50 °Brix sugar solutions with 89.22 mg/kg, respectively. While the phenolic content was higher in all samples dipped in grape molasses, the carotenoid content was higher in all samples dipped in sugar, which was one of the most important results of the study.