Improvement of Hot Air Dried Bitter Gourd ( Momordica charantia L.) Product Quality: Optimization of Drying and Blanching Process by Experimental Design

Bitter gourd ( Momordica charantia L.) is a plant species belonging to the Cucurbitaceae family, growing in tropical regions and containing health-promoting beneficial compounds. In the current study, bitter gourds prepared for drying were sliced in three different thicknesses (6, 8 and 10 mm) and dried in a hot-air dryer at three different temperatures (60, 70 and 80 °C) to preserve their medicinal efficacy. In the experiments, the samples were subjected to blanching at 93.5 °C and 2% salt water for 0, 2.5 and 5 min, and drying processes were conducted. After the drying process, drying time, total color change (∆E), total phenolic content (TPC), total antioxidant activity (TAA), and vitamin C properties were examined. The highest levels of TPC and TAA were found at lower drying air temperatures (DATs), and while these values increased with longer blanching times at lower DATs, they decreased with longer blanching times at higher DATs. According to the different drying temperatures used, it was discovered that the total color change peaked at 70 °C and that vitamin C levels declined as DAT rose. The optimal drying conditions for the 3D response surface methodology include 60 °C DAT, a slice thickness of 10 mm, and without blanching to maximize TPC, TAA and vitamin C content and minimize drying time and ∆E.