Abstract
The mung bean (Vigna radiata), guava (Psidium guajava), and bitter gourd (Momordica charantia) are notable legumes, fruits, and vegetables that are widely cultivated in Sri Lanka and are well-known for having high levels of dietary fiber. They have a high tendency to utilize their dried powders or extracted fiber concentrates to develop dietary fiber-incorporated functional foods to enhance the consumption of dietary fiber. Thus, in this study, plant sources underwent drying using three frequently practiced drying methods in Sri Lanka, hot-air drying, heat pump drying, and sun drying, to investigate the impacts of the application of drying methods on dietary fiber composition, along with the proximate composition, functional properties, and color characteristics of dried samples. The results revealed that the hot-air drying preserved the highest soluble dietary fiber content in all plant sources (mung bean: 4.25%, guava: 8.12%, and bitter gourd: 10.95%). Sun drying imparted the highest insoluble dietary fiber contents, particularly in guava (38.65%) and bitter gourd (51.04%), whereas bitter gourd showed the highest total dietary fiber (56.65%) with sun drying. Mung bean had a superior crude protein content of 32.57% under heat pump drying but was least effective in retaining guava protein (4.19%). The crude protein content varies considerably across the plant sources and drying methods, while the crude fat and ash contents show no significant variations across the drying methods. Heat pump drying maintained superior water-holding capacities, oil-holding capacities, and swelling water capacities in all plant sources, enhancing their functional properties. Color analysis of the dried plant sources revealed that hot-air-dried samples had the darkest coloration, whereas heat pump drying maintained the best natural hues of the dried materials. Our findings provide valuable insights for optimizing drying methods to enhance the important nutritional, functional, and visual qualities of dietary fiber-rich plant sources.