Application of Refractance Window dryer for papaya (Carica papaya L.) drying: Evaluation of physicochemical, nutritional, and antioxidant properties

Abstract

In many developing countries, both food loss and micronutrient deficiencies such as vitamin A, pose an alarming threat to public health. In this study, the ability of the reactance window drying (RWD) as compared to freeze drying (FD) methods of preserving quality, was examined on two varieties of papaya grown in Ethiopia (yellow- and red-fleshed). Physicochemical property evaluation revealed similar moisture and pH levels for both types; however, the red fleshed papaya had significantly higher total soluble solids (TSS) (10.35 °Brix vs. 9.36 °Brix), and a distinctly redder color (7.02 a* vs -1.24 a*). The water activity (aw) of the RWD powders was significantly lower (p < 0.05), than that of the FD powders, particularly for the red fleshed variety (0.32vs 0.48). Vitamin C retention was relatively similar for both drying methods (p > 0.05). However, the FD powders had higher concentration of β-carotene (42.09 µg/g and 38.58 µg/g), lycopene (8.70 µg/g and 7.65 µg/g), and folate (123.19 μg/100 g and 112.80 μg/100 g)) than the RWD powders for the yellow variety. A similar trend was obtained with the red-fleshed variety. Additionally, yellow-fleshed papaya powders demonstrated greater total phenolic content (TPC), total flavonoid content (TFC) and antioxidant capacity than red-fleshed powders, regardless of the drying method. Both the RWD and FD methods showed equal retention of minerals, such as potassium and zinc (p > 0.05). In conclusion, the RWD method is an effective and economical way to prepare papaya powder, offering stability and retention of vitamin C and minerals comparable to freeze-drying.