Investigation of nutritional quality evolution of papaya during intermittent microwave convective drying

Papaya is a highly popular tropical fruit with its unique aroma, taste, and excellent nutritional characteristics. Drying is widely applied as a preservation technique to reduce post-harvest losses and to increase the shelf life. However, traditional convective drying is a time-consuming process, and directly affects to the final quality of the dried product. Intermittent microwave convective drying (IMCD) is an advanced drying method, which has great potential to improve drying performance and energy efficiency. However, the impact of this innovative drying method the quality of dried papaya has not been adequately investigated. In this study, an extensive investigation was carried out to determine the effects of IMCD conditions on drying performance and some quality attributes of papaya samples. Ascorbic acid content, total polyphenol content, color, and water activity of IMCD dried papaya samples were determined using standard methods. For IMCD process conditions, combinations of different power loads (0.5–1.5 W g−1), intermittency ratios (4–6) and air temperatures (50–70 °C) were considered. The results indicate that drying times were significantly reduced in IMCD while the color change tended to increase with higher microwave power. The total polyphenol content was recorded to increase in some conditions while ascorbic acid remained high in most of the IMCD conditions. The water activity of all dried samples was within product storage stability and safety levels. The optimal condition for the IMCD of papaya was a microwave power load of 1.038 W g−1, intermittency ratio of 5.22 and hot air temperature of 50 °C. The optimized drying time was 235 min, color change ΔE = 12.34, water activity was 0.53, retention of ascorbic acid was 64% and total polyphenol content was 4% higher than the fresh sample. Empirical relationships for drying time, color, total polyphenol content, ascorbic acid content, and water activity in terms of IMCD process variables of papaya drying were developed for the first time. Predicted and experimental values closely matched, validating the proposed models.