Microwave drying vs hot-steam-air drying of seedless noni fruit: drying performance and post-drying quality

Abstract

Noni fruit contains several beneficial compounds for health, including scopoletin as its active component. The fruits contain a high moisture content, generally above 80%, rendering them to rot quickly. The drying process can potentially increase the fruit’s shelf life as it reduces the moisture content, stop the enzymatic reactions/microorganism activities and inhibit the quality degradation. This study compared the drying performance and post-process quality of noni fruit slices from the microwave and hot-steam-air drying at 50°C and 60°C. The drying performance parameters were time and rate. Several post-drying quality parameters stipulated in Indonesia pharmacopoea standard, such as scopoletin, total ash, and insoluble-acid ash contents, were observed. The results show the drying rate of noni fruit ranged from -3.51 x 10−3 % min−1 (for microwave-drying) to -2.45 x 10-5 % min−1 (for hot-steam-air drying at 50°C). Noni fruits from hot-steam-air drying at 60°C had the highest scopoletin content (22.47 mg kg−1) and the lowest total ash content (4.78%). Microwave-dried noni fruit had the lowest insoluble-acid ash content (0.02%). Drying methods significantly affected the drying rate, total ash content, and insoluble-acid ash content of noni fruit. Treatment scoring shows microwave- and hot-steam-air drying at 60°C are potential options for drying noni fruit.