Effects of Drying Techniques on Nutrient Retention and Phytochemicals in Selected Vegetables

Vegetables are a rich source of bioactive compounds and functional constituents that are beneficial to human health. However, the short shelf life of these vegetables can be a major cause of bio unavailability of nutrients when they are out of season especially during dry season. Drying is one of the most convenient technologies for the production of shelf stable food products. However, drying can lead to considerable loss of the available bioactive compounds due to thermal degradation depending on the drying method and temperature conditions. This study investigated the effect of three drying methods (oven, open sun and indirect solar (sun drying) on the retention of nutrients and nutri-pharmaceutical compounds. Samples were dried up to ~10% moisture content. The fresh and dried samples were analyzed for nutrient composition and nutri-pharmaceutical compounds. The results showed that the retention of nutrients and nutri-pharmaceutical compound was not significantly (p ≥ 0.05) affected by drying method and drying temperature with although differently affected. This study demonstrates that oven drying was the most effective in retaining the highest nutrients and bioactive compounds vegetables followed by indirect solar drying. Ethanol: Ethyl ether solvent was more effective in extraction for phytochemicals than n-Hexane. The effectiveness was based on their polarity of these solvents.