Assessment of nutritional quality and color parameters of convective dried watercress (Nasturtium officinale)

The purpose of this study was to evaluate the drying characteristics and the effects of convective drying temperature on quality attrib0utes of watercress, without any pretreatment. Drying temperatures of 40, 55, and 70 °C resulted in drying times of 230, 119, and 92 min, respectively. The nutritional parameters were negatively correlated with the drying temperature. Retentions of 12.5 ± 3.8−72.8 ± 4.2%, 51.1 ± 3.3−80.4 ± 4.8%, and 44.3 ± 6.1−92.1 ± 12.2% were obtained for vitamin C, total phenolic compounds, and total antioxidant capacity, respectively. Increased values of TCD (total color difference) and BI (browning index), and higher chlorophylls losses (26.1 ± 3.9−55.6 ± 14.9%) were also observed as the drying temperature increased. In conclusion, although longer drying periods are required for lower drying temperatures, these are more profitable in terms of watercress nutritional features and overall quality to the consumer. Practical applications: Dehydrated watercress has the potential to be a novel product, for food recipes or food supplements (functional food) due to its high nutritional content. Watercress is rich in nutrients such as vitamin C, minerals and other bioactive compounds, such as phenolics and antioxidants that may decrease cancer incidence. However, fresh watercress leaves are highly perishable with a short shelf life. Drying is one of the oldest processing methods to prolong shelf life of food products by reducing water content, hence decreasing microbial and biochemical activities. Choosing appropriate drying techniques is crucial to prolong watercress shelf-life, increase nutrients and quality retention, and decrease the storage and transportation costs. Dehydrated watercress is convenient to consume without requiring refrigeration or freezing storage, therefore reducing energy costs.