Effect of drying temperature on physicochemical properties, bioactive compounds, and antioxidant activity of watercress powder (Nasturtium officinale)

Abstract

This study was conducted to evaluate the effect of drying temperature on the quality, bioactive compound content, and antioxidant activity of watercress powder (Nasturtium officinale). The results indicated that drying temperature significantly affected all evaluated parameters (p<0.05). As the drying temperature, incleased the water activity (a_w) and lightness (L*) decreased, while vitamin C content, chlorophyll, total phenolic content (TPC), total flavonoid content (TFC), and antioxidant activity were progressively reduced. Among the investigated treatments, drying at 40°C provided a favoarable balance between drying efficiency and product quality preservation. Under this condition, watercress powder exhibited an a_w value of 0.45, acceptable color characteristics, and relatively high retention of bioactive compounds (TPC: 13.83 mg GAE/g, TFC: 6.66 mg QE/g, and DPPH radical scavenging activity: 14.64%). In conclusion, a drying temperature of 40°C is recommended as an appropriate condition for producing high-quality watercress powder with enhanced biological activity, providing a scientific basis for its application in functional food products.