Comparison of color and water extracts of Caragana sinica flowers dried at different air temperatures

Abstract

This study aimed to investigate the drying characteristics of Caragana sinica Rehder flowers, which are basic data necessary for increasing utilization. The flowers were harvested in mid-April and dried at different hot-air temperatures (50-90°C), and the physicochemical properties of the dried flowers were analyzed. It was found that the drying rate was proportional to the air temperature. The visual color of dried flowers was relatively strong in green when dried at 50°C, while browning was relatively severe when dried at 90°C. The greenness (−a* value) of the mechanical color of the powder decreased with increasing temperature, and the yellowness (b* value) decreased with increasing temperature above 70°C. The soluble solids of the hot water extract were maintained at a certain level after increasing up to 70°C, and the pH decreased with increasing temperature. The total polyphenol contents tended to increase with increasing temperature, and DPPH radical scavenging activity did not show a significant change after increasing up to 70°C. These results suggest that the hot-air drying temperature had a significant effect on the physicochemical characteristics of the C. sinica flower. The appropriate hot-air drying temperature was judged to be less than 50°C for maintaining the unique color, and approximately 70°C considering the high hot-water extraction yield and antioxidant capacity.