Effects of infrared freeze drying on volatile profile, <scp>FTIR</scp> molecular structure profile and nutritional properties of edible rose flower ( <scp> Rosa rugosa </scp> flower)

BACKGROUND Infrared freeze drying (IRFD) utilizes infraredradiationas a novel heating source in freeze drying (FD), leading to high-quality dehydrated products and less drying time. The present study aimed to investigate the effects of IRFD on the drying characteristics (drying time and energy consumption), volatiles, physical structure and nutritional properties ofRosa rugosaflower. In addition, freeze drying (FD) and hot air drying (HAD) were also evaluated in a comparison with the IFRD drying method with respect to product quality parameters. RESULTS Fifty-six volatile compounds were identified in fresh samples, whereas 53, 51 and 46 volatile compounds were identified in FD, IRFD and HAD samples, respectively. FD and IRFD were relatively more effective than HAD for better retention of volatile compounds ofRosa rugoseflower. E-nose analysis also exhibited similar flavor properties in FD and IRFD samples. The molecular structure properties of FD and IRFD samples measured by FTIR spectroscopy were also similar. As for nutritional properties, HAD dramatically (P< 0.05) reduced the nutritional values ofR. rugosaflower after drying. The content of vitamin C (from 14.83 to 12.15 mg 100 g(-1)), flavonoids (from 478.00 to 333.33 mg 100 g(-1)) and anthocyanins (from 220.70 to 196.90 mg 100 g(-1)) inR. rugosaflower is well retained by IRFD and no significant difference (P< 0.05) was observed between FD and IRFD samples. CONCLUSION IRFD was found to be effective in retaining the aroma, structure and nutrition ofR. rugosaflower, as well as demonstrating a lower energy consumption and shorter drying time. (c) 2020 Society of Chemical Industry