Yujing Sun,Li Zeng,Yuanzhong Xue,Tianbao Yang,Zongming Cheng,Peilong Sun
β- d -glucosidase can release aroma precursors to improve the flavor of plant food, but the hydrolysis efficiency of the enzyme is low; the purpose of this study was to improve the enzyme activity using ultrasound. The effects of ultrasound parameters on β- d -glucosidase activity were investigated, and the respective structures of enzyme activated and enzyme inhibited were further analyzed. Low temperature (20–45°C), low ultrasonic intensity (<181.53 W/cm 2 ), and short treatment time (<15 min) led to the activation of β- d -glucosidase, whereas high temperature (45–60°C), high ultrasonic intensity (>181.53 W/cm 2 ), and long treatment time (>15 min) led to its inhibition. Application of ultrasound lowered the optimum temperature for β- d -glucosidase activity from 50 to 40°C. Ultrasound did not change the primary structures of the enzyme, but changed the secondary structures. When ultrasound activated β- d -glucosidase, the α-helix contents were increased, the β-fold and irregular coil content were reduced. When ultrasound inhibited β- d -glucosidase, the contents of β-folds were increased, the α-helix and irregular coil contents were reduced.. In summary, activation or inhibition of β- d -glucosidase under ultrasound was determined by the ultrasound conditions. This study suggests that ultrasound combined with β-D-glucosidase can be used in aroma-enhancing.
Baking is widely accepted for aroma enhancement of black tea, and studies have mainly focused on the aroma or chemical substances under a specified baking condition. Understanding of the feedback between aroma substances and characteristics is urgently needed. Therefore, a mutual feedback platform (SES/MS) combined sensory evaluation system (SES) with gas chromatography–mass spectrometry (GC-MS) was established. Based on this platform, we found that baking at 90 °C for 4 h or 5 h could maintain the primary aroma attributes and increase characteristic aroma attributes—these were considered to be the best baking conditions for Yunnan congou black tea. Meanwhile, 47 volatiles were identified, among which, pyrrole and benzaldehyde appeared to have a caramel aroma, and 2-furanmethanol and α-terpineol presented a baked aroma. This study reveals the dynamic change of aroma profiles and compounds during the aroma enhancement, and provides an optional template for researchers, focused on the relationship between quality and aroma attributes of teas.Keywords:Yunnan congou black tea;aroma enhancement;aroma attributes;volatile compounds;multiple factor analysis
β-Glucosidase (BG) was immobilized on the surface of bifunctionalized nano-magnetic iron oxide with silica and amine groups (Fe3O4@SiO2-NH2). The aroma and flavonoid aglycone enhancement effect of BG in tea soup was investigated. The immobilized BG-synthesized nanocomposite morphology and structure were characterized by using different analytical techniques, including Fourier transform infrared spectroscopy and scanning electron microscopy. The immobilized BG showed enhanced pH and temperature endurance at an optimum pH of 5.0 and temperature of 65 °C. After seven cycles of reuse, immobilized BG showed 51.8% initial activity. Immobilized-BG treatment in green tea and black tea soup elevated the aroma content by approximately 16% and 48%, respectively. In addition, flavonoid aglycones, such as myricetin, kaempferol, and quercetin, in green tea and black tea soup increased by approximately 65- and 5-fold, respectively. These results suggested that immobilized BG showed excellent potential in the enhancement of aroma and effectively hydrolyzed the flavonoid glycosides to release flavonoid aglycones in tea soup. Hence, this study provides a green and sustainable approach for the tea industry to efficiently enhance tea soup properties.
危险品化学品经营许可证（带存储）