Abstract
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/cm2), 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/cm2), 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.
Highlights
Flavor compounds in fruits, occurring in their free forms, in which they contribute directly to fruit flavor, are present in bound forms
2.6 | Structural characteristics of β‐D‐glucosidase treated by ultrasound
Β‐d‐Glucosidase solution was sonicated, and its circular dichroism spectrum was measured with respect to buffer solution as the blank in a quartz cuvette of 1 mm optical path length at room temperature (20 ± 1°C)
Summary
Flavor compounds in fruits, occurring in their free forms, in which they contribute directly to fruit flavor, are present in bound forms. Glycosides of volatile compounds identified in fruits are mainly O‐β‐d‐glucosides or O‐diglycosides, rarely trisaccharide glycoconjugates. The method of β‐d‐glucosidase hydrolysis of glycosidically bound volatiles has a major drawback in that the hydrolysis time is too long which has limited its application in food industry. Fernandes, García‐ Pérez José, and Cárcel (2016) found that ultrasound‐assisted drying increased the activities of polyphenoloxidase, peroxidase, and peroxidase ascorbate in apples, but led to partial inactivation of pectin methylesterase. The objectives of this study were to evaluate the effects of ultrasonic power, time, temperature, medium pH, and duty cycle on β‐d‐glucosidase activity, to analyze the structures of the enzyme under its activation and inhibition conditions conducive to, and to explore the mechanism whereby ultrasound affects enzyme activity. The results could expedite the application of ultrasound in enhancing aroma in fruit juice
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