Abstract
Naringinase is an enzyme complex which exhibits α-l-rhamnosidase and β-d-glucosidase activity. This enzymatic complex catalyzes the hydrolysis of naringin (4′,5,7-trihydroxy flavanone 7-rhamnoglucoside), the main bittering component in grapefruit. Reduction of the level of this substance during the processing of juice has been the focus of many studies. The aim of the study was the immobilization of naringinase on chitosan microspheres activated with glutaraldehyde and, finally, the use of such immobilized enzyme for debittering grapefruit juice. The effect of naringinase concentration and characterization of the immobilized enzyme compared to the soluble enzyme were investigated. The maximum activity was observed at optimum pH 4.0 for both free and immobilized naringinase. However, the optimum temperature was shifted from 70 to 40 °C upon immobilization. The KM value of the immobilized naringinase was higher than that of soluble naringinase. The immobilization did not change the thermal stability of the enzyme. The immobilized naringinase had good operational stability. This preparation retained 88.1 ± 2.8% of its initial activity after ten runs of naringin hydrolysis from fresh grapefruit juice. The results indicate that naringinase immobilized on chitosan has potential applicability for debittering and improving the sensory properties of grapefruit juices.
Highlights
Naringin, a flavanone diglycoside, is the main component responsible for the bitter taste of citrus fruits
The optimum activity over acidic pH and optimum low temperature of naringinase revealed that this enzyme can this be suitable forcan application in acid such as immobilized naringinase revealed that enzyme be suitable forenvironments, application in acid citrus juice, while maintaining the nutritional and organoleptic nature of the juice
Be efficiently perceptibility by hydrolysis with naringinase immobilized on chitosan microspheres
Summary
A flavanone diglycoside, is the main component responsible for the bitter taste of citrus fruits. The concentration of naringin in grapefruit juice is low, it imparts a perceptible bitter taste to consumers. The bitterness of citrus fruits, mainly of grapefruit, is an undesirable quality for the juices industry [7]. The naringin level can be reduced by different methods such as adsorptive debittering [9] and β-cyclodextrin treatment [10]. The debittering of citrus juice can be achieved by naringin hydrolysis using naringinase. Naringinase treatment is a promising method due to the fact that it enhances the organoleptic properties while retaining its health-promoting properties [11]. The ability of naringinase to hydrolyze many glycosides, e.g., naringin, hesperidin, quercetin, diosgene, and rutin, is the main application for that enzyme [3,13]. Due to the health-promoting properties of hydrolyzed products, it can Molecules 2019, 24, 4234; doi:10.3390/molecules24234234 www.mdpi.com/journal/molecules
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