Characteristics of ß-glucosidase from oranges during maturation and its relationship with changes in bound volatile compounds.

ABSTRACT

BACKGROUND: The hydrolysis of glycosidically bound volatile compounds can release potential aromas in oranges during maturation. ß-Glucosidase is the key enzyme that influences the hydrolysis of bound volatiles. In this study the changes in ß-glucosidase and bound volatile compounds in Jincheng oranges during maturation were investigated. The relationship between ß-glucosidase activity and bound volatiles was analyzed. RESULTS: The optimal temperature and pH of ß-glucosidase from Jincheng oranges were 40 °C and 5-6 respectively. Its Km and Vmax values were 0.61 mmol L(-1) and 0.009 U mg(-1) respectively. The activity of ß-glucosidase was strongly inhibited by Zn(2+), Fe(2+), Cu(2+), Ag(+), Hg(2+) and Fe(3+). ß-Glucosidase activity in pulp increased gradually during maturation, while that in peel first increased and then decreased in November. In total, 12 and 14 bound volatiles were found in pulp and peel respectively of this orange during maturation. CONCLUSION: The concentration of bound volatiles in pulp and peel decreased with the rise in ß-glucosidase activity in pulp and peel during maturation. This indicated that bound volatiles in Jincheng oranges were released during maturation owing to the increase in ß-glucosidase.