Inactivation of glucose oxidase during heat-treatment de-crystallization of honey.

Glucose oxidase (GOD) is an enzyme which is secreted from hypopharyngeal gland of the bee into the nectar during the honey ripening process. Most honey types are supersaturated solutions of carbohydrates, as a result of which they are subject to crystallization, which is undesirable for many reasons. In order to prevent or eliminate honey crystallization, it is heat-treated and liquefied; however this results in decreased enzyme activity. We investigated how short-time heat treatment of honey affected GOD activity and stability at temperatures ranging from 20 to 70°C using a “Melitherm” heater and in air-tight vessels in a water bath. During honey de-crystallization at a temperature of up to 55°C, GOD remained stable, its activity varied only negligibly, while at 55–70°C it declined. Activation energy of GOD inactivation process at the heat treatment temperature ranges from 20 to 50°C and 50 to 70°C was calculated as 15 and 60.5 kcal mol-1 respectively and it was found to be related to crystal melting time and temperature.