Role of Invertase in Sugar Content in Highbush Blueberries ( Vaccinium corymbosum, L.)

Abstract

Six batches of ripe blueberries (Vaccinium corymbosum L.) were analysed for sugar content. Glucose and fructose were found to be the predominant sugars, and were present in approximately equal proportion (glucose:fructose ratio of about 1). Distinct differences were observed between the sucrose concentrations of all batches; the proportion of sucrose present ranged between 1.6 and 14.6 g per 100 g of total sugar. No sucrose synthetase and sucrose phosphate synthetase activity was detected in any of the batches, but each batch exhibited an invertase activity. This appeared to be inversely proportional to sucrose concentration. Variations in sucrose concentration were attributed to the action of the enzyme, and invertase activity was closely correlated with sucrose content. The optimum temperature for this enzyme was 60°C. Invertase can modify the sugar profile and affect the flavour of end products. Temperature control is suggested as a method to inactivate invertase, to prevent all modifications.