Preliminary Study on Glucose Oxidase–Catalase Enzyme System to Control the Browning of Apple and Pear Purées

Oxygen is a key factor in fruit purées browning. The use of a commercial glucose oxidase–catalase enzyme system (GOX) for oxygen removal and browning control of Golden Delicious apple and Kaiser pear purées during storage has been investigated. The effect of ascorbic acid and peroxidase has also been tested and results compared with control (no treatment). Colour change was quantified using the CIE L *, a *, b * system. Heating has been the unique treatment able to control the enzymatic browning of fruit purées, whereas GOX was the most efficient in reducing to low level the dissolved oxygen content in apple and pear purées (99% oxygen removed), and showed an interesting capability to control the nonenzymatic browning during fruit processing and purées storage. However, ascorbic acid decreased the nonenzymatic browning of fruit purées to a larger extent than any other chemical treatment used in this study. The Kaiser pear shows a fast enzymatic browning thus may represent a good ‘standard’ to measure browning kinetics.