Changes in the odours of apple juice during enzymatic browning

Changes in the odours of apple juice during enzymatic browning after squeeze at different time points (0-6 h) were investigated by sensory evaluation and gas chromatography (GC). Trained panelists assessed a decrease in green odour with an increase in sweet odour during the browning. Fresh, fruity and apple-like odours temporarily increased in the first 2 h of browning, and gradually decreased thereafter. In the GC determination, butyl-, pentyl- and hexyl acetate as well as trans-2-hexenal were used as the volatile representatives because of their highest aroma values. Volatile release which was estimated from the proportion of volatile concentration in the vapour phase to that in the juice phase was used to elucidate the changes in odours of apple juice. The decrease in volatile release of trans-2-hexenal and the increases in those of all acetate esters during the browning corresponded well with the low intensity of green odour and the high intensity of sweet odour, respectively.