Flavour losses in apple juice manufacture

Flavour losses occurring in apple juice manufacture were investigated by gas chromatography and sensory analysis in two factories A and B using different technologies and equipment. Samples were taken at different intervals during the processing season from the raw material, the pressed juice, the clarified and filtered juice, the apple juice concentrate and the apple flavour concentrate produced in plant A. The chromatograms of the pressed juice showed changes in volatile composition as compared to the raw material: the number of components was slightly reduced, although some new components could be detected, probably owing to enzymatic processes. The enzyme preparation and method used for clarification did not affect volatile composition to the extent expected. The volatile abstracting effect of vacuum evaporation for flavour recovery as performed in plant A seems to be compensated by flavour formation from precursors during pectolytic enzyme treatment. The greatest losses in both factories were encountered during evaporation concentration of the clarified and filtered juice. Chromatographically established volatile composition was distinctly different in the concentrated apple juice samples from the two plants, however, this difference was perceived by the sensory test panel only towards the end of the processing season. The apple flavour concentrate contained less than half of the volatile components present in the raw material. The gas chromatograms of the flavour concentrates produced at different times did not reflect the fluctuations observed in the volatile composition of the raw material and the intermediate and end products, however, sensory tests showed the samples from the beginning of the processing season to be superior to those from its end.