Procyanidin Contributions to Haze Formation in Anaerobically Produced Apple Juice

Procyanidins in apple juice and a model system were examined for their haze-forming potential. In anaerobically prepared juice, only unheated samples stored with an air headspace formed haze. Heated juice gave an immediate increase in turbidity, but turbidity did not develop further on storage at 20 °C for 216 d. Sephadex LH-20-isolated procyanidins did not develop turbidity over 216 d at 20 °C in malate buffer pH 3.5. Lack of headspace enhanced storage stability in all samples tested. Light microscopy supported the above findings relative to particle development, and staining with toluidine blue provided a more sensitive detection of particulate. The use of toluidine blue staining as a predictive test for haze development is suggested. Electron microscopy of negatively stained juice and model system preparations showed several particulate morphologies typical to each preparation. These particles probably grow and aggregate to form macroscopic haze.