HAZE AND CLOUD IN APPLE JUICES

Turbidity in apple juice is desirable or undesirable, depending on whe ther the product fits within consumer expectations. Desirable opalesce nce is due to soluble pectin and insoluble pectin stabilized particles that show considerable stability. Blanching treatments enhance this s tability by reducing particle size and character-solubilizing pectin, and possibly by the destruction of natural enzymes that may destabiliz e the cloud over time. Undesirable haze and sediments may arise in app le juice by several mechanisms, including starch (dextrin) retrogradat ion, protein phenol aggregation, phenol oxidation, crystallization of carbohydrate macromolecules extracted from cell walls, or difficulties during manufacture. The mechanisms of formation of each of these form s of haze are discussed and examples given from the literature. Where available, haze-sediment morphology by light and/or electron microscop y is documented and the possible role of recently developed ''macerase '' enzymes in haze/sediment formation discussed.