Submitted to: Food Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 28, 1998
Publication Date: N/A
Interpretive Summary: A critical review containing some new data of the role of juice cloud in citrus juices, its composition and how it is affected by species and cultivar. The effect of the native clarifying enzyme pectinmethylesterase (PME) on cloud, and means to prevent its action are discussed. Production of intentionally clarified citrus juices, and use of citrus juice byproducts as clouding agents for other beverages are also covered.
Technical Abstract: Juice cloud or turbidity is essential to the appearance, flavor and texture of most citrus juices, so a thorough understanding of juice cloud characteristics and conditions leading to cloud loss is essential to production of consistently high quality finished products. This critical review discusses the function of cloud in juice, its composition and cellular origins, and species and cultivar variation in cloud appearance. Although several circumstances may lead to cloud loss, pectinmethylesterase (PME) demethylation of juice pectins and the attendant precipitation of low methoxyl pectins by divalent cations is paramount. Conditions favoring this occurrence, and means to prevent PME-induced cloud loss are discussed. Some new data on the effects of PME isoforms on juice cloud loss is given, showing that they differ in clarifying efficacy at different temperatures. Procedures to stabilize citrus juice cloud primarily focus on interrupting the effects of PME. These include PME inactivation or inhibition, removal of low methoxyl pectins, or precipitation of divalent cations. Citrus juice byproduct streams also serve as excellent sources of natural clouding agents for juice-based beverages, although much work needs to be done in this area to improve their stability.