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ABSTRACT: Cloudy fruit juices, particularly from tropical fruit, are becoming a fast-growing part of the fruit juice sector. The classification of cloud as coarse and fine clouds by centrifugation and composition of cloud from apple, pineapple, orange, guava, and lemon juice are described. Fine particulate is shown to be the true stable cloud and to contain considerable protein, carbohydrate, and lipid components. Often, tannin is present as well. The fine cloud probably arises from cell membranes and appears not to be simply cell debris. Factors relating to the stability of fruit juice cloud, including particle sizes, size distribution, and density, are described and discussed. Factors promoting stable cloud in juice are presented.
KEY WORDS: opalescence, cloud, fruit, juice, stability, particulate.
I. INTRODUCTION
In Europe especially, the category of pulp-- containing or cloudy juices has become a fast-- growing sector.14 The Japanese market appreciates a premium cloudy juice,7 and more recently the North American markets are becoming open to freshly prepared opalescent or cloudy juices, especially tropical juices. Citrus juices have long been cloudy or opalescent, and tropical fruit nectars are usually cloudy drinks.14 The tropical fruit juice category is growing worldwide.
The visual appearance of a cloudy drink is a decisive factor for consumer acceptance. While the color and flavor of these products are important, they are not the primary determinant of the purchase decision. The customer expects that the drink will have neither a sediment nor a cream phase - that is, the drink will have a stable opalescence or cloud and sediments, or container ringing caused by a floating lipid phase, are considered to be defects. Most fruits and vegetables used to manufacture cloudy beverages do not contain significant oil; however, citrus and coconut may, and the more exotic fruits being developed for fruit juice manufacture such as sea buckthorn definitely have these problems.9 Opalescent apple juice has been known since its description by Pederson.37 The growth of the opalescent or cloudy juice category coupled with problems arising with cloudy juices made from pineapple, passion fruit, and strawberry30 have stimulated renewed interest in the factors determining cloud stability in cloudy juices and in better defining the manufacturing conditions contributing to the increased cloud stability of these drinks. Much of the literature...