The U.S. Food and Drug Administration (FDA) defines juice as "the aqueous liquid expressed or extracted from one or more fruits or vegetables, purees of the edible portions of one or more fruits and vegetables, or any concentrates of such liquid or puree'' . Produce production is beyond the scope of this chapter, but it is critical to recognize that fruit and vegetables used for juice manufacture should be produced, harvested, and transported using good agricultural practices (GAPs). Only high-quality produce should be used. Juice processing begins with the reception of the raw produce at the processing facility. Raw produce is inspected and culled according to established good manufacturing practices (GMPs). Removal of defective raw material is critical to the production of a quality juice product. This is discussed in greater detail in Chapter 16. Sound raw produce is then cleaned and sanitized prior to extraction or maceration. For some products, such as apples and oranges, a mechanical means of washing may be employed, such as a brusher-washer. Such methods can efficiently remove soil and extraneous materials, but may be too harsh for more fragile fruits, such as berries. Sanitizing follows cleaning, which generally results in some reduction of microbial load at the surface of the fruit. Both cleaning and sanitizing are described in more detail in Chapter 17.
After appropriate culling, cleaning, and sanitizing, most noncitrus produce is macerated. Generally, produce is mechanically conveyed to size reduction equipment such as a hammer mill, crusher, or a grater for processing into a mash or pulp-like material from which the juice may be extracted. Rice hull may be added to the mash to improve juice yield during extraction. Any such added ingredients must also be approved and used according to established GMPs. Following maceration, some product types, such as tomatoes or grapes, may be given a mild heat treatment to set color, inactivate enzymes, and/or improve yield. In general, this treatment is not an effective means to reduce microbial load. Extraction of the juice follows mild heat treatment, if it is employed.
The most common juice extraction method from a mash or pulp is batch hydraulic pressing. The whole or chopped raw fruit or vegetable is placed into bags that are stacked alternately with plastic separator grid interleaves and then subjected to hydraulic pressure. Pulpers, with tapered screws or paddles, that squeeze juice and puree through a cylindrical screen, while carrying the pomace to one end for discharge, are also common.
Juices may be marketed in both clarified and unclarified styles. For clarified juices, additional processing aids, such as approved pectinolytic enzymes, are added to facilitate removal of particles and cloud.
For citrus products an entirely different extraction procedure is commonly employed by large-scale manufacturers. Citrus fruits are generally not macerated; rather, the juice is extracted while largely maintaining peel integrity. This results in limited contact between the juice and the peel. Two types of equipment are in common use: a mechanical reamer and a pin-point extractor . Mechanical reamers first cut the fruit in half. The halves are then held against rotating burrs to extract the juice and pulp. A pin-point extractor contains a small hollow tube that punctures the peel at one point. Then, intermeshing mechanical fingers squeeze the fruit surface to force the juice and pulp out through the hollow extraction tube. Seeds and pulp are separated from the juice using cylindrical pulpers and finishers.
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