Apples from storage, fresh fruit eliminations, or apples directly from the orchard go to the processing plant. First, leaves, grass, and rotten fruit are eliminated. The fruit is thoroughly washed and sorted and may be trimmed if this can be done profitably. Removal of partly or wholly decayed fruit may be the single most important factor in producing high quality apple juice. If the decayed fruit is not eliminated, it produces off-flavors, increases the probability of microbial spoilage, and introduces possible microbial toxins into the finished product. Leaves and grass must be separated as they also can cause off-flavors in the juice. As a general rule, at least three cultivars of ‘eating ripe’ apples are blended prior to grinding. This gives a desirable blend of the sugar-acid ratio and a preferable aroma. Processing a single cultivar and blending the juice after it is concentrated is not economical. Sound fruit is sent to a grater or hammer mill to reduce the apples to a pulp. If the pulp is too coarse, the juice will be low in yield and soluble solids; if the pulp is too fine, it is difficult to press, and the juice has an excess of fine particles. Enzymatic browning of ground apples takes place in a few minutes and needs to be controlled by inhibiting the polyphenolase enzymes with heat, ascorbic acid, or sulfur dioxide. Ascorbic acid at 0.05 % can be added directly into the grinder, but the reaction is difficult to control. The tannins may be oxidized, destroying the desirable amber color. Next, the juice is ready to be extracted from the pulp。
