Most juices are derived from fleshy fruits and these may be conveniently subdivided for processing into three categories.
- Fruits which are pulped and their juices removed by pressing e.g., apple, berry fruits
- Fruits requiring the use of specialized extraction equipment, e.g., citrus fruits, pineapples
- Fruits requiring heat treatment before processing, e.g., tomatoes, stone fruits
In most large fruit processing operations the plant is usually dedicated to one type of fruit.
Citrus fruits are unusual because the outer skin or flavedo is rich in essential oils and other tissues such as the albedo or carpellary membranes contain substances that give rise to bitter flavors. The processing of citrus typically involves separation of these various components as an important principle and for certain products such as comminuted bases, the various components are recombined in different proportions.
The flesh of stone fruits is separated from the stones or pits, not only to facilitate ease of handling, but also because the stones are further processed to obtain both fixed oils and glycosides. Fixed oils, such as those from peach, have application in the cosmetics industry and glycosides may be used as a source of other natural flavoring ingredients such as benzaldehyde.
Another important aspect of the processing of fruits is the presence of pectins. These substances contribute to the viscosity of fruit juices and assist in the suspension of colloidal material and tissue fragments that make up its cloud.
When most fruits are pressed, pectolytic enzymes are released and these will, if not destroyed, clarify and or cause gelling of the juice. Rapid initial processing of freshly pressed juice is therefore an important factor in determining whether cloudy juice is obtained or clear juice, in which case enzymes are allowed to act and may enhanced by the addition of synthetic enzymes in further quantity.
Fruit Processing
