Concentration/evaporation of the juices
- Why concentrate a juice?
- Fruit juice technology
- Thermal processing
- Non thermal processing
- Juices concentration by evaporation
- Principles of recovery volatile compounds
- Evaporators for fruit juice concentration
The fruit juice processing industry is one of the world's major agro-based businesses. Orange juice dominates in juice trade worldwide. Juice is a liquid that is naturally contained in vegetable or fruit tissue. Juice may be supplied in concentrate form. Generally, concentrates have a noticeably different taste when compared to their "fresh-squeezed" versions. Juice should not be confused with squash, which is usually an artificial juice to be diluted with water. Common methods for preservation and processing of fruit juices include evaporation and spray drying.
Popular juices include apple, orange, lemon, cranberry, grapefruit, pineapple, tomato and grape. It has become increasingly popular to combine a variety of fruits into single juice drink. One of the most popular examples is Carrot, Orange and Ginger. Prepackaged single fruit juices have lost market share to prepackaged fruit juice combination's. A number of new companies have had considerable success supplying prepackaged fruit juice combination's on the basis of this transition. Fruit juice consumption overall, in Europe, Australia, New Zealand and the USA has increased in recent years, probably due to public perception of juices as a healthy natural nutrient source and increased public interest in health issues.
[...] Evaporator belongs to the class of the ?Falling Film Evaporators? and is widely used to concentrate cloudy and clear juices obtained from citrus, tropical and continental fruits which are known to be sensitive and easily spoiled when submitted to high temperatures even for short times. Concentration occurs by making water evaporate in subsequent stages called ?effects? or ?effects? being used for the steam circuit, for the product run. The T.A.S.T.E. system can be generally described as a continuous, single pass, long vertical tube falling-film type, multiple-effect stages, high vacuum, no vapor recompression, high temperature short residence time evaporator. [...]
[...] This can result in the generation of undesired, off-flavor compounds. In addition, heating the juice during evaporative concentration at high temperature for a too long period of time can greatly increase the viscosity of the resulting juice concentrate. Accordingly, evaporative concentration needs to be conducted in a manner which minimizes the generation of off-flavor compounds, as well as ensuring that the resulting juice concentrate has a relatively low viscosity. Principles of recovery volatile compounds One method for preserving the delicate aroma and flavor volatiles is to strip them from the juice before Evaporative concentration. [...]
[...] The main disadvantages are that juices are more expensive than processed juices, they have a shorter shelf life, a higher quality of fruit is required and the safety is an important concern. Thermal processing The acid nature of most juices permits pasteurization. Pasteurization is defined as, using temperatures near 100ºC to effect destruction of spoilage organisms. Although spores conceivably can survive at a pH less than outgrowth is unlikely. In contrast, at a pH greater than spore heat resistance dictates a process temperature of greater than 115ºC for an extended time. [...]