CitrusBotanically, citrus varieties are forms of berry fruits n which the hairs inside the ovary walls form juice sacs.
Epicarp is the familiar highly colored, oil bearing outer layer. Both juice and oils are now valuable commodities in all citrus varieties and the recovery of both material is important to the economics of processing.
Many different processes are used world-wide for citrus types with a two stage operation being widely employed. In a typical process, the fruit passes over an abrasive surface or roller where the sacs in the epicarp are pierced and oil washed away by water spray.
The resulting oil-in-water emulsion is screened to remove vegetable debris and oil is separated by centrifugation and then dried and packed.
The rasped fruit then moved onto an extractor where the juice is removed leaving albedo (pith) and peel (flavedo).
Various juice extractors have been used with fruit being encompassed in a roll mill or screw press, or the juice bearing material reamered out.
Expressed juice is subjected to screening (sometimes referred to as finishing) before being further processed.
Limes are normally processed in a slightly different manner. Washed fruit is compressed in a screw press to yield a pulpy juice that typically also contains the oil emulsion.
Larger pieces of pulp are screened out and in the classical process, juice and oil emulsion are fed to large tanks where a natural separation process occurs.
Naturally occurring enzymes, which may be enhanced by the addition of commercially available synthetic pectolytic enzymes, clarify the juice while the oil bearing emulsion and pulp settle to the top of the tank. At the same time other debris settles below the clarified layer.
Clarified juice is then typically filtered and concentrated while oil bearing emulsion is steam distilled. The process often requires a period of some hours of heating before actual distillation starts and it is in this way that the oil is brought to the specification required by the consumer.
Stream distillation of lime oils usually brings about a number of changes to the components present in the undistilled oil.
The fate of citrus juices both during and after processing will vary with their subsequent use. Whereas lime juice us normally available only as a clarified juice, lemon and orange juices are available both clear and cloudy.
Because of the very high natural acidity (up to 8% s citric acid) of lime and lemon juices, clarification can take place using unpasteurised juices which will not normally ferment.
Orange juice must be treated differently. Clarification is carried out by addition of pectolytic enzymes after pasteurization to destroy microbiological activity.
As with soft drinks fruit juices, the bulk of citrus are subjected to concentration to facilitate shipping and during the process, volatile component are usually collected separately from the juice concentrate.
Both oil an water phase volatile fractions are collected from processes and these are widely used in flavorings.
Citrus
