Fruits with colour indices of 3 or 4 are the most suitable for processing. For canning, use only fruits with a colour index of 3. Use only fruits that are not rotten, over-ripe or damaged. Wash fruits thoroughly in clean running water before processing.

At ambient temperatures, damaged carambola will darken in colour as a result of enzymatic activity. Heating fruit at 80ºC for 2 minutes reduces enzymatic activity by 95%.

Most of the partially processed products are in the form of juice or pulp that are frozen, canned or packed in aseptic containers. The products are sold in bulk to industrial end- processers e.g. fruit juice, jam, jelly, confectionary, dairy or fruit-based manufacturers.

The Helicoidal Juice Extractor produces both juice and pulp with a recovery rate of approximately 85%. Juice may be processed and kept in three forms: frozen, in cans after pasteurisation and in aseptic containers after sterilisation (See Flowchart 1).

Canned juice/pulp
After deaeration, the juice may be processed with two methods; either simultaneously or consecutively. In the simultaneous process, the juice/pulp is heated in a jacketed canning tank to 75-80ºC before being poured into cans that are then sealed and pasteurised. The cans are cooled immediately under water jets to approximately 40ºC. The cans are wiped dry before they are stored.

The consecutive process involves pasteurisation with the tubular scraped heat exchanger or plate heat exchanger to 95ºC. The product is then poured into cans and sealed, flipped over and left to cool for 2 minutes.

The product may be stored and transported at ambient temperature. However, storage areas should be cool and dry to prolong the product's shelf-life.

Juice/pulp in aseptic packaging
Aseptic processing involves heat preservation and food packaging in a sterile environment. It is a superior method to freezing. Aseptic packaging is the most energy-efficient process as it reduces the cost of storage and transportation. It also retains colour and taste better.

Standardised juice and pulp are heated via the high temperature short time (HTST) process with the tubular scraped surface heat exchanger to approximately 121ºC for 2-3 seconds. The juice and pulp are instantly cooled in the scraped surface cooler to 24ºC. The product is poured into sterilised containers and can be stored at room temperature.

The following are flowcharts for the processing of common processed products made from carambola from the MARDI Food Technology Division, Malaysia.

Flowchart 2: Carambola beverage processing

Under normal storage conditions, the fine pulp in the cordial may settle at the bottom. The problem may be rectified with the addition of chmoxymethyl cellulose (CMC) as a stabiliser at a concentration of less than 0.1%.

All cordial batches should be uniform in colour. The addition of ß-carotene is useful for this purpose. The preferred container for cordials are glass bottles. The dullness of the cordial colour may be mitigated with sodium metabisulfite at the concentration of less than 80 ppm. Storage in a cool and dark place is recommended.

Flowchart 3: Carambola cordial processing

Flowchart 4: Carambola jam processing

Flowchart 5: Confectionary jelly processing

Flowchart 6: Dried carambola processing

Flowchart 7: Canned carambola slices

All source come from: http://myfruits.mardi.my/main