Longan and Carambola - Tropical and Subtropical Fruits: Postharvest Physiology, Processing and Packaging - page 226

solids content of the slice should be 45 ◦ Brix. The drying
temperature should be approximately 55 ◦ Cinthefirst6
hours, and then reduced to 50 ◦ C as the process continues.
The water activity of the finished product should be less
than 0.75 (Wu et al., 2004).

Juice, concentrate, and juice blends
Carambola juice products are among the most important
processed commodities of carambola fruit. For juice mak-
ing, the mature fruit with yellow color (not fully ripened)
carambolas are used as raw material. The water content in
fresh carambolas often exceeds 90%. Juice extraction can
be done simply by crushing and pressing. The juice yield
is normally more that 60%. Various types of carambola
drinks have been developed, including fermented caram-
bola drink, sweetened carambola juice, carambola nectar,
and carambola juice blends (Wu et al., 2004).

Figure 12.4. Dried carambola and carambola
candies (products of Thailand).

Drying/dehydration
Fully ripened carambola fruit are sliced into approximately
1.2 cm in thickness, deseeded, immersed in 1500 ppm
sodium bisulfite solution for 10 min, and dried using a
hot-air oven at 60 ◦ C for 6 hours, and then held at 50 ◦ C
until the water activity of the product is less than 0.75.
Carambola preserves or osmotic dehydrated carambo-
las are usually prepared from semiripened carambola fruit.
The sliced and deseeded fruits are immersed in a solu-
tion of sodium bisulfite (NaS 2 ) and CaCl 2 for 1-2 days for
color and texture improvement. Then, they are blanched
and soaked in sugar solution before hot-air drying. The
stepwise sugar solution shall be used with a 30 ◦ Brix sugar
solution in the beginning. Within 24 hours, the sugar con-
centration should be increased to 50 ◦ Brix. The final soluble

Fermented carambola drink
Tart carambola containing high acids and tannic compounds
are usually too sour and tart to be consumed directly. Fer-
mentation helps improve the taste of these tart cultivars.
Fermented carambola juice is a traditional Chinese health
drink. It is believed to help soothing some uncomfortable
ailments such as sore throat. The carambola is washed,
weighed, and then placed in plastic vats or cement tanks.
Then, 8% w/w of salt is added in alternate layers. Small
amounts of licorice and other minor constituents, such as
mei (Japanese apricot) fruit, dried crab apple, and herbs,
may be added for smoother taste. After sprinkling salt on
the top layer of fruit, the container is covered with bam-
boo lath. A stone is placed on top of the lath to keep the
fruit submerged in the leaked juice as a result of osmo-
sis. The natural fermentation is allowed to proceed at room
temperature for 3 months. Major organisms responsible for
the natural fermentation are film-forming yeasts including
Candida gehellencus, C. krusei, C. tropiculis, Cryptococ-
cus neoromans, and Hanseniaspore gerilliermondii. The
pickled juice obtained from fermentation then is filtered,
pasteurized, and hot-filled in plastic drums for storage. The
shelf life can be extended by refrigeration. For direct con-
sumption, the juice is then diluted with water to a concen-
tration of 5-10% juice content, sweetened with sugar, and
then repacked in small aseptic packages such as 250-ml
Tetra Brik cartons (Wu et al., 2004).

Sweetened carambola juice
Some tart cultivars with sour taste and acceptable tartness
can be processed into sweetened unfermented juice. The

Figure 12.5. Carambola juices and carambola
candies from Taiwan.