Coconut - Tropical and Subtropical Fruits: Postharvest Physiology, Processing and Packaging - page 159

COCONUT KERNEL PROCESSING
AND FINISHED PRODUCTS

Usually, copra processing in a kiln system as described
previously by Thanaraj et al. (2007) is carried out as in-
termittent drying involving alternate heating and cooling
cycles until the moisture content of the kernel comes down
to 6-7%. Since bringing down the moisture content of co-
pra to ≤ 7% takes about 1 week, many attempts have been
made to accelerate the drying process. On the basis of past
experience, the observed temperature on the copra bed was
found to be 65 ◦ -75 ◦ C. In fact, there is a possibility to fur-
ther increase the copra bed temperature by augmenting the
amount of coconut shells used per firing cycle. An exercise
of this kind was previously undertaken for the processing
of milling copra intended for oil production, where the av-
erage drying time requirement was determined for drying
temperatures of 40 ◦ ,50 ◦ ,60 ◦ ,70 ◦ ,80 ◦ ,90 ◦ , and 100 ◦ C
(Guarte et al., 1996). This should be done with the con-
current monitoring of the quality of the final product since
quality degradation due to over drying might be possible.
For instance, raising the drying temperature above 80 ◦ C
in the processing of cup copra was found to cause some
case hardening as well as Maillard browning (Guarte et al.,
1996). Apart from this, increased flame in the firing cham-
ber might cause fire hazards, and hence some close super-
vision and precautionary measures would also be required.
Alternatively, the time duration of copra drying could be re-
duced by using charcoal dust as fuel. When using charcoal
dust in place of coconut shell as fuel, the total drying time
was reduced due to prolonged burning otherwise (Jayasun-
dara et al., 2004).

Copra processing
Copra is a dehydrated form of fresh kernel. It can be found
in two different forms, namely, cup copra and ball copra.
Cup copra is usually processed through kiln drying of split-
open nuts, while ball copra is a substance formed within
a fully matured whole nut due to natural dehydration of
coconut water. Cup copra processing is done mainly for oil
milling purposes, though a small portion of it is prepared
more hygienically for direct human consumption, which is
known as white edible copra (Marikkar et al., 2009).
Typically, processing of fresh nuts into cup copra is com-
pleted in a series of steps. According to the prevailing prac-
tices in some countries, freshly harvested fully matured nuts
are initially kept for seasoning for a period of 5-6 weeks.
While in seasoning, there is a possibility for the overripe
nuts to undergo germination. Owing to germination, regions
of the kernel that are closer to the embryo may become soft
due to various biochemical reactions (Islas-Flores et al.,
1998). This would lead to the appearance of a small hole in
the middle portion of the copra cups that are processed out
of these nuts.
As the first step of processing, nuts are dehusked and
split open into two halves allowing the water to drain out.
The split cups are predried under the hot sun in an open
cemented yard for about 6 hours; bright sunny days are
ideal for this process. Although pre-drying may save energy
cost, it can increase the chances of microbial contamina-
tion (Head, 1991). The partially dehydrated coconut halves
would be loaded onto a kiln dryer for further dehydration.
For developing countries, dehydration by a kiln drying sys-
tem would be more economical than other sophisticated
drying technologies. Although coconut shells and husks
could be used as fuel for the manufacture of milling co-
pra, the use of either shell charcoal or charcoal dust would
bring better quality for edible grade copra (Jayasundara
et al., 2004).
Although copra production is essentially a dehydration
process, the drying behavior of coconut kernel differs from
those of other edible crops in some respects. Unlike the
other agricultural commodities, coconut kernel possesses
a concave structure, where the moisture removal during
drying might take place in stages. For this reason, a cooling
period is required after predetermined heating time. If the
dehydration of coconut halves is done in a single stretch at
high temperature, there is a possibility of case hardening,
which may eventually hinder subsequent moisture removal
from the kernel.

Copra outturn, packing, storage, and quality issues
The moisture content of dried copra is about 6-7%, with
68% oil content (Nathanael, 1966). Copra yield, commonly
referred to as outturn, is normally dependent on varietal
differences, seasonal variations, and the maturity of the
nuts. The details of the copra outturn coming from differ-
ent hybrid crosses introduced in Sri Lanka are shown in
Table 9.5. Owing to the larger nut size, 'CRISL 98'
( Ta l l San Ramon ) gives a higher per nut yield of

copra. The copra yield of 'CRIC 65' ( Ta l l

×

× Dwarf

green and Dwarf green Ta l l ) is relatively lower than

that of the open-pollinated tall variety.
Per nut copra yield may also be affected by the maturity
of the raw nuts. For best yield recovery of copra, coconuts
should have at least 11 months of maturity (Anon, 2006).
Copra processed from immature nuts is not only lower in
yield but is of inferior quality. For instance, the cups often
turn rubbery and do not last long at ambient storage. The
problem of immature nuts is often due to nonuniformity in
the harvesting pattern.

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