Coconut Research Institute Repository

Mordue (Luntz) A.J.

Eeswara, J.P.

Wickramananda, I.R.

Allan, E.J.

Neem metabolities with insect antifeedant and growth regulatoryproperties are produced in tissue cultures. Abstracts

Ranasinghe, C.S.

Taylor, G.

Mechanism for increased leaf growth in elevated CO2: changes inleaf anatomy and in molecular weight distribution of xyloglucan

Vidhanaarachchi, L.P.

The effect of soil physical properties on growth and activity ofcoconut (Cocos nucifera L) roots

Vidhana Arachchi, L.P.

Somapala, H.

Mapa, R.B.

Yapa, P.A.J.

Study of the effective root zone of coconut in relation to soilcompaction

Tennakoon, N.A.

Soil biology in lateritic coconut soils of Sri Lanka

Rodrigo, M.C.P.

Amarasiriwardena, B.L.

Samarajeewa, U.

COCOS (1996), 11, 21 - 3 1 
Printed in Sri Lanka 
SOME OBSERVATIONS ON COPRA DRYING 
IN SRI LANKA 
M C P Rodrigo, B L Amarasiriwardene1 and U Samarajeewa 
Department of Food Science and Technology, 
University ofPeradeniya, Peradeniya, Sri Lanka 
ABSTRACT 
Twenty five commercial copra kilns in Sri Lanka were studied for variations of 
their dimensions and copra curing practices in relation to the "Standard Ceylon 
Copra Kiln" and the quality of copra produced. Changes in the height and the width 
of the platform resulting in probable changes in drying conditions of copra was 
noted. The use of powdered charcoal appeared to improve the quality of copra 
produced and more cost effective than use of coconut shells. Addition of sulphur dust 
to the fuel further unproved the quality of copra. 
INTRODUCTION 
Extraction of coconut oil by converting the coconut kernels to copra continues to 
be the most economical and efficient method in spite of several disadvantages 
(Samarajeewa, 1993). The production of copra is labour intensive, results in under 
dried and over dried kernels at times, uses most of the valuable coconut shells as 
fuel, and also results in deposition of polycyclic aromatic hydrocarbons (PAH) on 
the surface of kernels. Some of the PAH are carcinogenic and pass into, edible oils 
on extraction (Wijeratne et al . , 1996). 
The kilns used to dry coconut kernels vary from country to country in the South-
East Asian region (Timmins, 199S). The capacity, the methods of operation, the fuel 
used and the quality of coconut kernels used depends on the types of drying 
processes although they all basically operates on the direct drying principles. The 
quality of the copra produced varies widely depending on the types and operational 
conditions of the kilns. Some of the existing kilns (dryers) and the operational 
conditions are reviewed by Patel (1985). 
In Sri Lanka, coconut kernels were dried using the "Chula dryer" introduced in 
1923 for copra manufacture. The "Chula dryer" operates on indirectly heated air 
generated by a furnace. This dryer was replaced by the direct air heated "Standard 
Ceylon Copra Kiln" (STD) designed in 1960s. This model is still considered to be 
the most economical and drying is practiced following the guidelines stipulated with 
1
 Coconut Development Authority, Colombo, Sri Lanka. 
21 
the design of the kiln (The Ceylon Copra Kiln, 1965). The drying operation reduces 
the moisture content in the kernels from 43% to 8% (Nathanael, 1962). However, 
the design of the kiln and the drying procedure has got modified over the years in 
the hands of the copra manufactures. A study of 25 copra kilns was carried out to 
understand the modifications and the resulting effects on copra quality processed in 
the present kilns. Currently there is a need to improve the copra production methods 
to meet the demand for a quality copra - white in appearance and containing no 
smoke deposits, thus avoiding PAH. 
MATERIALS AND METHODS 
Twenty five copra kilns in the Marawila-Chilaw area were visited. The 
measurements of the copra kilns and the copra drying chambers were made. The 
method of copra drying in relation to the type of fuel used (coconut shells, coconut 
charcoal, other) the pattern of spread of the fuel on the surface (number and spacing 
of rows or other spreads) were examined. A breakdown of the quality of copra based 
on the commercial grading system (white edible, edible, milling superior, milling 
ordinary) was carried out in relation to each of the mills. 
RESULTS AND DISCUSSION 
General Information 
The general information on the over all dimensions of the copra kilns, the 
locations of the ventilation openings in the firing chamber and the operational 
procedure practiced in copra drying are summarized in the tables 1 to 3 respectively. 
All parameters show a wide range of variation compared to the kiln at the. Coconut 
Research Institute. With regard to the over all size of the kilns there are differences 
between the "Standard Ceylon Copra Kiln" (STD) described in the advisory leaflet 
and the one used at the Coconut Research Institute (CRI) too. The mean dimensions 
of the kilns in the field lie between that of the CRI and STD kilns. 
Of the different parameters, the width of the drying chamber and the distance 
between the floor and the drying platform are critical in the drying process. The 
mean width of the platform in commercial mills is 2.8 ± 1.2 m as against the widths 
of 1.1 and 1.5 m recommended and used in the STD and CRI kilns (Table 1). To 
compensate for the doubling in the width in commercial mills the copra producers 
lay two or more rows of shells to be burned instead of a single row recommended 
(Table 3). The variations in gaps between the rows of shells laid down in the 
different kilns and the number of lines of shells per row can result in overlap of heat 
cones and heat intensities or unheated gaps at the drying platform leading to uneven 
drying of copra. 
Most kilns operate with a much lower height (mean 2 ± 0.4) m as against 3 m 
22 
recommended in the STD kiln and 2.4 m used in CRI kiln (Table 1). The heights of 
the drying chambers are reduced, perhaps with the intention of catching the heat 
early, thus economizing on the fuel. However, it is not known whether the reduced 
height results in increased scorching of copra or the burning is adjusted in such a 
way to overcome possible scorching. The combination of wider platform and reduced 
height in the drying chamber would certainly affect the quality of copra. 
Overlap of Heat Cones 
It is assumed that the design of the "Standard Ceylon Copra Kiln" and construction 
of the CRI kiln have taken into consideration the most efficient heat distribution in 
each chamber. On the basis of the design of the drying chambers of CRI and STD 
kilns, one could assume the presence of an inverted heat cone with apex at the 
burning point of shells and base overlapping with the surface of platform containing 
copra to be dried. The angle at the apex of the inverted cone works out to be 26° 
and 28° for the CRI and STD kilns. 
When the concept of heat cone is extended to the commercial kilns examined, the 
drying appears to occur with overlapping of the base of heat cones in most of the 
kilns, sometimes resulting in 100% overlap on the basis of the diameter of the cone 
(Table 4). In situations with 30% to 50% overlap one could expect areas of higher 
temperatures and increased rates of drying. The high temperature areas on the drying 
platform may. result in case hardened and scorched copra. On the other hand if the 
rows of shells are too far apart leaving unheated or low temperature areas outside 
the heat cones during drying, copra may become slimy due to bacterial growth on 
the surface. It is. important to adhere to stipulated dimensions in the drying chamber 
and laying of the rows of fuel for uniform and efficient drying. The temperatures of 
the kernels at drying need to be monitored to understand the performance of the 
modified commercial mills. An examination of the percent distribution of under-dried 
or over-dried copra produced in the modified kilns may provide necessary 
information for required adjustments. 
Ventilation 
In addition to the door which allows entry of plenty of air during burning of 
shells, windows are kept for ventilation in most of the kilns in keeping with the 
requirements laid down in the CRI leaflet (Table 2). During drying of copra the door 
is normally kept closed for controlled burning of shells. 
The ratio of total volume of the copra drying chamber to the area of the 
ventilation openings (window or the window and the door together) varied widely, 
in the commercial kilns showing a very high standard deviation (Table 5). It is not 
known whether such variations do effect the quality of copra. The possible effects 
are worth examining. 
23 
Table 1. Overall measurements of copra kilns (m). 
Parameter CRI STD Commercial 
Length of copra kiln mean 21.6 30.2 20.4 ± 10.7 
range 6.0 - 40.8 
Width of copra kiln mean 6.0 3.8 3.8 ± 0.7 
range 2.7 - 5.8 
Width of the veranda mean 1.7 1.8 2.4 ± 0.9 
range 0.8 - 5.5 
Height of roof (lowest) mean 2.0 2.3 2.2 ± 0.4 
range 1 .2 - 3.0 
Height of roof (top) mean 4.0 4.6 3.8 ± 1.1 
range 3.0 - 7.0 
Number of drying chambers mean 16 18 8 ± 4 
range 3 - 16 
Depth of drying chamber below ground level mean 1.1 0.9 0.5 ± 0.4 
range 0 . 0 - 1.9 
Height of the drying chamber mean 2.4 3.0 2.0 ± 0.4 
range 1 . 7 - 3 . 1 
Width of the drying chamber mean 1.1 1.5 2.8 ± 1.2 
range 1.1 - 5.4 
CRI - Copra kiln used in the Coconut Research Institute 
STD - 'Standard Copra Kiln' recommended in the CRI Leaflet No. 15. 
24 
Table 2. Location of ventilation openings in copra kiln. 
Parameter CRI STD Commercial 
Windows per chamber mean 1 1 2 ± 0.6 
range 0 - 6 
Distance between two windows mean n.a. n.a. 0.5 ± 0.6 
range 0 - 2 . 1 
Height of window from floor mean 1.2 0.3 0.6 ± 0.5 
range t 0.1 - 1.4 
Distance of window from the wall mean 0.5 0.7 . 0.5 ± 0.3 
range 0.1 - 1.1 
Width of window mean 0.1 0.2 0.1 ± 0.1 
range 0 . 1 - 0.3 
Height of window mean 0.4 0.6 0.2 ± 0.2 
range 0.1 - 0 . 6 
Height of the door mean 0.8 1.2 0.8 ± 0.1 
range 0 . 6 - 1.2 
Width of the door mean 0.8 0.8 1.1 ± 0.2 
range 0 . 7 - 1.6 
CRI - Copra kiln used in the Coconut Research Institute 
STD - 'Standard Ceylon Copra Kiln' recommended in the CRI Leaflet No. 15. 
n.a.- not applicable 
25 
Table 3. Operations of copra drying (all lengths in m). 
Parameter CRI STD Commercial 
Sun drying + + + in 22 
- in 3 
Fuel shell shell shell in 18 
shell + S in 1 
char in 2 
char + S in 4 
Number of firings mean 
range 
8 8 5 ± 1 
2 - 8 
Number of double rows mean 
range 
1 2 3 ± 1 
1 - 8 
Width of a row mean 
range 
0.4 n.a. 0.3 ± 0.1 
0 . 3 - 0 . 4 
Distance between rows mean n.a. n.a. 0.8 ± 0.9 
range n.a. n.a. 0.3 - 1 
CRI - Copra kiln used in the Coconut Research Institute 
STD - 'Standard Ceylon Copra Kiln* recommended in the CRI leaflet No. IS 
char - charcoal powder 
S - sulphur powder 
+ - sundried prior to drying in the kiln 
directly kiln dried (no sundrying) 
n.a. - not applicable 
26 
Table 4. Overlap of heat cone during drying of copra in the individual drying chambers of the kilns. 
Mil l No. Platform of chamber Height No. of rows % Overlap by 
width (m) area (sq.m) (m) diameter of the cone 
STD 1.5 5.7 3.0 
CRI 1.1 6.6 2.4 1 
. 1 4.3 19.0 2.1 2 42 
2 1.7 5.9 2.2 2 25 
3 1.4 5.9 1.7 2 33 
4 4.9 21.6 2.1 4 52 
S 2.4 8.9 1.9 3 13 
6 4.4 14.5 2.0 4 46 
7 3.9 15.2 1.8 2 10 
8 1.9 6.2 2.4 2 35 
9 2.4 9.3 1.8 2 11 
10 3.4 11.2 3.1 5 100 
11 1.3 5.5 2.0 2* 30 
12 3.8 16.7 1.7 2 0.1 
13 4.0 15.6 2.1 4 0.1 
14 4.6 26.7 2.0 4 00 
IS 5.4 17.8 3.1 8 100 
16 3.1 8.7 2.3 4 00 
17 2.1 8.2 1.9 3 30 
18 2.1 7.3 1.8 3 6 
19 3.0 12.0 1.8 3 33 
20 1.9 8.2 1.9 2 0.14 m gap 
21 1.1 3.5 1.0 2 00 
22 3.0 9.6 2.1 2 36 outside cone 
23 2.3 8.3 1.7 2 9 
24 1.5 5.7 2.2 2» 30 
25 2.2 5.3 2.1 3 39 
Mean 2.8 10.1 2.0 3 
± 1.2 5.1 0.4 1 
* - Triple rows 
Table 5. The ventilation cavities of the chamber in relation to total area/volume of drying chamber. 
Parameter CRI STD Commercial 
Height of the chamber mean 2.4 3.0 2.0 ± 0.4 
range 1.0 - 3.1 
Volume of the chamber (v) mean 1S.S 17.1 22.8 ± 14.0 
(cubic meter) range 3 . 5 - 15.2 
Area of the window/s (w) mean 0.04 0.05 0.03 ± 0.03 
(square meter) range 0 - 0 . 1 5 
Area of the door (d) mean 0.6 1.0 0.9 ± 0.3 
(square meter) range 0 . 5 - 1 . 5 
v/w mean 395 342 546 ± 695 
range 0 - 3280 
v / (w+d) mean 23 16 25 ± 15 
range 6 - 5 6 
CRI - Copra kiln used in the Coconut Research Institute 
STD - 'Standard Ceylon Copra Kiln' recommended in the CRI Leaflet No. 15. 
28 
Table 6. Quality of copra in relation to the fuel used. 
Fuel Mill No. Grade of copra 
Coconut shells 
1 M 0 4 & 5 
2 M 0 4 & 5 
3 MS 1 & 2, 
5 M 0 4 & 5 
7 M 0 4 & 5 
8 M 0 4 & 5 
9 MO 4 & 5 
11 MO 4 & 5 
f2 M 0 4 & 5 
13 MO 1 
15 MS 1,2 & 
16 MO 1 & 2 
17 MS 2, MO 
18 MS 2, MO 
19 MS 2, MO 
24 MS 3, MO 
25 M 0 4 & 5 
Coconut shells and Sulphur dust 
14 
23 
MS 1 & 2, MO 
MS 1 & 2 
Charcoal and Sulphur dust 
4 
6 
10 
20 
21 
22 
MS 1, MS 2 
Edible, MS 1 & 2 
MS 1 & 2 
Edible, MS 1 
Edible, MS 1, MS 2 
MO 1-5 (only for oil) 
The presence of wide openings above the drying platform is necessary to 
allow outward flow of moist hot air. If the moist air is not removed the moisture 
tend to condense on the roof and drop back on copra. In six of the kilns observed 
there was no open walls to allow a cross wind above the drying platform. Two kilns 
contained only windows for air movement, which may be inadequate. 
29 
Fuel Used 
There are two types of fuel used in the copra kilns. While most of the kilns use 
shells as fuel, a few use charcoal. Addition of sulphur dust to the fuel is also 
becoming popular (Table 6). Judging by the over all grades of copra produced as 
determined by an expert on quality, the use of charcoal provides a distinctly 
improved quality in copra (MS and edible grades) and the use of sulphur dust 
(100 g per row) produces a white copra which could fetch better prices in the 
market. The use of sulphur is probably not. objectionable as sulphur dioxide is 
commonly used in fumigating the ship on carrying copra in bulk (Salunke et al., 
1992). 
The use of charcoal is coupled with certain advantageous modificaitons of the 
drying practices and cost effects. The charcoal dust, used is a low cost fuel (Rs. 
1500/- per ton) compared to the shells. It appears that one could increase the profit 
margin by converting the shells to high value charcoal and using the residual 
charcoal powder as a fuel. The copra producers using charcoal as fuel have also 
done away with initial sun-drying of kernels, but have introduced selection of only 
well matured kernels and arranging the kernel cups inverted on the drying platform. 
CONCLUSION 
It is important to investigate further, the effect of different layouts of shells for 
burning on the percent distribution of quality and moisture content of the copra. 
Since the use of charcoal and sulphur appears to carry a distinct advantage in relation 
to quality, shifting of the present drying method to use of charcoal powder may be 
worth giving consideration. 
ACKNOWLEDGEMENT 
The authors thank the Coconut Development Authority, the Coconut Research 
Institute of Sri Lanka and the copra manufacturers for assistance in this study. 
REFERENCES 
Nathanael, W R N (1962) Report of the chemist, Ceylon Cocon. Q., 14: (1/2) 21-24. 
Patel, R T (1985) Copra drying process and equipments. J. Plant. Crops, 13: (2) 
78-87. 
Rodrigo, M C P and Samarajeewa, U (1995) Production and utilization of coconut 
kernel products in Sri Lanka. Proceedings of the European Community Project 
Seminar on polyaromatic hydrocarbons in copra and derived products, 24-26 July, 
1995, Bogor, Indonesia. 
30 
Salunke, D K, Chavan, J K, Adsalf, R H and Kadam, S S (1992) World Oil 
Seeds: Chemistry, technology and utilization. AVI, Van Nostrand Reinho, New 
York. 
Samarajeewa, U (1993) Improvements in coconut processing in the South-East 
Asia. Proceedings of the Third International Food Convention. 7-12 September, 
1993. Mysore, India, pp. 166. 
The Ceylon Copra kiln (1965) Coconut Research Institute Leaflet No. 15. 
Timmins, W H (1994) Polycyclic aromatic hydrocarbons and copra. 
Proceedings of the European Community Project Seminar on Potyaromatic 
Hydrocarbons in Copra and Derived Products. 24-26 July, 1995, Bogor, 
Indonesia. 
Wijeratne, M C P, Samarajeewa, U and Rodrigo, M C P (1996) Polycyclic 
aromatic hydrocarbons in coconut kernel products. / . Nat. Sci. Council of Sri 
Lanka, (in press) 
31 


National Science Foundation of Sri Lanka

Not a member yet

Neem metabolities with insect antifeedant and growth regulatoryproperties are produced in tissue cultures. Abstracts

Mechanism for increased leaf growth in elevated CO2: changes inleaf anatomy and in molecular weight distribution of xyloglucan

The effect of soil physical properties on growth and activity ofcoconut (Cocos nucifera L) roots

Study of the effective root zone of coconut in relation to soilcompaction

Soil biology in lateritic coconut soils of Sri Lanka

Some observations on copra drying in Sri Lanka

Socio economic development and the energy situation in Sri Lanka

Conservation of coconut (Cocos nucifera L) biodiversity of SriLanka

The impact of elevated CO2 on leaf cellular mechanisms

Role of Gliricidia sepium on physical improvement of gravelly soil

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