Nutritional Composition of Selected Species of Sea cucumbers from Waters around Jaffna Peninsula , Sri Lanka

Biochemical studies (protein, fat, moisture and ash) were done on five species of holothurians namely Holothuria leucospilota, Holothuria scabra, Holothuria spinifera, Stichopus naso and Thelenota anax, which were collected from the waters around Jaffna Peninsula during November 2013 to April 2014. Moisture, ash, protein and lipid contents of collected sea cucumbers were measured and recorded. The average moisture, protein, lipid and ash contents were 84.52±0.88%, 10.06±0.04%, 0.25±0.02% and 1.90±0.07% in H. leucospilota, 85.21±0.78%, 4.96±0.02%, 0.34±0.03% and 5.72±0.34% in H. scabra,79.19±0.86%, 8.22±0.43%, 0.27±0.05% and 9.22±0.23% in H. spinifera, 92.55±0.66%, 3.00±0.04%, 0.33±0.01% and 1.62±0.02% in S. naso and 89.92±1.33%, 3.14±0.03%, 0.40±0.02% and 2.90±0.01% in T. anax, respectively. Marked significant differences (p<0.05) were observed among sea cucumber species for the mean moisture, protein, lipid and ash contents. In comparison showed that H. leucospilota and H. spinifera possessed higher protein, T. anax possessed higher lipid and H. spinifera possessed higher ash contents than other investigated sea cucumber species. Among the five analyzed sea cucumber species, H. leucospilota is the most recommended as one of the healthiest food for human consumption as it has low fat content and high protein content.


Introduction
*Correspondence: ketharani@gmail.commodulatory activities due to the presence of compounds such as sulponamides and diketones (Aminin et al., 2001).Many Asians believe sea cucumbers should be eaten to treat ailments such as cancer and arthritis, as well as intestinal and urinary dysfunctions (Purcell, 2010).In Sri Lanka, sea cucumber fishery is presently confined to the Northern cap from Kalpitiya on the Northwestern coast through the Puttalam Islands around Gulf of Mannar, Trincomalee, Pothuwil and Kalmunei in the Northeast and Eastern coastal waters of Sri Lanka.These are the major sea cucumber fishing areas in Sri Lanka.There are no records on local consumption of sea cucumbers in Sri Lanka.Beach-de-mer is the major commodity that is produced in Sri Lanka and the entire annual production is currently exported to Singapore, Hong Kong and China (Dissanayake, 2009).However, there were only a few reports about biochemical composition of aquatic food materials including sea cucumber.Furthermore, the biochemical composition of sea cucumbers are influenced by the local environmental factors and internal factors that could be within or between the species including size, maturity condition, feeding season and physiological conditions (Chandrashekar and Deosthale, 1993).Moreover, measurements of nutritional profiles such as protein, lipid, ash and moisture contents are often ensure that whether they meet the requirements of food regulations and commercial specifications or not.
The present work aims to highlight the nutritional value of some local sea cucumber species inhabiting the Jaffna Peninsula namely H. leucospilota, H. scabra, H. spinifera, S. naso and T.anax in order to evaluate their quality and their economic importance.

Sample collection
Five species of Sea cucumber samples were collected weekly from fishermen from their trawl catches or dived catches from each fish landing stations at Kurunagar, Allaippidi and Point Pedro (Figure 1).Regular field visits were made from November 2013 to April 2014.Approximately same total length (18.0 cm) of sea cucumbers were collected for the analysis.Immediately after collection, sea cucumbers were chilled before freezing (Graham et al., 1992) and brought to the laboratory by using an ice box.
Sea cucumbers were allowed to thaw slowly at room temperature and standard length (SL) and total body weight were measured.Sea cucumber samples were dissected.Reproductive and digestive organs were removed and rinsed with distilled water and placed in sterilized petri dish (60 mm Diameter) and labeled.

Chemical analysis
The percentage of nutritional constituents of sea cucumbers were determined by conventional m e t h o d o f A O A C ( 2 0 0 0 ) .Tr i p l i c a t e determinations were carried out for each chemical constituents.

Determination of Moisture content
Moisture was determined as the difference in weight of the specimen before and after dehydration (to constant weight in an electric oven maintained at 105°C for about 3 hours then cooled to room temperature in a desiccator and weighed).The moisture content was calculated according to the formula:

Sample preparation for analysis of protein, lipid and ash
Dried samples were powdered using motor and pestle.Powdered samples were transferred carefully to polythene bag and labeled and then stored in a freezer at -20 ˚C until further investigation.

Determination of Protein content
After the determination of moisture content, protein content of the remaining dried samples were determined according to the Kjeldhal method (AOAC, 2000).It involves the conversion of organic nitrogen to ammonium sulphate by digestion of sample with concentrated sulphuric acid in a kjeldhal tube.The digest was diluted, made alkaline with sodium hydroxide and distilled.The liberated ammonia was collected in a boric acid solution and total nitrogen was determined titrimetrically.The percentage of crude protein in the sample was calculated

% Moisture=
Weight of sample Difference in weight ×100 according to the formula % Crude protein content = % of Nitrogen x 6.25.

Determination of fat content
For the estimation of fat content, the dried samples left after moisture determinations were finely ground and the fat was extracted with chloroform and methanol mixture (AOAC, 2000).After extraction, the solvent was evaporated and the extracted materials were weighed.The percentage of the total fat content was calculated.

Determination of ash content
The ash content of a sample is the residue left after ashing in a muffle furnace at about 550-600 ˚C till the residue become white.The percentage of ash was calculated by subtracting the ash weight from initial weight.

Statistical analysis
Moisture, ash lipid and protein content of five species of sea cucumber were first analyzed by one way analysis of variance (ANOVA).
When the mean of the samples was significantly different, ANOVA was followed by Post hoc comparison of employing after means: Duncan's Multiple Range Test (DMRT) using SPSS software.The level of statistical significance was set at p<0.05.

Results
The moisture, protein, lipid and ash contents in the body wall of collected sea cucumber species examined are presented in Table 1.Comparison of mean values of moisture showed that there is significant difference between each species except between the H. leucospilota and H. scabra.Comparison of mean values of protein showed that there is significant difference between each species other than between the S. naso and T. anax.Comparison of mean values of lipid showed that there is significant difference between H. leucospilota and H. scabra, H. leucospilota and T. anax, and H. spinifera and T. anax.Comparison of mean values of ash showed that there is significant difference between each species other than the H. leucospilota and S. naso.
The comparison showed that H. leucospilota and H. spinifera possessed higher protein, T. anax possessed higher lipid and H. spinifera possessed higher ash content than other investigated sea cucumber species.

Discussion
In some parts of the world, sea cucumber is known to be used as food for centuries (Fabinyi, 2012 andJenkins andMulliken, 1999).Bordbar et al., (2011) stated that the commercially processed sea cucumbers are rich source of crude protein in comparison to most of the sea foods so far in use.Wen et al., (2010) investigated the chemical and nutritional composition of eight common commercially processed sea cucumber species such as Stichopus herrmanni, Thelenota ananas, T. anax, Holothuria fuscogilva, Holothuria fuscopunctata, Actinopyga mauritiana, Actinopyga caerulea and Bohadschia argus and found the protein contents to be within the range of 40.7 to 63.3%, and a relatively very low level of fat (0.3-1.9%), except for T. anax and A. caerulea, while the ash content is markedly high (15.4-39.6%).According to Chen et al. (2011), the fully dried sea cucumber material may contain protein content as high as 83 % and is sold in tabulated or capsulated forms as nutritive complement.
Fish proteins rich in essential amino acids (EAA), are easily digestible and nutritionally superior, to vegetable proteins.Likewise sea cucumbers also have considerable amount of proteins which includes the essential amino acids and non-essential amino acids such as glycine, lysine, threonine and valine which are used for medicinal purposes (Omran, 2013).

Conclusion
According to the present study, H. leucospilota showed the highest nutritional value than other species.Among the five analyzed sea cucumber species, H. leucospilota is recommended as one of the most healthiest food for human consumption as it has low lipid content and high protein content.The present study provides fundamental information about nutritional quality of sea cucumbers around the Jaffna Peninsula.

Table 1 : Nutritional composition (%) of the investigated sea cucumbers (mean values ± standard deviation).
dValues in the same column bearing different letters are significantly different (P<0.05).