Edible sea cucumbers are not often found on the fish menu but they are popular food on the Asia-Pacific Rim. Consumers are mostly found in China and Japan. There are about 1,400 species of sea cucumbers around the world of which 50 have food or medicinal value ((Bordbar et al., 2011; Toral-Granda et al., 2008). They belong to the phylum Echinodermata and are cyclindrical marine invertebrates. Fortunately, they are one of the most common invertebrates to be found in the ocean.

The world output is 30,000 mT per year from the Asia-Pacific rim and it is estimated that aquaculture could yield up to 140,000 mT per year in China alone given its popularity there (FAO, 2013).

The Body Wall Of A Sea Cucumber

The main edible part is the body wall of the sea cucumber and is rich in protein and mucopolysaccharide. The crude protein in dried sea cucumber can reach 83% of its dry weight. The insoluble collagen fibre accounts for about 70% of the protein in sea cucumber (Saito et al., 2002; Chen, 2003).

The collagen fraction may be the most important part of the animal although it contains fucoidan, a polysaccharide important in health and diet. Plenty of research has focussed on a number of functions associated with hydrolytic bioactive peptides, including damaged tissue repairing (Park et al., 2012), antitumor (Zhou et al., 2012b), antioxidant (Zhou et al., 2012a), and angiotensin-converting enzyme inhibitory activity (Zhao et al., 2009; Forghani et al., 2012).

The biological functions of collagen are mostly performed by pepsin-solubilized hydrolysates of collagen (PSC) or the partially hydrolysed forms itself. Investigations on the isolation, purification, and characterization of PSC have been carried out in some sea cucumber species, such as Stichopus japonicus (Cui et al., 2007; Saito et al., 2002), Parastichopus californicus (Liu et al., 2010; 2011), Stichopus vastus (Abedin et al., 2013), and Holothuria parva (Adibzadeh et al., 2014).

One of those tropical sea cucumber species looks extremely promising for aquaculture – Stichopus monotuberculatus (Family: Stichopodidae). It prefers tropical waters and naturally distributes itself in reefs and sandy bottoms alike on the Pacific Southwest coast (Bruckner et al., 2003). Research on the spawning, fertilization, embryo development, larval development, and juvenile growth of this species has already been explored and shows promise especially to the Chinese (Hu et al., 2010).

The collagen component is clearly the most interesting fraction of all and a paper to be released discusses this in greater detail (Zhong et al., 2015).

Processing Of Sea Cucumber

 Sea cucumbers tend to spoil quite easily compared to other invertebrates. They produce a lot of autolysing enzymes which rapidly breakdown cellular components almost as soon as they are harvested. 

Traditional methods of processing sea cucumbers rely on salting and drying to prevent as much autolysis as possible. Dried and salted sea cucumbers have to be rehydrated before they can be consumed and a number of attempts have been tried to establish the optimal rehydration method. It is probably the most critical step and the one affecting the eating quality of this desirable product.

Rehydration usually involves some form of heating to allow the body mass to easily reabsorb water. In that process, heating denatures and deactivates enzymes but also modifies the structural proteins of the sea cucumber and ultimately its flavour and texture (Gao et al., 2011).

References

Abedin, M.Z., Karim, A.A., Ahmed, F., Latiff, A.A., Gan, C.Y., Ghazali, F.C., Sarker, M.Z.I.(2013) Isolation and characterization of pepsin-solubilized collagen from the integument of sea cucumber (Stichopus vastus). J. Sci. Food Agric. 93(5) pp. 1083–8.

Adibzadeh, N., Aminzadeh, S., Jamili, S., Karkhane, A.A., Farrokhi, N. (2014) Purification and characterization of pepsin-solubilized collagen from skin of sea cucumber Holothuria parva. Appl. Biochem. Biotechnol. 173(1) pp. 143–54.

Bordbar, S., Anwar, F., Saari, N. (2011) High-value components and bioactives from sea cucumbers for functional foods—a review. Marine drugs 9(10) pp. 1761–805.

Cui, F., Xue, C., Li, Z., Zhang, Y., Dong, P., Fu, X., Gao, X. (2007) Characterization and subunit composition of collagen from the body wall of sea cucumber Stichopus japonicus. Food Chem. 100(3) pp. 1120–5.

FAO. (2013) Fisheries and Aquaculture Information and Statistics Service. Capture & production 1950–2011. FISHSTAT Plus-Universal software for fishery statistical time series. Available at: http://www.fao.org/fishery/statistics/software/fishstat/en.

Forghani, B., Ebrahimpour, A., Bakar, J., Abdul Hamid, A., Hassan, Z., Saari, N. (2012) Enzyme hydrolysates from Stichopus horrens as a new source for angiotensin-converting enzyme inhibitory peptides. Evidence Based Compl. Alt. Article ID 236384, 9 pages

Gao, X, Zhang, Z. H., Liu, L. F., & Liu, Q. (2011). Rheological changes of sea cucumber Stichipus japonicus during different heated times. International Journal of. Fisheries and Aquaculture, 3(14), pp. 258–262.  https://doi.org/10.5897/IJFA11.048 

Hu, C., Xu, Y., Wen, J., Zhang, L., Fan, S., Su, T. (2010) Larval development and juvenile growth of the sea cucumber Stichopus sp. (Curry fish). Aquaculture 300(1) pp. 73–9.

Liu, Z., Oliveira, A.C., Su, Y.-C. (2010) Purification and characterization of pepsin-solubilized collagen from skin and connective tissue of giant red sea cucumber (Parastichopus californicus). J. Agric. Food Chem. 58(2) pp. 1270–4.

Liu, Z., Su, Y., Zeng, M. (2011) Amino acid composition and functional properties of giant red sea cucumber (Parastichopus californicus) collagen hydrolysates. J. Ocean Univ. China 10(1) pp. 80–4.

Park, S.Y., Lim, H.K., Lee, S., Hwang, H.C., Cho, S.K., Cho, M. (2012) Pepsin-solubilised collagen (PSC) from Red Sea cucumber (Stichopus japonicus) regulates cell cycle and the fibronectin synthesis in HaCaT cell migration. Food Chem. 132(1) pp. 487–92.

Saito, M., Kunisaki, N., Urano, N., Kimura, S. (2002) Collagen as the major edible component of sea cucumber (Stichopus japonicus). J. Food Sci . 67(4) pp. 1319–22.

Toral-Granda, V., Lovatelli, A., Vasconcellos, M. (2008) Sea cucumbers: a global review of fisheries and trade. Food and Agriculture Organization of the United Nations.

Zhao, Y., Li, B., Dong, S., Liu, Z., Zhao, X., Wang, J., Zeng, M. (2009) A novel ACE inhibitory peptide isolated from Acaudina molpadioidea hydrolysate. Peptides 30(6) pp. 1028–33.

Zhong, M., Chen, T., Hu, C. and Ren, C. (2015) Isolation and Characterization of Collagen from the Body Wall of Sea Cucumber Stichopus monotuberculatus. J. Food Science, 80: C671–C679. doi: 10.1111/1750-3841.12826

Zhou, X.Q., Wang, C.H., Jiang, A.L. (2012a.) Antioxidant peptides isolated from sea cucumber Stichopus Japonicus. Eur. Food Res. Technol. 234(3) pp. 441–7.

___________________________ (2012b.) In vitro antitumor activities of low molecular sea cucumber Stichopus japonicus peptides sequentially hydrolyzed by proteases. Adv. Mater. Res. 393–395 pp. 1259–62.