Influence of processing techniques on quality and nutritional composition of the tropical sea cucumber Holothuria scabra

Ram, Ravinesh (2017) Influence of processing techniques on quality and nutritional composition of the tropical sea cucumber Holothuria scabra. PhD thesis, James Cook University.

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Recent years have seen increasing demand for consumer-friendly, non-dried, ready to cook sea cucumber products in Asian markets along with greater awareness on the potential health benefits of seafood consumption. On this basis, there is opportunity to develop new sea cucumber products that are more user friendly and with improved nutrient content. However, a major determinant of processed sea cucumber quality and value is the texture of the consumed product and so any future development in the processing and packaging of sea cucumber must account for texture as well and nutrient content. This study addressed issues relating to the impact of processing techniques on the quality and nutritional composition of the sea cucumber Holothuria scabra (Sandfish). The overall objectives of this study was to to generate improved information on the processing of sandfish relating to nutrient composition and texture, and the potential and implications of novel processing and packaging methods for this species. The study determined the recovery rates for eight commercial sea cucumber species from the Fiji Islands (Chapter 2); the effect of different processing techniques on the nutrient composition of bêche-de-mer produced from sandfish (Chapter 3); the effect of processing method on quality, texture, collagen and amino acid composition of sandfish (Chapter 4); isolation and characterization of collagen from the body wall of sandfish (Chapter 5); and assessed novel processing and packing methods on the quality and the nutrient composition of sandfish (Chapter 6).

Determination of the original weight and length of sea cucumbers processed and dried to become bêche-de-mer (BDM), is an important tool in sea cucumber fishery management. The only management mechanism for the sea cucumber fishery in the Fiji Islands is a minimum length prescribed for BDM for export. However, different commercial species have different shrinkage rates during processing and previous studies have suggested modification of fisheries management for sea cucumbers to include species-specific minimum harvest size limits. Chapter 2 determined weight-based and length-based recovery rates (i.e. the length/weight of BDM recovered after processing from the initial length/weight of fresh sea cucumber), for eight commercial sea cucumber species following processing to BDM; White Teatfish (Holothuria fuscogilva), Black Teatfish (Holothuria whitmaei), Tigerfish (Bohadschia argus), Surf Redfish (Actinopyga mauritiana), Hairy Blackfish (Actinopyga miliaris), Stonefish (Actinopyga lecanora), Prickly Redfish (Thelenota ananas) and Sandfish (Holothuria scabra). Length and weight recovery rates varied between species and ranged from the highest recovery values of 54.9% for length and 11% for weight in Black Teatfish, to the lowest recovery values of 32.6% for length and 3.0% for weight in Sandfish and Tigerfish, respectively. Length-based and weightbased relationships were generated for each species through the various stages of processing from fresh to dried (BDM) allowing estimation of initial fresh weight/length from partially or fully processed BDM and vice versa. Information generated in this study provides a basis for developing more species-specific harvest size restrictions for sea cucumbers in the Fiji Islands, and has application in stock assessment studies, estimation of harvest data, monitoring of harvest size limits and standardizing catch data.

Proximate and fatty acid compositions of fresh and processed sandfish, and the effects of salting on product composition, were determined in Chapter 3. Processing using dry salting (kenching) for up to 72 h and immersion in 15-25% brine solutions for 48 h produced significantly reduced protein contents in resulting BDM compared to non-salted BDM (845.90 ± 9.28 mg g⁻¹). BDM produced by 48 h kenching (717.52 ± 10.54 mg g⁻¹) and by 15% brine salting (713.93 ± 11.98 mg g⁻¹) had the highest protein contents among salted treatments. The lipid contents of BDM processed using salting did not differ significantly from that of the control non-salted treatment (13.89 ± 2.89 mg g⁻¹), but ash contents of salted BDM were generally significantly greater than that of the control product (111.13 ± 15.73 mg g⁻¹). Carbohydrate contents of BDM increased with increasing duration of kenching to 119.15 ± 36.16 mg g⁻¹ (72 h kenching). Inclusion of a salting step in BDM processing resulted in reduced levels of EPA in some treatments but did not significantly reduce Σn-3 PUFA levels. Results provide a basis for further development of processing methods for H. scabra that optimize the nutritional characteristics of resulting BDM.

Textural properties and collagen and amino acid contents of fresh (raw) and processed sandfish were compared in Chapter 4. Several processing procedures using different salting methods (brine and kench salting) were tested, and the resulting processed BDM were compared with partially processed tissue and BDM processed without salting and by smoke drying. Weight and length based recovery rates did not differ significantly across salting treatments or from the non-salted control treatment. There was a general trend of decreasing collagen content with increasing brine strength in the brining treatments, and sequential increases in the force required to shear reconstituted BDM processed with increasing brine strength. This has implication for BDM processing because the quality of reconstituted BDM is judged primarily by texture, not flavor, with softness and elasticity being of prime importance. BDM from most treatments was significantly less firm than cooked, partially processed tissue. The most abundant protein-bound amino acids in sandfish BDM were glycine, glutamic acid, proline, arginine, aspartic acid, alanine and hydroxyproline, but their levels did not vary significantly across treatments. Our results provide a basis for improvements to sandfish processing that optimize textural properties of resulting BDM.

The body wall of sea cucumbers is rich in collagen but there is limited knowledge of its structure, particularly in tropical species. Chapter 5 of this study focused on the isolation and characterization of collagen and pepsin-soluble collagen from the body wall of sandfish. The crude collagen fibrils were extracted using acid extraction and then digested using the porcine pepsin to extract the pepsin solubilized collagen. Resulting collagen was characterized using UV-vis spectrophotometer, Sodium dodecylsulfate-polyacrylamide gel electrophoresis (SDS-PAGE), V8 protease enzyme digested peptide maps, Fourier transform infrared spectroscopy (FTIR) and solubility tests. Maximum absorbance of the collagen samples was at 240 – 250 nm. The triple helix structure of the collagen molecule was determined by FTIR and SDS-PAGE and the 3 α1 chain with a molecular weight of 133.2 kDa. The maximum and minimum solubility was observed at pH 2 and 4 respectively. A sharp decrease in collagen solubility was found in between 2% and 4% NaCl concentration. The findings show that the collagen from Holothuria scabra was Type I and this result is consistent with those of other studies that have characterized collagen from sea cucumbers.

Research in Chapter 6 of this study assessed the potential of novel packaging for partially processed (cooked at 80-90°C [control], cooked and treated with essential oils, and cooked and cold smoked) as well as processed and reconstituted sandfish. Sandfish products were subject to modified atmospheric packaging (MAP), with a gas ratio of 60%CO₂/40%N₂ and 5%02/50%CO₂/45%N₂, and also vacuum packaging prior to shelf-life assessment tests. Microbial examination, nutrient composition, collagen content and texture were assayed for the samples. The control, essential oil treatment and the reconstituted samples were discarded from the shelf after 7 days because of high microbial and yeast and mold counts. The cold smoked samples, packaged using MAP and vacuum-packing, recorded 0 CFU/g at Day 0 for SPC, yeast and mold and this remained consistent throughout the shelf life. The cold smoked sandfish (MAP and vacuum-packed) recorded 0 CFU/g bacterial, yeast and mold counts until day 30. There were no significant differences between initial and 7 days samples for moisture, protein, lipid or NFE contents, across treatments. There were no significant differences in the levels of moisture, protein, lipid, ash and NFE between initial treatment samples. There were no significant differences (P>0.05) in the levels of the metabolically important fatty acids C20:4n-6, 20:5n-3, 22:6n-3 between samples from either day, across all treatments after 7 days of storage. This was also true of the total level of n-3 polyunsaturated fatty acids (PUFA) in the samples. No significant differences were observed in collagen composition or texture, however, the tissue toughened with the storage time. Successful use of MAP and vacuum-packing, combined with the preservative action of cold-smoking, demonstrates the potential of novel packaging methods for sea cucumber products.

This study assessed the effects of processing on yield, nutrient composition and texture of sandfish for the first time. It also assessed the potential of novel packaging methods for sandfish products for the first time. The new information generated has the following broad applications: (1) sea cucumber processing data have application in stock assessment studies, estimation of harvest data, monitoring of harvest size limits and standardizing catch data, and they provide a basis for developing species-specific harvest size restrictions for tropical sea cucumbers in Fiji Islands; (2) where salting is use to process BDM, the results of this study provide a basis for further development of processing methods that optimize both physical and nutritional characteristics of resulting BDM; (3) preliminary examination of the potential of novel packaging for sandfish products provide a basis for further development of these methods such as examination of different gas mixtures during MAP and the effectiveness of other preservative treatments/materials combined with MAP or vacuum-packing; and (4) characterization of the collagen of sandfish creates an opportunity for commercial production/processing of collagen from this species that is of high value compared to that of temperate species.

Item ID: 53905
Item Type: Thesis (PhD)
Keywords: amino acids, bêche-de-mer, collagen, Fiji Islands, Holothuria scabra, processing, recovery rate, sandfish, sea cucumber
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Publications arising from this thesis are available from the Related URLs field. The publications are:

Chapter 2: Ram, Ravinesh, Chand, Roveena Vandana, Zeng, Chaoshu, and Southgate, Paul C. (2016) Recovery rates for eight commercial sea cucumber species from the Fiji Islands. Regional Studies in Marine Science, 8. pp. 59-64.

Chapter 4: Ram, Ravinesh, Chand, Roveena V., Forrest, Andrew, and Southgate, Paul C. (2017) Effect of processing method on quality, texture, collagen and amino acid composition of sandfish (Holothuria scabra). LWT - Food Science and Technology, 86. pp. 261-269.

Date Deposited: 19 Jun 2018 23:52
FoR Codes: 07 AGRICULTURAL AND VETERINARY SCIENCES > 0704 Fisheries Sciences > 070401 Aquaculture @ 100%
SEO Codes: 83 ANIMAL PRODUCTION AND ANIMAL PRIMARY PRODUCTS > 8301 Fisheries - Aquaculture > 830199 Fisheries - Aquaculture not elsewhere classified @ 100%
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