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Shelf Life of Several Marine Fish Species of Bangladesh During Ice Storage

Md. Shaheed Reza
Department of Fisheries Technology, Faculty of Fisheries, Bangladesh Agricultural University, Mymensingh 2202, Bangladesh

Mohammad A. J. Bapary
Department of Fisheries Technology, Faculty of Fisheries, Bangladesh Agricultural University, Mymensingh 2202, Bangladesh

Chowdhury T. Ahasan
Department of Fisheries Technology, Faculty of Fisheries, Bangladesh Agricultural University, Mymensingh 2202, Bangladesh

Md. Nazrul Islam
Department of Fisheries Technology, Faculty of Fisheries, Bangladesh Agricultural University, Mymensingh 2202, Bangladesh

Md. Kamal
Department of Fisheries Technology, Faculty of Fisheries, Bangladesh Agricultural University, Mymensingh 2202, Bangladesh

Abstract/ Executive Summary:

Organoleptic, biochemical and bacteriological aspects of five tropical marine fish such as silver jewfish, Bombay duck, big-eye tuna, Chinese pomfret and ribbon fish stored in ice were studied. Organoleptically all fish were found acceptable for 10–13 days before becoming inedible. Proximate analysis showed that moisture content increased slightly; protein and lipid content decreased gradually and ash had little or no significant change. pH, TVB-N, peroxide and aerobic plate count values increased with increasing storage period but the values were within acceptable range up to 10 days of storage. Changes in myofibrillar ATPase activity and solubility of these fishes showed that Ca²⁺ ATPase in the presence of both 0.1 m and 0.5 m KCl decreased gradually whereas no marked changes were observed in the Mg⁺² ATPase activities in the presence ⁄ absence of Ca⁺². Myofibrillar protein solubility of all fish samples also decreased considerably during ice storage. The decrement in Ca²⁺ ATPase activity and solubility indicates denaturation of myofibrillar protein of fish samples during ice storage.

Keywords: ATPase activity, Ice storage, Myofibril, Organoleptic, Proximate composition

Location: Cox’s Bazar, Bangladesh

Start Date: 00-00-2007

End Date: 00-00-2007

Program Area: Postharvest and Agro-processing

Commodity: Marine fish

Objectives:

To report the shelf life of some commercially important tropical marine fish species of the Bay of Bengal during ice storage by determining organoleptic, biochemical and bacteriological aspects.

Methodology:

Raw materials: Fresh fish samples of silver jewfish (Johnius argentatus), Bombay duck (Harpodon nehereus), big-eye tuna (Scomberomorus gottatus), Chinese pomfret (Stromateus chinensis) and ribbon fish (Trichiurus haumela) of marketable size were collected from the landing centre at Kutubdiapara, Cox’s Bazar and the main landing centre of Bangladesh Fisheries Development Corporation (BFDC) at Cox’s Bazar, Bangladesh. The average length and weight of silver jewfish, Bombay duck, bigeye tuna, Chinese pomfret and ribbon fish were 21 cm and 150 g; 25 cm and 158 g; 40 cm and 350 g; 22 cm and 210 g; 42 cm and 125 g, respectively. Each species of fish weighing about 40 kg were collected and transported to the Department of Fisheries Technology, Bangladesh Agricultural University, Mymensingh, Bangladesh in insulated boxes. Fresh commercial block ice after crushing into small pieces was used for icing the samples immediately after collection. The fishes were kept in the insulated box containing ice and fish at 1:1 (w ⁄ w) ratio and fresh ice in the box was replenished on every alternate day until the termination of experiment. The icebox had a number of holes at the bottom to drain out the melted water. The quality change in ice stored samples was evaluated after every 3 days interval by determining organoleptic, biochemical and bacteriological aspects. Sampling procedure and sample preparation: At described intervals (starting from 0 day), four to five fish (depending on size) were randomly sampled and their sensory attributes were evaluated while keeping the fish in iced condition. Once the whole fish was subjected to sensory analysis, the ordinary muscle was separated and used for myofibril preparation. Two to three fish were sampled for chemical and microbiological analysis and were skinned and deboned. The dark muscle was removed and the light muscle was homogenised by mincing, and aliquots were taken for determinations of biochemical and bacteriological aspects. Organoleptic quality assessment: Sensory methods were used to assess the degree of freshness based on organoleptic characteristics such as odour, colour, general appearance, eyes, slime and consistency of flesh. Starting from 0 day, four to five fish were randomly sampled and their raw sensory attributes were evaluated. The organoleptic characteristics were judged by a trained panel of expert members during the storage period. The grading of fish using score on the characteristics has been followed by ECC freshness grade for fishery products with slight modification to judge the quality of the fish. Proximate composition analysis: Moisture content was determined by air drying of a given sample in a thermostat oven (Gallenkamp, HOTBOX, Manchester, UK) at 105 ^oC for 24 h until constant weight. Ash content was determined by igniting the sample in a muffle furnace at a temperature of 550^oC for 6 h. Crude protein was determined by the Macro Kjeldahl method by determining total nitrogen and applying the protein conversion factor of 6.25 to the results to convert total nitrogen into total protein, assuming that fish protein contained 16% nitrogen, and lipid content was determined by extracting required quantity of samples with petroleum ether for 16–18 h in a ground joint Soxhlet apparatus. The oil obtained by evaporation of the solvent on a steam bath was weighed in a sensitive balance and percent lipid was calculated. Physical and chemical analysis: pH was measured using a pH meter (Corning Model 250) after homogenising 2 g of fish muscles with 10 mL distilled water in a blender. The lipid fraction was extracted and the peroxide value (PV) was determined. Total volatile base nitrogen (TVB-N, mg N 100 g^–1) values were determined. Aerobic plate count (APC): About 10–15 g of whole fish sample was blended with appropriate volume of 0.2% peptone water in a sterilised blender for a few minutes until homogenous slurry was obtained. Total APC expressed as colony forming units per gram of muscle (CFU g^-1) of the representative samples was determined by standard plate count methods using plate count agar. Myofibril preparation and ATPase assay: Myofibrils were prepared from ordinary muscles immediately after excision with slight modification. The muscle was chopped by using a meat grinder and the chilled minced muscle (50 g) was homogenised for 1 min in 5 volumes of 39 mm borate buffer (pH 7.1) containing 25 mm KCl and 0.1 mm dithiothreitol (DTT). The homogenate was centrifuged for 15 min at 600 xg. The residue obtained was again homogenised and centrifuged for 15 min. The light-coloured upper layer of the residue consisting mainly of myofibril was recovered with small volume of 39 mm borate buffer (pH 7.1) containing 0.1 m KCl and 0.1 mm DTT. The suspension was centrifuged for 15 min to remove the supernatant. Myofibrils were resuspended in the same solution and coarse materials were removed by centrifuging at 400xg. The suspension was centrifuged again for 15 min at 600xg to sediment the myofibril. After the pellet was washed three times in the same way, myofibrils were suspended with a desired volume of 39 mm borate buffer (pH 7.1) containing 0.1 m KCl and 0.1 mm DTT to make a concentration of 10–15 mg mL^-1. The reaction mixture for the Ca²⁺-ATPase assay contained 25 mm Tris–maleate (pH 7.5), 5 mm CaCl₂, 0.1 m or 0.5 m KCl and 0.25 mg myofibril per millilitre. The reaction mixtures for the Mg²⁺-ATPase assay were prepared similarly as described before excepting that 5 mm MgCl₂ was used instead of 5 mm CaCl₂. For EGTA modified Mg⁺²-ATPase activity, 1 mm EGTA solution was used instead of 5 mm CaCl₂. The ATPase activity was measured at 25 ^oC for 6 min. After preparation of the reaction mixture, an appropriate quantity of myofibril suspension was pipetted into the reaction mixture followed by 2 min pre-incubation. The reaction was started by adding 1 mm ATP and was stopped by adding 1 mL of 10% (w ⁄ v) trichloroacetic acid. The supernatant obtained by 5 min centrifugation at 3000xg was analysed for the liberation of inorganic phosphate (Pi). Solubility test of myofibrillar proteins: Myofibrillar proteins were extracted from isolated myofibrils with 0.6 m KCl and 0.03 m Tris–HCl at pH 7.5. The suspension was stirred gently and kept overnight at 4^oC. Then the solution was centrifuged at 900xg for 30 min in a refrigerated centrifuge (Denley BR401 refrigerated centrifuge, Billingshurts, UK) and protein concentration in the supernatant was determined. Statistical analysis: Data from different biochemical measurements were subjected to t-test (P < 0.05). The statistical analysis package statview 5.0 for Macintosh (SAS Institute Inc., NC, USA) was used to explore the statistical significance of the results obtained.

Source of Information: International Journal of Food Science and Technology 2009, 44, 1485–1494

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Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

The shelf life study by determining organoleptic, biochemical and bacteriological aspects on five commercially important tropical marine fish species of Bangladesh such as silver jewfish, Bombay duck, bigeye tuna, Chinese pomfret and ribbon fish indicates that these fishes can be kept in iced condition for 10–13 days. However, the shelf life of big-eye tuna and Chinese pomfret can be extended for another 2–3 days compared to rest of the three species because they had already lost that shelf life in the storage facility of mechanised trawlers prior to sampling. The loss of quality in these fishes is due to bacterial and enzymatic activities during long time storage in ice, although the shelf life is dependent on various factors which may vary even within the same species. This information will be used by the government to improve the quality of fish landed and marketed throughout the country. The government has already introduced guidelines for improved handling, transportation and quality management systems of capture fisheries, and the national policy for improving the infrastructure for fish handling, storage, transport and marketing is now under way.

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