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Effect of Delayed Icing on Quality Changes and Shelf-life of Some Freshwater Fish from Bangladesh

M. M. Nabi
Department of Fisheries Technology, Bangladesh Agricultural University Mymensingh 2202, Bangladesh

M.N. Islam
Department of Fisheries Technology, Bangladesh Agricultural University Mymensingh 2202, Bangladesh

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

Abstract/ Executive Summary:

The quality and shelf-life of three freshwater fish species of Bangladesh, catla (Catla catla), magur (Clarias batrachus) and tilapia (Oreochromis niloticus) stored at room temperature and ice were evaluated. Live fishes were killed by cranial spiking and stored at room temperature (27-30 °C), ice stored immediately after death, 5 hr after death and 10 hr after death. The shelf-life and quality of the fishes were evaluated by organoleptic method, rigor-mortis studies and bacteriological assessment. Fishes kept at room temperature became organoleptically unacceptable within 16-20 hr duration. Ice stored fishes showed considerable differences in their shelf-life when icing was delayed for different duration. Shelf-life of catla ice stored immediately after death was 20 days but shelf-life reduced to 12 days when icing delayed for 10 hr after death. Similar trend was observed for two other fish species magur and tilapia. Rigor index of the fishes stored under different conditions also considerably varied among the three fish species, particularly effect of delayed icing was very much evident. Bacteriological study showed patterns of Aerobic Plate Count (APC) at the end of shelf life study when fishes became organoleptically unacceptable were more or less similar for all the three fish species stored under different conditions. No definite pattern was observed in the generic distribution of bacteria in different fish species under different storage conditions. Micrococcus, Coryneforms, Pseudomonas and Achromobacter were the dominant groups of bacteria isolated from the fishes spoiled at room temperature and ice stored condition.

Keywords: Icing, Shelf-life, Freshwater fish

Location: Bangladesh Agricultural University.

Start Date:

End Date:

Program Area: Postharvest and Agro-processing

Commodity: Fish

Objectives:

To study the effect of delayed icing on rigor-mortis, shelf-life and bacteriological changes in three commercially important freshwater fish species.

Methodology:

Fish samples: Three freshwater fish species catla (Catla catla), magur (Clarias batrachus) and tilapia (Oreochromis niloticus) were obtained either from local fish farm or from local fish market and put in an insulated box with chilled fresh water to transfer to the laboratory. On arrival to the laboratory fishes were killed by cranial spiking and kept either at room temperature or in ice in an insulated box in the ratio of 1:1 (fish: ice) immediately or after 5 and 10 hr exposure to the environmental temperature. The samples were taken out from ice at different time intervals to determine the quality of fish by organoleptic evaluation, assessing the progress of rigor-mortis and by bacteriological evaluation. Quality assessment: The guidelines and methods used here are based on the scores on the organoleptic characteristics of fish as described by European Commission (EC) freshness grade for fishery products with some modification. Rigor-index ofthe fishes were measured and used as parameter of rigor tension. At selected time intervals, rigor-index was calculated. The muscle of the fish was collected aseptically at the end of shelf-life study, weighed and blended in a sterile blender. The stock suspension of the muscle was prepared by homogenizing 10 g of sample with 90 ml of physiological saline (0.85% NaCl). Aerobic plate count (APC) expressed as colony forming units per gram of fish muscle (CFU/g) of the representative samples were determined by consecutive decimal dilution method using plate count agar (Hi media). For qualitative study, bacteria obtained during APC were isolated from the agar plates. All the colonies from a plate having discrete colonies were removed and obtained pure cultured by streaking and restreaking on to fresh agar plates and finally transferred to agar slants. The bacterial isolates were classified up to genus level according to an outline of the sequence of tests used in the screening of culture.

Source of Information: Bangladesh J. Fish. Res., 5(2), 2001:181-188

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

Rigor index of the fishes stored under different conditions also considerably varied among the three fish species, particularly effect of delayed icing was very much evident. Bacteriological study showed patterns of Aerobic Plate Count (APC) at the end of shelf life study when fishes became organoleptically unacceptable were more or less similar for all the three fish species stored under different conditions. No definite pattern was observed in the generic distribution of bacteria in different fish species under different storage conditions. Micrococcus, Coryneforms, Pseudomonas and Achromobacter were the dominant groups of bacteria isolated from the fishes spoiled at room temperature and ice stored condition.

Knowledge Management: Journal