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Effect of Washing and Chilled Storage on the Retention of Formalin and Quality of Rohu Fish (labeo Rohita, Hamilton)

T. Yeasmin
Department of Fisheries Technology, Faculty of Fisheries, Bangladesh Agricultural University, Mymensingh-2202, Bangladesh

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

M.N.A. Khan
Department of Fisheries Technology, Faculty of Fisheries, Bangladesh Agricultural University, Mymensingh-2202, Bangladesh

F.H. Shikha
Department of Fisheries Technology, Faculty of Fisheries, Bangladesh Agricultural University, Mymensingh-2202, Bangladesh

M.S. Reza
Department of Fisheries Technology, Faculty of Fisheries, Bangladesh Agricultural University, Mymensingh-2202, Bangladesh

Abstract/ Executive Summary:

There have been complaints from the consumers that fresh fish available in Bangladesh domestic markets are contaminated with formalin which might have been used intentionally to extend the shelf life. But the retailers argue that they never use any type of chemicals during handling and transportation of fresh fish. Studies were, therefore conducted on washing and chilling effects on formalin in a popular Indian major carp rohu fish (Labeo rohita, Hamilton). It was found that formalin in the fish body was removed within 60 mins by washing with tap water or when kept in melting ice and the time was directly proportionate with the concentration of formalin used to treat the fish. Organoleptic tests revealed that the fish possessed strong formalin odor emitting from fish whereas the gill became slightly blackish with slight loss of brightness in fish body. Microbiological properties showed that APC content was significantly lower in fish treated with 5 % and 10 % formalin, which became below the level of detection with the increase in formalin concentration. These tests could easily be followed to identify formalin contamination in fish available in the market.

Keywords: Formalin, Food safety, Retention, Shelf life

Location: Department of Fisheries Technology, BAU, Mymensingh.

Start Date: 00-06-2008

End Date: 00-00-2008

Program Area: Postharvest and Agro-processing

Commodity: Carp fish

Objectives:

1. To investigate the effect of washing of fish and chilled storage on the retention of contained formalin in the fish body which was added previously in some stage of the marketing channel.

Methodology:

Raw materials: Ten (10) newly caught rohu fish with an average body weight of 450 gm and size 30 cm were purchased in two different lots from Bangladesh Agricultural University (BAU) Fish Market, Mymensingh during the period of June, 2008 and transported to Department of Fisheries Technology, BAU, Mymensingh in an insulated box in ice (fish, ice ratio 1:1) for analysis. Fish treatment with formalin: Five (5) different concentrations of formalin solutions: 5%, 10%, 15%, 20% and 35% were prepared in 5 separate clean plastic containers, and fish were treated in two different lots for analysis, viz. ice storage with- and without washing. Effect of washing with subsequent ice storage: In the first lot, five (5) fish were allowed to dip at different concentrations of the formalin solution for 5 mins. The samples were then taken out and placed on plastic net for a while to drain out the solution. Again the samples were dipped into plastic container containing 2 litres of tap water for up to 10 to 240 mins. After a definite time interval, the samples were taken out from the water and allowed to drain water from the fish body. Then the surface of the each samples were washed with 5 to 10 mL of distilled water. Three (3) drops of washed out water was collected in clean test tubes for detection of formalin using ‘Formalin detection kit in food’ developed by Bangladesh Council of Scientific and Industrial Research (BCSIR). Briefly a portion of washed out water was taken in a test-tube using a dropper included in the kit. The kit contained three solutions (No. 1-3). Then 15 drops from solution No.1 was added in the test tube containing washed out water. After well stirring, the solution was allowed to wait for 30 second. Then 15 drops from solution No.3 was added in the same test tube. After adding No.3 solution, if the color of the solution changed into pink or red color, it indicated the presence of formalin (qualitative only). Unchanged color of the solution indicated no formalin in the sample. A triplicate sample was prepared for each treatment and used for analysis. Effect of ice storage without washing treatment: In the second lot, five (5) rohu fishes were treated in formalin under similar conditions as mentioned before. The samples were then put in an insulated box in ice (fish, ice ratio 1:1) for 10 to 240 mins. After definite time intervals, fishes were taken out and the presence of formalin was detected as above. Organoleptic quality assessment: Sensory methods were used to assess the degree of freshness based on organoleptic characteristics such as odor, color, general appearance, eyes, slime and consistency of flesh. The organoleptic characteristics were judged by a trained panel of expert members during the storage period between fresh and formalin treated fish. The grading of fish using score on the characteristics has been followed by Multilingual Guide to EC Freshness Grades for Fishery Products to judge the quality of the fish. Microbiological quality assessment: About 10–15 g of whole fish sample was blended with appropriate volume of 0.2% peptone water in a sterilized blender for a few minutes until homogenous slurry was obtained. Total APC expressed as colony forming units per gram of muscle (CFU / g) of the representative samples was determined by standard plate count methods using plate count agar (Hi-media, Mumbai, India). Statistical analysis: Scores of the organoleptic evaluation were analyzed by the analysis of variance (ANOVA) and data were subjected to t-test (p < 0.05). The statistical analysis package SPSS 9.0 (SPSS Inc, Chicago, IL, USA) was used to explore the statistical significance of the results obtained.

Source of Information: Discourse Journal of Agriculture and Food Sciences Vol. 1(6), pp. 118-122, June 2013

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

The information obtained in the present study will be useful for government officials to understand the influence of formalin on fish texture, color and odor and microbiological properties, thereby strengthen safety of fish in the domestic market. As washing effect exerts lowering of formalin concentration in a contaminated fish, general consumers can take precautions and ensure safety while buying fish from the market.

Knowledge Management: Journal