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Prevalence of Formalin Contamination and Its Effect on Organoleptic Characteristics of Giant Fresh Water Prawn (macrobrachium Rosenbergii, De Man) in Different Markets of Mymensingh

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

A. W. Newaz
Department of Fisheries, Sher-e-Bangla Agricultural University, Dhaka-1207, Bangladesh

B. Dewan
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:

Studies were conducted to evaluate the prevalence of formalin contaminated prawn (Macrobrachium rosenbergii, De Man 1879) in major fish markets of Mymensingh, a mid-northern town of Bangladesh. Various aspects of marketing, preservation and changes in organoleptic quality of prawns under different storage conditions were also investigated. Information was collected from fish retailers and consumers on the marketing and use of formalin for preservation of prawn through survey questionnaires. Survey areas included Bangladesh Agricultural University KR market (KRM); Kewatkhali Bazaar (KM); Mecchua Bazaar (MM); Natun Bazaar (NM) and Sankipara Bazaar (SM). Some commercially important prawns were coming from coastal region such as Satkhira, Bagerhat, Khulna, Jessore and other regions of Bangladesh through intermediaries. Based on modified QIM, calculated average defect point for large prawns collected from KRM, KM, MM, NM and SM were estimated 3.2, 2.6, 3.4, 2.8 and 1.6, respectively on a 5.0 point scale. Whereas, in case of locally caught small prawns, these values were estimated 4.8, 4.6, 2.4 and 2.0 for samples collected from KRM, KM, NM and SM, respectively. No large prawn samples were collected for Mechua Bazaar market (MM). Formalin was not detected in any prawn in locally produced or harvested in Mymensingh region. Another experiment was carried out to assess the effect of washing on prawn samples, contaminated artificially with formalin. In case of washing under tap water, formalin was removed from the body of both large and small prawns (treated with 5% formalin solution) after about 70 minutes. Whereas it took about 120 minutes to completely remove formalin from both size prawn samples by the washing effect of ice melt water.

Keywords: Macrobrachium rosenbergii, Giant freshwater prawn, Organoleptic quality, Formalin, Shelf life

Location: Mymensingh district.

Start Date: 00-00-2011

End Date: 00-00-2011

Program Area: Animal Health and Management

Commodity: Prawn

Objectives:

To assess the level of formalin contamination and its effects on different organoleptic characteristics of freshwater prawn collected from major markets in Mymensingh proper.

Methodology:

Collection of samples: Giant Freshwater prawn (M. rosenbergii) of two apparently different categories based upon their size was used for the present study. Those included small sized prawns with an average body weight of 11±2.08 g and 7±1 cm length and large prawns with an average body weight of 33.6±1.10 g and 14±1.5 cm length. Prawn samples were collected from different markets namely Bangladesh Agricultural University KR Market (KRM), Kewatkhali Bazaar (KM), Mecchua Bazaar (MM), Natun Bazaar (NM), and Sankipara Bazaar (SM) of Mymensingh Municipality area and carried to the laboratory of Department of Fisheries Technology, BAU, Mymensingh in an insulated box for organoleptic quality assessment. Survey of different fish markets: A survey was conducted in the above mentioned local fish markets of Mymensingh proper were through several visits. Information regarding marketing status and use of formalin and other chemicals in prawn for increasing shelf life was collected through interviewing of cross section of people associated with fish marketing. The information was collected using prescribed questionnaire through direct interview with the retailers and consumers. The major aspects of information collected during the survey included kind of prawn selling in the markets; source and use of ice; types of chemicals and other preservatives used; preventive measure for quality loss; mode of transportation; price structure and overall quality of the prawn. Organoleptic quality assessment: The collected prawns were immediately transported to the laboratory of Department of Fisheries Technology, BAU without using ice and subsequently tested for different freshness parameters by means of organoleptic method. The organoleptic assessment was performed by using the structured scaling method known as Quality Index Method-QIM. In this method, a number of important attributes such as appearance, shell and carapace colour, odour, firmness, texture of prawn etc. were measured on a limited scale and the scores were averaged to provide an index commonly known as defect point. Formalin detection: Formalin detection kit for food developed by Bangladesh Council of Scientific and Industrial Research (BCSIR) was used in this experiment. The kit contains three (1, 2 and 3) solutions. At first, the samples were washed with small quantity of water. Three drops washed-out water was taken in a test-tube using a dropper. Then 15 drops from solution 1 was added in the test-tube containing washed-out water. After stirring well, the solution was kept undisturbed for 30 seconds. Then 15 drops from solution 2 were added in the same test-tube containing sample. After stirring, the solution was kept for another 30 seconds. Finally 15 drops from solution 3 was added in the sample and waited for 30 seconds. Changes in colour of the solution into pink or red indicated the presence of formalin in sample. Conversely, an unchanged colour of the sample in test tube indicated absence of formalin. Triplicate samples were prepared and independently tested for each treatment. Preparation of prawn samples artificially contaminated with formalin: Another experiment was set to assess the effect of washing on formalin contaminated prawns. For this purpose, solutions containing 5% laboratory grade formalin were prepared and taken in 2 separate beakers. Then both large and small prawn samples were allowed to dip at 5% formalin solution in separate beakers for 5 (five) minutes. The samples were then taken out and kept in plastic net for a while to drain out the solution. Then both large and small formalin dipped prawns were divided into two groups each and taken into separate plastic sieves. After that, two sieves containing large and small prawn samples each placed under running tap water for 150 minutes. In other two sieves, large and small prawn samples were covered with sufficient ice and ice melt water was allowed to drain out. From all four sieves, prawn samples were taken out at 10 minutes interval and qualitative test of formalin was carried out using the procedure mentioned earlier.

Source of Information: App. Sci. Report. 2 (2), 2013: 32-38

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

Though none of the collected prawn samples from different markets of Mymensingh city showed formalin contamination, but the possibility of washing out formalin after their application cannot be ruled out as later experiment revealed complete absence of formalin in artificially contaminated prawns after couple of hours of washing under tap or ice melt water.

Knowledge Management: Journal