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Comparative Microbiological Analysis of Four Different Sea Fishes Collected from Local Market in Dhaka Metropolis

*Nur, I.T.,
Department of Microbiology, Stamford University Bangladesh, 51 Siddeswari Road, Dhaka-1217, Bangladesh

Mou, A.N.
Biotechnology and Genetic Engineering Discipline, Khulna University, Khulna 9208, Bangladesh

Habiba, U.
Department of Microbiology, Stamford University Bangladesh, 51 Siddeswari Road, Dhaka-1217, Bangladesh

Abstract/ Executive Summary:

The present investigation attempted to evaluate the existence and survival of spoilage microorganisms in four common sea fishes (Poma, Rupchanda, Koral and Tuna) available in Bangladesh and to determine the effects of cooking temperature to optimize the growth of fish microflora. Moreover, the status of fish in frozen condition after cooking was also studied. A total 4 categories of sea fishes were collected from the local shops in Dhaka city. Raw, cooked and frozen fish samples were analyzed for the existence of pathogenic bacteria through the conventional cultural techniques and the confirmative biochemical identification procedures. Total viable bacteria were present in all four fish samples in raw, cooked and frozen condition up to 6 log CFU/mL. Most of the raw fish samples were found to harbor a huge population of microorganisms up to 5 log CFU/mL including the fecal coliforms. Several specific bacterial species like E. coli, Klebsiella spp., Salmonella spp., Shigella spp., Staphylococcus spp., Pseudomonas spp. and Vibrio spp. were present in raw samples. However, the microbial load reduced from the fish after cooking and the status was static in frozen condition. Thus, the incidence of fecal coliforms in raw fish may be considered as a serious threat to the public health upon consumption of such fishes.

Keywords: Raw fish, Cooked fish, Frozen cooked fish, Pathogens, Microbiological quality

Location: Local market in Dhaka city

Start Date:

End Date:

Program Area: Pest Management

Commodity: Fish

Objectives:

The aim of our present studies is to determine the comparative microbiological quality among raw, cooked and cooked-frozen fish.

Methodology:

2.1 Study area and sample collection: For the analysis of microbial load, Four fish samples (Rupchada, Koral,Tuna, Poma) were collected from the local market in Dhaka city using a sterile aseptic container together with ice. A total of 20 g of raw, cooked and cooked frozen sample of each fish was homogenized with 180 g of sterile normal saline. The homogenized suspension was subjected to serial dilutions (10-fold) up to 106 with normal saline (APHA 1998). 2.2 Enumeration of total viable bacteria and fungus For enumerating total viable bacteria (TVB) and total fungal count, 0.1 mL of each sample was spread onto Nutrient agar (NA) and Sabouraud dextrose agar (SDA) respectively. For TVB, plates were incubated at 37°C. For fungal assay, plates were incubated at 25°C for 3 days (Sharmin et al., 2014). 2.3 Isolation of total coliform and fecal coliform For the isolation of coliforms and fecal 0.1 mL suspension was spread over MacConkey agar and mFC agar. For the isolation of E. coli and Klebsiella spp., plates were incubated at 37°C for 18-24 hrs. The presence of E. coli was further confirmed by the appearance of bluish-black colonies with green metallic sheen on eosin-methylene blue (EMB) agar. While for fecal coliforms, plates were incubated at 44.5°C for 24 hrs (Sharmin et al., 2014). 2.4 Assay of pathogenic bacterial load For the isolation of Salmonella spp., Shigella spp., Vibrio spp. and Staphylococcus spp., 0.1 mL of suspension was spread onto Xylose Lysine Deoxycholate (XLD), Thiosulphate Citrate Bile Salt Sucrose (TCBS) agar plates and Mannitol salt agar (MSA) respectively. After incubation at 37°C for 24 hrs, characteristic colonies were enumerated (Sharmin et al., 2014).

Source of Information: Food Research 4 (1) : 161 - 165 (February 2020)

Article Link (Online Journal): DOI: https://doi.org/10.26656/fr.2017.4(1).253

Funding Source:

Budget:

Total Budget (Tk.) :

Achievement/Findings:

The results of the current study confirmed the existence of contaminating microorganisms in sea fish especially in raw samples. In the current study, the cooked and frozen samples were quite satisfactory rather than the raw samples. This study tried to sort out the cooking effects on the reduction of existence microorganism in the fish samples as well as the various consequences may happen during the frozen condition. The bacterial load was remarkably reduced after cooking and even the quality was sustained in the frozen state. In the future, it would be important to evaluate the drug resistance traits of the fish microflora to ensure the consumer's health. However, the major outcome of this very study is the cooking effects in proper temperature may reduce the microbial spoilage in food and fish.

Knowledge Management: Journal