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Assessment of Microbiological Quality of Fresh-cut, Processed and Preserved Mushrooms Available in and Around Dhaka City

AS Mustafa Kamal
Food Microbiology Section, IFST, BCSIR, Dhaka

Fauzia Begum
Food Microbiology Section, IFST, BCSIR, Dhaka

Abul Khair
Department of Botany, Jahangirnagar University, Savar, Dhaka

Abstract/ Executive Summary:

The results revealed that 40% of fresh mushrooms, 93% of processed and preserved mushroom samples including mushroom-based food products were safe for human consumption from bacteriological point of view. The highest bacterial load recorded was 8.7 × 108 cfu / gm in the samples collected from Sutrapur area of Dhaka city. The results also indicated that 27, 13, 13 and 7% of the fresh mushrooms were contaminated with coliform, fecal coliform, E. coli and Salmonella sp. respectively. Thus those mushroom samples were not up to the mark for consumption, considering safety and sanitation point of view. In case of processed mushrooms and mushroom-based food products the results showed that 20% of dried mushrooms were contaminated with both coliform and fecal coliform, 7% of powdered mushrooms were contaminated with only coliform and 13% of mushroom soup powder were contaminated with coliform, E. coli and Salmonella sp. In case of preserved mushrooms, it was found that 7% of the canned mushrooms had count <10 cfu/gm which was unacceptable as per specifications for the canned food. However, the results also revealed that coliform, fecal coliform, E. coli and even Salmonella sp. were not detected in preserved mushrooms examined.

Keywords: Assessment, Microbiological Quality, Fresh-cut, Processed, Preserved, Mushrooms

Location: Food Microbiology Section, IFST, BCSIR, Dhaka

Start Date:

End Date:

Program Area: Quality and Nutrition

Commodity: Mushroom

Objectives:

To assess microbiological quality of fresh-cut, processed and preserved mushrooms available in and around Dhaka City.

Methodology:

The present study attempt to evaluate the microbiological quality of the fresh-cut oyster mushroom (P. ostreatus) dried mushrooms, dried and canned mushrooms. The experiment was conducted at Food microbiology section of IFST, BCSIR and Department of Botany, Jahangirnagar University, Savar, Dhaka in 2007. Collection of Samples - Mushrooms including fresh-cut, dried, powdered, mushroomi (blanched mushroom fried with powdered pulse), tikiya (fried powdered mushroom with boneless smashed fish), mushroom soup powder and canned mushrooms were collected through randomized sampling from the local market and mega-shops of eleven different areas of Dhaka city including Savar thana. Oyster mushrooms were grown at the cropping room using standard IFST practice, and picked only first and second flash, then packed on the day of the experiment. Mushroom-based products derived from oyster mushrooms were considered as processed mushrooms. Fresh-cut mushrooms were 5 to 11cm in diameter. Imported canned mushrooms (Agaricus spp.) were collected as preserved foods. The sterile marked containers were used for sampling and transported under ambient temperature within 1-2 hours to the laboratory, and stored at 4^oC for 4-6 hours if necessary. Culture media - Potato dextrose medium and Malt extract agar medium were used for isolation of contaminated moulds if any. All culture media were sterilized by autoclaving at 121⁰C (Model-MC 30321, ALP, Japan) at 15 psi for 20 minutes and the glassware by using oven (Model-BS75, Memmert) at 180^oC for 1 hours. Procedure A recognized procedure has been followed. All the cultures were incubated under aseptic conditions using Laminar Air Flow Cabinet (Model ER-17, Japan). The inoculated solid and liquid media were used for static growth conditions. The organisms were incubated at 32^oC temperatures. For microscopic characterization of bacteria, compound microscope (Model NoEUROMEX-9305346) was used. Preservation and maintenance of different microbial cultures, heat labile chemicals or reagents etc were carried out at refrigerated temperature (Model NoK644U123, SIEMENS). Total Bacterial Count (TBC) and Total Coliform Count (TC) - The total bacterial count was carried out by pour plate method and TC detection was done using MPN method. The number of colonies that appeared on the different plates was counted using digital colony counter and following formulae and expressed as log colony-forming unit per gram (log cfu/gm). In case of E. coli IMViC test was carried out for further confirmation. Qualitative detection of Salmonella species - A 25gm solid sample was weighted aseptically into a sterile Lactose Broth (LB) medium and after incubation 16-20 hours pre-enriched in Selenite Broth (SB) medium and then inoculated on BSA (Bismuth Sulphite Agar) and TSI (Triple Sugar Iron Agar) media. In case of positive result, confirmation was done by urease test. The experiment had been performed as recommended by International Commission on Microbiological Specification for Foods.

Source of Information: Bangladesh J Microbiol, Volume 27, Number 2, December 2010, pp 42-45

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

Spoilage of food is a special concern and from the economic point of view. Food and drinks with proper nutritional value, hygienic quality and appropriate in quantity is essential for good and active life. So, fresh mushrooms require minimal processing to consume. Conducting such type of experiments would enable us to decide as to what kind of processing methods should be adopted.

Knowledge Management: Journal