Isolation and identification of bacteria from four different frozen snacks of gazipur district of Bangladesh

Abstract

The study was designed to isolate and identify microorganisms from frozen snacks from local market of Gazipur district. For this, four different kinds of snacks (French fry 10, deshi porotha 9, dal-puri 8 and alo-puri 8) were tested for the isolation of microorganisms. For the isolation of bacterial species each food sample was inoculated onto EMB agar, Nutrient agar and MacConkey agar media. The isolated bacteria of each sample were identified by cultural, biochemical (Oxidase, catalase, indole, MR, VP, citrate, TSI, nitrogen reduction, gelatin, lactose, sucrose, glucose, fructose, maltose, mannitol, arabinose, sorbitol) and staining characteristics. The results obtained from the microorganisms associated with the spoilage of frozen snacks showed that the total aerobic counts for French Fry ranged from 1.10 x 106 to 2.20 x 106 cfu/g where Deshi Porotha ranged from 1.56 x 106 to 2.58 x 106 cfu/g, Aloo Puri ranged from 1.68 x 106 to 2.36 x 106 cfu/g, Dal Puri ranged from 1.88 x 106 to 2.56 x 106 cfu/g. Out of the total 35 samples the prevalence of Staphylococcus aureus was found highest following Bacillus cereus, Klebsiella aerogenes and Proteus mirabilis in all the four kinds of frozen food tested in this study. Where S. aureus were found 35%, B. cereus 31%, K. aerogenes 20%, P. mirabilis 14%. In this study S. aureus was found frequently from all food samples but K. aerogenes and P. mirabilis were mostly isolated from Dal Puri and Alu Puri. Frozen snacks has to be stable in the local market for a certain period of time, it is considered to be free from spoilage causing and pathogenic microorganisms and during consumption should not cause any discomfort to taste and health. Results of this study clearly indicates that all the four different isolates of bacterial species are responsible for potential cause of spoilage in frozen foods if there is any variation in storage temperature. Furthermore, the presence of the potential spoilage causing bacteria in the selected frozen foods also indicate that the food got contamination during processing, manipulation, packaging and storing.