Assessment of Pathogenic Bacteria from Ice Cream and Ice Pop Sold in Gaborone, Botswana

This study was intended to isolate the following pathogenic bacteria; Yersinia enterocolitica, Listeria monocytogenes, Staphylococcus aureus and Salmonella species. Out of these four organisms, L. monocytogenes was not found in all samples. Pathogens were isolated from 31.4% of the 150 samples of open ice cream and 12.0% was isolated from packed ice cream. The targeted pathogens were not found in ice pop. St. aureus was found to have the highest percentage from both samples (18.7% and 53.0% respectively) followed by Salmonella species (8.0%) and Yersinia (4.7%). Coliforms and faecal coliforms were also isolated and characterised. Open ice cream was found to have a large number of coliforms (88%) and faecal coliforms (34.8%) of the total samples tested. Address for correspondence: E-mail: [email protected] INTRODUCTION Different dairy products provide different nutrients and allow a certain group of the microorganisms to grow on them (Osamwonyi et al. 2011; Gucukoglu et al. 2013). The products also vary in pH and water activity (aw) thus providing different growth environments (Frank 1997; Aaku 2000; Caglayanlar et al. 2009). Ice cream though it is a dairy product, the temperature at which it is kept and its composition provides eliminating conditions especially for those organisms that cannot tolerate low temperatures. Possible sources of these microorganisms in ice cream have been reported to include raw materials used for the composition of ice cream mix such as separated milk and milk powder, cream, flavouring, colouring substances, stabilizers (Caglayanlar et al. 2009) and from air during processing (Osamwonyi et al. 2011). The presence of these organisms in pasteurized ice cream could be due to their ability to survive the pasteurization process as in the case with spore formers, (Aaku, 2000; Osamwonyi et al. 2011) and they may persist in ice cream product thereafter. Psychrotrophic microorganisms are therefore the major contaminants and pathogens associated with ice cream and other foods that are served in frozen or chilled state (Arnaut-Rollier et al. 1999; Caglayanlar et al. 2009). Psychrotrophic organisms are microbes that strive best in low temperatures (refrigeration temperatures as well as freezing temperatures) (Schroder 1984). The major psychrotrophic bacteria found in milk and milk products include species of Acinetobacter, Alcaligenes, Arthrobacter, Bacillus, Chromobacterium, Citrobacter, Clostridium, Corynebacterium, Flavobacterium, Lactobacillus, Microbacterium, Moraxella, Serratia, Streptococcus, Pseudomonas, Aeromonas, Enterobacter, Klebsiella, Staphylococcus, Micrococcus, Yersinia, Listeria and Escherichia (Schroder 1984; Sinell 1989; Eneroth et al. 1999). Some of the psychrotrophic yeasts that have been found in association with refrigerated foods include Candida, Cryptococcus, Rhodotorula, Saccharomyces, Hansenula, Debaryomyces, Kluveromyces, Torulopsis, Trichosporon, and Pichia (Sinell 1989) and the moulds include Alternaria, Aspergillus, Cladosporium, Mucor, Penicillium, Rhizopus, Fusarium and Trichothecium (Alexopoulos et al. 1996). Fungi predominate in refrigerated food spoilage when water activity, acidity, processing, or packaging conditions select for their growth over bacteria (Alexopoulos et al. 1996). The emergence of psychrophilic foodborne pathogens and the rising level of foodborne diseases have raised a lot of concerns about the safety of refrigerated food (Sinell 1989; Szabo et al. 2000). The pathogenic psychrotrophs that grow at or below 5°C include Aeromonas hydrophila, Clostridium botulinum, Listeria monocytogenes, © Kamla-Raj 2013 Ethno Med, 7(3): 195-203 (2013)