Antimicrobial Activity of Foods with Different Physio-Chemical Characteristics

The antimicrobial activities of orange juice, milk, cheese, honey, and yoghurt were determined against some recurrent bacterial pathogens and spoilage agents, including Salmonella typhimurium, Staphylococcus aureus, Escherichia coli, Pseudomonas, Bacillus, Micrococcus, and Proteus spp. Orange juice and the combination of yoghurt and orange juice had the broadest spectrum of activity followed by honey and then yoghurt, and then to a lesser extent the combination of yoghurt and honey, and honey and orange juice. In contrast, no inhibition was observed with milk or cheese. Staphylococcus aureus, Salmonella, and Pseudomonas spp. were most resistant to the action of the foods, whereas Micrococcus, Bacillus, and E. coli were remarkably sensitive. Low pH (pH 3.2) was shown to contribute to the inhibitory activity of orange juice. Whereas, water activity (a w ) was not the major factor in the bacterial growth inhibition caused by honey. In summary, it is good practice to include foods that restrict the growth of microorganisms in prepared foods such as school picnics and foods that may be inadequately stored such as camping meals. Orange juice, yoghurt, and honey were shown to meet these requirements. Their inclusion either individually or in combinations in ‘high risk” products such as salad dressings and sandwiches should be considered.