Microbiological analysis of common preservatives used in food items and demonstration of their in vitro anti-bacterial activity

ObjectiveTo quantify the microorganisms contaminating the common preservatives used in food as well as to detect their in vitro anti-bacterial traits.MethodsA total of 9 preservatives were subjected to conventional cultural and biochemical methods for microbial enumeration. Anti-bacterial activities were demonstrated through the agar well diffusion method.ResultsAll samples were found to be contaminated with bacteria up to 105 CFU/g and with the fungal flora within a range of 101−102 CFU/g. Escherichia coli, Pseudomonas spp. and Staphylococcus spp. were demonstrated in most of the samples. Sodium sulfite and citric acid possessed the strongest anti-bacterial trait against all of the test bacteria. Acetic acid exhibited activity against 6 out of 8 test bacteria while vinegar exhibited the activity against 4 bacteria. Activity of salt was demonstrated only against Listeria spp. and Bacillus spp., while activity of sugar and honey was found only against Escherichia coli and Klebsiella spp., respectively.ConclusionsAccording to the current investigation, sodium sulfite and citric acid samples were found to be satisfactory preservatives both in terms of microbiological criteria and their anti-bacterial traits.