Studies on the efficacy of some preservatives used in packaged orange drinks

Abstract

The antibacterial activity of benzoic acid and sodium benzoate was investigated against bacterial isolates from packaged orange drinks using agar well diffusion and broth dilution methods. The antibacterial activity of the test agents against the standard NCTC bacteria species was also tested. The bacterial count from the packaged orange drinks ranged from 3.0 x 10 5 cfu/ml and 1.43 x10 6 cfu/ml. The bacteria species detected consisted of Bacillus subtilis, Escherichia coli, Pseudomonas aeruginosa and Micrococcus sp. The zones of inhibition of benzoic acid ranged from 19.0 mm – 31.5 mm while that of sodium benzoate ranged from 13.5 mm – 36.5 mm. The Minimum Inhibitory Concentration (MIC) of the preservatives against the test bacteria ranged between 0.156 µg/ml and 0.625 µg/ml while the Minimum Bactericidal Concentration (MBC) ranged between 0.313 µg/ml and 500 µg/ml. The preservatives were more effective against the Gram positive bacteria than the Gram negative bacteria. The preservatives at the concentration used in the examined drinks are inadequate to keep off indicator organisms and to ensure their safe consumption.