The Effect of pH and Chemical Preservatives on the Growth of Bacterial Isolates from Some Nigerian Packaged Fruit Juices

Abstract

Bacterial pathogens were isolated from some Nigerian packaged fruit juices. The isolates were characterized and identified as Bacillus licheniformis, Aeromonas hydrophila, Bacillus circulans, Proteus morganii, Pseudomonas cepacia, Bacillus alvei and Pseudomonas chlororaphis. The antibiotic susceptibility profile of the seven isolates was determined and it was discovered that 65% of the microorganisms isolated were resistance to the antibiotic used while 35% were sensitive. The effect of pH, benzoic acid and sodium chloride concentration on the growth rate of isolates was investigated. It was found that as the pH of the growth medium increased from 3-9, the rate of growth of most isolates also increased except for Pseudomonas cepacia, which had optimum growth at neutral pH 7. As the concentration of sodium chloride increased from 2-5%, the rate of growth of all the seven isolates decreased. It was also noted that as concentration of benzoic acid increased from 250-1000 mg/l Bacillus licheniformis decreased from 1.330-0.167 nm, Aeromonas hydrophila decreased from 1.208-0.164 nm Bacillus circulans decreased from 1.158-0.299 nm, Proteus morganii decreased from 1.377-0.141 nm etc. The higher the concentration of benzoic acid the lower the rate of growth of the isolates.