Acidothermophilic and spore-forming bacteria Alicyclobacillus acidoterrestris can cause pasteurized fruit and vegetable juices to spoil. The effectiveness was examined of nisin and lysozyme used as natural preservatives to prevent apple juice from being spoiled by those bacteria. For each of the eight strains studied, a Minimal Inhibitory Concentration (MIC) level of nisin and lysozyme contained in the culture medium was determined. Depending on the strain, the MIC value of nisin was from 100 IU/cm3 to 1500 IU/cm3 of medium with regard to spores, and, with regard to vegetative forms, the MIC value ranged from 50 IU/cm3 to 1250 IU/cm3 of medium. The lysozyme prevented A. acidoterrestris spores from growing at a concentration level from 0.005 mg/cm3 to 0.2 mg/cm3 of medium, and the growth of vegetative cells was inhibited by the lysozyme at a concentration level ranging from 0.05 mg/cm3 to 0.2 mg/cm3 of medium. The results of the apple juice shelf life tests performed showed that the nisin was effective at the concentration levels equal to MIC. The growth of seven A. acidoterrestris strains was inhibited during their 28 day incubation period. The lysozyme at the concentration levels equal to MIC values guaranteed the durability of juice samples only during a period between 7 and 21 days.
Alicyclobacillus acidoterrestris, apple juice, nisin, lysozyme