Combined effect of natural antimicrobials and thermal treatments on Alicyclobacillus acidoterrestris spores

Commercial fruit juices are currently pasteurized at temperatures between 80 °C and 100 °C and Alicyclobacillus acidoterrestris spores can survive these thermal treatments. A. acidoterrestris produces several chemical off-odour compounds which cause the fruit juice spoilage. The purpose of this research was to evaluate the effect of the combination of a thermal treatment with natural antimicrobials (nisin, citral and limonene) on the survival and recovery of A. acidoterrestris spores. Heat resistance determinations at 95 °C in pH 3.5 McIlvaine buffer with or without the addition of these antimicrobials (alone or combined) in the heating or recovery media were performed. None of the antimicrobials reduced the heat resistance of A. acidoterrestris spores when added to the heating medium. However, nisin (1.5 mg L−1) alone was able to reduce the viable counts of this microorganism by more than two log cycles when added to the plating medium, even when no thermal treatment was previously applied. The different combinations of nisin with citral on the recovery medium, showed a strong synergistic effect on A. acidoterrestris. Limonene showed no inhibitory effect in either media (heating and recovery). The addition of natural antimicrobials such as nisin or citral, which would not affect the flavor or taste of citrus juices, alone or even combined, can help to the control of A. acidoterrestris.