Processors within the soft drinks industry utilise various methods to preserve the quality of juice products, which may include the use of chemical preservatives. Alicyclobacillus acidoterrestris, especially its spores, is acknowledged as a threat to the industry in that it is increasingly being reported as a cause of spoilage incidents. Propionibacterium cyclohexanicum has also been shown to cause spoilage, with one incident in orange juice reported to date. This study investigated the effect of the preservatives sodium benzoate and potassium sorbate and also the bacteriocin nisin on these two spoilage bacteria.
In apple juice at 30 °C 0.1 mg/ml sodium benzoate or potassium sorbate inhibit growth of 101 cells/ml A. acidoterrestris while 0.5 mg/ml inhibits growth of 104 cells/ml. Nisin at 5–10 IU/ml alone, and in combination with either sodium benzoate or potassium sorbate, is also effective in inhibiting multiplication of A. acidoterrestris.
Sodium benzoate (0.5 mg/ml and 1.0 mg/ml) and potassium sorbate (1.0 mg/ml), both alone and in combination with 2.5, 5 or 10 IU/ml nisin, inhibit growth of P. cyclohexanicum in orange juice at 30 °C with no viable cells detected at 29 days, although nisin alone at concentrations up to 1000 IU/ml were not effective in inhibiting multiplication of P. cyclohexanicum, suggesting that this organism may be resistant to nisin

Article available online from October 2007