Thermal Inactivation of Stationary Phase, Acid and Non-acid Adapted SalmonellaGaminara in Single-strength Orange Juice

Abstract

Thermal death time parameters of stationary phase, acid and non-acid adapted pathogens, primarily as cocktails of multiple strains, have been studied in various food products. The objective of this study was to evaluate the thermal tolerance of stationary phase and acid adapted SalmonellaGaminara, associated with an orange juice outbreak, in orange juice. The strain was grown in tryptic soy broth, supplemented with 1% glucose for acid adaption, and inoculated (≈109 CFU/mL) into single-strength pasteurized orange juice without pulp. Juice was sealed into microcapillary tubes. Tubes were immersed into water baths at 55, 58, and 60 °C, removed at predetermined time intervals, and placed immediately onto ice. Survived Salmonellapopulations were enumerated on a tryptic soy agar supplemented with 0.1% sodium pyruvate. D-values for acid adapted and non-adapted SalmonellaGaminara at 55, 58, and 60 °C were 0.89 ± 0.06 and 0.80 ± 0.10 min, 0.32 ± 0.05 and 0.33 ± 0.09 min, 0.15 ± 0.08 and 0.14 ± 0.08 min, respectively. No statistically significant differences were seen between acid adapted and non-adapted strains at all temperatures. Acid adaptation did not provide an increase of thermal tolerance. Evaluation of individual strains using the microcapillary tubes will allow the impact of strain to strain variability on public health to be evaluated.