Evaluating the Persistence of Salmonella Tennessee and Lactobacillus brevis in Non-Alcoholic Beer under Low Pasteurization

Abstract

Foodborne pathogens such as Salmonella have been shown to survive in non-alcoholic (NA) beer (< 0.5 % ABV). Standard pasteurization recommendations for NA beer range from 80-120 pasteurization units (PU; 73.3 to 74.5°C for 1 min). However, producers may want to use lower pasteurization temperatures to preserve product quality. Recent studies show that pasteurization at lower temperatures may be effective at reducing spoilage organisms in traditional beer, but the impact on pathogens in NA beer is unknown. Additionally, spoilage organisms may impact Salmonella survival in NA beer, as spoilage organisms have been shown to impact pathogen survival. This study aimed to (i) evaluate the impact of a lower 0.75 PU thermal treatment on the survival of Salmonella enterica across six months in NA beer and (ii) to compare this survival when co-inoculated with Lactobacillus brevis. NA beer was brewed, filtered, and inoculated with Salmonella Tennessee (n = 360) and a subset was co-inoculated with L. brevis (n = 180) both at approximately 8.0 log CFU/mL. Three treatments were applied using a water bath: standard pasteurization (73.9°C for 1 min), low pasteurization (52°C for 1 min), and no pasteurization. Samples were stored at 14°C and enumerated in duplicate on tryptic soy agar and xylose lysine deoxycholate agar at 0, 1, 7, 14, 31, 59, 99, 129, 150, and 183 days, and co-inoculation samples were additionally inoculated on universal beer agar with 0.1% cycloheximide. PCR was used to confirm presumptive Salmonella positives. Data were analyzed using Kruskal-Wallis test and Dunn's test (p < 0.05). Significant differences were observed between pasteurization treatments post-pasteurization where Salmonella populations in the Salmonella only samples reduced by 8.07 ± 0.00, 2.25 ± 0.13, and 0.00 ± 0.00 log CFU/mL for the standard, low, and no pasteurization samples, respectively. Similarly post-pasteurization Salmonella populations in the co-inoculation samples reduced by 7.96 ± 0.00, 2.15 ± 0.83, and 0.00 ± 0.00 log CFU/mL for the standard, low, and no pasteurization samples, respectively. After 150 days, the no pasteurization and low pasteurization Salmonella only samples significantly differed as Salmonella populations reduced by 5.10 ± 0.32 in the no pasteurization samples and 4.03 ± 0.15 in the low pasteurization samples. There were no significant differences observed due to co-inoculation. Findings show that Salmonella can survive for at least 150 days in NA under low pasteurization conditions and can survive despite the presence of a common beer spoilage organism.