Nisin based organic acids inactivation of Salmonella on Grape tomatoes: Efficacy of treatment using bioluminescences ATP Assay

Authors: BERRIOS-RODRIGUEZ, ARMARYNETTE - University Of Puerto Rico; Ukuku, Dike; Olanya, Modesto; Cassidy, Jennifer; ORELLANA, LYNETTE - University Of Puerto Rico; Mukhopadhyay, Sudarsan; Niemira, Brendan

Submitted to: Journal of Food Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/30/2019
Publication Date: 12/17/2019
Citation: Berrios-Rodriguez, A., Ukuku, D.O., Olanya, O.M., Cassidy, J.M., Orellana, L.E., Mukhopadhyay, S., Niemira, B.A. 2019. Nisin based organic acids inactivation of Salmonella on grape tomatoes: efficacy of treatment using bioluminescences ATP assay. Journal of Food Protection. 83(1):68-74. https://doi.org/10.4315/0362-028X.JFP-19-275.
DOI: https://doi.org/10.4315/0362-028X.JFP-19-275

Interpretive Summary: Inability of 200 ppm chlorinated water to kill all bacteria on produce surfaces led to development of nisin-base organic acid sanitizer (NOAS). The organic acid compounds used are generally regarded as safe. Antimicrobial activity of NOAS was compared to 200 ppm chlorine on tomatoes inoculated with Salmonella bacteria. In addition, bioluminescence ATP assay as a quick estimate on the efficacy of treatment was compared to plate count methods. The new sanitizer reduced Salmonella populations on tomatoes to less than 1 CFU/g and the results suggests that it is a better alternative sanitizer for controlling and enhancing microbial safety of tomatoes. However, the bioluminescence ATP method did not corollate with the plate count numbers of treated tomatoes.

Technical Abstract: An antimicrobial nisin-base organic acid sanitizer (NOAS) activity on viable bacterial population and on produce surfaces was compared to chlorinated wash water using bioluminescence adenosine triphosphate (ATP) technique and plate count methods. Antimicrobial activity of NOAS against viable populations of 109 CFU/ml Salmonella in PBS, ddH2O and BPW diluted with NOAS at 10% final concentration was tested first and then on Grape tomatoes purchased from local supermarket was inoculated with Salmonella at 2.5 log CFU/g. A similar batch of inoculated tomatoes were treated with 200 ppm chlorinated solution. All treatments were for 5 min and surviving populations were enumerated on selective and non-selective agar plates. In vitro bacterial inactivation by the NOAS solution averaged greater than 4 log reductions within 5 min compared to 20 min required for similar log reductions by 200 ppm chlorinated water. Salmonella inactivation on tomato surfaces washed with NOAS solution was significantly (p<0.05) greater than numbers determined for chlorinated washed tomatoes. A significant linear correlation coefficient (r2 = 0.99) between bioluminescence ATP assay and aerobic plate counts of inoculated and untreated grape tomatoes were recorded, but not with antimicrobial treated tomatoes. Also, results indicate that the NOAS solution is an excellent alternative antimicrobial wash solution compared to chlorinated wash water.