Efficacy of ATP assay for assessment of bacterial populations on grape tomatoes treated with gamma radiation and novel antimicrobial solution

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

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 12/10/2018
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: Introduction. Surface characteristic of produce plays an important factor on how and where bacteria is attached and, in most cases, impacts bacterial inactivation during washing treatments leading to lower or higher estimation of total populations. Purpose. The purpose of this study was to compare bacterial populations inactivated on grape tomatoes when treated with gamma irradiation and a new antimicrobial solution (Lovit), By using bioluminescence ATP assay and plate count methods, the efficacy of both antimicrobial treatments were determined. Methods. Grape tomatoes were inoculated with Salmonella and Listeria monocytogenes bacteria at 4.4 and 3.9 CFU/g, respectively before treatment with gamma irradiation at a range of 0 to 1 kGy and Lovit antimicrobial solution combination for 5 min. Results. There were significant (p<0.05) differences in ATP levels before and after treatments of grape tomatoes. A significant linear correlation coefficient (r2 = 0.99) between bioluminescence ATP assay and aerobic plate counts of untreated grape tomatoes were recorded, and those of samples washed with water (r2 = 0.99) but not with treatments of Lovit antimicrobial solution. On grape tomatoes stored at 20oC for 120 h, a lower correlation coefficient between the bioluminescence ATP assay and the inoculated bacterial pathogens were observed (r2 = 0.75) compared to those stored at 5oC (r2 = 0.98) without treatments. For pathogen estimation, a minimal ATP threshold corresponding to bacterial detection was established at 3 log10 fentogram of ATP/tomatoes to 4 log10 CFU/g, suggesting that bioluminescence ATP assay may be recommended for quick estimation of total microbial load of grape tomato surfaces treated with antimicrobials and designated for fresh-cut markets. Significance. These results indicate that bioluminescence ATP assay can be used for quick estimations of total bacterial populations on grape tomatoes and minimal correlation to total plate count can be set at 4 log10 CFU/g. However, bioluminescence ATP assay cannot distinguish individual ATP of each bacterium species.