ARS | Publication request: Inactivation of Salmonella on tomato stem scars by acidic sanitizing solutions

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: March 2, 2011
Publication Date: August 2, 2011
Citation: Gurtler, J., Smelser, A.M. 2011. Inactivation of Salmonella on tomato stem scars by acidic sanitizing solutions [abstract]. IAFP 100th Annual Meeting, July 31-August 3, 2011, Milwaukee, Wisconsin, 1:1.

Technical Abstract: Tomato stem scars are a likely contamination point for Salmonella, although they are recalcitrant to decontamination. Investigating stem scar sanitation may represent a worst-case-scenario model for inactivating Salmonella from externally-contaminated tomatoes. A composite of Salmonella Saintpaul, Montevideo, Newport, and Typhimurium were grown in TSB + 100 ppm nalidixic acid. Cells were washed and inoculated onto the stem scars of red round tomatoes at a high level (ca. 7 log CFU/stem scar) and a low level (ca. 4.5 log CFU/stem scar), and dried under a laminar flow hood for 3-4 hours. Tomatoes were then washed for 2 min in one of 58 different sanitizing solutions. Stem scars were excised, diluted in DE neutralizing broth, macerated with a hammer and pummeled in a stomacher. Homogenate was plated on TSAPN, and pre-enrichment and enrichments (for low inocula treatments only) were made with 2x TSBPN (24 h) and then TTP broth (24 h), respectively, and finally streaked onto XLD agar. Salmonella inoculated at the high level was reduced by more than 5 log CFU/stem scar with treatments of 0.2M sulfuric acid, or (3% lactic + 3% acetic acid), or (2% lactic + 2% acetic + 2% levulinic acid). Inoculated at the low level, all three previously-mentioned sanitizing treatments as well as a solution of 3% levulinic acid + 3% sodium dodecyl sulfate (SDS) + 5 g/L soil completely eliminated Salmonella, as determined by direct plating. The majority of selective enrichments were also negative for Salmonella. These results indicate that the following four acidic sanitizing treatments may be effective for decontaminating Salmonella from the stem scars of tomatoes: (1) (3% levulinic acid + 3% SDS with up to 5g/L soil), (2) 0.2M sulfuric acid, (3) (3% lactic + 3% acetic acid), and (4) (2% lactic + 2% acetic + 2% levulinic acid).