Purpose: The purpose of this study was to evaluate the efficacy of ethanol vapor produced by atmospheric and vacuum-assisted boiling to inactivate Salmonella on artificially-contaminated peppercorns.
Methods: A mixed biofilm containing four Salmonella serovars was established on the surface of black peppercorns. The contaminated peppercorns (5 g) were placed onto loosely packed glass wool in a modified glassware distillation apparatus. Ethanol (95%) was boiled at atmospheric pressure (AB) and vacuum-assisted boiling (VB; - 20 in Hg) conditions, and vapor was in contact with the peppercorns for 1, 5, or 10 min. During treatment, ethanol vapor temperature was measured in the distillation head downstream from the peppercorns. Following treatment, peppercorns were serially diluted in peptone-Tween-cellulase diluent, surface-plated onto XLT4 and TSA agars, and incubated at 37°C for 24 h prior to colony enumeration.
Results: Ethanol vapor temperature was 72 ± 2°C for AB treatments and 50 ± 2°C for VB treatments. Ethanol vapor treatment at AB conditions resulted in Salmonella population reductions of 3.90 and 5.95 log CFU/g on peppercorns after 10 min as determined by plating onto TSA and XLT4, respectively. Under VB conditions for 10 min, Salmonella populations decreased by 2.69 and 4.55 log CFU/g as determined on TSA and XLT4, respectively. Native microbiota of uncontaminated peppercorns decreased by only 1.15 log CFU/g (TSA only) after 10 min treatment under AB conditions.
Significance: Atmospheric ethanol vapor treatment produced greater than a 5-log reduction in Salmonella populations on contaminated peppercorns.