Investigation of the efficacy of winery cleaning and sanitization chemistries
This research focused on optimizing cleaner and sanitizer concentration and contact time for several different chemicals and spoilage microorganisms relevant to the wine industry. Minimum inhibitory concentration (MIC) and minimum biocidal concentration (MBC) assays were performed, which expose the microbes to dilution series of antimicrobial agents to determine at which concentration different species are either inhibited (MIC) or inactivated (MBC) by exposure to the antimicrobial. As the MIC/MBC assay involves contact times for the microorganisms that are greater than would be reasonable for the wine industry (24 hrs), fluorescence spectroscopy was employed to provide complementary kinetic inactivation data. Peracetic acid was used at several different concentrations to determine the minimum contact time for inactivating S. cerevisiae cells in suspension. In a similar experimental design as the MIC/MBC assay, a minimum biofilm eradicating concentration (MBEC) assay was employed to assess whether sessile communities would require elevated concentrations in order to inactivate or remove the biofilm populations from the microtiter plates. While many of the chemicals did require higher concentrations to inactivate sessile communities, cleaners that contained surfactants and other detergents were effective at lower concentrations, possibly due to the fact that they physically removed the biofilm from the well plate regardless of whether the cells were inactivated. In combination with previous research efforts (Final Report 2017_2123) these results were used to develop an optimized cleaning and sanitation framework for assessment in the winery at the pilot scale (2000 L), which were assessed using ATP swabbing and traditional plate counts. Results from those trials indicate that cleaning and sanitizing contact times are less important beyond 5-minute exposure than proper attention to critical control points in the shadow of spray balls or mechanical agitation. Worker diligence in manually addressing and cleaning these sensitive areas may have a greater impact in cleaning and sanitizing success than increasing contact time several fold.