Graduate Thesis Or Dissertation
 

Antimicrobial properties of a wine based disinfectant

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/00000280b

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  • Wine has recently been shown to be a possible protective agent against microbial foodbome illness. The chemical environment of wine makes it difficult, if not impossible, for microorganisms to survive. The low pH, high concentration of organic acids, relatively high ethanol concentrations, and the potential for high levels of sulfur dioxide provide a series of hurdles for any microorganism that comes into contact with wine. Each and every wine contains a different amount of these known antimicrobial parameters and the combination of these components contribute to its' ability of to inactivate microorganisms. The objective of this research was to determine the role these parameters contribute to the observed antimicrobial effect. Initial experiments focused on the addition of sulfur dioxide to increase antibacterial efficacy. Four bacterial strains of common household pathogens were used to measure antimicrobial activity in a suspension test, Klebsiella pneumoniae, Pseudomonas aeruginosa and two strains of Staphylococcus aureus. A Chardonnay wine was produced at Oregon State University and different levels of sulfur dioxide and 1.5% sodium chloride were added. As expected, different bacterial species displayed varying levels of sensitivity towards the wine samples. Kiebsiella pneumoniae and P. aeruginosa were significantly more sensitive to wine than S. aureus. The former strains were inactivated by all treatments in less than five minutes. Staphylococcus aureus cells were capable of surviving in some of the wine treatments for nine minutes. Increased sulfur dioxide concentration and the presence of sodium chloride enhanced the ability of wine to inactivate these microorganisms. Five commercial Chardonnay wines were analyzed for their ability to inactivate the most resistant strain S. aureus 649. Samples were enumerated after one and three minutes of exposure. Results were variable, however trends could be discerned. Sulfur dioxide concentration did not correlate with antimicrobial activity of the wines. Other wine components were measured: pH, titratable acidity, volatile acidity, and ethanol concentration. No single parameter correlated with efficacy from the suspension tests. It was determined that complex interactions between wine components and their availability for acting on the microorganism varied by wine system. It is possible that there are other wine components that contribute to efficacy that were overlooked (e.g. polyphenols). The final stage of this study involved evaluating combinations of pH, titratable acidity, sulfur dioxide, and ethanol in a wine background. Suspension tests were performed against Escherchia coli 01 57:H7 and Staphylococcus aureus with samples being taken after twenty minutes of exposure. Escherichia coli 01 57:H7 was significantly more sensitive than S. aureus to the wine treatments. Analysis of overall trends showed that titratable acidity and ethanol concentration were not ideal predictors of efficacy. Molecular sulfur dioxide concentration was found to be a relatively good predictor of antimicrobial effects. Hydrogen ion concentration (pH) levels appear to be the most important parameter for predicting inactivation of S. aureus. Varying pH levels are known to affect the antimicrobial effects of other components. Decreased pH shifts the equilibrium of organic acids to the more antimicrobial undissociated form. Decreasing pH also increases the concentration of molecular sulfur dioxide in solution. The antimicrobial effects of ethanol are known to be enhanced by lowering the pH of the solution. This study concluded that decreasing pH enhanced the antimicrobial effect of ethanol. Other combinations may also lead to some strong conclusions that may enhance the ability to predict disinfection ability of a given wine. Overall results suggest that Chardonnay wine contains a combination of antimicrobial parameters that contribute to disinfecting ability. Of the tested parameters, pH appears to be the most influential; however the combination of all the components is more important than any one parameter.
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  • File scanned at 300 ppi (Monochrome, 24-bit Color) using Capture Perfect 3.0.82 on a Canon DR-9080C in PDF format. CVista PdfCompressor 4.0 was used for pdf compression and textual OCR.
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