Lactobacillus wasatchensis (WDC04) is a novel, slow growing, non-starter lactic acid bacterium (NSLAB) causing late gas formation in aging cheese, which results in significant economic losses to the producer. During cheese aging, organic acids can be produced by other NSLAB organisms or purposefully added to the cheese during manufacture. Organic acids are often used as preservatives. They are often found naturally in foods, generally don’t affect flavor or product quality, and under acidic conditions, are able to enter bacterial cells effectively altering the cell’s proton motive force. The effect of selected organic acids in their natural concentration range (2.5-560 mM) in Cheddar cheese was investigated for their ability to inhibit Lb. wasatchensis. Five organic acids (lactic, formic, propionic, citric and acetic) that can be produced by NSLAB organisms were selected and added at minimum, median, and maximum concentrations to individual wells of a 48 well plate containing MRS broth with 1% ribose (MRS + R) inoculated with WDC04. Growth rates were determined on a Tecan Infinite 200 PRO plate reader over 40 hours and results graphed on Excel. Both formic and citric acid showed inhibition of Lb. wasatchensis. As formic acid concentrations increased, the inhibitory effect also increased. The maximum concentration (100 mM) showed the most inhibition, the median concentration (63.15 mM) had an inhibitory effect between maximum and minimum, and the minimum concentration (26.3 mM) caused minimal inhibition. The addition of citric acid at the minimum (12 mM) and median (13.5 mM) concentrations showed similar inhibition. The use of these acids at concentrations normally found in Cheddar cheese is a potential antimicrobial measure to prevent or reduce late blowing in aging cheeses.
