Evaluation of Some Organic Acids as Mold Inhibitors by Measuring CO2 Production from Feed and Ingredients , ,

A 15 × 150 mm test tube containing 5.5 cm3 of feed or corn meal and capped with a rubber septum was used to evaluate the antifungal properties of a commercial mold inhibitor, Mold-X, and its components, propionic, acetic, sorbic, and benzoic acids. Production of CO2 by the native flora was measured by injecting head-space gas into a gas chromatograph. In general, the higher the moisture content of the substrate the higher the concentration of inhibitor required to obtain a certain degree of inhibition. For example, the minimal inhibitory concentration of the commercial product was .125 mg/g of corn meal at 20% H2O, .25 mg/g at 25% H2O, and .50 mg/g at 35% H2O. All four components inhibited CO2 production. The order of effectiveness depended on moisture content and substrate. In corn meal of 20% H2O the order was propionic > benzoic > sorbic > acetic, while at 35% H2O the order was sorbic > propionic > acetic = benzoic. In a broiler starter mash of 20% H2O the order was sorbic > propionic = acetic = benzoic and at 35% H2O the order was sorbic > propionic > benzoic > acetic.