CHEMICAL PRESERVATIVES ACTION ON MICROBIAL-GROWTH IN A MODEL SYSTEM OF REFRIGERATED PREPEELED POTATOES

The effect of different concentrations of citric acid and ascorbic aci d (applied individually or in mixture's) on microbial growth in potato homogenate was analyzed and compared to the sodium bisulfite action d uring storage at 4-degrees-C in low gaseous permeability films. These experiments allowed one to simulate the behavior of prepeeled potatoes but with a known amount of added preservative to evaluate additive or synergic effects. Total viable microorganisms, Enterobacteriaceae, Ps eudomonas sp., Lactobacillus sp., molds, yeasts, Clostridium sulfite r educers, psychrotropic microorganisms, and aerobic and anaerobic viabl e spores were analyzed during storage time. Inhibition indexes produce d by the tested preservatives were calculated for the different microo rganisms. Sodium bisulfite solutions (100 ppm) had no inhibitory effec t. Concentrations of 3,500 ppm citric acid and 10,000 ppm ascorbic aci d showed antimicrobial action as well as mixtures of citric acid/ascor bic acid of the following compositions (in terms of total acids concen tration): 2,700/2,000, 3,500/2,000, and 2,700/3,000 ppm. A higher effe ct on Enterobacteriaceae was observed in comparison with other microor ganisms. The apparent synergic effect of these acids when they were ap plied together was demonstrated to be actually an additive effect when concentrations of undissociated acid in the mixtures were considered instead of total concentration.