Microbiological Characteristics and Shelf Life of Corn Tortillas with and without Antimicrobial Agents

Commercial corn tortillas were assayed for pH, moisture, a_w, aerobic plate count (APC) and mold and yeast count (MYC). The shelf life of commercial tortillas ranged from 3 to 60 days, depending on the amount and type of preservative added. High initial APCs of commercial tortillas were associated with poor sanitary conditions at the plants, airborne contamination and improper storage practices. Shelf life of tortillas was greatly enhanced by refrigerated storage with or without the use of antimicrobials. For tortillas stored at 25°C, substantial increases in shelf life were attained by acidification (0.45% fumaric acid) plus addition of K-sorbate or Ca-propionate, but particularly by combination of these two antimicrobials. For tortillas stored at 4°C, shelf life of non-acidified samples was somewhat enhanced by addition of parabens and combinations of K-sorbate and Ca-propionate. Shelf life of acidified tortillas at 4°C was somewhat enhanced by addition of parabens and K-sorbate but increased substantially by addition of Ca-propionate and combinations of K-sorbate and Ca-propionate.