Preventing Growth of Potentially Toxic Molds Using Antifungal Agents ¹

Mold inhibitors such as sorbates, propionates and benzoates have been used commercially for some time. Recently these and other potential inhibitors have been studied from the standpoint of their effects on growth of potentially toxic molds and mycotoxin production. In addition, other substances such as the antifungal antibiotic natamycin (pimaricin) and plant-derived products such as components of the essential oils of certain herbs and spices have recently been studied for their antifungal properties and effects on mycotoxin production. Some of these inhibitors inhibit mycotoxin production by greater than 70%, while only inhibiting growth of the mold by 25% or less. Of the organic acids, sorbic, propionic and benzoic, sorbic and its sorbate salts seems to be most effective over the widest range of conditions in preventing mold growth and mycotoxin production. Potassium sorbate is effective against toxic molds at levels of 0.10 to 0.15%. The antibiotic natamycin is very effective in preventing mold growth and toxin production at very low (0.001 to 0.005%) concentrations. A number of herbs and spices possess antifungal activity. At a level of 2.0%, in YES agar, cloves, cinnamon, mustard, allspice, garlic and oregano all completely inhibit mycotoxin production by a number of mycotoxigenic molds. Cloves, cinnamon and mustard seem to be the most effective of those tested, with complete inhibition occurring with amounts of spice less than 1%. Essential oils of orange and lemon also have antifungal properties at levels of 0.2 % and higher. Certain insecticides and fumigants also inhibit mold growth and mycotoxin production. The organophosphates naled and dichlorvos are both effective inhibitors at relatively low concentrations (0.002 to 0.01%). Phenolic antioxidants, particularly BHA, also inhibit toxic molds in concentrations of 0.025% and above. Naturally occurring methylxanthines, such as caffeine and theophylline, inhibit growth and aflatoxin production by A. parasiticus in concentrations of 0.1% and above. Chlorine, a commonly used sanitizer, will inactivate spores of toxic Aspergillus and Penicillium species at levels of residual chlorine commonly achieved with most sanitation procedures. Even though considerable information is available on inhibitory effects of a number of substances on mold growth and mycotoxin production, more work is needed to further define the conditions under which commercial antifungal agents are most effective in preventing growth of toxic molds and mycotoxin production.