Mycotoxins

Mycotoxins are toxic compounds produced as secondary metabolites by about 350 species of toxigenic fungi, occurring in food commodities and food stuffs such as cereals, soybeans, corn, sorghum, and peanuts. These are pathogenic and their consumption can lead to mycotoxicoses. Cardiac beriberi caused by toxins of Penicillium associated with rice, and alimentary toxic aleukia linked with Fusarium molds on wheat, millet, and barley are some of the serious problems faced by human beings. Aflatoxin, sterigmatocystin, zeara-lenone, patulin, ochratoxin, and fumonisin are some of the toxins which could lead to increased incidence of cancer. Aflatoxins B1, B2, G, and G2 are produced by A. flavus and A. parasiticus in cereal grains such as corn, wheat, sorghum, oats, barley, millet, and rice. Aflatoxin is heat stable at temperature above 212° F. A. flavus generally produces toxins at a optimum temperature of 81-86°F and optimum moisture content of 18-24%. Aflatoxin production by A. flavus isolates from peanuts, cottonseed, rice, and sorghum showed a higher percentage of aflatoxin-producing strains in peanuts (154). Milk products such as cheese could be contaminated by aflatoxin M-1 when manufactured with milk from dairy cattle that have consumed aflatoxin B-1 contaminated feeds. Zeralenone and deoxnivale-nenol are toxins produced by Fusarium sp. Fusarium trincintum, and some strains of Fusarium, produce T-2 and other toxic trichothecenes. T-2 mycotoxin, the only mycotoxin known to have been used as a biological weapon, is highly stable and resistant to UV light destabilization. Citrinin is produced by P. expansum in apple juice and, to a lesser extent, in grape juices (155). Frayssinet et al. (156) have discussed methods for the analysis of mycotoxins in foods. They have also outlined techniques for aflatoxins, trichothecenes, zearalenone, fumonisins, and ochratoxin A detection.

Production of mycotoxin in SSF depends on several factors such as temperature, water activity, food sources, and aeration (157). It was reported that aflatoxin production in SSF increased at higher aeration rates in the range of 0.01 to 0.04 ml of air/g of humid corn/min (158). Gonzalez et al. (160) reported that aflatoxin production on cassava bagasse was higher at 29°C, which decreased 8-fold at 35°C. They also reported that at above 40% moisture there was positive effect on aflatoxin production. Maggon et al. (159) reported that in SmF, depletion of the nitrogen or phosphorus source enhanced aflatoxin biosynthesis. A report by Gonzalez et al. (160) stated that when A. parasiticus and A. niger were grown together in SSF, aflatoxin production was completely inhibited, proving that mycotoxin production is inhibited by competition. Lindenfelser et al. (161) obtained a yield of 2.4g/kg ochratoxin on wheat, using a rotating drum type fermenter. In a study by Saxena et al. (162), it was found that ergosterol could be used as an indicator for potential mycotoxin production, because the concentration of ergosterol was found to be similar to the concentration of ochratoxin A produced by A. ochraceus NRRL 3174 and P. verrucosum NRRL 3260 cultured on white rice.

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