Naturally contaminated corn containing 127 μ total aflatoxin per kg was divided into kg samples and treated with Ca(OH)2 for making tortillas. The treatments varied in % Ca(OH)2, boiling time, and holding time. Samples were taken after each processing step. Afla‐toxin levels and mutagenic activity of acetone extractions of alka‐line and reacidified products were measured. All treatments caused a decrease of aflatoxin (up to 46%); however, acidifying products prior to analysis caused reformation of much of the original aflatoxin. All treatments also effected a decrease in the mutagenic potential of the products, except for that of the acidified tortillas which was higher than that of the control corn. The tortilla manufacturing process may not be as effective in aflatoxin destruction as originally surmised.

No abstract

Milks obtained from cows fed rations containing aflatoxin-contaminated cottonseed, ammonia-treated aflatoxin-contaminated cottonseed, and uncontaminated cottonseed were tested for mutagenic potential using the Salmonella/mammalian microsome mutagenicity assay using Salmonella typhimurium strains TA98 and TA100. Standard assay protocol was used with S-9 liver homogenate added. Samples including whole milk, nonfat dry milk powder, cream, and reconstituted whole milk were applied directly to the plates in triplicate. As a control, samples of whole milk, reconstituted whole milk, and nonfat dry milk powder from cows fed uncontaminated feed were spiked with aflatoxin B1 and tested for mutagenic activity. High levels of mutagenic activity were observed in all samples from cows exposed to aflatoxin-contaminated cottonseed and the aflatoxin-spiked milks. This high activity was not evident in whole milk and whole milk component samples from cows fed the ammonia-treated aflatoxin-contaminated cottonseed or nonaflatoxin containing cottonseed. A low level of mutagenic potential was evident in whole milk from the ammonia treated group using TA100 tester strain.

Spray-dried skim milk, naturally contaminated with aflatoxin M„ was added to either raw or pasteurized whole milk to a final concentration of 1.1 Mg aflatoxin M,/L milk. Formalin (37% w/w) was added to the milk solutions to final concentrations of 0, 0.025, 0.05, and 0.1% formaldehyde. Samples were stored in the dark at 21°C in plastic and glass containers and were analyzed for aflatoxin M, at 0,1, 2, 3, and 4 weeks. This experiment was repeated using only raw milk and glass containers. Aflatoxin M, analyses were done at 0, 1, and 2 weeks. Aflatoxin M, losses increased over time and with increased formaldehyde concentration. With both experiments, aflatoxin M, levels after 2 weeks were less than 0.05 iigfL in samples containing 0.1% formaldehyde.

The effects of glutathione (GSH) and the combination of GSH and glutathione-S-transferase (GST) on aflatoxin B1 (AFB1) mutagenesis in the Salmonella mutagenicity assay using Salmonella typhimurium strains TA98 and TA100 were tested. Ten concentrations of AFB1 (0-1.0 micrograms/plate) were added to a liver microsomal homogenate (S9 mix) or to S9 mix containing GSH or S9 mix containing the combination of GSH + GST. One-third of the samples were plated directly. Two-thirds were incubated for 30 min at 37 degrees C prior to plating, and of those, half included bacteria. All samples were plated according to Ames et al [1975]. The results show that the addition of GSH and GSH + GST affected AFB1 mutagenesis by forming the AFB1-GSH conjugate and decreasing the availability of AFB1-8,9-epoxide. The effect of GST on GSH activity varied with the strain because of the different amounts of S9 mix used. The formation of the AFB1-GSH conjugate was verified by using reverse-phase high-performance liquid chromatography for quantitation of AFB1 and detection of AFB1-GSH.