Abstract

Fumonisin B₁ (FB₁) is a mycotoxin from Fusarium verticillioides that is frequently associated with maize. Fumonisins have been implicated as the causal agents of a variety of animal diseases and are epidemiologically linked to the high incidence of human esophageal cancer in some regions of the world. Thermal treatments are used in many processes involving grain and its derivatives, but little is known about the effects of common processing methods on the fumonisin content of food. The objectives of this study were to determine the thermostability of this toxin in contaminated maize, at different time/temperature combinations, as well as to determine the effect of baking and frying on the stability of FB₁ spiked into maize-based foods. The identity of FB₁ in extracts before and after heat treatments was confirmed by high-performance liquid chromatography. For each thermal process, the fumonisin content was inversely proportional to the processing temperatures. An initial FB₁ concentration of 217 mg/g in the control, was reduced to 184 mg/g when treated at 100°C for 2 h. Oven temperature of 220°C for 30 min showed extensive reduction of FB₁ to a concentration of 1.1 mg/g as compared to 94 mg/g in the control. Baking maize muffins spiked with 1.25 μg/g (dry weight) FB₁ at 200°C for 20 min resulted in an average FB₁ loss of 70%. Frying of maize chips spiked with 5 μg/g (dry weight) FB₁ at 190 to 210°C for 5 to 10 min resulted in an average FB₁ loss of 67%. The results of this study indicate that boiling temperatures are ineffective in producing any significant reduction in FB₁ levels. Thus, there might be correlation between the under processing of fumonisin-contaminated foods and the high incidence of esophageal cancer in certain regions of South Africa.

Key words: Mycotoxins, Fusarium verticillioides, maize-based food products, esophageal cancer.