Control of Aspergillus growth and aflatoxin production using antioxidants at different conditions of water activity and pH

Aims: The effect of butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), trihydroxybutyrophenone (THB) and propyl paraben (PP) (at concentrations of 1, 10 and 20 mmol l(-1)) on germination, growth and aflatoxin B-1 production by Aspergillus section Flavi was evaluated. Methods and Results: Studies on the percentage of spore germination, elongation rate, growth rate and aflatoxin B-1 production were carried out in vitro in relation to water activity (a (w)) at 0.982, 0.937, 0.809 and 0.747 values. At 0.809 and 0.747a (w) values none of the isolates was able to germinate. Overall, PP and BHA were the antioxidants most effective at inhibiting germination of both species. In the presence of the lowest concentration of BHA and PP (1 mmol l(-1)) the conidial germination percentage ranged from 2 to 19% after 15 h of incubation at the highest water activity tested. BHA and PP at 10-20 mmol l(-1) completely inhibited conidial germination. The antioxidants more efficient in controlling Aspergillus elongation rate were PP, BHT and BHA. All strains were much more sensitive to all antioxidants tested on the percentage of spore germination and growth rate at 0.937a (w). The antioxidants PP and BHA completely inhibited aflatoxin B-1 production by all strains when added at 1 mmol l(-1). Decreased aflatoxin B-1 levels in comparison with the control, were observed with BHT at 1, 10 and 20 mmol(-1) with the strain T20 at 0.982a (w). In contrast, stimulation was observed with the antioxidant THB at 10 and 20 mmol l(-1) at 0.937a (w) with the strains T20 and T23. The effect of BHA and PP at 1 mmol l(-1) on lag phase and growth rate was maintained in the pH range between 6 and 8. At all pH values the inhibitory effect of BHA was higher than PP. No aflatoxin B-1 was detected at all pH values. Conclusions: The data show that BHA and PP could be considered as effective fungitoxicants for A. flavus and A. parasiticus. Significance and Impact of the Study: The information obtained show promise for controlling growth and aflatoxin B-1 in stored maize. Futher studies should be carried out to examine the potential for antioxidants, such as BHA and PP to effectively control both growth and aflatoxin production.