Effect of food grade antioxidant on Aspergillus carbonarius and Aspergillus niger growth and ochratoxin A production on peanut- based media.

MAGNOLI C.E.,; BARBERIS C.,; ASILI R.,; ASTORECA A.; DALCERO A.M

Florianópolis, Brasil,

Congreso; V CLAM & ENM´2006, V Congreso Latino- Americano Micotoxicologia.; 2006

Ochratoxin A (OA) is receiving attention worldwide because of the hazard it poses to human and animal health. OA was believed to be produced only by Aspergillus ochraceus, however, it has been clearly established as a metabolite of different species of the section Nigri, such as A. carbonarius and A. niger. OA is found in a wide range of foods and feeds such as cereals and cereal products, groundnuts and oilseed. Peanut (Arachis hypogaea L) is an important food commodity in Argentina. In commercial storage, peanut seeds are stored for extensive periods before being exported or used locally. The detection and control of these mycotoxicogenic species and their mycotoxins in agricultural raw material, has become important to evaluate and identify the risk of contamination and to prevent the entry into the human and animal food chain. The aim of this study was to evaluate the effect of the best food grade antioxidant: propilparaben (PP) on (i) the lag phase prior to growth, (ii) growth rate and (iii) control of ochratoxin A production by strains of A. carbonarius and A. niger under different water activity (aW) and temperature conditions. In this experiment A. niger (ANM176) and A. carbonarius (ANM 4) isolated from peanut in Argentina, were used. Peanut meal extract agar (PMEA) was prepared at 2%. The aW of the basic medium was adjusted to 0.995, 0.98 and 0.93 with glycerol, the medium was  autoclaved at 120 ºC  for 20 min, before cooling to 50 ºC were added  the PP at 1, 5, 10 and 20 mM. The plates were centrally needle-inoculated and incubated for 30 days at 18 and 25 ºC. All treatments were repeated four times. Radial growth rates (mm/dia) were calculated as the slope of the linear regression obtained from plotting the colony radius of the replicates against time. On each sampling occasion, three agar plugs were removed from different points of the colony and extracted with 1 ml of methanol. The extracts were filtered and injected into the HPLC. In the control treatments there was an increase in the lag phase and the growth decrease as aW and temperature decreased. Interaction with antioxidant showed a further increase in the lag phase in two strains. At all aW levels and temperatures, PP at 5mM completely inhibited the fungal growth. The optimum aW level for OA production was 0.98, with a range to 0.995 or 0.93 resulting in a reduction in the level of toxin produced. In the presence of the antioxidant treatment, PP completely inhibited OA production, at concentration of 5 mM. At 1mM of PP, 18 ºC and 0.995 or 0.98 aW, the OA production was increased when compared with controls. The use of antioxidants could be a good strategy to diminish the entry of ochratoxin A into de animal feed and human food chain.