In vitro control of Aspergillus niger and Aspergillus awamori growth using antioxidants at different environmental conditions.

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

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

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

A wide range of mycotoxigenic fungi is known to colonize peanuts post harvest. The dominant genera include Aspergillus and Penicillium species. Colonization of peanuts by Aspergillus niger aggregate has often resulted in ochratoxin A (OA) accumulation.  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. Recents in vitro studies showed that the growth of Fusarium verticilloides and F. proliferatum on culture media could be controlled by food grade antioxidants. This study was carried out to determine the efficacy of food-grade antioxidants butylated hydroxyanisole (BHA) and propilparaben (PP) under different interacting water activity (aW) and temperature regimes on the lag phase and growth rate by A. niger and A. awamori isolated from Argentinian stored peanuts. A. niger (ANM176) and A. awamori (ANM 179), were used in these experiments. 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 food grade antioxidants BHA and 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. Two diameters of the colony at right angles to each other were measured. The radius of the colony was plotted against time, and a linear regression was applied in order to obtain the growth rate. The lag phase was obtain by extrapolation of this line to the x axis. In the control treatments there was a parallelism between the increment of lag phase and the reduction of growth rate when aW decreased for all temperature levels and isolated. The antioxidants showed a further increase in the lag phase at higher concentrations. Interactions between aW and antioxidants reduced the growth rate of all the strains. At all aW levels, BHA at 20 mM and PP at 5mM completely inhibited growth. At 1mM and 0.995 or 0.98 aW, the antioxidants were relatively ineffective. Both species A. niger and A. awamori were more tolerant of BHA than PP. These results suggest that these antioxidants have potential to control the growth of Aspergillus niger aggregate species in stored peanuts.