The growth and aflatoxin production of Aspergillus flavus strains on a cheese model system are influenced by physicochemical factors

Abstract

Traditional cheeses may be contaminated by aflatoxin-producing Aspergillus flavus during the ripening process, which has not been sufficiently taken into account. The objectives of this study were to evaluate the influence of water activity (a_w), pH, and temperature on the lag phases, growth, and aflatoxin production of 3 A. flavus strains (CQ7, CQ8, and CG103) on a cheese-based medium. The results showed that the behavior of A. flavus strains was influenced by pH, a_w, and temperature conditions. The CQ7 strain showed the maximum growth at pH 5.5, 0.99 a_w, and 25°C, whereas for CQ8 and CQ103 strains, no differences were obtained at pH 5.5 and 6.0. In general, low pH, a_w, and temperature values increased the latency times and decreased the growth rate and colony diameter, although a_w and temperature were the most limiting factors. Maximum aflatoxin production on the cheese-based medium occurred at pH 5.0, 0.95 a_w, and 25 or 30°C, depending on the strain. This study shows the effect of pH, a_w, and temperature factors on growth and aflatoxin production of 3 aflatoxigenic A. flavus strains on a cheese-based medium. The findings may help to design control strategies during the cheesemaking process and storage, to prevent and avoid aflatoxin contamination by aflatoxigenic molds.