Assessment of minimum oxygen concentrations for the growth of heat-resistant moulds

This study evaluated the effect of both gaseous and dissolved oxygen (O2) concentration (0 - 21%) on the growth of six heat-resistant moulds (HRMs) (Neosartorya and Byssochlamys spp.) previously isolated from high-acid fruit products. The study was performed in acidified potato dextrose agar (aPDA) with all six HRMs and with B. fulva and N. fischeri in strawberry, apple and orange juice-based media. At ≥ 0.15% O2, visible growth of the HRMs occurred within 3-6 days. Complete inhibition on aPDA did not occur even at very low levels of dissolved O2 (ca. 0.01% O2). With the exception of B. fulva, decrease of the O2 concentration to ≤0.03% resulted in significantly (p