Impacts of Gaseous Ozone (O) on Germination, Mycelial Growth, and Aflatoxin B Production In Vitro and In Situ Contamination of Stored Pistachio Nuts.

Pistachio nuts can become colonized by mycotoxigenic fungi, especially , resulting in contamination with aflatoxins (AFs). examined the effect of gaseous O (50-200 ppm; 30 min; 6 L/min) on (a) in vitro germination, (b) mycelial growth, and (c) aflatoxin B1 (AFB) production on a milled pistachio nut-based medium at different water activity (a) levels and at 30 °C. This was complimented with in situ studies exposing raw pistachio nuts to 50-200 ppm of O. Exposure of conidia to gaseous O initially resulted in lower germination percentages at different a levels. However, 12 h after treatment, conidial viability recovered with 100% germination after 24-48 h. Growth rates of mycelial colonies were slightly decreased with the increase of the O dose, with significant inhibition only at 0.98 a. The production of AFB after O treatment and storage for 10 days was stimulated in colonies at 0.98 a. Raw pistachio nuts inoculated with conidia prior to O exposure showed a significant decrease in population after 20 days of storage. However, AFB contamination was stimulated in most O treatments. The relationship between exposure concentration, time and prevailing a levels on toxin control needs to be better understood for these nuts.