Evaluation of Mustard oil and temperature in the toxicity reduction of Aspergillus flavus in Walnut fruits

Abstract

   The study aimed to isolate and identify fungi that produce mycotoxins from walnut fruits and the possibility of limiting their presence in the fruits and reducing their toxic effects.  The molecular diagnosis in this study of the fungus Aspergillus flavus was carried out using the internal transcribed spacer (ITS) genetic marker. As for the results of testing the ability of some A. flavus isolates to produce aflatoxins B1 including the ammonia test, the results of this test showed the ability of four out (of six) isolates of A. flavus on the production of aflatoxin B1 by changing the color of the base of the coconut medium on which the fungus isolates are grown, with a percentage of 66.66 %. The results of the chemical analysis using TLC technology for Aspergillus flavus showed the ability of three isolates to produce aflatoxin B1 out of six isolates of A. flavus with a percentage of 50 %. As for the most important results of the effectiveness of mustard oil in inhibiting the growth of the fungus A. flavus in walnut fruits, the highest percentage of inhibition was at 15% concentration, which amounted to 57.33%. The most important results of the storage experiment after three months of storage, included the test of the effect of mustard oil and temperature on the growth and density of A. flavus. The test was the effect of mustard oil on the reduction ratio of aflatoxin B₁ as it reached the highest percentage of toxin reduction when adding mustard oil only, which amounted to 98.213%, compared to other treatments, the test was the effect of mustard oil and temperature on the amount of aflatoxin B1 toxin, which gave the highest rate when adding A. flavus to walnuts, which amounted to 13.425 micrograms/ g,. At a temperature of 5 °C, it gave the lowest rate of aflatoxin B₁ toxin, which was 0.880 µg.gm^-1. The highest rate was 8.620 µg.gm^-1, at 25°C.