Impact of Insect Densities Tribolium Castaneum on the Benzoquinone Secretions and Aflatoxins Levels in Wheat Flour During Storage Periods

The present study was prepared to investigate the impact of insect density, adult emergence of Tribolium castaneum on the secretion of Benzoquinones (BQs) consist of methyl-1,4-benzoquinone(MBQ) and Ethyl-1,4-Benzoquinone (EBQ), and accumulation of Aflatoxins (AFs) in wheat flour stored at different periods.

Forty grams of wheat flour were put into small glass jars (8 cm diameter and 12 cm length). Then T. castaneum was put in each jars at rates of 10, 20 and 30 unsexed pairs of insect adult. The jars were covered with muslin cloth and the rubber band was fixed to prevent insects to escape. A glass jar without any insects served as the control. The jars lifted on bench in the laboratory for two, three and four months of storage under laboratory temperature conditions (with average 28 ± 2⁰C and 65±5 R.H). The previous design was replicated three times. At the end of each storage period, the jars containing the flour were sieved thoroughly by 40 wire mesh size to separate the insects. The insects have been counted on the other hand wheat flour was prepared to determine MBQ, EBQ and AFs by HPLC methods.

The results indicated the levels of EBQ higher than MBQ in all infested samples at all insect densities (No. of insect pairs). The concentrations of MBQ in wheat flour released by ten adult pairs (10P) with the three storage periods two, three and four months were 10.42 ± 0.56, 22.38 ± 3.67, 27.06 ± 6.71µg/g, respectively. These results increased with insect densities to (30p) were 39.67 ± 0.10, 63.58 ± 2.35 and 106.24 ± 7.4 µg/g after storage periods two, three and four months, respectively. In addition to the concentrations of EBQ with (10P) were 67.45 ± 3.64, 98.0 ± 6.1 204.66 ± 5.8 µg/g with storage periods two, three and four months, respectively. In case (30P) the levels of EBQ were 376.7 ± 0.87, 570.1 ± 2.11 and 1558.66 ± 10.88 (µg/g). The highest concentration of the BQs 1664.90 ± 11.43 (µg/g) released by T. castaneum achieved with the highest adult emergence (1021 insect adult) and the highest insect density (30p) at four months storage period. In general, AFs levels enhanced with a period of storage and insect densities.

Levels of the BQs (MBQ and EBQ) increased with an increase of storage periods and insect densities. Therefore, the presence of this insect should be prevented in stored wheat flour reducing AFs contamination is possible by storage for short time and prohibit insects which causes an increase temperature of the flour and moisture, all of which promote production of AFs.