Infestation of wheat flour by flour beetles (Tribolium castaneum) affected in its chemical and toxicological properties and validity for human consumption

Wheat flour represents a significant worldwide food. In many Asian and African countries including Egypt, big quantities of the flour are stored in open shounas and/or shades. Under such conditions, flour is subjected to attack by various biological factors including insects. The tenebrionid beetles such as Tribolium confusum represents an important species of the insect pests of wheat flour. Therefore, the present study aims to investigate the chemical and toxicological properties of wheat flour as affected by flour beetles (Tribolium castaneum) infestation as well as its validity for human consumption. Twenty seven jars, 1 kilogram, of flour (extraction 82%) were used filled with wheat flour 82 % extraction. A100 larvae of Tribolium confusum were put into each jar and 15 jars, not infested, were kept as control. The samples were kept for the trial duration (2, 4, 6, and 8 weeks) at 25 ⁰C and 60% of relative humidity. At the end of this period, all samples were sieved to recover the insects and then analyzed. The obtained data indicated that, in the end of infestation periods (8 weeks), chemical alterations include a significant (p≤0.01) increasing in flour fat characteristics such total acidity and peroxide values which recorded 49.60 and  94.08% compared to 3.13 and 1.75% for the uninfested/control samples, respectively. The opposite direction was recorded for the iodine number. On the other side, infestation of wheat flour with insects leads to increase in quinones and malonaldehyde content, which represent some of the most extensively studied toxic, mutagenic and carcinogenic compounds, that significant (p≤0.01) increased by the rate of 264.71 and 26.53% compared to 1.02 and 2.04% for the uninfested/control samples, respectively. The same trend was observed with uric acid, as excretion of arthropods and main reason for the gout disease in human; and ergosterol, a steroid involved in some biochemical process in insects and  mould metabolite. In conclusion, all of these data means lipids of wheat flour become rancid as a consequence of oxidation and oxidative rancidity initiated by infestation with insects after 6 - 8 weeks of infestation.  Also, the presence of significant amount of the determined toxic compounds in infested wheat flour with beetles that introduced by substantial quantities into the bakery products may be represented a great concern/hazard for the community health