Effect Of Infestation By Tribolium Castaneum On The Quality Of Wheat Flour

The effects of infestation by Tribolium castaneum at four levels of Temperature (naturalconditions,15,25and30℃) and five population densities(0,2,4,6and8adults/500g) wereinvestigated. The disciplinary monthly determination of all the quality indices during the90d-150d storage period of wheat flour (there are different storage times due to thedeterioration of some indicators of quality) was done. The change of the storage quality,moisture content, protein, wet gluten, dry gluten, gluten index, whiteness, fatty acid value,falling number, dough water absorption, formation, stability, degree of softening, as well asthe secretions of methyl-benzoquinone content changes during the storage period wasinvestigated. The results were as follows.There was a negative correlation between storage temperature and the moisture contentof the wheat flour. The highest balance moisture content of wheat flour appeared at thestorage temperature of15℃. For the wheat flour infested by T. castaneum, the higher storagetemperature was, the higher the equilibrium moisture content the samples had. At the sametemperature, the higher population densitiy was, the higher the equilibrium moisture contentthe samples had.The crude protein content of the control wheat flour kept constant during the storage.For the protein, wet gluten, dry gluten and gluten index of wheat flour infested by T.castaneum, the higher storage temperature, storage time and insect density were, the higherthe downward trend the samples had.For the wheat flour infested by T. castaneum, the higher storage temperature, storagetime and insect density were, the higher the whiteness and fatty acid value had, and the lessthe falling number had. What’s more, the three quality indicators changed much more whenthe changes of storage temperature, storage time and insect density became much greater.There was a significant correlation between the three factors (storage temperature,storage time and insect density) and the absorption as well as softening degree of the wheatflour. However, there was a negative correlation between the three factors (storagetemperature, storage time and insect density) and the formation time as well as settling time of the wheat flour. With the increase of insect density, the glutenin decreased, the glutennetwork structurure was damaged, the dough elastic and thews decreased, water absorptionand degree of softening increased, the formation and stability time decreased, the decline inquality of the rheological.There was no methyl-benzoquinone in the control wheat flour. And the formation ofmethyl-benzoquinone was inhibited by the low temperature storage of15℃. For the wheatflour infested by T. castaneum, the higher storage temperature, storage time and insectdensity were, the higher the content of methyl-benzoquinone had. There was less than1ppmmethyl benzoquinone during the storage period under the tested insect density and infestationperiod, which was no harm to human health.The correlations were significant between the three factors (storage temperature, storagetime and insect density). The quality indicators of wheat flour were not isolated, and theyinteracted each other. There was a negative correlation between the moisture concent andprotein, whiteness as well as fatty acid value. However there was a significant correlationbetween the protein and whiteness. The correlations were significant between the protein andquality indicators related to protein that contained wet gluten, dry gluten, gluten index, doughdevelopment time, settling time, water absorption, and the degree of softening. There was asignificant correlation between the fatty acid value and water absorption as well as the degreeof softening.The water absorption, dough development time, settling time, the degree of softening,moisture content, wet gluten, fatty acid value and falling number could be used as indexs toestimate the quality of the wheat flour.