Spectrofluorimetric, spectrophotometric and chemometric analysis of wheat grains infested by Sitophilus granarius

Invisible infestation of wheat grains by Sitophilus granarius during postharvest handling is one of the main problems particularly for small enterprises and farm grain storage facilities due to the lack of cheap and fast methods for early detection of infestation, especially when only a small proportion of grain is infested by larvae. In order to determine whether the spectrofluorimetric, spectrophotometric or chemometric analysis of various extracts of wheat grains infested by S. granarius larvae could be used for detection of infested grain, four different types of extracts: 50 mmol dm−3 Tris–HCl pH 8.9, aqueous iso-propanol (φ = 0.55), methanol, and aqueous trichloroacetic acid (γ = 0.2 mg cm−3), of non-infested and infested wheat grains have been examined for fluorescence properties and UV/VIS spectral characteristics, while the chemometric analysis included determination of protein, reactive amino groups, polyphenols and soluble sugar content. Analysis of extracts revealed significant differences in UV/VIS spectral characteristics, level of reactive amino groups and polyphenol content between infested and non-infested grains. The results obtained indicate that instrumental analysis of spectral characteristics of grain extracts could be used as a method for determination of grain infestation.

► Various extracts of granary weevil infested wheat grains were analysed. ► Analysis included spectrofluorimetry, spectrophotometry and chemometry. ► Trichloroacetic acid extracts were most suitable for infestation detection. ► Grain infestation resulted with twofold increase of absorbance at 265 nm. ► Grain infestation resulted with twofold increase of reactive amino group content.