Qualitative and semiquantitative analysis of annatto and its content in food additives by photoacoustic spectrometry

Photoacoustic spectrometry in the ultraviolet, visible and near-infrared regions was employed to study the absorption behaviour of the colourant annatto and to determine its content in commercial seasoning products via the intensity of an absorption peak compared with the absorption of standard samples with a known content of annatto. Owing to strong absorption and as a consequence saturation of the signal of the pigment in the ultraviolet and visible regions, a peak of weak absorption in the near-infrared region was used, guaranteeing a linear relationship between peak intensity and annatto content for the usually applied low to medium levels of dye contents in commercial products.

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