Study on decomposition products of norbixin during bleaching with hydrogen peroxide and a peroxidase by means of UPLC-UV and mass spectrometry

► Under bleaching conditions, unsaturated aldehydes and ketones are formed as decomposition products of norbixin. ► A reaction scheme for the decomposition of norbixin is proposed. ► Decomposition products of norbixin may react with endogeneous compounds in whey. The decomposition products of norbixin, a component of the natural colouring agent annatto, have been studied under bleaching conditions in water and in a whey matrix. In water, several unsaturated aldehydes and ketones of carboxylic acids were identified with UPLC-UV/MS and high resolution mass spectrometry techniques. Based on these products a reaction scheme for the decomposition of norbixin is proposed. In whey, the norbixin is also degraded during bleaching, but no decomposition products are detected. Most likely these products react with endogenous compounds from the whey matrix. For one of these compounds, i.e. cysteine, the formation of a reaction product with 3-acetylacrylic acid (decomposition product of norbixin) was shown.