Mass Spectrometry of Food Pigments

Abstract

Foods are naturally colored or could be colored by adding a variety of pigments and colorants such as chlorophylls, anthocyanins, betalains, carotenoids, curcuminoids, azaphilones, anthraquinones, phycocyanins, and caramels. In this chapter, mass spectrometry (MS) applied to three selected chemical classes is developed. C-phycocyanins, large proteins with chromophore groups, are very popular as a blue colorant in food. In C-phycocyanin analysis, MS has been used for de novo sequencing, characterization of subunit isoforms and chromophore structure, the oligomeric state’s definition, and identification of post-translation modifications. Carminic acid (CA) is a hydroxyanthraquinone glucoside extracted from insects. Red, violet, pink colors from cochineal extracts, CA, and carmines are used in a wide variety of food products. CA is a polar non-volatile small molecule easily ionizable both in positive and negative ion modes with a soft ionization source. Azaphilone pigments are hexaketides belonging to the structurally diverse polyketide class of compounds produced as secondary metabolites by filamentous fungi such as Monascus or Talaromyces. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry has proven itself an extremely precise, sensitive, and reliable analytical tool for the characterization of fungal biomolecules that can also be applied to polyketide and/or azaphilone pigments.