Coffee is one of mankind's most popular beverages obtained from green coffee beans by roasting. Much effort has been expended towards the chemical characterisation of the components of the roasted coffee bean, frequently termed melanoidines, which are dominated byproducts formed from its most relevant secondary metabolites - chlorogenic acids. However, impeded by a lack of suitable authentic reference standards and analytical techniques sufficiently powerful for providing insight into an extraordinarily complex enigmatic material, unsurprisingly little structural and mechanistic information about the products of coffee roasting is available. Here we report on the characterisation of low molecular weight melanoidine fractions of roasted coffee using a conceptually novel combination of targeted and non-targeted mass spectrometrical techniques. We provide an unprecedented account of the chemical composition of roasted coffee beans. Using a targeted analytical approach we show for the first time, by comparison to authentic reference standards obtained by chemical synthesis, that chlorogenic acids follow four distinct reaction pathways including epimerization, acyl migration, lactonisation and dehydration. The analytical strategy employed in a non-targeted approach uses high resolution mass spectrometry to identify the most abundant molecular formulas present in roasted coffee samples and model roasts followed by van Krevelen and homologous series analysis. We identified the molecular formulas formed from reactions of chlorogenic acids, carbohydrates and proteins, both between classes of compounds and within same classes of compounds. Furthermore, we identified two new classes of compounds formed from chlorogenic acids during roasting, chlorogenic acid acetates and O-phenolic quinoyl and shikimoyl esters of chlorogenic acids.

Caramel is one of mankind's best known dietary materials obtained from carbohydrates by heating. Much effort has been expended toward the chemical characterization of the components of caramel but impeded by a lack of suitable analytical techniques sufficiently powerful for providing insight into an extraordinarily complex material. This paper reports the characterization of caramel formed by heating from glucose, fructose, and saccharose using a conceptually novel combination of mass spectrometrical techniques. The analytical strategy employed uses high-resolution mass spectrometry (MS) followed by targeted liquid chromatography-tandem MS experiments. Caramel is composed from several thousand compounds formed by a small number of unselective and chemoselective reactions. Caramelization products include oligomers with up to six carbohydrate units formed through unselective glycosidic bond formation, dehydration products of oligomers losing up to a maximum of eight water molecules, hydration products of sugar oligomers, disproportionation products, and colored aromatic products.

In this contribution we review our work on the characterisation of processed food. We review novel methods and analysis strategies developed to account for the composition of extraordinarily complex materials such as black tea thearubigins, coffee melanoidines and thermally treated carbohydrates. Our methods are mainly based on modern mass spectrometry and are introduced and critically discussed. A series of novel previously unpublished data interpretation strategies are presented as well. Finally an evaluation of the insight obtained in the composition of selected processed foods is given discussing potential consequences for assessing beneficial and adverse health effects of processed food.

Thermal treatment of food changes its chemical composition drastically with the formation of “so-called” Maillard reaction products, being responsible for the sensory properties of food, along with detrimental and beneficial health effects. In this contribution, we will describe the reactivity of several amino acids, including arginine, lysine, aspartic acid, tyrosine, serine and cysteine, with carbohydrates. The analytical strategy employed involves high and ultra-high resolution mass spectrometry followed by chemometric-type data analysis. The different reactivity of amino acids towards carbohydrates has been observed with cysteine and serine, resulting in complex MS spectra with thousands of detectable reaction products. Several compounds have been tentatively identified, including caramelization reaction products, adducts of amino acids with carbohydrates, their dehydration and hydration products, disproportionation products and aromatic compounds based on molecular formula considerations.

Many dietary products containing polysaccharides, mostly starch and cellulose, are processed by thermal treatment. Similarly to the formation of caramel from mono- and disaccharides, the chemical structure of the carbohydrates is dramatically altered by heat treatment. This contribution investigates the products of thermal decomposition of pure starch and cellulose as model systems followed by an investigation of bread obtained at comparable conditions using a combination of modern mass spectrometry techniques. From both starch and cellulose, dehydrated oligomers of glucose and dehydrated glucose have been predominately observed, with oligomers of more than four glucose moieties dominating. Moreover, disproportionation and oligomers with up to six carbohydrates units are formed through unselective glycosidic bond breakage. MALDI-MS data confirm the presence of the majority of products in toasted bread.