In this study, we monitored the thermal formation of early ribose-glycine Maillard reaction products over time by ion cyclotron resonance mass spectrometry. Here, we considered sugar decomposition (caramelization) apart from compounds that could only be produced in the presence of the amino acid. More than 300 intermediates as a result of the two initial reactants were found after ten hours (100 °C) to participate in the interplay of the Maillard reaction cascade. Despite the large numerical variety the majority of intermediates follow simple and repetitive reaction patterns. Dehydration, carbonyl cleavage, and redox reactions turned out to have a large impact on the diversity the Maillard reaction causes. Although the Amadori breakdown is considered as the main Maillard reaction pathway, other reactive intermediates, often of higher molecular weight than the Amadori rearrangement product, contribute to a large extent to the multitude of intermediates we observed.
Reactions between sugars and amino acids in the Maillard reaction produce a multitude of compounds through interconnected chemical pathways. The course of the pathways changes depending on the nature of the amino acids and sugars as well as the processing conditions (e.g. temperature, water activity). Some partial pathways have been elucidated using labelled precursors but the process is very time intensive. Here, we use rapid, non-targeted analysis with Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) to deliver the molecular formulae and ion intensities of the compounds generated from reaction of four amino acids with ribose (10 h at 100 °C) to study the effect of amino acid side chains on the reaction pathways. Using van Krevelen diagrams, known chemical changes during the reaction (e.g. dehydration or decarboxylation) can be studied. Comparison of the data from the four amino acids studied, showed a common pathway, which involved 73 Maillard reaction products (MRPs) where the differences were due only to the nature of the amino acid side chain. From the more than 1400 different molecular formulae found, pathways unique to the amino acids were also identified and the order of reactivity was lysine >cysteine >isoleucine ≈ glycine. While unequivocal identification of the compounds cannot be achieved with FT-ICR-MS, applying known chemical transformations found in the Maillard reaction, not only identifies new and known pathways, but also integrates the MRPs into a general Maillard reaction scheme that better represents the totality of the Maillard reaction.
We present concepts of complexity, and complex chemistry in systems subjected to biotic and abiotic transformations, and introduce analytical possibilities to disentangle chemical complexity into its elementary parts as a global integrated approach termed systems chemical analytics.
As a complex microbial ecosystem, wine is a particularly interesting model for studying interactions between microorganisms as fermentation can be done by microbial consortia, a unique strain or mixed culture. The effect of a specific yeast strain on its environments is unique and characterized by its metabolites and their concentration. With its great resolution and excellent mass accuracy, ultrahigh resolution mass spectrometry (uHRMS) is the perfect tool to analyze the yeast metabolome at the end of alcoholic fermentation. this work reports the change in wine chemical composition from pure and mixed culture fermentation with Lachancea thermotolerans, Starmerella bacillaris, Metschnikowia pulcherrima and S. cerevisiae. We could clearly differentiate wines according to the yeast strain used in single cultures and markers, which reflect important differences between the yeast species, were extracted and annotated. Moreover, uHRMS revealed underlining intra species metabolomics differences, showing differences at the strain level between the two Starmerella bacillaris. non volatile metabolomics analysis of single and sequential fermentations confirmed that mixed fermentations lead to a different composition. Distinct metabolites appeared in wines from sequential fermentation compared to single fermentation. this suggests that interactions between yeasts are not neutral.Microorganisms coexist in most environments and interact with each other. These interactions happen in nearly every niche on the planet and in numerous processes such as bioremediation of pollutants, farming, biotechnology, medicine or food-processing 1,2 . Under oenological conditions, when yeasts grow simultaneously during alcoholic fermentation, they often do not coexist passively, and in most cases, physiological and metabolic interactions are established between them. The interactions between the different strains of Saccharomyces and non-Saccharomyces yeast can be direct or indirect, through the physicochemical changes in the environment caused by one strain reacting to the other. In oenology, the effect of these interactions is characterized as being positive, negative or neutral 3 . Genomics and proteomics provide an understanding of the interaction 3-5 but none of them could yet provide significant progress on the microbial interaction mechanisms. Recently, high resolution mass spectrometry has been used to elucidate interactions between yeasts and bacteria in the malolactic fermentation by comparison of extracellular metabolic profiles 6 . Even more recently, ultrahigh resolution mass spectrometry (uHRMS) confirmed that cell-cell contact influences the metabolism of L. thermotolerans and S. cerevisiae 7 . Therefore, metabolomics seems to be a suitable tool to better understand the microbial interactome in order to control fermentation by multi-starters. Metabolomics is defined as the study of all metabolites given in a biological system under particular physiological conditions 8 . The analytical techniques developed for metabolomics studi...
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