Metabolite profiling of barley: Influence of the malting process

A metabolite profiling approach based on gas chromatography–mass spectrometry (GC/MS) was used to investigate time-dependent metabolic changes in the course of the malting process of barley. Barley grains were subjected to a micro-malting procedure involving steeping, germination and kiln-drying. Samples taken in the course of the malting process were subjected to an extraction and fractionation procedure covering a broad spectrum of lipophilic (e.g. fatty acid methyl esters, hydrocarbons, fatty alcohols, sterols) and hydrophilic (e.g. sugars, acids, amino acids, amines) low molecular weight barley constituents. Investigation of the obtained fractions by GC resulted in the detection of 587 distinct peaks of which 173 were identified by means of MS. Statistical assessment of the data via principal component analysis demonstrated that the metabolic changes during the malting progress are reflected by time-dependent shifts of the scores. Analysis of the corresponding loadings showed that polar metabolites were the major contributors to the malting time-driven changes in the metabolic profiles. Quantifications based on standardised peak heights revealed dynamic changes of the metabolites in the course of the different malting stages.