Metabolite fingerprinting of buckwheat in the malting process

Abstract

With aims to better optimize and improve the industrial buckwheat maling process, metabolite analysis was carried out by gas chromatography–mass spectrometry (GC/MS) and high pressure liquid chromatography (HPLC) to investigate the time-dependent metabolic changes during buckwheat malting. Sixty-four metabolites, which covered a broad spectrum of polar (e.g. amino acids, sugars, acids and phenolic compounds) and non-polar (e.g. fatty acid methyl esters, free fatty acids, sterols) buckwheat constituents with low molecular weights, were identified and quantified. Results show that content of polar metabolites, such as sugars and amino acids, increased during malting. Meanwhile, levels of most of non-pollar metabolites, including fatty acid methyl esters, free fatty acids and sterols changed very little or kept constant. The statistical assessment of the metabolic data was derived by principal component analysis (PCA). Results demonstrate that the metabolic changes during the buckwheat malting process can be reflected by time-dependent shifts in the PCA loading scores. The analysis of the loadings further showed that polar metabolites, including sugars, amino acids and some of phenolic acid compounds, were the major contributors of the malting time-driven changes during buckwheat malting. The changing rule of these metabolites was explored nutritionally. Free fatty acids were the superior energy supplier during steeping and initial germination phase compared with sugars in the buckwheat malting process. Buckwheat malt is a potential material for the beer brewing industry.