Amino acids and glycation compounds in hot trub formed during wort boiling

Abstract

The aim of this study was to investigate the amino acid composition and the amount of individual glycation compounds in hot trub formed during boiling of wort prepared from different malts. Compared to the initial amino acid composition of the used malts, some Maillard reaction products (namely MG-H1, pyrraline) and hydrophobic amino acids (leucine, isoleucine, valine, phenylalanine) accumulated in the hot trub, whereas hydrophilic amino acids remained in the boiled wort. For MG-H1, a threefold increase was observed during wort boiling, whereas the other Maillard reaction products, namely CML, CEL, pyrraline and maltosine increased only slightly (1.1–2-fold). Furosine as a hallmark for peptide-bound Amadori compounds showed a small decrease. The results suggest that mainly glycated amino acids derived from small dicarbonyl compounds such as methylglyoxal and glyoxal are formed during wort boiling. Furthermore, the studies indicate that the modification of the protein structure as a result of the Maillard reaction has an influence on the hydration of the denatured proteins during the wort boiling process, thus affecting the coagulation process and, therefore, precipitation of the hot trub. The work carried out contributes to the understanding of the chemical reactions influencing the amino acid and Maillard reaction product transfer from malt to beer.Graphical abstract