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

Role of Proteins in the Formation of Melanoidins during Coffee Roasting

“…To avoid overestimation of amino acids by hydrolytic cleavage of unstable amino acid modifications, the samples were additionally hydrolyzed enzymatically. , To counteract the incomplete release of amino acids during enzymatic hydrolysis and to compare between acid and enzymatic hydrolysis, we normalized the amino acid contents to an internal reference amino acid measured after enzymatic hydrolysis. , Thus, differences in the hydrolysis yields of different samples can be considered, and corrected absolute contents of the amino acids can be calculated with the use of the absolute amino acid content calculated from acid hydrolysis. For the choice of the reference amino acid, we made a few assumptions.…”

“…Therefore, it represents the protein as a whole. In the past, the amino acids leucine , and alanine were used for this purpose depending on the suitability in the specific case. In our case, it has been shown that alanine fulfills the set requirements best.…”

“…Analysis of CML, CEL, Pyrraline, MG-H1, and Maltosine. The analysis of the Maillard reaction products CML, CEL, MG-H1, pyrraline, and maltosine was conducted as previously published 34 with some small adjustments. A mixture of 10 μL of internal standard solution containing isotope-labeled CML (c = 1.0 mg/L), CEL (c = 0.75 mg/L), MG-H1 (c = 1.0 mg/L), pyrraline (c = 1.0 mg/L), and maltosine (c = 0.75 mg/L), 44 μL of concentrated NFPA, and 600 μL of the filtrated enzymatic hydrolysate was applied to a previously prepared solid-phase extraction (SPE) cartridge (Chromabond HLB 60 μm, 200 mg).…”