/ WORT, BEER AND BEER-BASED BEVERAGES / Wort and Beer / Low Molecular Weight Nitrogenous Compounds

B-400.13.133 [2020-10] Amino Acids in Wort and Beer – HPLC

Low molecular weight nitrogenous substances, especially amino acids in the wort, have an influence on the course of fermentation and the formation of fermentation by-products. For a beer’s aroma profile, the concentration and composition of the amino acids are therefore of considerable significance. Due to their reactivity with reducing sugars (Maillard reaction), this is most apparent during kilning in the malthouse as well as mashing and boiling in the brewhouse. The reaction products influence the redox potential, the color and the aroma of a beer.

Aside from the quantitative determination of the individual amino acids (methods using an ion exchanger, HPLC, GC), cumulative methods of determination are customary. However, these methods also measure NH₄⁺ ions and amines to some degree.

With methods involving color reactions, the amino acids display color at different levels of intensity. Therefore, the reaction is based upon a “standard amino acid”. Glycine usually serves as the standard amino acid for comparison.

With the ninhydrin method, the color yield varies with the individual amino acids between 70 and 105 %, based on glycine. Up to approx. 30 % of ammonium salts are quantified using this method and up to approx. 7 % of proline.

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Application/Purpose

Determination of the amino acid content in wort and beer

Scope of Application

This modified Kroemer method is suitable for wort and beer [1].

Principle

Amino acids are polar in their natural state and only rarely possess chromophores, which absorb UV light.

Fluorescing derivatives are formed by means of derivatization in the precolumn with ortho-phthaldialdehyde (OPA). These are separated using HPLC and detected with a fluorescence detector.

Amino acids are essential for yeast metabolism during fermentation. A deficiency can lead to considerable disruptions during primary fermentation and in the formation of fermentation by-products as well as to delays in the maturation process.