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Brewing Chemistry Analysis – Brewing Chemistry Analysis –

Esters & Aldehydes Amino Acids

Esters provide the fruity flavor found in ales and wheat beers. transferase (AAT) which is mainly responsible for ester Generally, there are two methods for a beer’s color, not sugars decompose through pyrolysis. These reactions not only
However, in lagers, esters maybe considered undesirable. Volatile production during fermentation. Other methods for controlling including using additives. One is by the Maillard Reaction in add color, but also add flavor to the beer. Thus, when brewing
organic compounds such as esters, aldehydes, and alcohols are esters include fermentation at a higher temperature, which which an amino acid and a reducing sugar go through a beer, it is important to know the free amino acids available.
formed through the fermentation process. Esters are formed increases yeast growth and, in turn, AAT, resulting in a higher chemical reaction. This is the same reaction as browning meat There are a number of methods for analyzing amino acids and
through a process called esterification in which an alcohol (i.e. concentration of esters. Similarly, if the yeast is under pitched, or toast. The other reaction is a caramelization process where below is a sampling by GCMS, UHPLC, and LC-MS/MS.
ethanol) and an acid react to form such compounds as ethyl yeast will grow quickly, thus increasing the AAT and boosting
acetate and isoamyl acetate. Ethyl acetate can have flavor the ester concentration. Also, under oxygenation of the wort
characteristics similar to that of a pear at low concentrations or a will result in higher levels of esters in the beer. (x100,000)
TIC 13
solvent-like flavor at higher concentrations. Isoamyl acetate Aldehydes such as acetaldehyde are also a byproduct of the 7.0
provides a banana-like flavor found in beers. Ethyl acetate and fermentation process, providing flavor and aroma similar to
6.0
isoamyl acetate are produced from the reaction of ethanol and that of green apples. 1
isoamyl alcohol, respectively, with acetic acid. Analysis of ethanol, esters, aldehydes, and other volatile 5.0 7
5
The amount of esters produced is mainly controlled by the type compounds in beer is performed by headspace gas 4.0
12 20
of yeast used. Yeast contains an enzyme called alcohol acetyl chromatography (GC) with a flame ionization detector (FID).
3.0 3
29
2.0 31
O 1.0 4 8 10 14 16 18 19 27

1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 min
O O Total ion current chromatogram for 31 amino acid derivatives in beer by GCMS-QP2010 Ultra*

Ethyl acetate mv
13 14
300
15
O 250 11 12
200 1 9
26
150 16
3 5 10
O O 100 2 4 7 18 19 20 23
Shimadzu Nexis GC-2030 or GC-2014 with HS-10 50 6 8 21 22 25
Headspace Autosampler for analysis of esters in beer Isoamyl acetate 17 24
0
0.0 2.5 5.0 7.5 10.0 12.5 15.0 min
Chromatogram of 23 amino acids using pre-column derivatization by
Ethyl Acetate isoamyl alcohol Pro Beer
Nexera UHPLC with SIL-30AC Autosampler and RF detection
#

Acetaldehyde n-Propanol isobutyl alcohol 2-Methyl-1-butanol isoamyl acetate Phe Trp Ala Gly Ser Asn

Asp
Thr
Leu Tyr 4.5 4.6 4.7 4.8 4.9 5.0 5.1 min His Lys Arg
Ile Val Glu Gln
Met (Cys)2
2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 min
Chromatogram of esters, acetates, and alcohols by headspace GC-FID Analysis of 20 amino acids in beer without derivatization by LC-MS/MS %

* Shimadzu GCMS Application Data Sheet No.1: “Analysis of Amino Acids Contained in Alcohol”
# Shimadzu Application News No. L437: “High Speed, High Resolution Analysis (Part 45) Analysis of Pre-Column Derivatized Amino Acids by the Nexera SIL-30AC Autosampler (Part 2)
% ASMS 2014 Poster TP-510: “Simultaneous quantitative analysis of 20 amino acids in food samples without derivatization using LC-MS/MS”

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18 Analytical and Testing Instruments for Beer 19