Biology Reference
In-Depth Information
weight polypeptides. Other than barley proteins, yeast proteins are
eluted into beer in the fermentation process.
Beer proteins have been extensively analyzed and they are
important components of beer quality traits such as foam, haze
(clarity), gushing, and mouthfeel. Protein Z and lipid transfer pro-
tein 1 (LTP1) are abundant in beer. Therefore, a series of beer
protein analyses have been conducted on these proteins. A negative
effect on hordein or its derived polypeptides has been known to
cause coeliac disease [
1
-
3
] with clinical symptoms of fatigue, diar-
rhea, abdominal distension, weight loss, and neurological disorders
[
4
]. However, the molecular weight and amino acid sequences of
hordein-derived polypeptides in beer are contentious.
These beer proteins have been analyzed by sodium dodecyl
sulfate polyacrylamide gel electrophoresis (SDS-PAGE), Western
blotting, and enzyme-linked immunosorbent assay (ELISA) using
specifi c antibodies. Since the 1980s, two-dimensional gel electro-
phoresis (2DE) has been applied to analyze beer protein profi les.
However, proteins were not precisely identifi ed in older studies
[
5
-
7
]. In recent reports, beer proteins were analyzed by 2DE fol-
lowed by mass spectrometry [
8
-
11
] and liquid chromatography
mass/mass spectrometry (LC-MS/MS) followed by searches in
DNA and/or protein sequence databases [
11
,
12
]. In this chapter,
these beer and wort proteome analyses are reviewed, and the meth-
ods of 2DE analysis of beer and wort samples are described.
2
Progress of Proteomics Analysis in Beer and Wort
The massive generation of nucleotide sequences in barley and yeast
accelerated the studies to fi nd the protein sequences responsible for
specifi c traits in the target beer samples. In addition, the high sensi-
tivity mass spectrometry systems improved the chances to fi nd a
number of expressed protein spots with the help of the database
search engine. With this proteome approach, novel proteins have
been identifi ed in worts and beers as they are mapped on the gel. We
can call these as proteome maps. The proteome map is the founda-
tion stone for the quantifi cation of trait-related proteins among the
beer samples made from different materials and treatments.
2.1 Earlier Studies
of Beer Proteins
A pioneering analysis of beer by 2DE was done by Marshall and
Williams [
5
]. They analyzed commercial beer samples without
concentration and simply compared their 2DE images. Dale and
Young [
6
] analyzed beer samples by 2DE to compare the protein
profi le between the samples. They detected four specifi c protein
spots in the beer from malt with 20 % wheat fl our, which were
absent in the all malt beer. Williams and Marshall [
7
] developed a
high-resolution 2DE method for beer analysis comprising high-
resolution 2DE and ultrasensitive silver staining for simultaneous
