3. FOOD ChEMISTRy & bIOTEChNOLOGy 3.1. Lectures

Chem. Listy, 102, s265–s1311 (2008) Food Chemistry & Biotechnology
P15 SEPARATION OF COMPLEx
OLIGOSACChARIDES FROM wORT AND
bEER uSING hPLC
JAnA CABáLKOVá and JAnETTE BOBáľOVá
Institute of Analytical Chemistry of the AS CR, v. v. i., Veveří
97, 602 00 Brno, Czech Republic,
cabalkova@iach.cz
Introduction
Oligosaccharides (OS) including maltooligosacharides
(MOS) are essential non-volatile compounds in fermentation
processes appeared in a wide range of food products and
beverage production involving beer. Specifically, monitoring
of changes in carbohydrate pattern before, during, and after
the malting is of great fundamental and practical significance
for brewing technologies and the sensory characteristics of
the beer. 1−3
The intent of the study was to optimize analytical conditions
for separation and quantification of the OS in the congress
wort, hopped worth, green beer, and lager beer.
Experimental
M a t e r i a l s a n d M e t h o d s
Standards of MOS (Sigma-Aldrich, St. Louis, USA)
with degree of polymerization (DP) from maltotriose (MA3)
up to maltoheptaose (MA7) were used for the primal identification
and column calibration. Separation was achieved
on 1100 Series HPLC system equipped with refractive index
(RI) detector (Agilent Technologies) on Prevail Carbohydrate
ES analytical column (250 × 4.6 mm, 5 μm; Alltech) using
Fig. 1. Separation of congress wort (full line), hopped worth
(dotted line), green beer (dashed line) of the same variety and
lager beer (broken line) using hPLC. Detail of separation in
the low-weight range (A) and higher oligosaccharides (b). Peak
numbers correspond to the DP
s608
a mixture of acetonitrile (ACn)/water 3 : 2 (v/v) with a flow
rate of 1 ml min –1 and 10 μl injection loop.
S a m p l e s
Eleven defined varieties of wort samples (congress wort,
hopped worth, and green beer) were harvested during the year
2006 in different regions all around the Europe. For comparison
one sample of home-made lager beer with 5.0 % (v/v)
of ethanol was used. Samples were sonicated for 10 minutes,
centrifuged and filtered with 0.22 μm PVDF Millipore filter
(Millipore, Bedford, USA) before analysis.
Results
Standards of non-derivatized MOS from MA3 up to
MA7 were separated using different ratio of ACn/water to
find optimal separation conditions. The ratio of 3 : 2 (v/v)
enabled simultaneous and sufficiently selective separation
in 20 minutes duration. Then, calibration dependencies were
determined. Standard solutions of MOS in the concentration
range of 0.25–10.0 mg ml –1 for MA3, 0.25–5.0 mg ml –1 for
MA4, and 0.2–2.0 mg ml –1 for MA5, MA6, and MA7 were
prepared by dissolving in mixture of ACn/water 1 : 1 (v/v).
Triple injections were used for each standard solution and
the peak areas were plotted against the corresponding concentration.
The concentration dependencies were linear with
correlation coefficients about 0.99 for all standards.
After optimization, samples of eleven different barley
varieties of congress wort, hopped worth, green beer, and
the lager beer were separated using HPLC according to their
DP. Elution time below 45 minutes for all wort samples was
observed (Fig. 1.).
Individual peaks in chromatogram (Fig. 1.) were labeled
by DP in their increasing order. In general, the retention times
Fig. 2. Differences in concentration profiles of OS in the congress
wort prepared from variety Maltasia (full line) and Quench
(dashed line) using hPLC. Detail of separation for low-weight
OS. Peak numbers same as in Fig. 1.