DETERMINATION OF LIPID CONTENT AND FATTY ACID REPRESENTATION IN BARLEY CARYOPSES AND MALT

Importance of Topic

The lipid content and fatty acid composition in barley and malt have a direct impact on beer flavor stability, rancidity development and overall quality. Understanding extraction efficiency and chromatographic separation of fatty acid methyl esters supports reliable quality control in brewing and cereal science.

Aims and Overview of the Study

This work addressed two complementary objectives:

• Develop and optimize a modern fluidized-bed extraction method to quantify total lipids in barley caryopses and corresponding malt.
• Determine the profile of fatty acids in extracted lipids using gas chromatography and assess barley grain quality parameters from the 2008 Czech Republic trials.

Methodology and Instrumentation

• Lipid extraction: 5 g ground sample, 60 ml petroleum ether, 6 cycles of 2.5 h each on fexIKA® dive-in control fluidized-bed extractor; residue evaporation by vacuum rotary evaporator; drying 2 h at 105 °C; RSD 2.1 %.
• Transesterification: 50–70 mg fat in isooctane reacted with methanolic KOH, neutralization with NaHSO4, collection of isooctane layer containing FAMEs.
• Chromatography: GC/FID analyses on Thermo Trace Ultra with FID; capillary column SLB-IL 100 (60 m×0.25 mm×0.25 μm) selected for superior cis/trans resolution; comparison with Supelcowax column; carrier gas He 5.0, injector and detector temp. 250 °C; temperature program 40→220 °C at 4 °C/min.
• Grain quality: according to ČSN 461100-5; measurement of protein (N×6.25), starch content, grain size distribution, sprouting and damage levels.

Main Results and Discussion

• Total lipids in barley and malt ranged 1.3–2.5 % d.m.; six extraction cycles ensured completeness.
• Fatty acid profile in barley: linoleic acid dominated (49–54 %), followed by palmitic (19–22 %), oleic (12–14 %), linolenic (5–6 %); minor C20–C24 saturated and unsaturated acids 0.01–0.3 %.
• In malt, polyunsaturated acids increased (linoleic 58–61 %, linolenic 8–11 %), while oleic acid dropped tenfold, likely due to autooxidation catalyzed by lipoxygenase.
• SLB-IL 100 column provided enhanced separation, distinguishing oleic and elaidic cis/trans isomers critical for flavor compound precursors.
• 2008 barley harvest quality: favorable weather yielded protein ~11.9 % (spring) and 11.4 % (winter), starch ~64 %; grain was large, uniform, sprouting and damage minimal; >87 % of grain above 2.5 mm sieve.

Benefits and Practical Applications

• Fluidized-bed extraction offers reproducible lipid quantification for breeding and quality control.
• Highly polar GC columns enable precise cis/trans FAME analysis relevant for predicting beer staling.
• Comprehensive grain quality data from 2008 guide selection of high-performance barley varieties for malting.

Future Trends and Potential Applications

Emerging areas include coupling fluidized-bed extraction with MS detection for detailed lipidomics, exploration of lipoxygenase pathways to design oxidation-resistant barley lines, and application of ionic liquid stationary phases in GC for broader cereal lipid profiling.

Conclusion

The optimized fluidized-bed extraction and GC/FID on SLB-IL 100 enable accurate determination of lipids and fatty acids in barley and malt. The high grain quality observed in the 2008 Czech trial supports robust malting performance and informs ongoing analytical and breeding strategies in the brewing industry.

Reference

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