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Malt volatile compounds (Part I)
Herrmann, M., Gastl, M., Thiele, F., Back, W.

The measurement of the malt volatiles targets Maillard-products, Strecker-aldehydes, higher alcohols and compounds of the lipid metabolism of barley. These substances act as indicators for a multiplicity of technological factors, like proteolysis or thermal load during kilning. The effects of using malts with different loads of volatile compounds for beer production will be discussed in Part II of this publication series. This paper shows the improved method of analysis for these substances and the influence of various malting parameters on the formation of the volatile compounds using a statistically planed experimental design termed Response Surface Methodology. The differences between the formation of the volatiles within typical maltings parameters is very large and concentrations thus differ up to a factor 26. If one considers only malts within brewing specifications a factor of up to 7 still remains. Green malt moisture and germination temperature are the main influencing factors; high germination temperatures are suited to produce malt with low volatile concentrations if higher malting losses are acquiesced. The measurement of the malt volatiles targets Maillard-products, Strecker-aldehydes, higher alcohols and compounds of the lipid metabolism of barley. These substances act as indicators for a multiplicity of technological factors, like proteolysis or thermal load during kilning [1, 2, 3, 4]. The effects of using malts with different loads of volatile compounds for beer production will be discussed in Part II of this paper. This paper shows the method of analysis and results obtained from experimental maltings under various conditions and their effects on the malt volatile compounds.The analysis is based on the various water vapour distillation methods published by Mebak [5]. The sample's volatile compounds are expelled by water vapour distillation. The ethanolic distillate is alkalized and furthermore being saturated with NaCl. The volatile compounds are then extracted via Dichloromethane; the volume of the organic phase is further on reduced by a nitrogen flow. The addition of ammoniac is used to separate organic acids as they are often accountable for coelutions with relevant substances. Hewlett Packard HP 5890 with Split- /Splitless-injector, 2 capillary columns (HP Innowax (Polyethylene Glycol) 60m * 0.20mm * 0.40m; HP Ultra 2 (5%Ph.- 95%Me-Si) 60m * 0.20mm * 0.33m) and 2 flame ionization detectors.Hewlett Packard HP 7673 A Automatic Sampler Heraeus-centrifuge with cooling: Varifuge RF Turbula-shaker Distillation unit: Bchi K-314 Chemicals

Descriptors: malt, malting, flavour stability, Maillard-products, Strecker-aldehydes, higher alcohols, lipid metabolism, analysis, gaschromatography, analytical method, volatile compounds, statistics, statistical

BrewingScience - Monatsschrift fr Brauwissenschaft, 60 (July/August 2007), pp. 110-117