Chemical research has shown that the a-acids are the main quality factors of hops and that the bitter taste of hopped beer derives from the iso-a-acids. This has provided the basis for improvements in hop breeding, conditioning, extraction, use, analysis etc. Structural chemical development of hop con stituents was completed about ten years ago. At the present moment the accent of chemical research is on analytical aspects, mainly using High Performance Liquid Chromatography.From the standpoint of the brewery the situation of chemical research is not completely satisfactory, since a clear understanding of the more subtle chemical quality factors of hops and their impact on beer quality is still lacking.Hops are much more important for beer than is generally estimated, even in brewery circles.
SummaryThe selection of stationary phases in capillary gas chromatography is discussed. Methyl silicone, phenyl methyl silicone, trifluoropropyl methyl silicone, biscyanopropyl silicone, and high molecular weight (HMW) polyethylene glycol are considered to be the basic phases. Selectivities and polarities between these phases are obtained by selectivity tuning. Selectivity tuning can be performed in three different ways, namely by synthesizing a tuned stationary phase, by mixing the basic phases, or by coupling capillary columns of different selectivities. In coupling capillary columns the variables are column length, @-value, temperature, and/or pressure.
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