Identification of the peasy off-flavour note en Central African coffees
The chemical composition of a coffee defect which is known as "peasy" was investigated. Chemical analysis was done by means of two dimensional GC/MS and simultaneous sniffing port analysis (Sichromat 2-system). Sensory evaluation of GC runs from Likens-Nickerson extracts via sniffing analysis revealed two interesting "peasy" regions in the chromatograms of "peasy" samples. Subsequent MS analysis of the corresponding peaks yielded two different alkoxypyrazines: 1) 2-isobutyl-3-methoxypyrazine (IBMP), 2) 2-isopropyl-3-methoxypyrazine (IMP). The IBMP amounts measured in "peasy" samples did not differ from the "non peasy" samples or were even lower, whereas the IMP amounts were about 30 times higher in "peasy" compared to "non peasy" samples. Moreover, the odour of IMP was found to be more typical with regards to the "peasy" taste in coffee. For these reasons, IMP was considered to be responsible for the "peasy" off-flavour.To answer the question of IMP contamination in single beans, hand selections of whole roasted beans were made. The ratio of "peasy" to "non peasy" beans in the investigated Ruanda sample was found to be 1:3750 in average. Subsequent GC headspace analysis of single selected beans on the Sichromat 2 GC revealed an IMP content which was up to 1000 times higher in "peasy" vs. "non peasy" beans. Similar results as with roast coffee were obtained with green coffee, suggesting the IMP formation taking place during the growth or the preparation of the coffee bean and not as a result of the roast process
| Main Authors: | , , , , , |
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| Format: | biblioteca |
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París (Francia)
1988
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| Subjects: | COFFEA, PROCESAMIENTO, GRANOS ANORMALES, GRANOS STINKERS, COMPUESTOS VOLATILES, MUESTREO, ANALISIS QUIMICO, PALATABILIDAD, PROPIEDADES ORGANOLEPTICAS, AFRICA, |
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| Summary: | The chemical composition of a coffee defect which is known as "peasy" was investigated. Chemical analysis was done by means of two dimensional GC/MS and simultaneous sniffing port analysis (Sichromat 2-system). Sensory evaluation of GC runs from Likens-Nickerson extracts via sniffing analysis revealed two interesting "peasy" regions in the chromatograms of "peasy" samples. Subsequent MS analysis of the corresponding peaks yielded two different alkoxypyrazines: 1) 2-isobutyl-3-methoxypyrazine (IBMP), 2) 2-isopropyl-3-methoxypyrazine (IMP). The IBMP amounts measured in "peasy" samples did not differ from the "non peasy" samples or were even lower, whereas the IMP amounts were about 30 times higher in "peasy" compared to "non peasy" samples. Moreover, the odour of IMP was found to be more typical with regards to the "peasy" taste in coffee. For these reasons, IMP was considered to be responsible for the "peasy" off-flavour.To answer the question of IMP contamination in single beans, hand selections of whole roasted beans were made. The ratio of "peasy" to "non peasy" beans in the investigated Ruanda sample was found to be 1:3750 in average. Subsequent GC headspace analysis of single selected beans on the Sichromat 2 GC revealed an IMP content which was up to 1000 times higher in "peasy" vs. "non peasy" beans. Similar results as with roast coffee were obtained with green coffee, suggesting the IMP formation taking place during the growth or the preparation of the coffee bean and not as a result of the roast process |
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