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  • QA 146
    Question:
    Why 'steam-clean' robusta coffee?
    Background:
    Q&A 144 says that 'modern technology has made it possible to increase the proportion of neutral tasting robustas in many blends'. We take it this refers to the practice of 'steam cleaning'? If so can you give us some details of what this process is about and what it does? Thanks.
    Asked by:
    Researcher - Brazil
    Answer:

    The steam-treatment of coffee was developed by Professor Karl Lendrich, and was patented in Germany in 1933 already.

    The objective was to make coffee more 'acceptable' to certain consumers who were reporting varying degrees of stomach discomfort when drinking regular coffee.  The discussion as to exactly which chemical components of the coffee bean were/are responsible for this is ongoing, but 'mild' or 'stomach-friendly' coffees have been a regular feature of the German market ever since. Germany is the typical and possibly only significant market for this kind of product.

    The original procedure consists of a relatively gentle steam-treatment lasting between 30 and 60 minutes during which the beans undergo chemical and physical changes.  It is mostly if not only used on arabica where it reduces certain acids and also causes certain taste changes.

    More recently however steam-treatment has been used to treat robusta because it was found that steam-treated robusta coffees were milder and could even develop some 'acidity'.  This became of interest during periods of high coffee prices when the differential between arabica and robusta made it attractive to include a certain percentage of steam-treated robusta in a blend. However, this type of steam-treatment is more severe in that higher temperatures are applied for longer periods. The end-result of the harsher treatment results in a different taste experience and it is unlikely such coffees will be used to any great extent in high quality blends.

    We cannot estimate the extent to which steam-treated coffees are being used except to say that the never-ending quest to reduce costs will certainly keep this process under the spotlight, particularly if at some stage coffee prices were to rise substantially again. There are, however, no statistics available as to actual usage.

    It is worth noting as well that further research has shown that certain phenolic compounds (causing off flavours or taints) can also be reduced or eliminated through steam-treatment or steam-cleaning. This then makes it possible to 'clean' coffees that otherwise would not have been useable, to a 'useable standard'. Therefore, if for example the differential between arabica and robusta was to narrow substantially, then the steam-cleaning of certain arabicas may also become a regular feature...

    Posted 26 April 2007

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