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The bitter truth about bitterness units

Determining the EBC bitterness units in beer is, in itself, very simple:

the absorption value of the beer is simply multiplied by 50.

The 50 is an empirical value which means that 5/7 of the bitterness comes from the iso-alpha acids, the remainder from other substances. This is often correct for beers in the range of 15-35 bitterness units, but unfortunately not always, because several factors can interfere with the measurement of bitterness units and prevent hard and fast conclusions. These include the storage temperature of the hops, the age of the hops and the type of hop product used, for example. Particularly in the case of a wide distribution of HSI values (Hop Storage Index), which give information about the age or storage conditions of the hops, the bitterness units become arbitrary numbers.

In identically brewed beers, our own experiments showed a value of 34 bitterness units for hops with a normal HSI value (and 25 mg/l iso-alpha acid according to HPLC) and 78 bitterness units (and 17 mg/l iso-alpha acids) for hops with a very high HSI.

Because bitterness unit measurement is non-specific, even unhopped beers usually have 1-4 bitterness units! But things become even more complicated, because during the aging process of the beer, iso-alpha acids break down. Although this breakdown is accompanied by a reduction in bitterness units, it nevertheless proceeds at a relatively faster rate than can be shown by measuring the bitterness units. For the beer we tested, this means that the differences between the iso-alpha acids in mg/l and the bitterness unit values become even greater! If hopping is carried out using isomerised pellets or extracts or downstream extracts, then other empirical factors come into play between 58-73. But even in such cases the method remains non-specific and personal experience often decides the appropriate factor.But these are only the shortcomings in determining bitterness units from an analytical angle. What we actually want is to use the bitterness unit value to find out how bitter a beer actually TASTES.

This is where the tongue comes into play and with it another bitter truth: human beings have many talents and abilities, but evaluating bitter taste is not generally one of them. Up until now, evolution only required that we should be able to recognise a bitter taste in order to be able to avoid it, thus preventing potential poisoning. Bitter taste can, however, be produced by more than 1,000 structurally different molecules. There is still an enormous need for research into the perception of bitter taste, but it has been shown repeatedly that the sensation of bitterness is a very individual matter. Some people are very sensitive to bitter tastes, others hardly notice them even in high concentrations.

Do we really need to be able to determine bitterness units, if, on the one hand, they are analytically non-specific and, on the other, bitterness is perceived very differently by different individuals? There is indeed justification for determining them in quality control, in order to be able to establish whether, for the manufacture of the same beer using the same raw materials, the bitterness units lie within a limited range of variation. It is very important to have personal experience of bitterness unit determination in the brewery itself in order to be able to correctly assess the individual values.

In the long term, it would certainly be useful to have a simple, cost-effective, but specific measurement method, not least to be able to rule out comparisons of apples and oranges, or IPAs with Lagers…

One Response to “The bitter truth about bitterness units”

  1. Michael Plum says:

    Hallo, Klasse Artikel mit vielen interessanten Details, vielen Dank!
    Gibt es eigentlich irgendwo eine Liste mit den Bittereinheiten (deutscher) Biere? Manche Brauereien machen da ja – für mich unerklärlich – ein echtes Geheimnis draus. Von wegen Geheimrezeptur, unterliegt der Geheimhaltungspflicht und so weiter.

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