Interpretation of Hop Analysis Results

The basis for evaluation for the analysis results of hop products is the statistical data of the methods recommended in Chapter 7 of ”Analytica-EBC“. This annually updated collection of methods will soon be available on-line (www.europeanbreweryconvention.org). All the prescriptions have been tested in ring analyses which provide a reliable source for the determination of statistical data. In some cases coefficients of variation (CV) and/or standard deviations (s) are used to characterize accuracy. Newer methods which have been tested according to the Norm „Accuracy (trueness and precision) of measurement methods and results“ (ISO 5725:1994), specify the errors of repeatability (r95) and reproducibility (R95) of an analysis with a statistical certainty of 95%.

Based on this information, the determination of a permissible deviation is carried out using the critical difference (d-critical) according to the following formula, which is explained in more detail with the help of statistical data from the Analytica-EBC 7.7 Method (HPLC-Method for the determination of alpha- and beta- acids in hop products):

(equaltion)

Our business partners can use this formula in order to fix the acceptable limit of deviation of an analytical verification of the nominal value of a hop delivery. The example demonstrates the alpha content of hop pellets as 10% according to the HPLC method. The statistical data provided by the EBC 7.7 method result in a critical difference of 0.57%, i.e. a claim would be justified for any deviation above this level. Generally Sales Contracts include a maximum acceptable deviation expressed in relative % terms. In practice, a relative tolerance of 5% in Sales Contracts is very common. As is shown in the example, this level of analysis tolerance is appropriate. In fact, the method could even tolerate a higher level of deviation up to 5.7% relative.

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