There are several methods for determining beer color according to the EBC and ASBC organizations. However, very dark and/or hazy beers present a problem when using the currently accepted methods. Clarification and/or dilution is often necessary for the necessary optical spectroscopy. The generally accepted presumption is that Beer's law holds for beer—meaning that one can obtain a true standard reference method (SRM) for the undiluted sample, after dilution. But, is this true? The applicability of Beer's law assumptions was investigated in this report in the context of the ASBC single-wavelength beer color measurement (SRM) for a diverse set of beer styles. In every 0.2-µm filtered beer examined, even those not passing the ASBC turbidity criterion at 700 nm, strong adherence to linearity upon dilution was demonstrated. In addition, it was shown that hazy beers may still exhibit a linear relationship between SRM and dilution, even though the answer obtained would be entirely wrong. Practically speaking, these results indicate that a brewer can be confident in SRM determination of diluted beers so long as the beer is optically clear or turbidity is corrected via instrumentation.

Keywords: Beer's law, color, haze, SRM, turbidity​