The IBU Assay

The spectrophotometer is among a small set of tools and equipment that are essential for a quality control lab to be adequately productive and accurate in a brewery setting. The reason for this is the BU assay which, apart from the HPLC, offers the best and most direct way to analytically measure the bitterness of beer that is available to brewers today. Relative to HPLC, the BU assay lacks precision, accuracy and sensitivity. But what makes it appealing are a number of things, foremost being the price: a couple thousand dollars can net you a new UV/Vis spectrophotometer and some supplies, whereas an HPLC can be an order of magnitude more expensive. Convenience, simplicity, and to some extent reliability are also among the benefits of this method, since HPLC, indeed chromatography in general, can be fickle and prone to error if rigorous procedures are not followed. Here, we’ll explore various aspects of the BU assay, including its origins and the fundamentals behind it.