A Low-Cost Image Analysis System to Upgrade the Rudin Beer Foam Head Retention Meter

Abstract

Beer foam is one of the first characteristics consumers visually perceive. Even if their opinions vary, generally, beer foam should be stable and long lasting. In this work, the conventional foam head retention method developed by Rudin (1957) was improved by resorting to three different automatic data acquisition systems. The first one made use of a mouse time tracking software offered at no cost. The second one was an Accurate Image Analysis system using a high-definition camera and a script written in MATLAB. Finally, the third one was an automatic low-cost image analysis (LCIA) system incorporating a Raspberry Pi single-board computer and a camera module (Raspberry Pi Foundation, UK). The latter was able not only to acquire the whole foam decay curve but also to fit the time course of the beer–foam interface position and extract the characteristic beer foam half-life (t½). All the data acquisition systems yielded t½ values practically coincident at the probability level of 0.05, this confirming their substantial equivalence. Once the lager beer had been laced with increasing doses of a foam agent (i.e., tetrahydro-iso-α-acid) to enhance its foam persistence, the resulting foam half-life, as estimated using the above Rudin-based methods, was highly correlated (r2 = 0.99) to the foam collapse time, as derived from the NIBEM Foam Stability Tester. Finally, thanks to the LCIA acquisition system developed here, the Rudin test might represent a fast, flexible, and cheaper alternative to the generally recommended but expensive NIBEM tester, as well as other commercial automated Rudin apparatuses.