Comparison of the Rudin and NIBEM Methods for Measuring Foam Stability with a Manual Pour Method to Identify Beer Characteristics That Deliver Consumers Stable Beer Foam

Abstract

A survey of the preferences of brewing professionals with respect to beer presentation and amount of beer foam was conducted at the ASBC Brewing Summit meeting in Providence, Rhode Island, in 2010. The survey showed that beer presentation in the Samuel Adams Boston Lager Perfect Pint glass was not only aesthetically pleasing but also promoted hop aroma and flavors in particular. Most of the survey participants preferred the presence of lacing on the glass during or after consumption and, on average, considered approx. 20 mm of foam immediately after dispensing into a glass as being optimal. The conventional NIBEM and Rudin methods for foam stability testing were compared with a simple method of manually pouring a beer into a Perfect Pint glass (approx. 35 mm of foam formed) and visually scoring the stability after 5 min to determine the foam stability score (FSS). The NIBEM and Rudin foam stability measures were significantly but relatively poorly correlated (r = 0.371). In part, this relatively poor correlation resulted from a wide range of beer viscosity in the sample set that inordinately influenced the Rudin results. In general, the NIBEM and Rudin foam stability measures were significantly correlated with bitterness, beer-foam-promoting proteins measured as Coomassie blue binding protein assay, beer color, alcohol, CO2 content, and pH, which was broadly consistent with previous studies. Although lipids are widely acknowledged as foam damaging, the measurement of total fatty acids (a lipid proxy) was not well correlated with either of the foam stability analysis methods. The FSS was significantly correlated to and largely predicted by CO2 content and beer-foam-promoting protein levels. These insights are discussed in relation to how brewers could design and consistently provide beers to customers that fulfill their foam quality requirements and expectations.