Gluten reduction in beer: Effect of sorghum:quinoa ratio and protein rest time on brewing parameters and consumer acceptability

The combined effects of the grist composition (sorghum:quinoa ratio) and mashing conditions (protein rest time) were investigated with the aim to reduce gluten content in beer and to evaluate their impact on the physicochemical parameters and consumers' acceptability of final beer. Principal Component Analysis results, which explained 72.65% of data variability, showed a good separation of beer samples according their grist composition. Using high sorghum concentrations (34 and 40%) led to a significant reduction (p < 0.05) in extract, Free Amino Nitrogen (FAN), alcohol, total nitrogen content and the colour of the final beer. Protein rest time showed a significant impact on the sensory attributes of beer samples; therefore, it should not exceed 30 min. Beer with the best brewing performance in terms of physicochemical attributes and consumers’ preference (considered as “like moderately” by 90 consumers) was formulated with 6 and 34% of unmalted sorghum and quinoa, respectively, and by performing 20 min of protein rest. Results from this study suggested that the use in brewing of unmalted sorghum and quinoa, in an optimized combination, allows to develop beer brewed with unconventional grains without adversely affect consumer acceptance and purchase intention.