Pilot plant production of gluten-free craft beers by enzymatic and precipitation treatments

Celiac disease is an autoimmune disease of the small intestine caused by the ingestion of gluten proteins. Gluten proteins are mainly composed of prolamins and glutelins located in the starchy endosperm of some cereal. Beer is produced from barley malt and sometimes wheat or wheat malt and since both contain prolamins, it is a potentially harmful beverage for sensitive subjects. The gluten level of beer is highly variable as a function of style. Hence, technological approaches of brewing are often mandatory to bring gluten content below 20 ppm and to achieve a beer labelled as "Gluten Free". Gluten free beer can be obtained starting from grains that do not contain gluten or by processing standard beers with deglutinisation treatments. Two different principles of deglutinization are known: precipitation process based on silica gel and enzymatic process based on AN-PEP (Aspergillus Niger Prolyl Endoprotease). In the present study, we verified the efficacy of the two aforementioned deglutinisation treatments in a pilot plant scale production (1 hL) of a top fermented American IPA beer. To compare the effect of treatments, standard quality attributes, chemical composition of iso-alpha acids, and sensory profiles were performed according to Analytica EBC methods. Gluten quantification was carried out by the RIDASCREEN Gliadin competitive assay. Furthermore volatile compound profiles were evaluated by HS/SPME/GC/MS. Both deglutinisation treatments were able to reduce gluten level below 20 ppm and showed different behaviour due to the different mechanism of action. Results of chemical-physical analyses showed differences between treated and untreated beer, while sensory analyses performed by triangle test didn't show differences between the two sets of samples. These results can be considered as a first step towards the production of high quality gluten-free craft beers in microbreweries. Our data show that starting from a standard recipe and without using specific equipment or expertise, both enzymatic and precipitation processes are able to achieve gluten-free craft beers from traditional ingredients, keeping the sensory profile unaltered of the original recipe.