Parameters improvement in the brewing process with unmalted sorghum

Abstract

In using alternative grains in brewing for people with celiac disease, such as sorghum, malted or unmalted grains could be used. Here, studies using unmalted sorghum aimed to reduce grain tannins and improve wort FAN (Free Amino Nitrogen) development during mashing are presented. The brewing process starts with a pretreatment of the grains, which consists in sanitization, tannin extraction and chemical treatment. This is followed by a decoction, which enables gelatinization of the starch to proceed, and then the mashing process using temperature steps and the addition of two exogenous enzymes, amylase and papain. Sorghum (Sorghum bicolor) of the northeast region in Argentina is characterized for its high tannin content. Compounds which are able to bind amylase enzymes in the brewing process, limiting their action during mashing. For this reason, it is necessary to reduce tannin concentration in order to not compromise the process performance. For this purpose, a first extraction using hot water was made followed by pretreatments during 2 and 4 days with dilute solutions of sodium hydroxide 0,1%, sodium hypochlorite 0,5% and distillate water as control. The 4-days conditioning was made without solvent replacement. However, the 2-days pretreatment process was made with and without solvent replacement every 12 hours. It was found that the procedure with sodium hypochlorite during 4 days was the one that achieves the best tannin reduction.In order to improve FAN levels, an experimental design using two concentrations of alpha amylase (2 and 3% of dry grain weight), three concentrations of papain ((0,5; 1 y 1,5 g/kg dry sorghum) and no enzymes (control), was performed. The statistical analysis indicates an interaction effect between enzymes during mashing. The maximum FAN value was 11,39mgN/l, using 1,5g/kg papain and 3% alpha amylase (p < 0,05); however, this value is still not enough for a correct fermentation of the wort. This could be due to the interaction of the enzymes during the process, insufficient amount of enzymes, or a poor gelatinization of starch.