Effect of the extrusion process on the production of a precooked adjunct for American-Lager beer, with the aim of reducing energy and water consumption

Abstract

Lager beer style is the most consumed beer in North America, and Mexico is the 4th biggest exporter of Lager in the world. Among the Lager styles, the American-Lager beer is one of the most consumed due to its crispness and light mouthfeel, mainly caused using adjuncts. Brewing adjuncts represent another source of fermentable sugars (FS) for the fermentation. The main sources of adjuncts are corn and rice, but their use during mashing is limited by the necessity of cooking them in a different tun to gelatinise them and allow barley malt enzyme to hydrolyse them. Consequently, in this research, extrusion cooking parameters were evaluated on white degermed corn grits to gelatinise and obtain the highest FS conversion yield. 2 corn grits (MS: Vixim MS-60 and VX: Vixim Cereal) were extruded to produce 9 different treatments at different screws speed (200 rpm, 300 rpm and 500 rpm) and moisture (15%, 20% and 25%). Brewer's worts were produced with each extruded adjunct, and with non-extruded corn starch and the two raw corn grits. It was found that extrusion cooking is capable not only to equalise the FS yield of the wort produced with corn starch but also to produce, in 10 out of 18 treatments, an average increase of 32.01% in FS yield at different extrusion conditions. Condition at 300 rpm and 20% moisture resulted in the treatment with the highest FS yield with 46.72%. Free Amino Nitrogen and protein content were quantified, and in VX treatments, a significant decrease of 37.4% and 59.3% respectively, was observed, mostly due to a higher presence of Maillard reaction during extrusion. Through an Artificial Neural Network (ANN) and the FS yields produced, the extrusion parameters were analysed and optimised to produce a condition (MS10) where the FS yield was maximised at 64% (16.2% moisture, 233 rpm, 159.6°C product temperature, 234.6°C extrusion barrel temperature and 341.8 SME). The wort produced with MS10 adjunct presented a 28.29% FS yield, 4.22 SRM colour, 1.25 mL/min filtration speed, parameters not statistically different to the wort produced with corn starch, while FAN concentrations were reduced by 12.4%. The use of MS10 as a brewing adjunct produced a 33.54% and 15.13% reduction in mashing energy and water usage, respectively. The water usage was also reduced by 35.78% by using MS10 instead of corn starch as an adjunct.