Assessment of the Effects of Agitation on Mashing for Beer Production in a small scale vessel

Mashing is the brewhouse operation concerned with producing the fermentable sugars necessary for the successful fermentation of wort into beer. The process involves adding grist to water and heating to promote the enzymic conversion of malt starch into sugars. The conversion process depends on several factors including raw materials, the final product specifications and on the equipment used downstream in the subsequent unit operations to recover and stabilize the wort. Although the biochemistry of the process is well understood, the interactions between operating parameters and mash quality are less so, despite the fact that this information holds the key to process improvements in the brewing industry. A study of the effects of agitation in mashing has been carried out, to examine the impact of this parameter on mash quality and to investigate agitation as a possible process intensification route for brewing. Experiments have been carried out in small-scale agitated vessels with well characterized geometry. Results of the studies suggest that for the materials studied here the conversion of starch into fermentable sugars is independent of the agitation conditions. Agitation does not provide a viable route for process intensification. The primary effect of increasing agitation speed is to increase the number of fine particles formed, which may compromise the efficiency of downstream recovery operations through reduced filtration rates. Under agitation conditions encountered in industrial mash tuns, solubilization of beta-glucan from the grist and the proposed consequent increase in viscosity is unlikely to be the reason for the increased separation times reported. Likewise, processing conditions are such that the viscosity of the mash itself cannot be considered to present a challenge to the agitation requirements of the process.