Laboratory Studies of Wet Milling

American malt milled commercially in a wet mill contained a higher proportion of large particles than commercially dry milled malt and occupied 30% more volume. Wet-milled kernels fragmented less than dry-milled kernels, and the husk was less broken and shredded. Amylolysis appeared to have occurred during malt steeping, before wet milling. In model systems, malt steep temperature influenced water uptake more than did time of steeping. Mill-gap setting and milling style strongly affected particle size of the milled malt and influenced extract yield in standard mashes. However, regardless of the milling style used, particle size controlled extract yield, partly as a function of diffusion. The effect of particle size on the rate of diffusion of extract from particles, run-off rate, and bed compaction was clearly demonstrated in mash/lauter models. A system of malt steeping and wet milling may permit some temporal separation between extract production and extract recovery, which occur simultaneously in traditional dry milling/mashing/lautering systems. Development of this idea may permit wet mills to make a greater contribution to highly efficient North American brewhouses.