is a term used by brewers to describe the extraction or washing through of wort from a mash separation vessel such as a lauter tun, mash tun, or mash filter. In a lauter tun or mash tun, the mash in a vessel is sprayed with hot water, which rinses the soluble material from the mash and is “run-off” from the slatted bottom of the vessel. The rinsing process is called “sparging” and involves brewing water at approximately 168˚F (75°C). See sparging. This temperature is important because it is a temperature above which malt enzymes are deactivated, removal of sugar is efficient, and the viscosity of the wort is lowered, allowing it to filter down more easily through the grain bed. Optimizing the run-off rate is very important in ensuring an efficient brewhouse operation. The brewer’s objective is to run-off wort as fast as possible to achieve the best possible extract and quality from the malt. The run-off rate is determined by the type of vessel used, the depth of mash, and the composition of the grist. In a mash tun (approximate mash depth 1.5–2 m) the run-off will be slower than in a lauter tun (approximate mash depth 0.5 m) with the run-off from a mash filter (approximate mash depth 5 cm) being the fastest. Another very important feature of run-off is wort clarity. Most brewers want clear worts which they believe give beer of the best quality. Generally, the deeper the mash depth, the brighter (clearer) the wort, so mash tuns generally give clearer worts than mash filters. However, modern engineering and process control has enabled clear worts to be produced from lauter tuns and mash filters without slowing the process.
See also lautering, mash filter.
