How the Mash Works
To the best of my knowledge, the temperature rest (holding period) for phytase is no longer used by any commercial brewery. However, this regime (95-113°F) is sometimes used by brewers for "Doughing In"- mixing the grist with the water to allow time for the malt starches to soak up water and time for the enzymes to be distributed. The debranching enzymes, e.g. limit dextrinase, are most active in this regime and break up a small percentage of dextrins at this early stage of the mash. The vast majority of debranching occurs during malting as a part of the modification process. Only a small percentage of the debranching enzymes survive the drying and kilning processes after malting, so not much more debranching can be expected. With all of that being said, the use of a 20 minute rest at temperatures near 104°F (40°C) has been shown to be beneficial to improving the yield from all enzymatic malts. This step is considered optional but can improve the total yield by a couple of points.