Last time I toyed with the idea of “reverse mashing”, I found that an unheated kitchen isn’t a great place to do mashing experiments in the winter. Fortunately, I have a new toy available in the form of an oven with a “Warm” (170°F – 77°C) setting, and so I was able to perform two additional mashes utilizing longer rests.
For details on how the experiment was conducted, refer to the first post on the subject. Once again, the reverse mash was performed first, to determine the overall length of both mashes. Total time was 100 minutes, and the temperature profiles for all four mashes are shown below.
All other variables were kept constant between the two sets of mashes, with the exceptions of size and fermentation temperature. Since I needed starter wort for some upcoming brewing, I doubled the size of the mashes, to 1000 g of grain each. Fermentation took place in my new fermentation chamber, with the air temperature set for 20°C ± 1°C. The test worts were allowed to ferment for six days, then rested for one day at 8°C before gravity readings were taken.
The reverse mash fermented from 12.0°P to 1.0093 SG, and the control from 12.4°P to 1.0068. As expected, the conventional step mash exhibited both higher efficiency and higher attenuation than the reverse mash. While the efficiency values for both new mashes are significantly improved, however, the attenuation values are similar. While increasing mash efficiency is desirable in most situations, home brewers may well find that a very short step mash provides fermentability on par with a more conventional longer mash, and that the time savings outweigh their comparatively modest financial investment. In a commercial brewing setting, however, the traditional lengthy mash with α- and β-amylase rests is clearly the better option.