Mashing mixes crushed malt with brewing liquor so malt enzymes can break starch into soluble sugars and dextrins. The resulting liquid is wort.
What the enzymes do
Beta-amylase releases highly fermentable maltose from starch chains and works effectively at the lower end of typical saccharification temperatures. Alpha-amylase cuts chains more randomly and remains active at somewhat higher temperatures, producing a broader mixture including dextrins. Real mashes use overlapping activity rather than one isolated enzyme.
Temperature and fermentability
A rest around the low-to-mid 60s °C generally favours a more fermentable wort; a rest toward the upper 60s °C often leaves more body. Malt quality, crush, liquor-to-grist ratio, pH and time also change the outcome, so temperature alone does not predict final gravity.
Infusion and decoction
Single-infusion mashing holds one conversion temperature and suits well-modified malt. Step mashing moves through several rests. Decoction removes and boils part of the mash before returning it, raising temperature and intensifying thermal reactions; it is associated with several Central European lager traditions.