Enzymów bedzie akytwny jak nie są denaturowane. Aktywność jest bardzo wolno jak jest zimno. Tylko na wysoka temperatura bedą denaturowane. Teraz coś po Angielsku od ekspert enzymów jęczmien:
Firstly, the mash must be heated to around 65°C to achieve a relatively rapid rate of starch gelatinization to enable the DP enzymes to rapidly degrade it. However, at that temperature, depending on amount of solutes (KI, osmolyte conc, etc) and mash thickness, the enzymes (esp b-amylase and limit dextrinase) will denature. When you cool the mash down, depending on when you do it, a proportion or all of these enzymes will already be denatured. However, on cooling (particularly on ice, not sure of other temps), some of the enzymes that may not have been irreversably denatured, may refold (re-nature - JP) returning some of the enzymes activity. This is the difference of the Sd1 type b-amylase thermostability compared to the Sd2H type.
On cooling the mash, why you would bother(?), some enzyme may refold (?). If it is limit dextrinase, it may reattach itself to its inhibitor (?). The DP enzymes will be active at say 15-20°C because barley germinates and grows from the seed at this temperature. The rate of the enzyme action will of course be slower at the lower temperature, and I would not rule out changes in the starch structure that might hinder hydrolysis.