First of all I am glad I spend several days of researching this subject because it opened my eyes, its not that I can see now but the image is more clearer than it was before
. I realized that biochemical precesses in mash are too complex so there is no pattern for enzimatic activity (diastatic power) which can be used as rule of thumb in every mash.
This is caused by several factors.
between enzymes plays critical role in starch conversion, which I didn't know.
Mash product will be different if only one-by-one enzyme is active versus mash where all enzime contributes diastatic activity. Interaction of alpha and beta amylase leads to more effective conversion than if we encourage independent enzyme activity eg. 1st alpha amylase and then beta amylase. Also, it is tough to keep one enzyme active while denaturation the other (without adding some chemical inhibitors), so most of time there will be synergic relationship between them.
Alpha-amylase converts starch into dextrin and oligosaccharides, which then become substrates for limit-dextrinase and beta-amylase, so interaction is very important.
It is interesting that some enzymes inhibits action
of others: alpha-glucosidases inhibits action of beta-amylase while limit dextrinase and beta amylase are competetive enzymes competing for common substrate- chains of oliggosaharides.
Another factor that impacts enzyme activity are mash conditions
like pH, temperature, mash thickenss and calcium content. Optimal pH for beta-amylase is 4.5 while alpha is more active at higher pH (5.5), I assume this is why suggested pH for most beers styles is between 5.2 and 5.5. While beta-amylase is temperature unstabile and it starts to deactivate at temperatures higher than 65°C (149F), alpha is more stabile at those higher temperatures. Also, enzymatic activity is higher in thicker mash, especially with beta-amylase being more liable on thicness changes. Alpha-amylase seems to like calcium, and therefore increases activity if there is higher amount of calcium ions.
Altrough some enzyme prefers one condition over other, it is tough to completly dectivate one and force activity of other enzyme: even at 90°C (194F) there is still some activity of beta-amylase, and higher activity of alpha.
also plays great role in these biochemical processes. After 60 minutes (at 65°C-149F) approximately half of the alpha amylase activity remained, whilst less than ten per cent of the original beta amylase activity was present. Increased alpha amylase activity is because it is more stable than beta amylase at 65°C.
All of this factors affects fermentability
since it is caused by action of amylase enzymes. Decreasing mash thickness and increasing temperature will lead to less fermentabile wort- fermentability fell at temperatures over 63°C, to about 30% at 75°C (167F), and being 90% of the maximum at 67°C (153F). This is also beacuse of beta amylase temperatue unstability. This is proven with fermentation test where two worts were tested: 1st was mashed at 65°C (149F) and 2nd at 80C (176F).
The growth of yeast was monitored over a period of 72 hours- by 24 hours, when the yeast in the normal wort was growing vigorously, fermentation in the wort from the 80°C mash was almost complete.
Logically, this is caused by less maltose content in wort.
At the end, I can conclude that "schedule" of enzymatic activity is in close relationship with enzyme interaction and it depends on mash conditions and time. There is no simple pattern and several factors needs to me managed in order to adjust wort fermentability (thickness, pH, temperature, amount of calcium..), and there is still lot of space to assay these factors and how they interacts with each other.
I couldn't fine any experiment where different mash schedule was applied (eg. mash from 165F to 145F) and how that impacts fermentability, I see it like big challenge and maybe I"ll perform it one day.
Few great articles on this subject (for geeks