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Old 08-29-2012, 06:25 AM   #1
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Default Mash time and fermentability (schedule of enzymatic activity)

Last night I listen BYO/BBR experiment about mashing time (10-30-60 minutes @ 159F). One of conclusions was that shorter mashes resulted with higher attenuation wort (more fermentable sugars). Kai mentioned that beta amylase first becomes inactive while alpha proceeds to convert starch and long dextrin chains into unfermentable sugars, so after 10 minutes there was greater activity of beta amylase, while alpha continues to be active after that.

I am wondering is this the case only at higher temperatures (as in experiment) or beta amylase usually gets denatured before alpha (in temperature range where both enzymes are activated).

I would imagine that (at eg. 155F) alpha is first to convert starch into long/unfermentable chains, and beta amylase is converting starch and part of those large sugar chains into fermentable sugars.

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Old 08-29-2012, 01:21 PM   #2
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If you haven't looked at it yet, the wiki entry on mashing is wonderfully complete and ultimately answers your questions.

In short, yes, beta denatures (>160degF) before alpha (>176degF, hence mashout temps). To go deeper into your question, beta is actually even MORE active at lower temps, being most active somewhere around 145degF. You can do a relatively short rest at this temperature and get almost all fermentable sugar (maltose).

Does that answer your question?

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Old 08-29-2012, 04:04 PM   #3
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I read it long time ago, but its always good to revise the knowledge...
Actually this could be the article where I understood that beta continues to convert after alpha has done its job:

Quote:
But since it (beta amylase) cannot get past the branch joins, Amylopectin cannot completely be converted by beta amylase. Alpha Amylase is able to split 1-4 links within glucose chains. By doing so, it exposes additional non-reducing ends for the beta amylase. This allows for the further conversion of Amylopectin.
I found some information on wikipedia which also says (as I understood) that beta keeps converting longer than alpha:

Quote:
(about Amylopectin) Glucose units are linked in a linear way with α(1→4) glycosidic bonds. Branching takes place with α(1→6) bonds occurring every 24 to 30 glucose units, resulting in a soluble molecule that can be quickly degraded as it has many end points for enzymes to attach onto. In contrast, amylose contains very few α(1→6) bonds, which causes it to be hydrolyzed more slowly but have higher density and be insoluble.
Since amylose and amylopectin are made up from glucose molecules (difference is complexity of bonds), wouldn't it be logical that amylopectin is firstly converted by alpha (to long dextrin chains) and then by beta amylase, which further converts amylopectin?
If this is the case (??) then for producing most fermentable wort it would be benefit to mash at 165 (alpha breaks amylopectin) and then at 145 (beta breaks amylose and non-reducing ends of amylopectin).

I guess I am oversimplifying chemistry of mash, but I suppose there is some rule in schedule of enzymatic activity.
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Old 08-29-2012, 04:51 PM   #4
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I'm sure you're not the first to ask these questions. But, what are you trying to gain by mashing high then going low that you can't achieve by using a time-tested step mash schedule? If you're just curious about the chemistry, I completely understand.

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Old 08-29-2012, 07:40 PM   #5
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It started with curiosity, but the more I meet the substance the more questions opens, so I"d like to know science in behind especially with these contrary informations.
Also, I would like to experiment with different approach but before it I want to analyze the subject.
I will google it, if something interesting appears I"ll post it here.

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Old 08-29-2012, 11:16 PM   #6
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It's only a guess but when working at brewery scales, going from say 165 down to 145 would probably be impractical for the difference in fermentability. It's much easier for those large operations to heat quickly than cool quickly. Our techniques are mostly derived from large scale operations and I have asked myself the very question you pose. Someday I might be motivated enough to experiment with it.

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Old 08-30-2012, 07:29 PM   #7
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Quote:
Originally Posted by helibrewer View Post
It's only a guess but when working at brewery scales, going from say 165 down to 145 would probably be impractical for the difference in fermentability. It's much easier for those large operations to heat quickly than cool quickly. Our techniques are mostly derived from large scale operations and I have asked myself the very question you pose. Someday I might be motivated enough to experiment with it.
I say go for it, guys. Let us know what you find out. Of course, I think the preferred method would be to brew it side-by-side with both the traditional and experimental mash method and hold everything else constant.
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Old 09-08-2012, 03:38 PM   #8
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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.
Interaction 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.

Time 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 ):
http://www.scientificsocieties.org/j...1_97_2_085.pdf
http://www.scientificsocieties.org/j..._102_2_097.pdf
http://www.scientificsocieties.org/j...2-0611-02R.pdf

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