Why does amylase work at high temperatures? - Home Brew Forums
Home Brew Forums > Home Brewing Beer > Brew Science > Why does amylase work at high temperatures?

Reply
 
Thread Tools
Old 12-05-2010, 06:27 PM   #1
apeltes
Recipes 
 
Mar 2009
Central Florida
Posts: 37
Liked 3 Times on 3 Posts



Alpha amylase is optimized to work in germinating barley seeds. They certainly don't get up to the temperatures we use to mash. Why is the optimum temperature, then, for mashing 150-160F? That seems to be WAY outside the logical range for this enzyme.



 
Reply With Quote
Old 12-05-2010, 06:32 PM   #2
Yooper
Ale's What Cures You!
HBT_ADMIN.png
 
Yooper's Avatar
Recipes 
 
Jun 2006
UP of Michigan, Winter Texan
Posts: 69,005
Liked 7600 Times on 5350 Posts


There are many enzymes, and it's oversimplistic to say that alpha amylase only "works" at XXX temperature. Here's some good but simple reading on enzymatic activity and mash temps, along with a chart: http://www.howtobrew.com/section3/chapter14-1.html


__________________
Broken Leg Brewery
Giving beer a leg to stand on since 2006

 
Reply With Quote
Old 12-05-2010, 08:41 PM   #3
remilard
Recipes 
 
Nov 2008
Kansas City
Posts: 3,654
Liked 43 Times on 41 Posts


Quote:
Originally Posted by apeltes View Post
Alpha amylase is optimized to work in germinating barley seeds. They certainly don't get up to the temperatures we use to mash. Why is the optimum temperature, then, for mashing 150-160F? That seems to be WAY outside the logical range for this enzyme.
Lots of organisms (plant, animal, bacteria) use alpha amylase so it is wrong to say that it is adapted to work in germinating barley.

 
Reply With Quote
Old 12-05-2010, 08:50 PM   #4
david_42
 
david_42's Avatar
Recipes 
 
Oct 2005
Willamina & Oak Grove, Oregon, USA
Posts: 25,593
Liked 151 Times on 142 Posts


Because evolution does not optimize. Alpha enzyme is most efficient (aka fastest) at 160F, but it works fine, if somewhat slower, at room temperature.

Survival of the "good enough", not the fittest, is the truth. Just look at what a lousy arrangement the human eye is, but it's good enough.
__________________
Remember one unassailable statistic, as explained by the late, great George Carlin: "Just think of how stupid the average person is, and then realize half of them are even stupider!"

"I would like to die on Mars, just not on impact." Elon Musk

 
Reply With Quote
Old 12-05-2010, 09:51 PM   #5
BigEd
Recipes 
 
Nov 2004
Posts: 2,579
Liked 191 Times on 160 Posts


Quote:
Originally Posted by apeltes View Post
Alpha amylase is optimized to work in germinating barley seeds. They certainly don't get up to the temperatures we use to mash. Why is the optimum temperature, then, for mashing 150-160F? That seems to be WAY outside the logical range for this enzyme.
The ~150F mash temperature is the best for brewing beer because that provides the maximum alpha amylase activity for breaking down starch chains into fermentable sugars. As has been said above that is not the only thing alpha amylase might do nor does it mean that alpha amylase does not work at all at different temperature ranges.

 
Reply With Quote
Old 12-05-2010, 10:11 PM   #6
RogerMcAllen
Recipes 
 
Apr 2009
Decatur, IL
Posts: 623
Liked 6 Times on 6 Posts


Quote:
Originally Posted by david_42 View Post
Because evolution does not optimize. Alpha enzyme is most efficient (aka fastest) at 160F, but it works fine, if somewhat slower, at room temperature.

Survival of the "good enough", not the fittest, is the truth. Just look at what a lousy arrangement the human eye is, but it's good enough.

I'd say it is perfectly optimized to do what it needs to at lower temperatures. The barley produces amylase after it germinates (malting), to turn stored starches into food. It has to be slow for a few reasons.
A growing plant doesn't need a ton of sugar all at once. but rather a slow continuous supply
If you convert the starch into sugar all at once, the water activity inside the seed would drop like a rock and suck the moisture from the growing sprout.

 
Reply With Quote
Old 12-06-2010, 05:04 AM   #7
apeltes
Recipes 
 
Mar 2009
Central Florida
Posts: 37
Liked 3 Times on 3 Posts


The alpha amylase in barley evolved to work best in germinating barley seeds (and evolution, natural selection specifically, DOES optimize things).

Any enzyme tends to have one temperature at which it works best. Any higher or lower, and it loses efficiency. For example, human digestive enzymes work best at approximately 98F. Any higher or lower, and they become less effective.

Why does mashing work best at almost 170F? Why doesn't mashing work best at the temperature at which barley germinates?

 
Reply With Quote
Old 12-06-2010, 05:42 AM   #8
ajdelange
HBT_LIFETIMESUPPORTER.png
Recipes 
 
Aug 2010
McLean/Ogden, Virginia/Quebec
Posts: 8,905
Liked 1362 Times on 1037 Posts


I'm way out of my league here but will venture a WAG. The efficacy of an enzyme depends upon its shape and its shape is controlled by the charges on the acid residues. Whether an acid residue gives up its proton or not depends on pH and the pK for that residue and the pK depends in turn on temperature. Thus temperature effects the conformation of the enzyme. Coupled with that is the fact that reactions generally take place faster at higher temperatures. OTOH, if the temperature gets too high the enzyme is denatured. Put all these together (if I'm right in my hypothesis) and there is an optimal temperature and pH for each enzyme whether this be the temperature at which it operates in nature or not. Amylases do not need to work at optimum rate to perform their functions in nature nor indeed in brewing. But in brewing speed is important. We don't want to have to wait overnight for the starches in our mashes to convert.

 
Reply With Quote
Old 12-06-2010, 02:24 PM   #9
david_42
 
david_42's Avatar
Recipes 
 
Oct 2005
Willamina & Oak Grove, Oregon, USA
Posts: 25,593
Liked 151 Times on 142 Posts


Quote:
(and evolution, natural selection specifically, DOES optimize things).
No, check out the efficiency of photosynthesis using chlorophyll. The most primitive photovoltaic cells do a better job.
__________________
Remember one unassailable statistic, as explained by the late, great George Carlin: "Just think of how stupid the average person is, and then realize half of them are even stupider!"

"I would like to die on Mars, just not on impact." Elon Musk

 
Reply With Quote
Old 12-06-2010, 03:02 PM   #10
apeltes
Recipes 
 
Mar 2009
Central Florida
Posts: 37
Liked 3 Times on 3 Posts


Evolution via natural selection doesn't necessarily (or usually) produce the best possible configuration, but that's not what I mean by "optimize". I'm saying that natural selection favors the most adaptive version of a trait given a range of available genetic variation. Thus, for enzymes, we can usually trust them to work best under the conditions in which they evolved.

I think the best hypothesis we have so far is that alpha amylase obviously works well within a very broad temperature range. It's not as "sensitive" as the enzymes I'm more familiar with. For example, many mammalian digestive enzymes slow significantly at a few degrees above normal body temperature (or below). Perhaps we need to mash at such high temperatures to compensate for the reduction in concentration produced when we crush and mix with water? Within limits, reduced concentration equals reduced reaction rate.



 
Reply With Quote
Reply
Thread Tools


Similar Threads
Thread Thread Starter Forum Replies Last Post
Partial Oatmeal Mash with Just Alpha Amylase.. h4rdluck Brew Science 3 07-16-2009 02:33 PM
Aspergillus oryzae vs. Amylase digdan Brew Science 5 07-06-2009 12:33 PM
Data on amylase denaturing and starch conversion? stoutaholic Brew Science 4 06-19-2009 11:29 PM
Barley derived Amylase? Brewster2256 Brew Science 10 06-12-2009 04:33 PM
Amylase in the mash? rabeb25 Brew Science 6 05-24-2009 08:36 AM


Forum Jump