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Kaiser 05-18-2009 06:18 PM

Why does a mash tend to settle at or near the right pH for mash enzymes
 
Have you ever though that it is not a coincident that the mash pH that we get when we mix malt with moderately hard water is just the right pH for enzyme activity?

I think that the barley seed wants to create a pH that is good for its enzymes and thatís why there are mechanisms (phosphate buffers, phytase enzyme) that allow this pH to be reached and stabilized.

Not necessarily a world changing discovery but something that came to mind when I thought about pH stuff this weekend.

Kai

menschmaschine 05-18-2009 06:40 PM

Quote:

Originally Posted by Kaiser (Post 1331097)
I think that the barley seed wants to create a pH that is good for its enzymes and thatís why there are mechanisms (phosphate buffers, phytase enzyme) that allow this pH to be reached and stabilized.

I think this is true... not that the barley seed has a will of it's own... unless it's on "The Happening", but it makes sense that barley developed mechanisms through evolution that give it a greater chance of seed germination and subsequent plant development/survival. Soil pH varies from place to place, even field to field, so the plant evolved methods of controlling the pH inside the endosperm.

pjj2ba 05-18-2009 07:00 PM

Yup, had that point driven home while a TA in grad school and one of the labs we did was a time course of germination days and amylase activity in barley.

What if find more amazing is the thermal stability of the amylases. Most plant enzymes can't handle much over 45 C. Can you imagine what brewing would be like if you couldn't heat the mash over 120 F? It would be a lot slowly and more than likely sour.

Kaiser 05-18-2009 07:11 PM

Quote:

Originally Posted by pjj2ba (Post 1331209)
What if find more amazing is the thermal stability of the amylases.

We did luck out with this one as there seems to be no "evolutional reason" why it would be able to survive well past 45C.

Kai

david_42 05-18-2009 07:14 PM

I can think of a good reason and any compulsive composter can back me up. Decaying vegetable matter gets hot. Enzymes that stay active at temperatures that kill most bacteria would be highly advantageous to a germinating seed.

pjj2ba 05-19-2009 02:41 PM

I don't think its is an evolutionary advantage. Only a few plants generate any heat at all - the ones that do are the plants that use a rotting flesh smell to attract flies as pollinators. 45 C would kill most germinating embryos. Seeds have a whole host of defenses to prevent microbes from getting to the tasty morsels inside, many of them are simply physical. The seed for the super sweet corn varieties is almost always treated with a fungicide. Since they don't store much starch, mostly sugar, the seeds really collapse as they dry down making all kinds of cracks in the pericarp - easy access points for soil microbes.

Since plants are non-motile, and "cold blooded" a lot the their enzymes have evolved to be active over a very wide temperature range. Unlike warm-blooded animals where quite a few enzymes only operate in a 10 C window around 37 C. I seem to recall however that even salivary amylase is quite temperature stable, like it's plant counterpart.

mrkristofo 05-19-2009 04:07 PM

Quote:

Originally Posted by pjj2ba (Post 1331209)
What if find more amazing is the thermal stability of the amylases. Most plant enzymes can't handle much over 45 C. Can you imagine what brewing would be like if you couldn't heat the mash over 120 F? It would be a lot slowly and more than likely sour.

I found that amazing, too, especially when you consider that the major differences in thermostability among different strains of barley is a result of 3 very specific mutations: R115C, V233A and L347S.

I can understand how arginine to cysteine could increase thermostability, and leucine to serine by increasing hydrophilicity, but valine to alanine? Odd, indeed.

Edit:

Quote:

Originally Posted by david_42 (Post 1331250)
I can think of a good reason and any compulsive composter can back me up. Decaying vegetable matter gets hot. Enzymes that stay active at temperatures that kill most bacteria would be highly advantageous to a germinating seed.

Well done. I'd buy that.

ghack 05-20-2009 01:18 AM

Let's not forget selective breeding of the base cereal grain for several thousand years..or you could just say God did it and forget about the whole "science" thing.

Kronin 05-20-2009 01:35 AM

Quote:

Originally Posted by ghack (Post 1334239)
Let's not forget selective breeding of the base cereal grain for several thousand years..or you could just say God did it and forget about the whole "science" thing.


I totally agree, with a caveat :-)

I believe in higher intelligence aka godly entity, but I don't think it disproves the science of it... god makes science... it is complicated as hell for us lowely men and women, but for a being like god(dess) it is all done with the blink of an eye. :)

and thank the gods they did it so we can brew! :tank:

rocketman768 05-20-2009 02:47 AM

Quote:

Originally Posted by Kaiser (Post 1331097)
Have you ever though that it is not a coincident that the mash pH that we get when we mix malt with moderately hard water is just the right pH for enzyme activity?]

No. If it weren't the case, then we wouldn't be making beer...just like the anthropic principle.


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