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Starch to Sugar conversion

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Cape Brewing

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FIRST BABY!!!


Oddly enough I actually have a "science question". My HBC did a mashing presentation recently and we were talking about different processes that take place at different temps and I have a basic question...

Is all starch conversion done during the malting process and then mashing is simply "washing away" and then breaking down those sugars into simplier sugars for the yeast to then munch away on?
 
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Is all starch conversion done during the malting process and then mashing is simply "washing away" and then breaking down those sugars into simplier sugars for the yeast to then munch away on?
not really - the malting process prepares the starches to be converted...

that's why the grain is dried after it's germinated long enough.

Here's what Mr. Palmer has to say on the subject:

How to Brew - By John Palmer - What is Malted Grain?
 

menschmaschine

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Congrat's Cape on being the first.

As I understand it and as a generality (some of us in this forum will get caught up in details;)) and for "base" grains, malting is essentially "tricking" the barley "seed" into germinating (Sorry for all the air quotes:)). When it does this, it has created the enzymes that we want for mashing. The starch in the barley is largely left as starch. Then germination is stopped by drying it out and kilning it. So, what you're left with instead of just starch is starch and enzymes. At certain temperatures, and in the presence of water, these enzymes will convert the starch to sugar (this is mashing). There are other enzymes that will break down proteins, etc., but that's really outside your question.

So, no mashing is not simply "washing away" sugars. That's what lautering is for. Mashing is taking advantage of the enzymes formed during malting to convert starches to sugars. Then you wash away the sugars (wort) during the lauter.
 

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Wheeee! A sub-forum for nerds! I'm in! Must have more exclamation points!!!!!!!!!!!!!!!!!!!!!!!!!
 

menschmaschine

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Just wanted to tack onto this thread. I was paging through Fix (Principles of Brewing Science) and saw a table indicating the starch/sugar content of raw barley and barley malt:

.........................................Starch %........................Sugar %
Barley....................................63..................................2
Malt.......................................58..................................8

You can see that some sugars are already present in raw barley and that some starches are converted to sugars during malting.
 

Kaiser

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The only malt where complete starch conversion happens during the (greater) malting process is crystal or caramel malt. Here the endosperm of green malt is coverted though heat before the malt is kilned.

The germinating seed converts starch only at the rate as it needs sugar for its growth. If all the starch was converted during germination, all that sugar would be consumed by the growing barley plant and the yield would be extremely low. The goal of germination in malting is to create enzymes and the cytolysis (breakdown of cell walls) and let the seedling burn as little sugar as possible.

Kai
 

Gordie

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Right. What Kai said.

Conversion only happens through coaxing enzymes, through temperature, to get to work. That's why we have mash temps. The lovely thing about malting is that the enzymes that are needed to convert the starch are self contained in the barley once they've been coaxed into germinating through the malting process.

And god bless the mods for creating this subforum.
 
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CAPE - Is this something that the presenter was saying? That we aren't actaully converting starches and just rinsing? You're first question should have been, "Then why do we hold in for 40-90 minutes and not just stir and drain?"
 
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Cape Brewing

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CAPE - Is this something that the presenter was saying? That we aren't actaully converting starches and just rinsing? You're first question should have been, "Then why do we hold in for 40-90 minutes and not just stir and drain?"

No, that wasn't the point of the presenter... we were talking though the different enzymes (alpha/beta amylase), what temps they are the most active and what they do individually.

We didn't really get into the conversion of starch to sugars that explicitely but rather talked about the breaking down of complex sugars through out the mash process. I understand the mash temp/time (to your above point about what my question should have been) process fairly well (I think) but was just simply curious about the one-step backwards... and that was where the bulk of the starch was first converted to sugar.

My impression was that a bulk of the starch was converted during the malting process and then the mashing process was essencially just using temp/time to prod the enzymes into breaking the complex sugars into simplier sugars whis are THEN "washed away" through the lautering process. I knew the "washing away" part and just did a crappy job of saying it in the orig. post.

But no... it sounds like there is quite a bit of starch conversion done during the mash process.
 

pjj2ba

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It is not just the production of enzymes that is important during mashing. During the germination stage, the starches are converted into a more soluble form. I'm not talking sugars here, but long chain carbohydrates that are soluble and will give a positive iodine test (you get some sugars too of course).

My wife teaches a general Botany course and I often get roped into helping her out. She used to have the students do a classic barley half-seed experiment in the class but is was a real pain to set up and run. Since this is the science section I'll give the gist of this exp. A barley seed is cut in half such that one side has the embryo and one doesn't. The embryo is responsible for producing a hormone (gibberellin) which moves to the cell layer surronding the endosperm. Here it stimulates enzyme production. So for the lab they take petri plates with a media containing a soluble starch in it and various levels of gibberellin. Some plates get embryo containing seed halves, and others get halves without. After several days the seeds are removed and the plates flooded with an iodine solution. What you see is halos where the starch was degraded with the size corresponding to the amount of enzymes produced. More gibberillin, larger halos. No embryo, no halo. All in all pretty cool, but a pain to set up and for the students to properly execute.

Back to my point. We ditched that lab and now basically do a mashing experiment comparing starch conversion rates in various base malts (ie 6-row vs Vienna). In developing this lab, I also ground up some unmalted barely with the idea of showing no starch conversion as malting is required for enzyme production. So I set up my various reactions (10 ml mashes!) and took some time zero readings and was initially surprised that the time 0 for the unmalted barley was negative for starch (it looked like full conversion). Then it dawned on me that the starch in the unmalted barley in not soluble at mashing temps and therefore the solutions will give a negative starch reaction. To solve this I ended up adding some soluble starch to the unmalted barley mash so you could see there were no enzymes as there was no change in the levels of the added soluble starch.

Geek on!
 

Kaiser

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During the germination stage, the starches are converted into a more soluble form.
What exactly happens there? To my knowledge the starch granules are not gelatenized. But could it be that the germination degrades protein which makes the starch less accessible. Or is it that germination just releases some of the amylose/amylopectin which can then be detected with iodine?

Kai
 

pjj2ba

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What exactly happens there? To my knowledge the starch granules are not gelatenized. But could it be that the germination degrades protein which makes the starch less accessible. Or is it that germination just releases some of the amylose/amylopectin which can then be detected with iodine?

Kai
Breakdown of starches starts to occur very early during germination (and of course then malting) The same reactions that are occurring when we mash are happening during the malting process. Being a plant scientist I always find the talk about gelatinizing a bit odd. I looks at things from a growing plant perspective, and then how it relates to brewing, not vice versa. The seeds are perfectly able to convert all of the starches at 50 F. Obviously no gelatinization. My take on gelatinization is that this is was WE do in order to get conversion to happen in a time frame that works for US.

I did a little looking for some older lit. as that might have a decent overview. I found a paper from '82 that is not bad. From the paper: "....degradation was preceded by extensive breakdown of cell wall material and the protein matrix of the endosperm." This would be during the time equivilant to that during mashing. This helps to get the enzymes and the starch together to do their thing. The enzymes are not made in the majority of the endosperm, they are made in the layer that surrounds the endosperm and must diffuse into the starchy endopserm. Breakdown of the cell walls and protein matrix helps in this. The production of brewing enzymes during mashing is obviously important, but I think less appreciated (at least by the homebrewer) is the general collapse of the endosperm matrix, which greatly facilitates the access of the starch granules to the enzymes. As with mashing, the first activities in germination (malting) are going to be the actions of alpha amylase on the really long starch chains which will help with the solubilization. Starch Degradation in Endosperms of Barley and Wheat Kernels During Initial Stages of Germination

I recall reading somewhere that after malting, approx. 1/3 of the gravity potential is already present as fermentable sugars. Mashing is done to convert the remaining starches.

Found some more nice tidbits. This is from a 2008 paper - this one is laregly focused on comparing two different techniques used to analyze gene expression in germinating barley, not the malting process, but it does have some pertanant info.
Malting is driven by the co-ordinated activity of hydrolytic enzymes and endoproteases that modify the cell walls and protein matrix, exposing the starch granules of the endosperm to depolymerisation. The relative rates of protein and carbohydrate modification probably play the most important role in the application of malt in the brewing process; however transcriptional control of the associated modifying enzymes remains largely un-investigated.

The major polymers to be broken down during germination are stored in the endosperm and the enzymes that act to depolymerise these polypeptides are released from outside the cell walls. It is therefore essential that the cell walls be removed early in germination. The starchy endosperm walls consist of approximately 70% (1-3,1-4)-beta-glucans [23]. During mobilisation of the endosperm (1-3,1-4)-beta-D-glucanase (EC 3.2.1.6) contributes to the break down of the cell walls by hydrolysing the 1,4-beta-D-glucosidic linkages in beta-D-glucans that contain 1,3- and 1,4-bonds
Differential LongSAGE tag abundance analysis in a barley seed germination time course and validation with relative real-time RT-PCR

I like this one as it as the two techniques used are pertinant to my work - same techniques, different subject
 

Kaiser

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I recall reading somewhere that after malting, approx. 1/3 of the gravity potential is already present as fermentable sugars. Mashing is done to convert the remaining starches.


This is in contradiction to what I found here : http://books.google.com/books?id=zV9bpyykNtMC&pg=PA11&dq=briggs+malting#PPA123,M1

Table 4.16 inidactes that only about 10% of the starch is converted during malting.

I wanted to attach the table but it doesn't seem to be easily possible with the forum software used here.

Kai
 
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So would it be accurate to summarize at a high level:

Starches are already being converted during the germination process, it is then encouraged to speed up a bit during the malting process and then the mashing process will complete conversion while also breaking down complex sugars into simple sugars?

It sounds like (to your previous point Kai) that the level of conversion varies from grain to grain along the process.
 
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