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Topic: Converting corn starch to glucose.  (Read 15290 times)

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Offline Zip

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Converting corn starch to glucose.
« on: April 05, 2014, 01:23:41 PM »
Hello, I am a homebrewer from Michigan, and I am looking for a cheap alternative to buying malt extract at $4/lb. I began looking into converting cornstarch, which is made up of long chains of glucose molecules, and found a method explained here, and also below:  I would like some help turning this process into more of a recipe that can be used by others, and I have several questions. I will also include the info below, along with a breakdown of the steps as I understand them, and my questions. I appreciate any help that you can offer. Thanks in advance.

To convert this polymer into its monomer, the amylase enzyme is used. The amylase enzyme can be classified into three categories: α-amylase, β-amylase, and glucoamylase. α-amylase will break the α-1,4-glycosidic bond randomly, giving molecules of dextrins. α-amylase can also break the α-1,6-glycosidic bond, but at a much slower rate (usually the enzym pullulanase is added to accelerate the breakage of α-1,6-glycosidic bond). β-amylase breaks the α-1,4-glycosidic bond from the non-reducing end, giving molecules of maltoses. And glucoamylase breaks the α-1,4-glycosidic bond also from the non-reducing end, giving molecules of glucose (Wiseman, 1985).

The α-amylase used is obtained from the bacteria B. subtilis or B. licheniformis, whereas the β-amylase is obtained from Aspergillus sp. and Rhizopus sp.

This conversion took place in a couple of steps:

    First, we make a solution from the starch. In Wiseman (1985), a 30-40% solution w/w is preferred, which will -after the conversion reaction- give a 94-97% glucose in equilibrium mixture.
    Then, we gelatinized this solution. Gelatinization is the process of breaking down the intermolecular bonds if starch molecules in the presence of water and heat.
    After the starch solution is gelatinized (by heating), the solution became very viscous, just like the starch (kanji) we used to stiffen our clothing items. This is where the α-amylase is added, at 90 degreesdegrees Celsius and stirred for approximately 2 hours. This is the process of liquefying the starch. See, this α-amylase will break down the α-1,4-glycosidic bond, but not the α-1,6-glycosidic bond. Therefore, the reaction yields molecules of branched but short glucose. Branched molecules are soluble in water, whereas linear ones are insoluble. In other words, the branched molecule will make a less viscous solution that the linear ones. Hence the viscosity of the starch solution will decrease as the α-amylase works (Wiseman, 1985).
    Liquefying can also be done with acid (HCl), in room temperature and acidic condition (pH 4.5-5). The downside of using acid is that acid can hydrolyze protein into amino acid, which will cause the browning reaction (or the Maillard reaction: reaction between amino acid and reducing sugar which will result in the presence of flavour. This is of course not desirable, because in order to get a pure glucose (or high concentrated, at least), the starch has to be really rid of impurities, where as an enzymatic reaction is specific and only the starch will be converted.
    After the liquefying process, saccharifying is done with glucoamylase. The temperature for this step is 55-60 degreesdegrees Celsius. Saccharifying literally meant to convert into sugar (saccharose). Or, in more scientific words, saccharifying is the process of converting a sugar derivative or complex carbohydrate into a simple soluble fermentable sugar by hydrolysis.
    The conversion is assumed to be done. A sample of the sugar is to be taken repeatedly at a time interval, and analyzed. Here we use the Fehling's reagent. The Fehling's reagen consisted of Fehling A (blue, copper sulfate solution) and Fehling B (colorless, potassium hydroxide and potassium sodium tartrate solution). This reagent specifically oxidize reducing sugars (glucose is a reducing sugar), and will result in a change of color from blue to red (cuprous sulfate). A standard solution of pure glucose is used to standarized the Fehling's reagent.

After obtaining the glucose concentration at every interval of the reaction, these data is plotted according to the Michaelis-Menten kinetics.

Step 1- Make a 30%-40% solution of corn starch to water ( How does this convert?)

Step 2- Heat mixture to 90C/194F, add Alpha Amylase and keep at that temp, and stir for 2 hours. (Will this work? If so, how much do I add? If not, where can I find what I need? Do I have to stir continuously for 2 hours? Is there an acceptable temperature range if I am unable to keep it at exactly 194F?)

Step 3- Drop temp to 55-60C/131-140F and add glucoamylase. (How long do I stay at this temp? Where do I get glucoamylase? How much do I use?)

That's what I have so far. What am I missing? I apologize for the length and complexity. Thanks again.

Offline student123

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Re: Converting corn starch to glucose.
« Reply #1 on: April 22, 2014, 06:43:32 AM »
Amylase you get in for example mouth or in stomach. But I don't know which kind of amylase. I am also asking how can be made solution of corn starch in water and sturches don't dissolve in water.

Offline Arkcon

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Re: Converting corn starch to glucose.
« Reply #2 on: April 22, 2014, 07:08:27 AM »
Zip:, your suggestion is pretty routine for home-brewers.  Web forums dedicated to beer making will give you insights into the recipes you need to carry on this sort of conversion.  Note that something made from amalyse digested corn will definitely lack character in its flavor, and will just be alcohol.  So the web forums for brewers may be indifferent to your plan.  Anyway, the manufacturer may be able to help you with recipes.
Hey, I'm not judging.  I just like to shoot straight.  I'm a man of science.

Offline Corribus

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Re: Converting corn starch to glucose.
« Reply #3 on: April 23, 2014, 09:49:01 AM »
Totally agree with Arckon. Malted grains are one of the most important ingredients in beer. If you're going to cut out and basically just use sugar, what's the point? It won't really taste like beer.

In any case, if you're just after glucose syrup, why don't you just buy corn syrup, which is the same thing you're trying to do and cheaper I would wager than $4 a pound. In fact, you can buy dark corn syrup (Karo brand), which has molasses added, for no significant extra cost. This would at least give you back some of the malted, treacle flavor you'll be losing if you just use glucose as your sugar source.

I guess it's all relative, but $4 for 1 POUND of malt extract doesn't seem like very much. Doesn't that stuff go a long way?
What men are poets who can speak of Jupiter if he were like a man, but if he is an immense spinning sphere of methane and ammonia must be silent?  - Richard P. Feynman

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