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Date: 06 Aug 2006 03:33:34
From: Adam Preble
Subject: How do refractometers treat starch?
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Does starch cause problems in measuring brix in a refractometer? I am
testing my wheat malt by trying to mash a few ounces of it in a pot.
About 20 minutes in around the 138-148 range, I am seeing 5.5 brix. I
don't have any way to test starch tonight--I'll go to the LHBS and try
it on this test batch tomorrow. In the mean time, I am kind of curious
what to consider of the measurement I have.
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Date: 10 Aug 2006 22:58:52
From: rjwhite6
Subject: Re: How do refractometers treat starch?
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On Sun, 06 Aug 2006 03:33:34 GMT, Adam Preble
<rockobonaparte@hotmail.com > wrote:
>Does starch cause problems in measuring brix in a refractometer? I am
>testing my wheat malt by trying to mash a few ounces of it in a pot.
>About 20 minutes in around the 138-148 range, I am seeing 5.5 brix. I
>don't have any way to test starch tonight--I'll go to the LHBS and try
>it on this test batch tomorrow. In the mean time, I am kind of curious
>what to consider of the measurement I have.
Not a definitive answer, but my refractometer has tracked very close
to my hydrometer readings in various different kinds of wort.
So it seems to me that starch doesn't have an effect.
But now I am curious and will test this at various stages of the
conversion on my next all grain batch.
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Date: 11 Aug 2006 09:01:07
From: John Krehbiel
Subject: Re: How do refractometers treat starch?
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Just a guess, but I would expect that unless the starch is dissolved it
won't effect refraction.
I don't know if starches in grain are soluble. Cornstarch is not, but
potato starch is, provided that you get it hot enough to gelatinize.
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Date: 11 Aug 2006 16:23:05
From: John 'Shaggy' Kolesar
Subject: Re: How do refractometers treat starch?
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On 11 Aug 2006 09:01:07 -0700, <j_krehbiel@hotmail.com > wrote:
> Just a guess, but I would expect that unless the starch is dissolved it
> won't effect refraction.
>
> I don't know if starches in grain are soluble. Cornstarch is not, but
> potato starch is, provided that you get it hot enough to gelatinize.
Grain has both kinds. The soluble starch is what gets converted to
sugars during the mash. The insoluble starch is mostly left behind in
the grains or filtered out during the sparge.
John.
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Date: 11 Aug 2006 18:34:39
From: rjwhite6
Subject: Re: How do refractometers treat starch?
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After sleeping on it last night, I realized a flaw in my observation
(see earlier post).
While I have observed the refractometer closely tracking with the
hydrometer. I surmised from this (and posted) that the starch did not
seem to affect the hydrometer.
The flaw in my observation is that the starch may or may not affect
both measuring devices, so I should not have come to the conclusion
that the refractometer is not affected by starch.
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Date: 13 Aug 2006 07:41:47
From: John Krehbiel
Subject: Re: How do refractometers treat starch?
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rjwhite6 wrote:
> The flaw in my observation is that the starch may or may not affect
> both measuring devices, so I should not have come to the conclusion
> that the refractometer is not affected by starch.
Suspended solids will affect the hydrometer reading, and dissolved
substances will affect the refractometer. Overall, I doubt the amount
is all that much. When alcohol affects the refractometer, it really
throws it off. If starch made enough of a difference to worry about, I
suspect you would notice it.
John
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