pH testing - sample volume and rate of conversion - question?
Posted: 06 March 2011 02:13 PM   [ Ignore ]
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I know that sometimes, if you have a smaller volume of something, a chemical/enzyme reaction might happen more quickly.

But here’s something interesting.

Today I’m making a stirred cheddar and monitoring pH.  I took out a small sample and took the pH.  It was at 6.60.

A little bit later I took the pH of the same sample I took before.  It was at 6.58.  I then rinsed the sample dish, took a fresh sample with sanitized equipment, then measured the pH of the fresh sample.  6.58.

So this got me thinking.

Suppose I just take out a small sample of the milk at the beginning and put it in a small container, insulate it to maintain temperature, and keep checking the pH of that same sample, until it gets in range. Then when I figure I’m getting close to my desired pH for rennet addition, I can take a fresh sample and check it, just to be sure.  This eliminates having to take a bunch of samples every time I want to check the pH progress.

Any thoughts?

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Posted: 06 March 2011 09:30 PM   [ Ignore ]   [ # 1 ]
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the chain reaction on small samples and large sample differ. Unless their “perfectly” insulated they will alter at diff rates it may not make much of a diff but I thing the larger the batch the more the diff will be to the small sample that is maintained.  Best be safe and use the actual batch, however if it works for u then great smile

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Posted: 07 March 2011 02:47 AM   [ Ignore ]   [ # 2 ]
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I’ll agree with Neal.  There’s probably going to be some slight variance between the sample and the batch itself, but it should be minimal.  However, since the really critical point is draining, it shouldn’t be too major a point to have a slight difference at earlier stages.  I may be doing it all wrong, but I only measure for the drain point pH level, and it’s worked for me.

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Rich

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Posted: 07 March 2011 01:30 PM   [ Ignore ]   [ # 3 ]
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Thanks guys.  The main thing I am trying to avoid as I learn the timings is just taking too many samples.

Suppose I am aiming for a drain pH of 6.1 for example.  I might take a sample and be like… nope I’m at 6.3.

so 15 minutes later I take another sample… now I’m at 6.28

A few minutes later another sample…. now I’m at 6.24

Another sample a few minutes later…  now I’m at 6.2….

etc etc etc until I finally hit my 6.1 target.  I could take 20 samples until I finally hit the pH I am looking for, and in the meantime I feel like i’m risking contamination every time I take a sample, not to mention, removing some of my yield, even if it is only half a teaspoon at a time….

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Posted: 07 March 2011 03:22 PM   [ Ignore ]   [ # 4 ]
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As long as you clean whatever you’re using to draw the sample, you’re not going to contaminate anything.  And you will lose no yield at all because you’re drawing off whey, not curd.  It does sometimes get tedious when you’re closing in on that target.  In my experience the first 1/2 hour shows little or no movement; but when you get to the lower readings it really starts cooking.  Better to do frequent samples then, than to risk going too far.

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