Author Topic: pH Meters & Dairy - Measuring, Calibration, & Maintenance  (Read 4521 times)

Offline Nitai

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pH Meters & Dairy - Measuring, Calibration, & Maintenance
« on: April 19, 2011, 10:55:20 PM »
I asked this elsewhere recently but there were no responses, so I am asking again because I am a persistent bastard :)

I have an extech 110 with the flat electrode, but I find when trying to test surface PH of a wheel that has been pressing for a while the reading leaves me uncertain. It seems to fluctuate more than it does in liquid and I just never trust it. I know I can collect whey and test that, but I am doubtful that it acidifies at the same rate, especially because I imagine it cooling more. Thoughts, suggestions?


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Re: pH Meters & Dairy - Measuring, Calibration, & Maintenance
« Reply #1 on: April 19, 2011, 11:29:29 PM »
Dear persistent bastard,  ;)

I am certainly no expert on pH testing, but here's my experience:

I have an Extech 100. Virtually the same device except that you don't refill it like you do with the 110. In my most recent two wheels I removed the wheel from the press and pressed the flat electrode perhaps 1/4 inch into the top of the wheel. The reading stabilized after a couple seconds and I took that as my reading. The surface of the cheese wasn't damaged and sprang back after I was finished. The pH reading has to be done where there is some residual moisture. The surface you're trying to test cannot be dry. Since I had just removed the wheel from the press, this was okay. If I had waited until it had air-dried, my meter would have had a difficult time trying to register a pH.

Hope that helps.

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Offline Nitai

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Re: pH Meters & Dairy - Measuring, Calibration, & Maintenance
« Reply #2 on: April 19, 2011, 11:46:13 PM »
Thanks boofer. That is what I have done too, but I suppose maybe mine stabilizes a bit slower and I am an *impatient* persistent bastard (slightly oxymoronical, I know). I'll see how it goes tomorrow when I test the Asiago that is in the press. I also can't help but think that the internal PH in a wheel might be different than the outside...

Offline iratherfly

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Re: pH Meters & Dairy - Measuring, Calibration, & Maintenance
« Reply #3 on: April 26, 2011, 01:35:42 PM »
I have to admit that my fancy Extech 407227 spends most of its time in the box for those exact reasons. It takes about 20 minutes to calibrate this piece of junk (and it has an automatic temperature compensation and thermometer electrode... but that needs its own calibration too).  Once I finally have it figure out I hate sticking it in my cheese as it does leave dents and holes that later become clogged with wash or whey and develop mold.  I didn't want to spend $100 for the flat electrode considering how lame this whole instrument is.  During calibration the numbers are inconsistent and fluctuate wildly for several minutes.  I dip it in 7.00pH liquid, get a 6.56 reading, shake it a bit and it goes to 7.7pH reading etc. Adjust it to 7.00ph. Wash the liquid off, dip it in 4.01pH liquid and get 3.4pH, shake it, it jumps to 4.6, adjust it to 4.01ph. wash the liquid off, dip it again in the 7.00pH liquid and the reading is now 6.7pH, adjust it again. Now the 4.01liquid shows as 3.9pH and so forth until it stops fluctuating.

By the time this nonsense is done either my cheese has gotten over-acidified or I missed cutting the curd.  Even when it's finally balanced, I stick it in the cheese and it reads 5.2pH. I do it again 5 minute laterand it shows 5.6pH, I do it again and it shows 5.1pH.  As you can imagine, more often than never, the pH meter guarantees I will mess up and spoil the cheese rather than actually help control its quality.  This isn't my meter; my $30 Hanna Checker (Hi98103) acts no difference, only here I have to calculate with a separate thermometer.  I feel that the only solution is industrial food lab meter with automated calibration and compensation and those are $1,000+ instruments.  Very frustrating

Offline Nitai

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Re: pH Meters & Dairy - Measuring, Calibration, & Maintenance
« Reply #4 on: April 26, 2011, 04:40:14 PM »
Sounds like your Extech is a lemon!  :o


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Re: pH Meters & Dairy - Measuring, Calibration, & Maintenance
« Reply #5 on: April 26, 2011, 05:31:55 PM »
Sounds like your Extech is a lemon!  :o

Man, I am loathe to jinx this, as I had such horrible luck, but, if we're talking lemon,

my 3rd Extech seems to be performing brilliantly, equally well in liquids, curds/whey slurry, or finished wheel.

-He says sheepishly, begging the H+ ion gods not to curse him for his turophilic hubris.  A)
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Offline linuxboy

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Re: pH Meters & Dairy - Measuring, Calibration, & Maintenance
« Reply #6 on: April 26, 2011, 05:37:26 PM »
Yoav, if you're experiencing oddity, condition your meter, and if it still doesn't work, send it back.

To condition

- First remove oil. Do this by washing with regular detergent. Soapy water
- Second, remove protein. Do this either by soaking in 1% pepsin/rennin with HCl added (.1 M... about 2 pH) to activate it; or if you don't have pepsin/rennin, use those enzymatic contact lens cleaner solutions like Renu. They work just as well and are really cheap.
- Third, remove salts. Do this by soaking in an acid solution. Something like .1 HCl, or even vinegar, or citric acid.
- Fourth, unplug everything. Do this by soaking the end of the probe in hot, 80C saturated KCl solution (3-4 M concentration)

The big one is protein and KCl. If you do that and it's still wonky, not too much more you can do. except refill the reference solution, and/or replace the junction.
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Re: pH Meters & Dairy - Measuring, Calibration, & Maintenance
« Reply #7 on: April 26, 2011, 06:55:42 PM »
if we're talking lemon,

my 3rd Extech seems to be performing brilliantly, equally well in liquids, curds/whey slurry, or finished wheel.

-He says sheepishly, begging the H+ ion gods not to curse him for his turophilic hubris.  A)
Now you are challenging forces just beyond your grasp. If you're not careful, they may set the clock on your camera to the correct date.  ;)

I have reached an agreement with my ExStik. It only comes into view at certain moments when I am sure it won't screw up my cheese. I have substituted incense and chants to make it somewhat successfully through a make. I have confidence that guided me last Friday with my Goutaler.

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Offline iratherfly

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Re: pH Meters & Dairy - Measuring, Calibration, & Maintenance
« Reply #8 on: April 26, 2011, 09:44:36 PM »
Linuxboy - I am afraid these instructions and most of the acronyms are beyond my understanding.  That's part of the problem of using pH meters in my opinion; it is easier to pre-flight check a Cessna 206 and trust your life to that hunk of junk in the sky than it is to condition this thing and trust it will work.  The Extech 100 may be easier to use because the probe is flat and wont poke holes in cheese (and easier to clean). It's a bit more modern. 

I don't think my unit is a lemon. What I describe is my experience with every pH meter I've ever used.  How do you use yours? Do you just put in pH solution, turn a screw to the right number, rinse and do again in the other pH solution and then you rinse and ready to go? In a perfect word this should work but this seems to never work that well. (I never understood why you need to use that screw. It's a computer; why not just tell it you are looking for the number 7.00???)

Boofer - I hear you.  I practice looking, feeling and smelling the curd. There is 7,000 year track record for doing that before pH meters came along. It would be great if this was something I can use as a reference for my commercial recipes and to replicate success and track problems, but realistically when you have a meter that shows your 7.00 pH solution as 7.00 one minute and 2 minutes later it thinks it's 6.7ph - it obviously cannot be trusted to tell you if your cheese is 5.2pH or 5.5pH.

My meter by the way is a heavy duty portable lab model.  Does anyone here have a pH meter they actually trust and can be calibrated in less than 2 minutes and keep calibrated for more than 60 minutes?  Am I asking too much?

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Re: pH Meters & Dairy - Measuring, Calibration, & Maintenance
« Reply #9 on: April 26, 2011, 09:57:24 PM »

Now you are challenging forces just beyond your grasp. If you're not careful, they may set the clock on your camera to the correct date.  ;)

Hahah...OK, OK, I promise I'll uh, remember to change...uh....what was I supposed to change again?  ;D

I have reached an agreement with my ExStik. It only comes into view at certain moments when I am sure it won't screw up my cheese.

I have substituted incense and chants to make it somewhat successfully through a make. I have confidence that guided me last Friday with my Goutaler.

-Boofer-

Boof, was that a clockwise incantation, or counterclockwise?  And a white, or black athame?  Just curious, cuz' crying seemed to work well for me with this third demon, but I could use a backup, for sure.   8)
- Paul


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Offline linuxboy

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Re: pH Meters & Dairy - Measuring, Calibration, & Maintenance
« Reply #10 on: April 26, 2011, 10:07:16 PM »
Quote
Linuxboy - I am afraid these instructions and most of the acronyms are beyond my understanding. 
Oh. Well HCl is hydrochloric acid. KCl is potassium chloride. Molarity you don't have to worry about, I included it here only for reference. The rest I thought was straightforward? Rennin is about the same as rennet. You can buy all these products prepackaged. Hanna sells all of them, for example, if you want to spend the money.

Not sure what's not clear about first washing with soapy water to remove oil, the soaking in Renu contact lens solution to remove protein, then soaking in vinegar to remove salts, and finally heating some water, dumping in potassium chloride until no more will dissolve, putting the meter in there and letting the water cool down?
Quote
I don't think my unit is a lemon. What I describe is my experience with every pH meter I've ever used.  How do you use yours? Do you just put in pH solution, turn a screw to the right number, rinse and do again in the other pH solution and then you rinse and ready to go?

Yes, except screw? You mean calibrate? Often, I don't even calibrate because my probes keep their calibration. But, I do take good care of the probes using the details specified for cleaning and maintenance.
Quote
My meter by the way is a heavy duty portable lab model.

Do you take care of the probe?
Quote
  Does anyone here have a pH meter they actually trust and can be calibrated in less than 2 minutes and keep calibrated for more than 60 minutes?  Am I asking too much?
All of mine do that.
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Offline Nitai

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Re: pH Meters & Dairy - Measuring, Calibration, & Maintenance
« Reply #11 on: April 26, 2011, 10:12:54 PM »
I have an extech110 and it works quite well. After 3 months unused it registered PH7 solution at 6.9, and steadily. In the course of a cheese make I usually break it out, was gently with soap, dry, leave to sit cleaning solution, rinse, dry and use. If I calibrate I do it before use. Afterwards I wash with soap, dry, and cap it again. I know I am not up to Linuxboy standards, but so far my ignorance has been blissful.


Offline linuxboy

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Re: pH Meters & Dairy - Measuring, Calibration, & Maintenance
« Reply #12 on: April 26, 2011, 10:28:39 PM »
I don't do all those every make. It's an approach for each issue. If you have protein buildup, use an enzyme. If there's fat stuck, clean with detergent. If you left it sitting out and the junction dried up, soak in some KCl. If your reference liquid is fouled up, then replace the reference liquid. In cheesemaking, though, the biggest thing I tend to find is protein. Every so often, I'll need to let it sit and let the enzymes do their work.
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Offline dthelmers

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Re: pH Meters & Dairy - Measuring, Calibration, & Maintenance
« Reply #13 on: April 27, 2011, 08:32:12 AM »
I have an Extech 110, and I'm quite happy with it. I calibrate it in 4.0 and 7.0 buffer before each make. I find that the reading flashes all over the place until it adjusts to the temperature, then it gives a stable reading. I keep it standing in water about the same temperature as the milk so that I can get a quicker reading because of this. I make sure that the cap is wet before storing, and I always store it upright. On cheeses that I've made a number of times I can go by sensory input, but if it's a new style or one I haven't done repeatedly the meter is my good friend.
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Re: pH Meters & Dairy - Measuring, Calibration, & Maintenance
« Reply #14 on: April 27, 2011, 08:46:24 AM »
I seem to be developing an understanding of how to utilize my ExStik 100. It calibrates fine in the reference solutions. It seems to display a reasonable reading most of the time.

The problem is that I could take a reading during ripening, wait for a period of time, and take another reading. This latest reading may be significantly higher than the previous one, which makes no sense because I expect for the reading to be dropping...not climbing. A subsequent reading a short time later may then come back to where I would expect, showing lower...reasonable because the acidity is increasing. This has happened on several makes. I have come to expect that anomaly and I try to adjust around it.

Other readings seem reasonable: at rennet time, wash time, before the pressing, after the pressing. Those do make the meter useful and offer some confidence. Following guidance (probably Iratherfly's and linuxboy's) here on the forum, I am trying to develop a sense for the milk, curds, and cheese and everything that affects them. The meter is a tool to assist me along the way, but it is not a crutch. I do not rely solely on it to tell me what the make is doing.

Iratherfly, as far as I know, on the ExStik there is no user adjustment. It either works or it doesn't. Linuxboy's directions on proper electrode maintenance should be recorded somewhere in the forum as a reference for future meter diagnostics. Very clear.

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