pH Meter, Extech Brand - Random pH Readings

[george13]

When I first turn on the unit, it seems to be randomly moving around the ph scale.  Should I wait for the movement to stop before I take a reading.  Also, it appears that whenever I stabilize on a ph reading, the second decimal place number keeps moving (usualy lower) should I wait for it to stop completely and then register the reading.  It just seems that I can sit there for over two minutes and it still is adjusting. Is this normal?

[linuxboy]

Brand new unit or used?  With pH, you should not be targetting absolutes, but rather changes in pH as compared to time. So for example, pre-rennet, you're looking for a .1-.15 drop with normal milk. And then pre-mold, you're looking for a drop that corresponds with the calcium retention target of the cheese type. If it doesn't completely stabilize, could be indicative of an issue with the meter, such as fouling.

I would go through a clean and recalibrate cycle, like the one I have posted here before (for example, https://cheeseforum.org/forum/index.php/topic,6917.msg49656.html#msg49656) , and then see if it stabilizes faster. If it doesn't, still, meter may be defective.

[george13]

Thanks, I will apply your recomendations and hope I can stabilize the eratic readings.

[rev.cheesy]

Is there a chart with the pH levels one should be trying to hit for different cheeses throughout the process?

I have only been cheesemaking for about a year, we have had some good batches, and some not as good using the 200 easy cheese recipes book.  I am wanting to improve the final product.

[dthelmers]

George13,
Is the meter perhaps adjusting to the temperature? I found the same thing happening with mine: there was movement on the second decimal place, and it keeps moving until the correct temperature is reached - watch the temperature section. I've gotten around that by standing it in water around the same temperature as my curd until I'm ready to take the reading, so the temperature doesn't take so long to stabilize. I first calibrate the meter, then stand it in a measuring cup of hot water, about the same temp as what I want to measure. Then when I take a reading it seems to stabilize quickly.

[linuxboy]

Is there a chart with the pH levels one should be trying to hit for different cheeses throughout the process?

No, this only exists in the minds of various people right now. No literature except a few internal materials at INRA and other French cheese resources even attempt to cover the calcium/pH equilibrium with levels. And all of those are in French. Ask for a cheese you're making if you can't find the answer and we'll help.

I am wanting to improve the final product.

Post your core perceived faults and we'll explain causes and resolutions.

Is the meter perhaps adjusting to the temperature?

Yes, this is also a common cause of drift.

[george13]

Dave,  you are absolutely correct in your process, I played around with it, and I too realized that the adjustment period if too great, the results were questionable.  Now I calibrate to 7 just before use, and at times I remove 1/2  cup of whey just before I take a reading so as to stabilize to a near proximity.  All in all it's a decent little meter for what we do.
Regards,
George

[Tomer1]

You need patience,it can take up to a minute to finally stabilize. its mainly the temp correction system responsible for the shifting so keeping the meter in warm water close to your make temp is a good advice.
I try not to keep it in whey to reduce deposits on the electrode.