Can temperature affect pH reading?

Hi all, 

Lately our finished product which is ice pH reading lower than stipulated standards, lab operator was saying this is due to pH checking not done at room temperature? Wondering how true is it?   

Hi Carine,

I hadn't heard of this being the case but a little Googling suggets your lab operative may be right:

https://www.preclabo...ph-test-strips/

https://www.westlab....ature-affect-ph

Yes, it can definitely be affected by temperature - having more (or less) thermal energy in the system will potentially affect the concentration of H+ ions, and this is effectively what pH is measuring.

It's often overlooked, but to be useful a pH tolerance and method should really reference the temperature at which the measurement is made.

We had this issue: temperature fluctuated in cooled and room temp products. Here's the lab scientist's explanation:

pH is defined as being at room temperature.  Higher or lower temperatures vary the pH by a small percent either way.  See the chart attached.

We had this issue: temperature fluctuated in cooled and room temp products. Here's the lab scientist's explanation:

pH is defined as being at room temperature.  Higher or lower temperatures vary the pH by a small percent either way.  See the chart attached.

My apologies: not temperature fluctuated, the pH.

It's true, have been in more ice manufacturers than I can count and the testing method is what your lab person is saying.

It's true, have been in more ice manufacturers than I can count and the testing method is what your lab person is saying.

IN that case, what are the solution for this since u have many experience in ice manufacturing. This made me cracking my head, because our ingredient is pure water and doesn't add in anything into process till it form ice, so maintaining the pH abit difficult to us.  

If you always take the pH reading at the same temperature, it should be pretty consistent

If you're using a probe, some of them compensate for temperature, it just takes a while for them to equalize.

https://support.hach...ph-measurement?

IN that case, what are the solution for this since u have many experience in ice manufacturing. This made me cracking my head, because our ingredient is pure water and doesn't add in anything into process till it form ice, so maintaining the pH abit difficult to us.  

If you're having issues hitting your pH range then I'd start by looking at your historical data to assess what the actual range of your water source is. Whilst some potable sources are relatively consistent, some are inherently somewhat variable. If there is a large natural variation then it's possibly also worth considering what may cause this, as whilst natural variation is not a problem, you do need to be able to be sure that this is indeed natural and not some sort of other factor that could affect the potability of the supply. If you're using a mains/municipal supply then the authority from whom you source the water will almost certainly be able to provide summary data from their own monitoring, which will be a useful guide/starting point.

Does pH matter in the product? i.e. what is the consequence of it being out of spec? If it's just a guide to reflect the expected range of the raw material then you should be able to align the two based on the nature of that raw material.

Otherwise, making ice with a pH range that is different to the water from which it's made sounds very much like a situation that will create unnecessary challenges!

Yes.  Is there anything in the ice by chance?  Or just water?  If you have other things, additives, flavors, etc you can get different pH readings due uneven distribution and the measurement only able to test the surface.

If it isn't an issue I'd melt the ice before testing.  It will give you a more repeatable and representative pH.  Make sure to use an probe with ATC compensation.

I attended a Mettler-Toledo webinar about pH mesurament yesterday. pH depends on the temperature of your sample and they said that the pH must always be accompanied of the temperature at what you did the analyse. They also said that you don't "compensate", the device is giving you the pH at that particular temperature (I thought that the pHmeter compensates temperature, I was wrong). So the best thing to compere pH values of a product is to analyse always at the same temperature. 

Dear pHruit, 

In our country raw water and ice shared same standard under the food act, in other words, pH for raw water n ice will be the same which is 6,5-8.5  . To me not a big deal if pH of the product out of spec, but  from local authorities view , our finished product is not comply to the law, and we have to take corrective action on this. 

If you're having issues hitting your pH range then I'd start by looking at your historical data to assess what the actual range of your water source is. Whilst some potable sources are relatively consistent, some are inherently somewhat variable. If there is a large natural variation then it's possibly also worth considering what may cause this, as whilst natural variation is not a problem, you do need to be able to be sure that this is indeed natural and not some sort of other factor that could affect the potability of the supply. If you're using a mains/municipal supply then the authority from whom you source the water will almost certainly be able to provide summary data from their own monitoring, which will be a useful guide/starting point.

 

Does pH matter in the product? i.e. what is the consequence of it being out of spec? If it's just a guide to reflect the expected range of the raw material then you should be able to align the two based on the nature of that raw material.

Otherwise, making ice with a pH range that is different to the water from which it's made sounds very much like a situation that will create unnecessary challenges!

Thanks for the info 

I attended a Mettler-Toledo webinar about pH mesurament yesterday. pH depends on the temperature of your sample and they said that the pH must always be accompanied of the temperature at what you did the analyse. They also said that you don't "compensate", the device is giving you the pH at that particular temperature (I thought that the pHmeter compensates temperature, I was wrong). So the best thing to compere pH values of a product is to analyse always at the same temperature. 

No, just water itself, nothing was added. 

Yes.  Is there anything in the ice by chance?  Or just water?  If you have other things, additives, flavors, etc you can get different pH readings due uneven distribution and the measurement only able to test the surface.

 

If it isn't an issue I'd melt the ice before testing.  It will give you a more repeatable and representative pH.  Make sure to use an probe with ATC compensation.

Looks like an old problem being resurrected ?

https://www.ifsqn.co...be-ice-product/

https://www.ifsqn.co...on/#entry152614

I guess they didn't like the answers in December

It sounds like you are monitoring pH to meet a regulatory requirement which states "water" with pH in the range.  Doesn't tell you what state the water has to be in...gas, liquid, solid.  As such, make your life simple and melt the ice before you conduct your testing.  If you can, melt to a consistent temperature so all testing is at that same temperature.

Dear pHruit, 

 

In our country raw water and ice shared same standard under the food act, in other words, pH for raw water n ice will be the same which is 6,5-8.5  . To me not a big deal if pH of the product out of spec, but  from local authorities view , our finished product is not comply to the law, and we have to take corrective action on this. 

So is the water itself coming in at 6.5-8.5 but then once you've frozen it to produce the ice then thawed it to test, it's no longer in this range?
Or is it the case that the water isn't always between 6.5-8.5?

For the former, it suggest there is possibly something else happening to the water during the freezing process - e.g. contamination with an acid/alkali of some sort. Possibly wouldn't need to be significant quantities as the water itself won't have a large buffering effect.

For the latter it suggest the issue is really a raw material one, and you'd really then need to look at your water source in more detail.