pH analysis

[spud]

If I want to check for pH of food, which is in solid stage. Can I just simply grind and blend them with distilled water before testing with a pH meter? Does the ratio of product to water make a difference in pH reading?
Thanks..

[robin]

Hi spud,

Yes, the ratio of product to water does make a difference. Dilution by a factor of 10 changes pH by 1 unit.

For example, if you had 100 ml of acid with a pH of 4 and you diluted it with water until the volume was 1000 ml, the pH of the diluted acid would be 5.

So just ensure you don't drown your samples with water and you should be okay.

[spud]

Thanks so much. Good to know that. So, I think I'm going to add just enough water to liquify it so that it can be tested with the pH probe. One more question, should I be using a standard 7 pH buffer solution or DI water to best represent the pH of the product?

[robin]

The buffer solution's job is to maintain a constant pH. You want to measure an actual pH, so use DI water.

[spud]

Sound good. pH of DI water is 5.20. If I use a ratio of 100:25 of product to DI water and have a pH of 5.38. Would I calculate the ratio of DI water I use and say the product itself has a pH of 5.425? Sorry for so many questions. I have no idea how to measure product pH when it's not in liquid form. Thanks again.

[robin]

I don't know how precise you're expected to be in your measurements. If it was me, I'd just add the least amount of water I could, measure the pH and accept that as the answer. I'd only try to do the fine adjustments you're talking about if I'd been told I really had to.

[spud]

Make perfect sense. Will discuss that with my peer. Thanks so much for taking time to respond.

[robin]

Glad to help.

[KathChem82]

hi spud. If the pH of the DI is like that, then it would already affect the pH of your food. Try dealing with distilled water. or maybe CO2-free water (by boiling so much and covering container with no air space). As much as possible, we want to limit the [H+] and [OH]- contribution from water. Keeping it at pH=7 or very close to that is the trick. But using a buffer is definitely not a good idea. :-)

[eri]

hi...please can u help me with some materials for the technology of the production of mayonaisse...because it is needed for my job...i know i am out of disscusion but if you have the possibility please help me....