pH Meters and Test Strips

[Chris Hennes]

I'm considering buying an electronic pH meter: does anyone have one they can recommend? There are lots of them available at Amazon.com, in particular the HM Digital PH-200 Waterproof pH Meter seems promising for use in the kitchen.

I've been making a lot of dry-cured salami recently, so on my last order from Butcher and Packer I picked up a roll of low-range pH test strips. These are the kind where you make a slurry of a test sample of the sausage and dip the strip in: the strip changes, color and you match it up to the color on the little card that comes with the kit. The problem I am having is that a) the gradations on the test card are too large and too subtle (the upper range is a color swatch at 4.8 and then one at 5.2, and they both look pretty similar when it comes to comparing the little strips), and b) the appropriate pH of 4.9 (according to Ruhlman) is perilously close to maxing out the upper range of these strips, since it will appear to be somewhere between the last two color swatches.

[dougal]

I'm considering buying an electronic pH meter: does anyone have one they can recommend? There are lots of them available at Amazon.com, in particular the HM Digital PH-200 Waterproof pH Meter seems promising for use in the kitchen.

I've been making a lot of dry-cured salami recently, so on my last order from Butcher and Packer I picked up a roll of low-range pH test strips. These are the kind where you make a slurry of a test sample of the sausage and dip the strip in: the strip changes, color and you match it up to the color on the little card that comes with the kit. The problem I am having is that a) the gradations on the test card are too large and too subtle (the upper range is a color swatch at 4.8 and then one at 5.2, and they both look pretty similar when it comes to comparing the little strips), and b) the appropriate pH of 4.9 (according to Ruhlman) is perilously close to maxing out the upper range of these strips, since it will appear to be somewhere between the last two color swatches.

Chris, my understanding of pH meters is that they require constant recalibration and their sensor lifetime can be harmed by, for example, 'muck' in the sample. If you want to use it on a food slurry (without filtering), I'd suggest checking with the manufacturers for their ideas as to suitability. Mostly, these things are intended for testing "water" rather than slurry. Sadly, the manufacturers don't seem to have posted the manual online for the product you linked, so I'm afraid you'd have to ask them. You might also care to check the availability and cost of spares.

Colours on test strips - the colour of the light you are using to look at the strip can matter greatly when matching. Use daylight to be sure.

pH range - the pH scale is fearfully sensitive in this sort of range (which leads to the calibration problem, etc). The important thing is that you are somewhere in the right range. I believe that means below about 5.5 for C bot protection - and pretty much as low (sour) as you care to go. For example http://www.informaworld.com/smpp/content~db=all~content=a713631816 (note btw the reference to 'protective cultures' - acidifying bacteria!) For a commercial production (QC) test that a product was within the acceptable sourness range, specifying something like 4.7 ± 0.1 might be appropriate. At home, trying new recipes, your endpoint pHs will tend to be variable. I'm going to presume that what you are after is a sanity and safety check that it HAS acidified adequately - so anywhere less than wooo about 5.2 (perhaps) should be happily safe. I think that's about all the info you should really NEED for safety.

Hence, I'm not sure that the range on the strips that you have is best suited for what you are wanting to do.

[Chris Hennes]

First, regarding the meters: you're right, the one I link to above (and most of those available on Amazon.com) turn out to be intended for measuring the pH of liquids: a meat slurry is not quite liquid, so I'm sure I'd be wearing through the sensor much faster than the manufacturers intended. Plus, making the slurry is annoying. So I've switched modes to looking at sensors designed to test the pH of soils. For example, the FieldScout SoilStik pH Meter looks promising. From the writeup:

[...] the SoilStik pH Meter’s flat surface electrode measures pH in soils, semi-solids, solids and liquids. No more electrode breakage or clogged junctions. An indicator tells you when it’s time to replace your electrode and when to re-calibrate the meter - which eliminates guesswork.

I think this sounds like a promising route, though the price is getting a bit high. Also, as you note, calibration is important, and needs to be done relatively frequently: there are kits available to help with this, but of course they will increase the total cost of ownership.

My first concern with the pH is safety: as I make more and more dry-cured salami and branch out into different strains of bacteria, and as I shared them with more and more people, I want to make sure I'm not going to give anyone botulism. So on that count, getting the pH down into the vicinity of 5 is important, and I'd really like to be able to measure this with some degree of confidence. Is it worth the $150 that sensor I link to above costs? I don't know. But I only have high-range and low-range test strips: nothing that really allows me to confidently distinguish between a pH of 4.5 and a pH of 5.5.

Beyond just safety, the engineer in me simply wants to know the number and record it in my notebook .

[dougal]

Chris, I fear the engineer in you just wants another meter!

Have a look instead for something like these http://www.indigo.com/Test-Strips/gph-test-strips/ph-paper-4-7.html

Narrow pH range 4.0-7.0; resolution is 0.5 pH unit

...

$7,25 for 50 strips

[Chris Hennes]

Of course I want another meter, digital readouts are far more high-tech-looking than little paper strips! Next I'll be looking for a data logger so I can make plots of pH versus time... and then comes the PowerPoint!

Alright, alright, I'll order up some of these strips and give them a go... thanks for the assist.

[Doodad]

Having worked haz waste and geology at one time, I would definitely not recommend the meter for something this mundane. pH meters were my absolute least favorite of all our electronics. Constant calibration with solutions, getting crusted up from accumulating salts, bad sensors. Bah. I used strips on all my beer brewing.