if you use juices, there is one but not sure if this exactly what you are looking for but this is what I use.
https://www.sheltondentistry.com/patient-information/ph-values-common-drinks/
On this study you can see the standard deviation was 0.01. Which means the results were consistant.
Product reviews on Amazon - Personally I trust them about as much as the car salesman at the local New Car lot. (That's a shade better than the Used car salesperson.) If you really read through reviews you are going to find reviews of totally different products, reviews by people with a hostile attitude and a variety of reasons you really have be pretty skeptical about them overall.
The way I evaluate product reviews is 1) How many reviewers (More than 50, More than 500, more than a thousand? More reviews provides a broader spectrum of purchasers - IF there an a bunch of unrelated reviews. 2) What percentage of reviews are 1 star and 2 star? Obviously if they are about the right product than anything over 10% -15% One or Two stars and there is likely to be a cause for concern. 3 This is the biggee for me - A consistent complaint. Screen fails, power button stops working or as you mentioned a bunch of claims of inaccurate readings.
So it still comes down to a leap of faith and recommendations by other users on forums like this. I try to keep in mind how complex an item is to use and in this case what does it take to calibrate the tool. My very first pH meter is still my favorite design. I had to manually turn a screw on it to set the reading to match the buffer I put it in. Auto calibration is fine but again if you don't follow the directions EXACTLY each time than results can get screwed up.
Finally how accurate does it really have to be. Do we need to worry about a difference of .05 or less? All the guidance I've seen gives recommended pH ranges in tenths not hundreths so if one meter says 3.41 and another says 3.47. Yeah I'll recheck but really that's in the ball park where I need to be. 3.4 vs 3.6 no, that's a fail.
Finally how accurate does it really have to be. Do we need to worry about a difference of .05 or less? All the guidance I've seen gives recommended pH ranges in tenths not hundreths so if one meter says 3.41 and another says 3.47. Yeah I'll recheck but really that's in the ball park where I need to be. 3.4 vs 3.6 no, that's a fail.
* in the ideal world wine would be formulated with a stable pH around 2.4 like sodas, this provides a high level of preservative action. We have two problems which prevent ideal, 1) yeast don’t like to live below pH 3.0 and if they produce CO2 which drops the pH anything under 3.1 risks creating a stuck fermentation. 2) the crops as grape frequently have higher pH as white grape 3.4 or red grape 3.6 , , , which actually works better since the grape skin has natural antioxidants that reduce the need for adding chemicals.. . Some ideal ph values for wine are around 3.3
. . Kind of like you dont have to reinvent the wheel. . . if you do the math. to get blended ph of 3.3 you will need 24% of passion juice and 76% of mango.
I don't think that's recreating the wheel but again this could be semantics.your logic is good if you only look at synthetic clean chemical systems
* in the ideal world wine would be formulated with a stable pH around 2.4 like sodas, this provides a high level of preservative action. We have two problems which prevent ideal, 1) yeast don’t like to live below pH 3.0 and if they produce CO2 which drops the pH anything under 3.1 risks creating a stuck fermentation. 2) the crops as grape frequently have higher pH as white grape 3.4 or red grape 3.6 , , , which actually works better since the grape skin has natural antioxidants that reduce the need for adding chemicals.
* It is not as simple as one gram plus three grams average to two grams of pH, ,,,, yes industry frequently reinvents the wheel. The buffering capacity/ type of acid will vary from fruit to fruit. If literature for mango said it should have between 0.34 to 0.84 grams of citric (mostly) acid per 100 grams and my 2019 mango actually tested at 0.28 gram acid per 100 ml of juice I will need to add two or three times as much mango to contribute grams of buffering capacity to push the pH up or acid to push the pH down. Another variable is does the fruit contain a di-proton acid like malic or a triprotic acid like citric or mono proton acid like lactic. A term to look at is the “sugar free dry extract” and then ask what the chemical soup (buffering) is inside that extract. ,,,, a partial translation is that if the sugar/ ripeness (yeast fermentable) increases then the percentage of acid per ml goes down.
On the product development bench we will add citric acid as a fudge on the label to guarantee that we accomplish the micro or chemical rule which food and drug require us to follow.
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