[kjbnyc]

Using a Milwaukee Instruments food-grade pH meter, I tested the pH of Whole Foods' 365 brand roasted tomatoes, garlic & capers in a jar of vegetable oil. The pH was around 5.6. I was quite surprised considering there was citric acid in it and my understanding is that it wouldn't be considered safe with a pH above 4.6. Is the pH overstated since the pH of vegetable oil cannot be measured?

 

[sgsvirgil]

The pH of vegetable oil can't be measured because vegetable oil doesn't have pH. That means its presence does not effect one way or another the overall pH measurement. In other words, the vegetable oil is not going to raise the pH of the canned tomato product.

However, chances are that the tomato product in question was canned using an industrial version of a pressure canner, which is required for acidic products that have an inherent pH higher than 4.6. Its perfectly safe for tomato products and other inherently acidic ingredients with a pH above 4.6 to be canned as long as they are canned using the pressure method. Otherwise, additional acid has to be added to lower the pH to 4.6 or lower.