What is a tomato's pH level?

Answer 1

Tomato Acidity

Tomatoes are generally considered a high acid food item with a pH below 4.6. Unfortunately, a lot of misinformation has been printed in the popular press about "low acid" tomatoes referring to those with a sweet, non-tart taste. These tomatoes are often white, yellow, or pink in color but are not low in acid content. The higher sugar masks the acidic flavor. Researchers at USDA and at the University of Minnesota have found that most underripe to ripe, cooked tomatoes have a pH below 4.6. Unfortunately, a few varieties may have a pH above or close to 4.6. These include Ace, Ace 55VF, Beefmaster Hybrid, Big Early Hybrid, Big Girl, Big Set, Burpee VF Hybrid, Cal Ace, Delicious, Fireball, Garden State, Royal Chico, and San Marzano. Some of these are grown for commercial purposes and are not found in home gardens. However, safely canning these varieties requires additional acid for water bath processing or a pressure canning process similar to low acid vegetables.

source: University of Minnesota Extension at http://www.extension.umn.edu/distribution/nutrition/DJ1097.html