“We are in the middle of our harvest (very good, thank you!) and we are canning tomatoes. My wife is concerned that the persimmon tomatoes may not have sufficient acid for canning (being that they are a yellow type). Can you advised us on the acid content of a persimmon compared to a red variety? Thank you, B.”
As is one of my favorite things to do on this blog, it is time to dispel yet another myth often found in the horticultural world.
Scenario: Your granny (or other character as appropriate to your life) cannot eat red tomatoes because of the acid. She tries yellow tomatoes and -VOILA!- problem solved.
Myth: Yellow tomatoes have less acid than red tomatoes.
Truth: Yellow and Red Tomatoes all have the same range of pH (generally, 4.8 or below. Remember that lower pH = more acidic). Some of the problems are that it’s “all in Granny’s head” and also that sugars are able to better stablize the usual stomach acid problems.
So why is it that you can eat yellow tomatoes with no problems? It has to do with a couple different things:
1. The sugar content is “higher” in yellow tomatoes. This is for the same reason why Cucurbita moschata is the squash to use for pumpkin pies: regular sugar crystallization. At the microscopic level, the sugar crystal are fine-grained and evenly spread throughout the tissues. While mg for mg you may have the same amount of sugar in both yellow and red tomatoes, the receptors on your tongue react more quickly to fine-grained sugar and trigger the thought, “this yellow tomato is sweeter” in your head. They also work faster in your stomach to quell the usual acid problems experienced by eating tomatoes.
2. Beta Carotene vs. Lycopene. Depending on the yellow/gold tone density of your tomato, darker=more Beta Carotene. In food science studies on tomatoes at a number of different universities, it has been found that foods with a lighter yellow pigmentation scored higher in sweetness than those that were darker or red. The crazy thing is: both had the same sugar content. Color plays a large role in our mental perception of the flavor.
As for canning, you should have no problems canning yellow tomatoes or any other odd color: pink, white, brown, black, etc. Researchers at the USDA have found that most types of ripe, cooked tomatoes have a pH below 4.6. The only thing I recommend is to safely can them in a boiling water bath or pressure canner based on the guidelines for low acid vegetables. For the most accurate information for your particular area, it is best to check with your local home economist agent (usually at the courthouse or other related state or county extension program). He or she will be able to give you the proper processing times and pressures needed to do things safely… and if you have a dial pressure canner, you can have it in for it’s annual calibration too!
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