Can't say without seeing the recipe or at least knowing the ratio of vinegar to solids, other low acid ingredients used, and if there is any dilution of the vinegar called for in it.

The tested and approved recipe for it calls for straight vinegar so they would pose no problems using it.

http://nchfp.uga.edu/how/can_06/green_tomato_relish.html

Dave

Well, my question was more general, such as, when tomatoes start to ripen, do they become significantly less acidic? But here is the recipe, and it does call for straight vinegar.

GREEN TOMATO RELISH

Courtesy of Best of Bridge Home Preserving:120 Recipes for Canning Fruits & Vegetables

7 1/2 pounds green tomatoes, thinly sliced

5 green bell peppers, quartered, seeded, and sliced

4 red bell peppers, quartered, seeded, and sliced

4 large onions, halved and sliced

1 cup pickling or canning salt

6 cups granulated sugar

2 tablespoons pickling spice

1 tablespoon ground turmeric

1 teaspoon ground cinnamon

1 teaspoon ground cloves

4 cups white vinegar

1. In a large bowl, combine tomatoes, green peppers, red peppers, onions, and salt. Cover and let stand at a cool room temperature overnight.

2. In a colander lined with cheesecloth, working in batches, drain vegetables and rinse well. Drain again and squeeze out excess liquid. Set aside in the colander to continue draining.

3. In a large pot, combine drained vegetables, sugar, pickling spice, turmeric, cinnamon, cloves, and vinegar. Bring to a boil over medium heat, stirring often. Reduce heat and simmer gently, stirring often, for about 30 minutes or until onions are translucent and relish is slightly thickened.

4. Ladle hot relish into sterilized jars to within 1/2 inch of rim. Remove any air pockets and adjust headspace, if necessary, by adding hot relish; wipe rims. Apply prepared lids and rings, tighten rings just until fingertip-tight. Process jars in a boiling water canner for 15 minutes. Turn off canner and remove lid. Let jars stand in water for 5 minutes. Transfer jars to a towel-lined surface and let rest at room temperature until cooled. Check seals; refrigerate any unsealed jars for up to 3 weeks.

*Notes: Makes about 10 pint jars of relish. All 10 jars may not fit in your canner at once. Only fill and seal as many jars as fit in your canner and keep the remaining relish hot. Once the first batch is almost finished processing, fill the remaining jars with the remaining hot relish.

This relish makes a nice accompaniment to a grilled cheese sandwich or a savory meat pie, or a delicious spread for a turkey or chicken sandwich.

Yes, as they start to ripen they become less acidic. How significant that variation in pH is depends on the variety, the soil pH they were grown in, the degree of ripening, and the pH of the water they have absorbed. Since most city and suburban water is a pH of 7+ then the difference in the fruit can be very significant.

So how well the recipe can cope with that additional higher pH is the issue.

The approved and tested recipe calls specifically for "hard, green" tomatoes and the same amount of vinegar as in her recipe. So if she uses partially ripe fruit, in theory, she would need more added acid.

Personally, I have used some with some color when making it as long as the majority are still hard green. But I also increase the amount of vinegar to 5 cups so that the brine is more acidic and the mixture isn't as dry, is more soupy. Then I just slightly drain it after opening the jar.

Hope that helps.

Dave

I'd be more inclined to just add a quarter teaspoon of citric acid to each pint jar instead of upping the vinegar. Less chance of changing the flavor that way. But having more liquid in the jars makes sense as well.

Rodney