you can freeze the soup but you may not be happy with the way they veggies come out when you reheat. they will be mushy. cabbage is really bad to mush up. depends on what veggies you use for soup. you can use about a 1/2 teaspoon of baking soda to 2 quarts soup to take out the acidity. it will foam up for a minute but after that subsides just stir it in.
Don't know about re-freezing, but you can reduce acidity in any tomato based product by adding a touch of granulated sugar.
A little sugar will reduce the acid.I don't know about the soup though. Hope this helps.
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