I have steadfastly refused to discard any starter. If my starter goes too sour, I add 1/2 teaspoon of baking soda and a little water, mixing well with a plastic chopstick. The chemical reaction will calm down in about 5 minutes, at which time I taste it. Depending on how acetic it is, I add a little more baking soda and retest. This way, I have no waste at all and the yeast quickly perks up. Then I use some, or add more flour and water and return it to the fridge.

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