Alum Not Needed
In my younger days, pickled cucumbers called for alum to keep the vegetables crisp in home canning recipes. But nowadays, recipes for pickled vegetables do not call for alum. Why is it no longer used? —H.K., Las Cruces, New Mexico
Years ago, it was common to see alum listed in canned pickle recipes. According to the USDA, alum may still safely be used to firm fermented cucumbers, but it does not improve the firmness of quick-process pickles. If you use good-quality ingredients and follow current canning methods, alum is not needed.
If you do use alum, do not use more than 1/4 teaspoon per quart of pickling liquid. Excess will cause bitterness. For up-to-date canning recipes, contact your local county Extension agency.