Alum’s primary culinary use is as a crisping agent for pickles. It is used as a soak, which means that you will have to wash the pickled items before using them. The next most significant culinary use for it is in baking powder. In either case, there are reasons that you may want to find an alternative. There are health concerns with alum in food. While the USDA states that alum is perfectly safe when used correctly, you may feel more comfortable with one of the alternatives. This is especially so if you need it in a hurry since alum is not a common ingredient.
Your best bet: Calcium chloride
When it comes to making pickles crisper, calcium chloride is an excellent alternative to alum. It is a calcium salt that acts on the pectin in foods to form calcium pectate and make them crisper. It has a secondary benefit in that it helps to speed up fermentation. It is also easier to use than other crisping agents (no rinsing necessary); it is affordable; a tiny amount goes a long way.
The most significant difference between calcium chloride pickles and alum pickles is the taste. Alum offers a more astringent flavor that many people enjoy. Calcium chloride is quite different because it is very salty and can increase the food’s saltiness without sodium.
A decent second choice: Calcium hydroxide
Calcium hydroxide is the classic option for firming up pickles. Calcium hydroxide is otherwise known as lime and is a traditional additive for pickles made in the Southern US; in particular, cucumber and green tomato pickles.
Like calcium chloride, it reacts with the pectin in the fruits and vegetables to form calcium pectate and keeps them firm like alum. As with alum, you should thoroughly rinse your fruits and vegetables after using calcium hydroxide. It is recommended that you soak and then rinse them three times with both crisping agents.
Note that calcium hydroxide will raise your pickles’ pH, which means that it will make them less acidic. The loss of acidity means that you may not want to use it for all types of pickles if you want tart notes. Another area of concern is botulism. Lower acidity makes the environment more hospitable to botulinum bacteria.
In a pinch: Cream of tartar
If you are trying to replace alum in homemade baking powder, you can try using cream of tartar. Cream of tartar has been in use for longer than alum powder when it comes to being utilized for its leavening effects. It is acidic like alum, which means that it will deliver the impact that you want by reacting with the baking soda to produce gas. It is this gas that causes batters with baking powder to rise.
It is also a good idea to add a filler like corn starch or rice flour to help absorb moisture if you plan on storing your baking powder.
If you are looking for a completely herbal alternative to alum, certain plants’ leaves are an effective option. The leaves commonly used as crisping agents include oak leaves, grape leaves, and sour cherry leaves. The active ingredient in them is tannin, the same compound that is found in tea leaves. Tannin has the same effects on pickled fruits and vegetables as alum. Place the leaves at the bottom of your crock before adding the brine and the fruits or vegetables.