Sour salt is crystallized citric acid, a weak acid derived from citrus fruits such as lemons and limes. Sour salt is used as a seasoning to add a soft pucker to lemonade, borscht and other recipes. It also is used in canning and helps preserve foods such as apples and pears, which otherwise darken or soften.

Buy a small container of sour salt from your supermarket or spice dealer. Although sour salt is inexpensive and stores well, its flavor is strong and a little goes a long way. Store in a dry place out of direct sunlight along with other herbs and spices.

Substitute sour salt for table salt in recipes if you are on a low-sodium diet. Don't substitute sour salt for table salt at the table, in uncooked dishes or after cooking: Its powerful sour flavor works best cooked into recipes instead of where it can make direct contact with the tongue.

Add a pinch of sour salt to liquid-based recipes that also include sugar or other sweet elements such as lemonade or cold beet borscht. Include the sour salt early in the cooking process to give it time to dissolve thoroughly and disperse throughout the ingredients.

Stir a tiny amount of sour salt in with the sugar before adding sugar to citrus-flavored confections such as lemon cheesecake or lemon custard filling for pies or layer cakes. Sour salt provides a substitute for, or complement for, lemon juice in recipes in which the addition of more lemon juice would disturb the balance between wet and dry ingredients. Add grated lemon zest to enhance the specific lemon flavor because sour salt adds tartness but usually without a well-defined sense of any particular citrus flavor.

Add sour salt to the liquid ingredients used in home canning, including the syrup to be used in canning fruit such as apples or pears, the juice in canned pickles or any liquid tomato product. Add the sour salt to the liquid while cooking or place just a few grains in each jar before sealing and placing in the boiling-water-bath or pressure canner. Sour salt helps preserve the canned food's color but also adds acidity that improves the safety and longevity of home-canned goods and may alter flavor less than vinegar used for the same purpose.