Citric acid can be good to have when you're short on lemons.
Lemons are expensive, so here is a good way to save: Keep citric acid in your pantry. This compound, the primary acid in citrus, can be used as a substitute for lemon juice in applications where complex lemon flavor isn't necessary, only brightness or acidity. Citric acid is sold in powder form as “sour salt” in natural foods stores and many grocery stores; look for it in the spice aisle. (Note: Citric acid shouldn't be confused with “crystallized lemon juice” products that contain citric acid plus other ingredients.) Here are some ways that citric acid can come in handy.
In recipes where lemon juice mainly provides an acidic punch, from pan sauces to risotto to hummus, substitute ⅛ teaspoon of citric acid dissolved in 1 tablespoon of water for every tablespoon of lemon juice needed. Do not use this substitute in recipes calling for zest, since citric acid has none of its aromatic complexity.
Use ½ teaspoon of citric acid to replace every ¼ cup of lemon juice in recipes for fresh cheeses such as ricotta or mozzarella, which need an acid to coagulate the milk proteins.
Mix in ⅛ teaspoon of citric acid for every 3 cups of water needed to create acidulated water for soaking produce such as apples and celery root.
Boost the acidity of low-acid juices with citric acid to use them in place of lemon juice in recipes where acidity is essential to flavor and/or texture (such as ceviche, posset, cocktails, or lemonade). Add 2 teaspoons of citric acid to every cup of grapefruit juice and 2½ teaspoons to every cup of orange or pineapple juice.