Acidity in food imparts a sour (tart) taste on the tongue that is one of the four basic flavors. The most common forms are citrus juice, vinegar, wine and tomatoes. Acidic ingredients (yogurt and buttermilk included) also affect the texture, color and shelf life of foods. A bit of acid can make a pie crust more tender, stabilize whipped egg whites, and bring a shine to copper cookware.
For each quart (4 cups) of cold water, add 4 tablespoons lemon juice. Or add a different acidic ingredient, such as 2 teaspoons vinegar or 1/2 cup of white wine.
Toss the cut food with lemon juice or vinegar. This method will keep cut apples, potatoes, bananas and other low-acid foods from turning brown. Or place the cut food in acidulated water until needed.
A bit of citrus juice or vinegar enhances the flavors of fruits, vegetables, poultry and seafood by complementing natural sweetness. To decrease acidity, add a sweet ingredient such as sugar, honey or syrup. Start with a ration of 1 part sweetener to 3 parts acidic ingredient. Increase the ratio as desired. Equal amounts give a pleasant sweet and sour flavor.