Preparing Vegetables Fresh vegetables need to be washed to remove dust, bacteria, and insect spray. Depending on your recipe, you may need to pare, chop, or cook fresh vegetables. Some vegetables, like eggplant and potatoes, darken when they are peeled and sliced. You can prevent browning by heating them, sprinkling them with an acid, such as lemon juice or vinegar, or soaking them in water. Science in the Kitchen Cabbage Colors The pigment that gives red cabbage its color is aff ected by whether the cooking water is acid, base, or neutral. Almost all liquids are either acid or base. Whether the liquid is acid, base, or neutral depends on the type of atoms the liquid contains. Atoms are very small particles that combine to make up matter. Matter is anything that takes up space. Water, people, and sand are examples of matter. An acid has more atoms with a positive electrical charge than pure water. Lemon juice, coff ee, tomatoes, and colas are examples of foods that are acidic. A base has more atoms with a negative charge than pure water. A liquid that is a base also is called alkaline. Adding baking soda to water creates a base solution. Pure water is neutral because it does not contain extra positive or negatively charged ions. Most tap water is either slightly acidic or slightly basic. You can make it more acidic by adding acid, such as orange juice. To make it more basic, stir in baking soda. If you balance the amount of acid and base in the water, the water will be neutral. Scientists use a special type of paper to determine whether a liquid is an acid, base, or neutral. This paper is called litmus paper. It contains a natural dye that turns red when the liquid is acid. It turns blue when a solution is a base. The color does not change if the solution is neutral. Red cabbage naturally contains a dye like the one used to make litmus paper. As a result, red cabbage will change color if the cooking water is acidic or basic. Red cabbage becomes a brighter red when the cooking water is slightly acidic. It turns blue when the water is basic. It remains purple if the cooking water is neutral. The most attractive red cabbage is red or purple. What can you do to prevent it from turning blue? Try this to fi nd out! Finely slice eight leaves of red cabbage. Place the cabbage in a saucepan with one cup of water. Cook it on medium heat for 10 minutes. Let cool. What color is the cabbage? Compare it to the cabbage in the photo. Do you think the cooking liquid was acidic, neutral, or basic? Divide the cooking liquid from the cabbage into three clear glasses. Add ½ teaspoon of lemon juice to the fi rst glass and ½ teaspoon of baking soda to the second glass. Which glass of liquid turned more red? Which turned blue? Why? How can you use this information to be sure the red cabbage you cook looks delicious to eat? Viktor1/Shutterstock.com Acidic Cooking Liquid Basic Cooking Liquid Neutral Cooking Liquid 367 Copyright Goodheart-Willcox Co., Inc. Chapter 15 Versatile Vegetables