The lemon is the common name for Citrus limon. The reproductive tissue surrounds the seed of the angiosperm lemon tree. The lemon is used for both culinary and nonculinary purposes throughout the world. The fruit is used primarily for its juice, though the pulp and rind (zest) are also used, primarily in cooking and baking. Lemon juice is about 5% (approximately 0.3 mole per liter) citric acid, which gives lemons a tart taste, and a pH of 2 to 3. This makes lemon juice an inexpensive, readily available acid for use in educational science experiments. Because of the tart flavor, many lemon-flavored drinks and candies are available on the market, including lemonade. Lemons are used to make lemonade, and as a garnish for drinks. Many mixed drinks, soft drinks, iced tea, and water are often served with a wedge or slice of lemon in the glass or on the rim. The average lemon contains approximately three tablespoons of juice. Allowing lemons to come to room temperature before squeezing (or heating briefly in a microwave) makes the juice easier to extract. Lemons left unrefrigerated for long periods of time are susceptible to mold. Fish are marinated in lemon juice to neutralize the odor. The acid neutralizes the amines in fish by converting them into nonvolatile ammonium salts. Lemon juice, alone or in combination with other ingredients, is used to marinate meat before cooking: the acid provided by the juice partially hydrolyzes the tough collagen fibers in the meat (tenderizing the meat), though the juice does not have any antibiotic effects. Lemons, alone or with oranges, are used to make marmalade. The grated rind of the lemon, called lemon zest, is used to add flavor to baked goods, puddings, rice and other dishes. Pickled lemons are a Moroccan delicacy. A liqueur called limoncello is made from lemon rind. When lemon juice is sprinkled on certain foods that tend to oxidize and turn brown after being sliced, such as apples, bananas and avocados, the acid acts as a short-term preservative by denaturing the enzymes that cause browning and degradation. Lemon juice and zest are two ingredients in the lemon curd portion of lemon meringue pie.