Chapter 17 Planning Healthy Meals 411 Copyright Goodheart-Willcox Co., Inc. The heat flows to the top of the cavity because hot air rises. An oven must be preheated for at least 10 minutes to allow it to reach the selected temperature before baking or roasting. Once preheated, a thermostat maintains the desired cooking temperature. When broiling, the heat source is located above the food. Inside a gas oven, a gas burner found on the bottom of the oven generates the heat for baking or roast- ing. When broiling, this same burner on the oven floor doubles as the heat source for the broiler found in a compartment below the main oven cavity. In recent years, the broiler has been moved into the oven cavity, where a dedicated gas burner is found on the ceiling of the oven. In an electric oven, metal heating elements gener- ate the heat rather than gas burners. In a convection oven, a fan circulates hot air around the inside of the oven cav- ity, allowing foods to cook more evenly and quickly. The cooktop consists of either gas burners or electric heating elements, con- trolled by knobs, or dials. On a gas cooktop, these knobs open a valve to release gas to the burner and regulate the size of the flame. A small gas flame called a pilot light burns continuously and lights the larger burner flame when needed. In modern gas ranges, an electronic spark ignition replaces the pilot light. The dials on an electric cooktop control the temperature of the heating element. Professional chefs prefer gas cooktops because they give instant heat when turned on and exceptional temperature control. An electric element must preheat for a short time before it reaches the desired temperature. Likewise, electric elements take longer to respond when the control dial is changed to a lower temperature. Conventional freestanding ranges combine a cooktop with an oven all in one unit. However, some ovens are built into the cabinetry. Many times, built-in ovens have two ovens, or a double oven. Built-in ovens are paired with a separate cook- top that is built into the kitchen counter. These cooktops sit flush with the counter to give a sleek look. Refrigerator-Freezer The refrigerator-freezer is the cold storage center of your kitchen. The refrig- erator portion holds beverages and perishable foods at safe temperatures above freezing but below 41°F. Full-size refrigerator-freezers range in size from 10 to 35 cubic feet. Most have two outer doors with the freezer located above, next to, or below the refrigerator. Some of the smaller models have one outer door and an inner compartment for the freezer. Compact, or mini, refrigerators range in size from one to four cubic feet and some have small freezers. They are much smaller than average refrigerators and take up very little space. They are easy to transport, making them perfect for dorm-type settings. Dishwasher Dishwashers have spray arms that distribute detergent and rinse water over, under, and around the dishes to loosen and remove soil. The dishwasher does this in several cycles, removing the dirty water from the machine after each phase of the cycle. Contrary to popular belief, the dishwasher uses a relatively small amount of water, approximately 6 to 10 gallons, depending on the wash-level setting. The water temperature in a dishwasher should remain above 140°F to dissolve detergent, remove grease from dishes, and to sanitize. To ensure the water is hot enough, you should run water in the kitchen sink until it is hot before starting the dishwasher.