FOOD PREPARATION (1) Principles underlying cooking (2) Methods of cooking (3) Transfer of heat

Cooking is simply the application of heat to food to make it safe, easier to digest, and more delicious. When you heat food, chemical and physical changes occur that transform raw ingredients into meals we can enjoy. Think of cooking jollof rice: the heat softens the grains, allows them to absorb water and flavour, and makes the starches easier for your body to use.

There are several ways heat reaches food. Direct heat comes from flames or hot surfaces, like grilling meat. Indirect heat surrounds the food evenly, like in an oven. Water-based heat transfers through boiling or steaming, perfect for cooking vegetables. Each method affects food differently, changing texture, colour, and nutritional value.

Understanding these principles helps you cook better and answers exam questions correctly. You need to know why we cook, how heat travels, and what happens to food during cooking.

Cooking food is essential for several important reasons. First, it makes food safer by killing harmful bacteria and microorganisms that cause diseases like typhoid and food poisoning. When you cook jollof rice properly, you destroy pathogens that raw ingredients might contain. Second, cooking improves digestion by breaking down tough food fibres and proteins, making nutrients easier for your body to absorb. This is why cooked beans are more digestible than raw beans.

Third, cooking enhances flavour and makes food more appetizing. The heat creates new tastes and aromas that make eating enjoyable. Finally, cooking increases the availability of certain nutrients and helps preserve food longer. Some vitamins become more accessible when heated, while cooking reduces moisture that bacteria need to grow.

Moist heat cooking means using water or liquid to cook food. The heat transfers from the hot liquid to your food, cooking it thoroughly. Common moist heat methods include boiling, steaming, and stewing. When you boil, food sits directly in hot water at 100°C. Steaming cooks food above boiling water using steam, keeping nutrients better. Stewing combines small pieces of food with liquid in a covered pot, cooking slowly until tender.

Think of cooking jollof rice or Nigerian pepper soup—you're using boiling water to cook the rice or keep the soup simmering. These methods work well for tough cuts of meat, dried beans, and root vegetables because the prolonged moist heat softens them. Moist cooking also helps dissolve minerals and flavours into the liquid.

Dry heat cooking means preparing food using direct heat without added liquid. The heat transfers directly to the food, making it brown quickly and develop nice flavors. Common dry heat methods include baking, roasting, grilling, and frying.

Baking uses an oven's hot air to cook food evenly. Think of how your mum bakes chin chin or bread at home—the dry heat surrounds the food completely. Roasting is similar but typically uses higher temperatures for meat and vegetables. Grilling exposes food directly to intense heat from below or above, perfect for suya preparation. Frying involves cooking food in hot oil, like how you fry plantains or akara.

The main advantage is that these methods create crispy, golden exteriors through browning reactions that develop delicious flavors. However, foods can dry out if cooked too long, so timing matters greatly.

When you cook food, heat moves from the source to the food in three main ways. Conduction happens when heat travels through solid materials—like when a metal pot handle gets hot from the stove flame. Convection occurs in liquids and gases as hot particles move upward while cooler ones sink—this is why water boils from bottom to top. Radiation transfers heat through space without touching anything—your skin feels warm standing near a fire.

Different foods respond differently to heat. Proteins in meat tighten and turn brown through a process called denaturation. Grains like rice absorb water and soften when heated. Fats can burn if heated too much. When you fry plantains in hot oil, conduction transfers heat through the oil to cook the plantain evenly and give it that golden colour.