Methods of Heat Transfer

To cook, food has to be exposed to a heat source. The 3 methods of heat transfer are:

• Radiation - heat travels directly from its source, e.g. grill bars, salamander, open fire, spit roast and blow torch
• Convection - heat travels in another medium, e.g. hot air in an oven, boiling liquid, hot fat in deep fryer and through steam
• Conduction - heat is transferred from the source to a cooking vessel, e.g. from a gas burner to a pot and from electric coils to a pan

Methods of Heat Transfer

Why do we use various methods of heat transfer? Think about the following:

• Origin of the dish - the local ingredients and equipment dictate how dishes should be cooked, e.g. Argentinean cooking uses radiation for grilling beef, Chinese cooking uses conduction with woks, Indian cooking uses convection in tandoors
• Texture and taste - some items are better when cooked using a particular method, e.g. tougher meat cuts are stewed or braised, rather than fried, to improve tenderness and taste
• Visual impact - brûlée is finished with a blowtorch to glaze the sugar, which provides a contrasting texture and colour
• Cooking times - some cookery methods do not require much time, e.g. deep-frying, while others require a longer time, e.g. stewing. Generally, the tougher an ingredient, the longer it must be cooked

Heat Transfer Examples

It is important to understand the principles of heat transfer, so that you can choose the most appropriate cookery method for your dish. Take a look at these pictures to see a few examples of each type of heat transfer used in cooking.

Create a google doc: provide a definition and food examples for each example shown:

E.g.

Blowtorch: A kitchen blowtorch can be used in a number of ways to add a professional finishing touch to your food. The handheld blowtorch uses intense controlled heat which can get much hotter than a grill, making it great for caramelising and charring foods.

Top uses for a blowtorch/food examples:

• Creme brûlée- the intense heat will melt the fine layer of sugar to create a rich and flavourful caramel sauce.
• Lightly toast meringues- keep the soft marshmallow centre of your meringue while crisping the top for a golden finish.
• Sear meat or other proteins- create a caramelised crust on fish, poultry or meat while retaining the juices on the inside.
• Skin peppers and tomatoes: instead of roasting your peppers and tomatoes in the oven for 15 minutes you can quickly blast them with a blowtorch to easily peel their skin.

1a. Sources of Heat

The heat for cooking can come from a variety of sources. Wood, coal and oil have been used for heating stoves, however maintaining the correct temperature is difficult and labour-intensive. Electricity and gas are the most commonly used heat sources in a commercial kitchen.

Electricity can be used to power ovens, cooktops and bakers' deck ovens, which allow several items to be cooked at the same time. Gas is most often used for cooktops, but can also be used in ovens. Most commercial kitchens will have a combination of equipment that uses gas and/or electricity as the heat source.