1. Heat Transfer in Cooking Chapter 6

2. Introductory Foods, 13 th ed. Bennion and Scheule © 2010 Pearson Higher Education, Upper Saddle River, NJ 07458. All Rights Reserved. 2 Heat Kinetic energy Movement of molecules Temperature Measurement of heat

3. Introductory Foods, 13 th ed. Bennion and Scheule © 2010 Pearson Higher Education, Upper Saddle River, NJ 07458. All Rights Reserved. 3 Why Cook Food? Food safety and shelf life Making foods edible Example: Dried Legumes Digestibility and Nutritive Value Aesthetic Appeal

4. Introductory Foods, 13 th ed. Bennion and Scheule © 2010 Pearson Higher Education, Upper Saddle River, NJ 07458. All Rights Reserved. 4 Temperature Measurement Sensible heat Measured by thermometers Fahrenheit scale Celsius (Centigrade) scale

5. Introductory Foods, 13 th ed. Bennion and Scheule © 2010 Pearson Higher Education, Upper Saddle River, NJ 07458. All Rights Reserved. 5 Change of State The physical state of matter changes as a result of energy in the form of heat. Solid Ice Liquid Water Gas Steam

6. Introductory Foods, 13 th ed. Bennion and Scheule © 2010 Pearson Higher Education, Upper Saddle River, NJ 07458. All Rights Reserved. 6 Gas or Steam Gaseous molecules hovering over water create vapor pressure Bubbles form in a liquid as the vapor pressure is increased to a point greater than the atmospheric pressure.

7. Introductory Foods, 13 th ed. Bennion and Scheule © 2010 Pearson Higher Education, Upper Saddle River, NJ 07458. All Rights Reserved. 7 Effect of Pressure Water boils Sea level (212°F / 100°C) Water boils at lower temperatures at higher elevations Why? Food cooked in boiling water at high elevations Cook slower? Cook faster? Why? Food cooked in a pressure cooker Cook slower? Cook faster? Why?

8. Introductory Foods, 13 th ed. Bennion and Scheule © 2010 Pearson Higher Education, Upper Saddle River, NJ 07458. All Rights Reserved. 8 Heat Capacity of Water Heat capacity or specific heat of water = 1.0 1 calorie required to increase temperature of 1 gram of water 1 degree Celsius

9. Introductory Foods, 13 th ed. Bennion and Scheule © 2010 Pearson Higher Education, Upper Saddle River, NJ 07458. All Rights Reserved. 9 Latent Heat Latent heat = heat required to change state without changing temperature 1 gram ice liquid water 80 calories needed 1 gram water vapor or steam 540 calories needed

10. Introductory Foods, 13 th ed. Bennion and Scheule © 2010 Pearson Higher Education, Upper Saddle River, NJ 07458. All Rights Reserved. 10 Types of Heat Transfer Conduction Direct contact: frying pan on a stove top Convection Currents in the air or liquid distribute the heat Radiation Energy transferred as waves or rays vibrating at a high frequency (broiling) Induction Magnetic current generated by a high-frequency induction coil

11. Introductory Foods, 13 th ed. Bennion and Scheule © 2010 Pearson Higher Education, Upper Saddle River, NJ 07458. All Rights Reserved. 11 Cooking Materials Conduction Copper, aluminum, iron are good conductors Cast-iron holds heat well Stainless steel does not conduct heat evenly Radiation Dull, dark, rough surfaces absorb radiant heat Bright, shiny, smooth surfaces reflect heat Induction Need iron content Cast Iron, magnetic stainless steel, enamel over steel

12. Introductory Foods, 13 th ed. Bennion and Scheule © 2010 Pearson Higher Education, Upper Saddle River, NJ 07458. All Rights Reserved. 12 Media for Heat Transfer Air Water Steam Fat

13. Introductory Foods, 13 th ed. Bennion and Scheule © 2010 Pearson Higher Education, Upper Saddle River, NJ 07458. All Rights Reserved. 13 Cooking Methods Moist heat Dry heat Combination