Lesson 4.4!

Heat transfer, any or all of several kinds of phenomena, is considered as mechanisms, that convey energy and entropy from one location to another. The specific mechanisms are usually referred to as convection, thermal radiation, and conduction. Conduction involves transfer of energy and entropy between adjacent molecules, usually a slow process. Convection involves movement of a heated fluid, such as air, usually a fairly rapid process. Radiation refers to the transmission of energy as electromagnetic radiation from its emission at a heated surface to its absorption on another surface, a process requiring no medium to convey the energy.

Three Kinds of Heat Transfer

Conduction

Touching a stove and being burned
Ice cooling down your hand
Boiling water by thrusting a red-hot piece of iron into it

Convection

Hot air rising, cooling, and falling (convection currents)
An old-fashioned radiator (creates a convection cell in a room by emitting warm air at the top and drawing in cool air at the bottom).

Radiation

Heat from the sun warming your face
Heat from a light bulb
Heat from a fire
Heat from anything else which is warmer than its surroundings.

What is Conduction?

Conduction is the process of heat being transferred between objects through direct contact, and it's the most common type of heat transfer
A deep fryer also uses conduction heating as the hot oil cooks the food when it comes into direct contact with it. Additionally, conduction heat is responsible for moving heat from the outside of the food to the inside. As a result, conduction heat also happens when cooking with convection and radiation heating methods.
Conduction is the slowest method of heat transfer, but the direct contact between the cooking surface and the item to be heated allows food to be cooked from the outside in.

Examples of Conduction Cooking

Here are a few examples of conduction heating:

Burning your hand on a hot piece of metal
Grilling steak, chicken breasts, or pork chops
Using ice water to blanch vegetables after steaming to keep them from losing their color

What is Convection?

There are two types of convection that are based on the movement of the heated molecules.

(1) Natural Convection

(2) Mechanical Convection

Natural Convection

Natural convection occurs when molecules at the bottom of a cooking vessel rise and warm while cooler and heavier molecules sink.
For example, when a pot of water is placed on the stove to boil, conduction heat warms up the pot, which then heats the water molecules inside. As these molecules heat, convection causes them to move away from the interior of the pot as they are replaced by cooler molecules. This continuous current creates convection heat transfer within the water.

Mechanical Convection

Mechanical convection occurs when outside forces circulate heat, which shortens cooking times and cooks food more evenly. Examples of this include stirring liquid in a pot or when a convection oven uses a fan and exhaust system to blow hot air over and around the food before venting it back out.

What is Radiation?

There are two main radiant heat cooking methods:

(1)Infrared radiation

(2)Microwave radiation.

Infrared Radiation

Infrared radiation utilizes an electric or ceramic heating element that gives off electromagnetic energy waves. These waves travel in any direction at the speed of light to quickly heat food and are mainly absorbed at the surface of whatever you're preparing. Examples of things that create infrared radiation are glowing coals in a fire, toaster ovens, and broilers.

Microwave Radiation

Microwave radiation utilizes short, high-frequency waves that penetrate food, which agitates its water molecules to create friction and transfer heat. If you're heating a solid substance, this heat energy is transferred throughout the food through conduction, while liquids do so through convection.
Microwave heat transfer usually cooks food faster than infrared radiation, as it is able to penetrate foods several inches deep. Keep in mind that microwave radiation works best when cooking small batches of food.

Examples of Radiation Cooking

Here are a few examples of how heat transfer via radiation works:

Warming your hands over a fire
Lying in the sun to get warm
Heating up dinner in the microwave

Heat Transfer

Radiation heat transfer is the mode of transfer of heat from one place to another in the form of waves called electromagnetic waves. Convection and conduction require the presence of matter as a medium to carry the heat from the hotter to the colder region. Some common examples of Radiation are Ultraviolet light from the sun, heat from a stove burner, visible light from a candle, x-rays from an x-ray machine.

Whether you're using a pan on a stove, a convection oven, or a heavy-duty microwave, conduction, convection, and radiation are all around us. Knowing and understanding what heat transfer is, how it works, and which type of heat transfer is happening as you cook can help you better understand the science of cooking and improve your skills as a chef.

The Science of Baking

Flour Provides the Recipe Foundation

Flour gives the structure for the product. The gluten, or protein, in flour, combines to form a web that traps air bubbles and sets. Starch in flour sets as it heats to add to and support the structure. In cakes, cookies, and quick bread, we want little gluten formation, which makes products tough. Fats and sugars help prevent gluten formation.
In most baked goods, all-purpose flour is a good choice; it has less gluten than bread flour.

Fat Holds it All Together

Fat coats gluten molecules so they can't combine as easily, contributing to the finished product's tenderness. In many cakes, fat also contributes to the fluffiness of the final product. When sugar is creamed with fat, small pockets of air form from the sharp edges of the crystals interacting with the fat. These pockets form a finer grain in the finished product. Fats also carry flavors and add to a tender mouth-feel.
Commonly used baking fats include butter, shortening, coconut oil, and (less rarely these days) lard.

Sugar Is Sweet and Helps Tenderize

Sugar adds sweetness, as well as contributing to the product's browning. Sugar tenderizes a cake by preventing the gluten from forming. Sugar also holds moisture in the finished product. Sugar crystals cutting into solid fats like butter help form the structure of the product by making small holes which are filled with CO2 when the leavening agents react.

Eggs Add Texture

Eggs are a leavening agent and the yolks add fat for a tender and light texture. The yolks also act as an emulsifier for a smooth and even texture in the finished product. And the proteins contribute to the structure of the baked good.

Liquids Add Leavening and Tenderness

Liquid helps carry flavorings throughout the product, forms gluten bonds, and reacts with the starch in the protein for a strong but light structure. Liquids also act as steam during baking, acting as a leavening agent and contributing to the tenderness of the product.

Salt Adds Flavor and Weight

Salt strengthens gluten and adds flavor. Salt enhances flavors. In yeast bread, salt helps moderate the effect of the yeast so the bread doesn't rise too quickly.

Leavening Agents Baking Soda and Baking Powder

Baking soda and baking powder form CO2, which is held by fat pockets, gluten, and starch, which makes the baked product rise. Baking soda and powder are not interchangeable; be sure that you have the product the recipe calls for.
Too much leavening agent will make the bubbles too big, then they will combine and burst, leading to a flat cake or bread. Too little leavening agent will result in a heavy product, with soggy or damp layers.

Video Materials

Learning Activity 12

Read the Instruction carefully:

This is an individual activity.
Make a video presentation, answering the following questions.
The video must be 3-5mins only.
Submit your video at the Google Drive Link given below
Your output's file name must follow this suggested format: (Monteverde.Dave_OLM_LA1)

Questions :

Explain, convection, conduction, and radiation.
Is the science of baking important? Why?

Video presentation rubrics.docx

References

Learning Materials

[1]https://physicsabout.com/radiation/?fbclid=IwAR3aahTKPgZS8aYQ0wr8jiGIxbRkx1EEM90K4DdOsgi1WbZfxgU35aHSAQY

[2]https://www.webstaurantstore.com/blog/postdetails.cfm?post=976

[3]https://www.thespruceeats.com/baking-ingredient-science-481226

Video Materials

[1]https://www.youtube.com/watch?v=fJAG9HgBnc0

[2]https://www.youtube.com/watch?v=MBouLt-hXDU

[3] https://youtu.be/v62ilJCaMFk

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