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Leavening Agents. Chapter 21. Air. Air is not the main leavening agent ,but gives many products a “lift” Air is the principal leavening agent in meringues and angel food cakes These products are based on egg foams (beaten egg whites)

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Leavening agents l.jpg

Leavening Agents

Chapter 21


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Air

  • Air is not the main leavening agent ,but gives many products a “lift”

  • Air is the principal leavening agent in meringues and angel food cakes

    • These products are based on egg foams (beaten egg whites)

    • Protein traps the air bubbles in the foam, creating a light and fluffy texture.


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Steam

  • All recipes for baked goods include some liquid.

    • The water in the liquid produces steam when heated

    • The temperature of the oven usually at least 204ºC ( what is that in ºF)

    • Baking coagulates the protein, setting the structure

    • Making large pockets or whole appear in food


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Carbon Dioxide (Co2)

  • Two basic methods for creating carbon dioxide:

    • Using baking soda, baking powder to create a chemical reaction that yields the gas

    • Using yeast in a biological process to create gas

    • http://recipes.howstuffworks.com/bread.htm


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Baking Soda

  • Baking Soda = chemical compound sodium bicarbonate

  • Baking soda releases sodium carbonate as well as carbon dioxide when heated

    • Sodium carbonate gives food a bad taste and a yellowish color.

    • However, baking soda is always used with an acid, which alters the chemical reaction to prevent sodium carbonate from forming

      • Some examples of acid are buttermilk, vinegar, lemon juice, molasses, honey, fruits, fruit juices, and cream of tartar.


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Baking Powder

  • Baking Powder = leavening compound that contain baking soda, dry acids and starch or some other filler.

    • The filler in baking powder, usually cornstarch or calcium carbonate, absorbs moisture in the air, which helps prevent a chemical reaction from taking place too soon.

  • Baking powder comes in two types:

    • Single-acting baking powder = as soon as liquid is added, carbon dioxide starts to be released

      • The quick reaction occurs because the acid in baking powder is soluble in a cold liquid

  • Double-acting baking powder = usually preferred, contains two acids, one that reacts with cold liquid and one that reacts with heat.

    • Some carbon dioxide is released as soon as liquid is added, but most is produced as the batter heats in the oven


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    The Strength of Baking Powder

    • http://chemistry.about.com/cs/foodchemistry/f/blbaking.htm?p=1

    • By federal law, baking powder must yield at least 12%. of carbon dioxide, most home used are at 14%

      • To much baking powder will cause the walls of the flour mixture to stretch too far, break, and collapse.

      • Too little will mean a compact product

      • http://images.google.com/imgres?imgurl=http://static.flickr.com/102/307198454_c1432aab3d.jpg&imgrefurl=http://thewanderingeater.wordpress.com/2006/11/10/the-best-of-croissantspart-2/&h=392&w=500&sz=126&hl=en&start=29&um=1&tbnid=qVDAkULXAM8q2M:&tbnh=102&tbnw=130&prev=/images%3Fq%3Dpicture%2Bof%2Ba%2Bcroissant%26start%3D20%26ndsp%3D20%26svnum%3D10%26um%3D1%26hl%3Den%26rlz%3D1T4RNWN_enUS220US221%26sa%3DN


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    Ammonium Bicarbonate

    • Baking soda and baking powder are the most common chemicals used to produce carbon dioxide, however ammonium bicarbonate can be used.

      • Ammonium bicarbonate produces carbon dioxide as it decomposes

      • Mostly used in crackers and certain types of cookies because of the affect to taste


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    Producing Carbon Dioxide (CO2) with Yeast

    • Yeast is a microscopic organism that produces carbon dioxide through fermentation = biological reaction that slowly splits complex organic compounds into simpler substances

      • During fermentation, yeast converts sugar into ethyl alcohol and carbon dioxide, ethyl alcohol evaporates while the carbon dioxide causes the product to rise

      • Yeast is killed in high baking temperatures


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    The Origins of Yeast

    • Thousand of years ago a little yeast landed on some bread dough and started to ferment, making the dough rise.

      • Ancient Egyptians first leavened bread by using yeast piece of leftover dough.

        • They started getting the same results using beer froth which also contains yeast

        • The word “yeast” originally meant the froth or sediment of a fermenting liquid

        • In ancient Rome, grape juice was mixed with wheat bran, ferment to develop yeast. The cakes were cut and used for bread later.

        • Sourdough bread is made by keeping the yeast alive from one batch of bread in order to start the next one.


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    • http://video.google.com/videoplay?docid=2261363315131027664&q=yeast&total=1220&start=10&num=10&so=0&type=search&plindex=9

    • Picture of yeast dividing (producing CO2)


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    Batters and Dough

    • Pour batters – made with an equal ratio of flour to liquid, usually flour (ex. waffle and pancake)

      • Steam is the main leavening agent in pour batters

  • Drop batters – mixing about two parts flour to one part liquid

    • Make muffins and some cookies, baking powder and steam are both leavening agents

  • Soft dough – three parts flour to one part liquid

    • Needs more mixing to develop gluten, example yeast breads, pizza crust and baking powder biscuits

  • Stiff dough – six to eight times as much flour as liquid

    • Drier consistency is needed for some products example pie crust

    • Steam leavens all flour mixtures


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    Yeast Products


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    Making Yeast Products

    • Beside yeast, the basic ingredients these breads are flour, liquids, and salt

      • Flour – provides the starch as well as the proteins that produce gluten

      • Liquid – usually water or milk. Milk is often chosen for nutritious reasons and also helps bread stay fresh longer

        • During baking, the steam from the liquid combines with the carbon dioxide produced by the yeast, which helps the bread expand and rise

    • Sugar, fat, and eggs – sugar helps the crust brown, fat makes the bread tender (softer), eggs makes the bread richer in texture and flavor.


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    Making Quick Breads

    • Quick Bread = needs no time to rise. These products are made with a leavening agent other than yeast, usually steam or carbon dioxide that is produce with baking powder or baking soda. Ex. muffins, coffee cakes, biscuits etc.

      • All quick breads contain flour, liquid and salt, plus a chemical leavening agent.

      • When making quick breads, DO NOT OVERSTIR, this will develop gluten, producing a tough product.


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    Questions

    • What are the three main leavens in bake goods?

    • How do each of the two natural leavens work?

    • What are two methods for producing carbon dioxide for leavening?

    • How does baking soda work as a leavening agent?

    • What would happen if you let out the lemon juice in a recipe that called for lemon juice and baking soda?

    • Compare single-acting baking powder with double-acting baking powder.


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    Question Continued

    • How much baking soda is in a recipe that calls for 2 teaspoons of baking powder. How do you know this?

    • Why does the amount of baking powder used in a recipe matter?

    • Describe how yeast produces carbon dioxide for leavening.

    • What is the scientific basis for the ancient Romans’ choice of grape juice and a grain products for growing yeast?

    • Should yeast be refrigerated? Why or why not?

    • Why do batters need to be thin when steam is the main leavening agent?

    • Are cakes leavened with only one leavening agent? Explain


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