Leavening Agents

1. Leavening Agents Chapter 21

2. 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.

3. 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

4. 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

5. 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.

6. 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

7. 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

8. 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

9. 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

10. 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.

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

12. 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

13. Yeast Products

14. 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.

15. 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.

16. 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.

17. 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