Nappanee Advance-News, Volume 109, Number 35, Nappanee, Elkhart County, 22 January 1986 — Page 14

Page 14

I Nappanee Advance News Wednesday, January 22,1906

Common Science

Joe Jeffers, Ph.D.

The chemistry of biscuits

This week, The Advance-News begins a new series of columns entitled “Common Science’’, prepared by Joe Jeffers, a science educator at Quachita Baptist University In Arkansas. Please let the staff know your reaction to the columns A series of columns is planned, and, at the end of 36 weeks, an evaluation form will be printed, which readers will be asked to complete and mail to Mr. Jeffers. Everyone has eaten good biscuits--iight, flaky, beautiful enough to adorn the cover of a Betty Crocker cookbook. Everyone has also been faced with those other biscuits, some like rocks, some like rubber balls. What does it take to make a good biscuit? In the hands of some folks it’s an art; for everybody it’s science. Read on. Moses ate unleavened bread, a flat, chewy concoction that did not contain the ingredient that makes breads light. What makes breads light? Two things, a gas to make the dough rise, and a structure to trap the gas. Moses’ bread had the structure, but there was nothing to generate the gas. Leaven was missing Yeast is used to provide leaven. As the yeast grow they convert sugar or starch to carbon dioxide and ethyl alcohol The carbon dioxide (CO-2) is a gas and makes the dough rise Modem breads and rolls, of course, are made using yeast. The structure that traps the CO-2 develops from a couple of proteins found in wheat flour. Gliadin becomes gluey when it soaks up water; glutenin becomes rubbery. Neither of these qualities would seem attractive to a bread maker. However, if gliadin and glutenin are forced together as they take up water, they form gluten, a combination of the two that has just the right amount of cohesiveness and elasticity As a result the dough holds together, yet it can stretch and expand Gluten is formed by kneading the dough. If it is not kneaded enough, too little gluten will form and the dough will be difficult to handle. It will tear easily and stick to anything. If it is kneaded too long, too much gluten will form and the dough will become rubbery. The tendency to form too much gluten is controlled by adding an antirubber ingredient-shortening. Shortening is a fat that coats strands of gluten, waterproofing them, thus preventing their continued growth. It “shortens” the average gluten strand and makes the dough more Bellamys appear at Wagon Wheel The Bellamy Brothers will appear at the Wagon Wheel Playhouse, Warsaw, Friday, February 7, for twoshows-at6:3op.m. and9:oop.m. In the 10 years since they first jumped into the charts, the Bellamy Brothers have crafter, experimented with and refined their music until it is right where they want it to be? Their premiere worldwide hit “Let Your Love Flow” lifted them to prominence in 1976, in country music, but especially in pop circles. For ticket information, call 267-8041

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manageable. This elastic structure traps CO-2 as the yeast ferments, causing the dough to rise. There is only one problem with this process. It takes time. Two hours or more are required for the dough to rise, be punched down to sub-divide the gas cells and rise

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again. When that kind of time is not available, quick breads fill the void. There is where biscuits come in. Instead of using a biological leavening like yeast, a chemical leavening is needed. Baking soda, sodium bicarbonate, gives off CO-2 when it is heated. It does not produce good biscuits, however, because it is too stable. It doesn't decompose soon enough. As a result, the dough is setting by the time the temperature is high enough to release much CO-2. Baking powder is used instead. It contains sodium bicarbonate and an acid which allows sodium bicarbonate to release CO-2 sooner. In this case, sodium bicarbonate is a base or alkali that is neutralized by an acid, giving off CO-2 and water. As long as the materials remain dry, there is no reaction. Corn starch

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is added as a filler to absorb moisture and increase the shelf life of the baking powder. Most baking powders actually contain two acids, one that reacts with sodium bicarbonate at room temperature (calcium and phosphate) and another that reacts in the oven (sodium aluminum sulfate). Biscuit dough is kneaded slightly to form just enough gluten so it will roll without tearing and form into laye: a . Each layer has gluten coated with fat. As the biscuits bake, the fat layer melts. Water vaporizes into steam and the dough separates into flakes. Couple that with the action of CO-2, and beautiful, light biscuits result. Bring on the butter and jam or gravy. Let’s take a closer look at this biscuit chemistry. Any acid will cause baking soda to release CO-2.

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In fact, many biscuit recipes use reduced amounts of baking powder while adding baking soda and an acid ingredient like buttermilk. To demonstrate the ability of the acid materials to neutralize sodium bicarbonate and release CO-2, conduct the following kitchen experiments. Add a teaspoon of baking powder to a glass of water. Notice the speed at which the bubbles are released. Now add one teaspoon of baking soda to each of six glasses of water. Stir to dissolve. Notice if any bubbles (CO-2) are forming in the water. To one glass add cream of tartar; to another, add vinegar. Similarly add to the other glasses lemon juice, apple juice and honey. All of these are acidic enough to cause CO-2 to form. Do they all cause bubble forma-

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tion at the same speed? Warm the sixth glass of solution in a saucepan to see if heat will cause CO-2 to be released. Since some bubbles will form from heating just water, you may wish to heat a second sauce pan containing water for comparison. As you can see from baking powder solution, a steady, gentle release of CO-2 is desirable for biscuits. From the experiments above, if you were out of baking powder, what ingredients could you substitute for it? The kitchen is a wonderful laboratory for learning about chemistry. Additional inside views of the chemistry of cooking can be found in "The Cookbook Decoder Or Culinary Alchemy Explained” by Arthur E. Grosser (Beaufort Books, New York). Ask your library or bookstore about it. Bon appetit!