Q. Doesn't baking soda need an acid to work?

A. Yes. These ingredients/foods are commonly used with baking soda in leavening: citrus, vinegar, cranberries, rhubarb, apples, berries, apricots, orange juice, honey, yogurt, sour cream, buttermilk, bananas, carrots, pumpkin, molasses, cocoa and chocolate (listed in decending order from high acid - pH of 2.0 to lower acid - 6.0).

Baking soda is an alkali, or a base, and it reacts with acid to make carbon dioxide. Without acid, baking soda can't properly do its job. But think of it as "lightening" the baked good because of the carbon dioxide, not just leavening, because eggs also contribute leavening.

Exception to the rule (isn't there always one!): Occasionally you find a recipe that doesn't contain an acid counterpart. There's still some carbon dioxide produced, just not as "lively". The baking soda that is left unnutralized can have a soapy, bitter taste. That's another reason to sift, or thoroughly mix, dry ingredients together to make sure they are evenly distributed throughout the bulk of the ingredients, and to break up a soda "lump" that can remain because of the quick mixing techniques normally used on chemically-leavened baked goods. The alkalinity can also cause color changes - yellowing the pigments in flour, can accelerate browning, and alter the colors of chocolate and molasses.

If the recipe also has cream of tartar in it, that's also an acid that is used to complete the reaction of the soda.
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Q. Doesn't baking soda begin to react with the liquids immediately?

A. The liquid ingredients cause the blending of the acid and alkali ingredients in a mixture to create a chemical reaction that makes carbon dioxide. Not just the liquid. If the acid ingredient is a liquid (sour milk, yogurt, etc.,) it is the cause of the reaction. It may take the blending of the dry ingredients into the wet ingredients to perform the reaction.

Baking powder reacts once with the liquid, and then again with the heat from the oven (hence, double-acting baking powder).

Hence - the tests for activity level of chemical leaveners. You mix soda with vinegar (a liquid acid) to test it's activity level, while baking powder only needs to be tested with hot water.
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Q. Can the batter be frozen in balls if only baking soda is used, or will they go flat when later thawed and baked?

A. Generally speaking, you can freeze cookie dough, even when only leavened with soda. Occasionally you find a recipe that doesn't perform as well when the dough is frozen. Eggs also perform part of the leavening.

-Grainlady

Grainlady,

Maybe you can help me with my question. I made chocolate chip cookies and they turned out flat instead of plump.

The baking soda was fresh, oven was preheated, test cookie was perfect, and I even added extra flour (2 1/3 cups instead of 2 1/4 cups). But most of the cookies were flattened out.

I used butter for the shortening, if that makes any difference.

blueheron - You'll find there is more moisture in butter than shortening, plus butter has a lower melting point - so it melts quicker than shortening.

Several things can help prevent flat cookies:

1. You already added more flour, that's a good first step. You might try baking 2-3 cookies as a test so you can make adjustments, if necessary.

Flour amounts in recipes are always nothing more than a good guess because of differences in the moisture level of flour. Flour stored in a humid kitchen in the paper bag it comes, or the flour canister is left open in a hot/humid kitchen, will absorb moisture. This, and differences in protein levels of different brands of flour, and you may need to adjust the flour amount because of that.

As an example... If you've always used a National Brand all-purpose flour (Gold Medal or Pillsbury) and you switch to King Arthur All-Purpose, you'll find there's more protein in the KA flour and you may need less flour. Gluten (protein) absorbs a lot of hydration.

2. Chill the dough so the fat hardens again before you begin baking the cookies. If there's a "marathon" baking going on and the kitchen is hot, be sure to set the bowl of dough in the refrigerator while baking is going on. A warm kitchen will pre-melt the fat in the dough just sitting in a hot kitchen.

3. Make sure you only bake on cool baking sheets. I always use 3 or 4 baking sheets to make sure I always fill a cool sheet.

4. You may like the results using 1/2 shortening and 1/2 butter. Shortening will give you that higher melting point and butter the great flavor. For those of use who avoid shortening, we just learn to adjust the recipe and/or use these hints...

5. Make sure you don't have your butter TOO soft when making the dough. Avoid squishy or half-melted butter (which often happens when it's softened using a microwave). Butter that is too soft can cause cookies to spread too much.

Softened (room temperature) butter is 65-67°F when you test the temp. with an instant read thermometer. Perfectly softened butter should give gently to pressure (you should be able to leave a fingerprint and a SLIGHT indention on the stick) but shouldn't be soft in appearance, nor should you be able to press completely through the butter.

6. I prefer parchment paper. I think it helps prevent spreading cookies.

7. Don't grease the cookie sheets. Greasing them will promote spreading.

Hope you find something there that helps.

-Grainlady

Thank you, Grainlady

I will try adding more flour and chilling the dough.

Grainlady: thank you for your reply. You have confirmed what I always thought to be true.