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August 2009

Ounces Weight vs Fluid Ounces Volume

Isn't it true that 16 oz of dry goods is different than 16 oz of liquid measure.  If a recipe calls for 8oz of flour, you should measure it using a scale rather than using a cup (which is a liquid measure, no matter what kind of cup you use).  I'm confused.
--SM
 

The confusion comes from the fact that in English we use the word "ounce" when talking about both the weight of something or the volume  it occupies.  In cooking, if you are talking about the volume of something, technically you should refer to the measure as "fluid ounces" and if  you are weighing something then you can say just "ounces."

Ingredients such as beans, sugar or flour can be conveniently measured by volume in cups, pints, quarts, liters and all of the other units that are used to calculate volume, including fluid ounces.  They can also be weighed in pounds, kilograms and ounces.

Depending on what ingredient you are measuring, the weight in ounces and the volume in fluid ounces may be close to the same or vastly different.  Sixteen fluid ounces of water weigh very close to 16 ounces (1 pound)*.

Sixteen fluid ounces (2 cups) of flour will weigh around 8 ounces (1/2 pound) if it is sifted, and somewhat more, around 9 ounces, if it is unsifted.  This is just a rough estimate, though.

So, if your recipe calls for "fluid ounces" then you are definitely using a volume measuring device, such as a liquid or dry measure.  See the post Difference Between Dry and Liquid Measuring Cups for guidance on which to use and how.

If the recipe just says "ounces", for some ingredients you may be able to assume that the author means to measure by weight.  For ingredients like flour, though, the author may mean either weight or volume so you need to be careful to understand which is being used.  In books on baking there is frequently a section near the start on techniques where sometimes they may clarify which measure they are using.

As a further note, fluid ounces may be abbreviated in recipes as "fl. oz." and ounces as just "oz."

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* The scientist in me wants to say that is true provided that the water is close to room temperature and the ambient air pressure is close to standard pressure at sea level, but for most practical purposes you can consider them to be equivalent.


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Due to the volume of questions received, not all can be answered, nor can we guarantee we will answer questions immediately
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Baking Soda and Baking Powder - The Saga Continues

What on earth!   Here is my internet journey, seeking the answer to "Baking soda vs. baking powder."
  1. Baking powder can replace baking soda
  2. Baking powder cant replace baking soda
  3. Baking powder can't replace baking soda and vice versa.
Here are some excerpts:

So which one is it?

If baking is all about accuracy, then why is it that I constantly find conflicting information, all from experts?  How does anything ever get baked and turn out edible, if everyone has so many different opinions?

I am starting to believe that bakers are actually other-worldly beings that are unknowingly just manipulating ingredients with their minds.
--Curtis
 

OK, before you go reporting a Close Encounter, let's see if we can set this straight.

First, just a touch of chemistry.  Baking soda or bicarbonate of soda (NaHCO3) is a mild base that has a number of applications in baking.  Among those are to cause chemical leavening by releasing bubbles of carbon dioxide gas when combined with an acid, and changing level of acidity or basicity of a recipe.

The acidity/basicity can be important in a number of ways.  For example, cookies that are slightly basic will spread more and brown more than ones that are slightly acidic.  If you are making a chocolate cake that is too acidic, it will turn the chocolate color from dark brown to light brown to red.  That's part of the secret to a Red velvet cake.

Baking powder is baking soda with an acid added to cause the chemical leavening.  The type of acid varies with different formulations and applications, as can be found in the KitchenSavvy article mentioned above.

As discussed in Let Them Eat Cake, as well as the above KitchenSavvy article, when recipes use both baking soda and baking powder, there is usually another acidic ingredient such as molasses, brown sugar, buttermilk or sour cream that combines with the baking soda to create bubbles.

So, which of the above is it? 

Since baking powder contains baking soda, you can indeed use it to replace baking soda.  The problems is that the leftover acid that is not neutralized in your recipe will affect the flavor and may also affect the result.  A cookie that is supposed to spread during cooking likely won't, and it may not brown properly, or may end up over cooked if you try to brown it enough.  Also, the final color of the product may not be what you expect since the product is acidic.  So, point 1 above is technically correct, as far as it goes, but you may not like the result. 

If you insist on trying, though, you will need up to four times as much baking powder as the amount of baking soda that was called for in the recipe.   Just don't say I told you it was a good idea!

Point 2 is correct, since what you are actually doing when you combine baking soda with cream of tartar is making your own homemade baking powder.  What you are really doing is substituting baking powder that someone mixed up for you with baking powder you made yourself.  The cornstarch is just filler to make up 1/4 more so the total volume works out the same but isn't really necessary.

And point 3 is correct, since you can't just swap them one for one.  As the referenced site goes on to explain, if you don't have baking powder you can make your own homemade stuff by using 1/4 the volume of baking powder specified of baking soda plus 1/2 the volume of cream of tartar.  Since you need to include the cream of tartar, you are really not just substituting one for the other.

The postings referenced in points 2 and 3 pretty much agree in what they say.  The problem with the first reference is it ignores the other aspects of food chemistry that come into play when you start altering the acid/base ratios in recipes.

Hopefully, all of this helps.


If you have food or cooking questions, send them to Questions@KitchenSavvy.com



Due to the volume of questions received, not all can be answered.
© Lost Hobbit Enterprises 2004 onward



Due to the volume of questions received, not all can be answered, nor can we guarantee we will answer questions immediately
© Lost Hobbit Enterprises 2004 onward