Gastro Friday: How to Reduce a Recipe (Culinary Math 101)

March 5th, 2010

Ever since culinary school, I have had one formula stuck in my head: how to reduce a recipe. You take what you need and divide it by what you have to get your conversion factor, and then multiply all the ingredients by the conversion factor to get the new recipe measurements.

I vaguely remember learning another, more difficult formula in culinary school that was more precise…or rather, I remember trying to learn it but failing miserably and assuming the one I had memorized would do me fine.

Then I tried to reduce a baking recipe and got the bread that ate Chicago.

You see, the conversion method I was using did not account for the weight of the ingredients and making sure that balance was still there when the quantities were increased or reduced–after all, baking is nothing but a giant science experiment.

So I decided it was time to dust off the old culinary math book and see if after earning three degrees, I could finally conquer the proper recipe conversion method. I used Food and Beverage Cost Control by Miller, Hayes and Dopson, Second Edition, pp. 61-63. They call this the percentage method. I don’t disagree.

Oh, and it helps to use a published guide for ingredient weight conversion, something that gives exact weights for flour, sugar, and other common baking products (I used my Baking book from culinary school for this). A lot of internet guides will vary on their weights, and that makes for a messed up recipe in the end.

5 steps to PROPER recipe conversion via the percentage method:

Figure out the total weight of the recipe and convert to ounces
Figure out the percentage of each ingredient by dividing it by the total original recipe weight.
Figure out the portion size, and how many portions the recipe makes.
Take the number of portions you need and multiply it by the serving size to get your new recipe weight needed.
To receive the new recipe measurements, multiply the % total of the ingredient item by the total new recipe weight needed.

I know, it sounds like it might take forever, but I promise, with some dilligent work and a calculator, you’ll be fine, and what’s more–you’ll have a properly altered recipe.

Let’s practice with this recipe:

Original Recipe for Pudding:

3 qt. heavy cream

3 qt. half n half

24 yolks

5 cups sugar

8 T cornstarch

2 # dark choc. Chips

4 T butter

Recipe weight in ounces:

96 oz heavy cream

96 oz half n half

16.94 oz. egg yolks

44 oz sugar

32 oz chocolate

2oz butter

2 2/3 oz cornstarch

Total weight: 289.6 oz

Figure out what percentage of the total weight each ingredient is:

96/289.6= 33.1%

16.94/289.6=5.8%

44/289.6= 15.2%

32/289.6=11%

2/289.6= 1%

2.66/289.6= 1%

289.6=72 servings

Need 6 servings= 24 oz

Convert recipe:

33.1% x24 = 7.94 oz

5.8% x24= 1.39oz yolks

15.2% x24= 3.65oz sugar

11% x24= 2.64oz chocolate

1% x24= .24 oz butter

1% x24= .24oz cornstarch

New recipe

7.94 oz heavy cream

7.94 half n half

1.39oz yolks

3.65 oz sugar

2.64oz chocolate

.24oz butter

.24 oz cornstarch

I’m no math whiz, and I’ve had my husband check my math on most recipes, but so far, I’ve had success with this method. Let me know if you have any questions…will do my best to answer!

~LTG!

This entry is filed under Gastro Fridays, Other, The Gastronomical Leena.
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chris

Finally, an excellent rule of thumb thats not about guessing! Maybe I will not suck at baking anymore as a result. Wait, who am I kidding, I cringe at the sight of baking powder.
http://www.leenaeats.com/ LeenaEats

Thanks Chris. Baking powder may scare you, but I bet yeast would be your friend. The trick is to know as much as you can about the ingredient you are using (like how yeast is sensitive to temp.) and be prepared to adjust the recipe accordingly if it doesn't look right. Practice makes perfect!
Michelle

Good thing I stumbled upon your blog. This is great, thanks for the information.But one question, do the same rules apply when you're converting salt & pepper? or strong spices in other words. I heard that it's best, especially salt, to go by taste but never to increase too much? I'm lost, help!
http://www.leenaeats.com/ LeenaEats

Hi Michelle,

It really depends on what kind of recipe you are making. In some recipes, like many baking recipes, salt plays a chemical reaction, and needs to represent a certain percentage of the recipe weight, so this method would work well. But when it comes to strong spices in a baking recipe, you can go by taste. If you are using a cooking recipe, then most likely you can go by taste with salt (same with strong spices) unless it plays a specific role, like seasoning boiling water before boiling spaghetti. Hope this helps!
Michelle

Good thing I stumbled upon your blog. This is great, thanks for the information.But one question, do the same rules apply when you're converting salt & pepper? or strong spices in other words. I heard that it's best, especially salt, to go by taste but never to increase too much? I'm lost, help!
http://www.leenaeats.com/ LeenaEats

Hi Michelle,

It really depends on what kind of recipe you are making. In some recipes, like many baking recipes, salt plays a chemical reaction, and needs to represent a certain percentage of the recipe weight, so this method would work well. But when it comes to strong spices in a baking recipe, you can go by taste. If you are using a cooking recipe, then most likely you can go by taste with salt (same with strong spices) unless it plays a specific role, like seasoning boiling water before boiling spaghetti. Hope this helps!

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