Pastry Flour vs. All Purpose Flour...Difference?


J13

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What is pastry flour? How does it differ from all purpose? When should you use it (if you should use it at all)? In which baked goods? Obviously, you should avoid it for products that require a lot of gluten like bread, and I assume it's not good for cakes, either, but would it be good for any old pastry? Pies, biscuits, puff? Or just certain ones of those?
 
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All purpose is usually a hard red winter wheat. It may be bleached or unbleached. Unbleached flour will have a higher protein content.
  • Extraction 70% - 80% ( removal of bran and germ)
  • Ash 50% - 60% ( mineral content)
  • Protein 10% - 11.5%
  • Flour Treatment: usually malted to aid browning

Pastry flour is usually a soft white wheat, so naturally lower in protein. Flour may in US is often bleached, but no always. The distinction between cake flour and pastry flour is cake flour is always bleached
  • Extraction 60% - 70% ( removal of bran and germ)
  • Ash < 50% ( mineral content)
  • Protein 8.5% - 9.5%
  • Flour Treatment: none
 

J13

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Pastry flour is usually a soft white wheat, so naturally lower in protein. Flour may in US is often bleached, but no always. The distinction between cake flour and pastry flour is cake flour is always bleached
  • Extraction 60% - 70% ( removal of bran and germ)
  • Ash < 50% ( mineral content)
  • Protein 8.5% - 9.5%
  • Flour Treatment: none
Okay, I’ll bite...why is bleaching good for cake but not good for pastry? I mean, I get that unbleached is preferable if you’re making bread because unbleached = more protein which = more gluten. But what about if gluten isn’t an issue as in cakes and pastries?
 
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Okay, I’ll bite...why is bleaching good for cake but not good for pastry? I mean, I get that unbleached is preferable if you’re making bread because unbleached = more protein which = more gluten. But what about if gluten isn’t an issue as in cakes and pastries?

It changes the rate of protein denaturation and starch gelatinization.


Starch gelatinization is when the starch molecule expand with heat as they absorbs the free water molecules in the batter or dough. They eventually become saturated and burst. While this is happening, the dough is stretching and expanding from the the gas created by the leavening.


When the starch molecules burst, they begin to coagulate and set a structure around the gas bubbles creating the porous structure.


Starch gelatinization happens with all flours. But bleached cake slows the rate of starch gelatinization which allows for more rise time.


Protein denaturation reduces the strength and extensibility in the flour. Heat causes protein denaturalization so the temperature in which it occurs is important. Cake flour is low protein, so already weaker flour. The bleaching cause a higher denaturation temperature, so it gives the cake batter more time to rise. Once that peak hits, then the extended starch gelatinization has happened and the batter sets.


So bleached cake flour produces a fluffy, taller cake than pastry flour and all purpose flour. In fact angel food cake can only be made with bleached cake flour. Any other flour and the angel food cake will collapse or be a gummy dense mess.


Bleaching actually happens naturally with oxidation as flour ages. But mills can’t afford to wait for bleaching to occur, they need to sell their flour. So they chemically bleach it.


Where bleaching is prohibited, cake flour is high heat treated to trigger some starch gelatinization and protein denaturation.

Despite all those blogs claiming you can make cake flour by mixing cornstarch and all purpose flour, it not true. You have to understand the science of bleaching flour. And it has nothing to do with adding more starch or a hygroscopic starch to flour.

Cornstarch is a thickener. Cornstarch is so incredibly hygroscopic it creates the opposite texture in cake. Instead of a light airy cake that rises high, the cornstarch sucks up all the moisture and turns thick and gummy. Cornstarch does the opposite of what is desired in cake. And it’s because cake batter contains liquid—significant free water molecules just waiting to bind with the cornstarch. It’s one thing to add some cornstarch to shortbread dough where there’s almost no free water molecules. Quite another to add it to cake batter where there’s significant free water molecules.


http://www.icef11.org/content/papers/epf/EPF493.pdf

https://www.sciencedirect.com/science/article/pii/S0308814696002610
 

J13

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Cool! And yes, I have seen websites telling me how to make cake flour. That’s really interesting about the Angel Food cake. I made such a cake once and only once. I think it came out right (didn’t collapse). But maybe it didn’t as, after tasting it, I couldn’t see what the big deal was. It was a good cake, airy-light and all that, but it didn’t seem worth all the trouble. It was a long time ago, but I think I used Swan’s Down cake flour for it.
 
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Cool! And yes, I have seen websites telling me how to make cake flour. That’s really interesting about the Angel Food cake. I made such a cake once and only once. I think it came out right (didn’t collapse). But maybe it didn’t as, after tasting it, I couldn’t see what the big deal was. It was a good cake, airy-light and all that, but it didn’t seem worth all the trouble. It was a long time ago, but I think I used Swan’s Down cake flour for it.
Yeah, I don’t get all the fuss over angel food cake either. It was all the rage in the 60s and early 70s. But I was never a big fan. I was thought the texture was weird. I preferred chiffon cake.
 
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It changes the rate of protein denaturation and starch gelatinization.


Starch gelatinization is when the starch molecule expand with heat as they absorbs the free water molecules in the batter or dough. They eventually become saturated and burst. While this is happening, the dough is stretching and expanding from the the gas created by the leavening.


When the starch molecules burst, they begin to coagulate and set a structure around the gas bubbles creating the porous structure.


Starch gelatinization happens with all flours. But bleached cake slows the rate of starch gelatinization which allows for more rise time.


Protein denaturation reduces the strength and extensibility in the flour. Heat causes protein denaturalization so the temperature in which it occurs is important. Cake flour is low protein, so already weaker flour. The bleaching cause a higher denaturation temperature, so it gives the cake batter more time to rise. Once that peak hits, then the extended starch gelatinization has happened and the batter sets.


So bleached cake flour produces a fluffy, taller cake than pastry flour and all purpose flour. In fact angel food cake can only be made with bleached cake flour. Any other flour and the angel food cake will collapse or be a gummy dense mess.


Bleaching actually happens naturally with oxidation as flour ages. But mills can’t afford to wait for bleaching to occur, they need to sell their flour. So they chemically bleach it.


Where bleaching is prohibited, cake flour is high heat treated to trigger some starch gelatinization and protein denaturation.

Despite all those blogs claiming you can make cake flour by mixing cornstarch and all purpose flour, it not true. You have to understand the science of bleaching flour. And it has nothing to do with adding more starch or a hygroscopic starch to flour.

Cornstarch is a thickener. Cornstarch is so incredibly hygroscopic it creates the opposite texture in cake. Instead of a light airy cake that rises high, the cornstarch sucks up all the moisture and turns thick and gummy. Cornstarch does the opposite of what is desired in cake. And it’s because cake batter contains liquid—significant free water molecules just waiting to bind with the cornstarch. It’s one thing to add some cornstarch to shortbread dough where there’s almost no free water molecules. Quite another to add it to cake batter where there’s significant free water molecules.


http://www.icef11.org/content/papers/epf/EPF493.pdf

https://www.sciencedirect.com/science/article/pii/S0308814696002610

Thats a treatise, I'd add, all flours see the chemicals one way or the other.
Silos have to be treated by law, so unless its organic or self milled.....
its in there. Last I looked they were using bromide gas, it just passes through and vents out.
Its not like drinking bleach.
 

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