Tuesday, August 13, 2013

Today, I want to talk about something geeky. It's about wheat flour. Few weeks ago, my friend asked me if she can substitute all purpose flour with whole wheat flour for her cake. I'm pretty sure, a lot of bakers can give her a good answer. But some of us maybe do not quite sure about it or maybe never even heard about whole wheat flour. It tickles me for days. I decided to do some small research, read my old books, and open my university final essay. Oh yeah. I learned about this kind of thing back than in university. But it was like 7 or 8 years ago and I haven't touched it again for that period of time. I'm a little bit rusty now.  But let's see how far i can remember and refresh my memory. First, let's talk about wheat flour. :)

Wheat Flour

Wheat flour is product that is made from wheat by removing the brown surface coating (the bran) and the
embryo (the germ) and reducing the particle size (by grinding and sifting) into a fine product. It can be used and even the largest ingredients for many kind of baked product, for example, bread, cake, biscuit, cookies, crackers. Wheat flour has a very important protein which is called gluten. Gluten plays very important role to give specific characteristic for each baked product. It gives elasticity and extensibility of the product.

Gluten is formed by 2 kinds of protein which are gliadin and glutenin. Gliadin will give elasticity to the dough, and glutenin will give firm and tough texture at the dough. With presence of water and kneading process, gliadin and glutenin will make crosslinks and bond together to create a stretchy, net-like matrix.  The protein content and the quality of gluten in flour is dependent on the type of wheat that were used. Therefore,  based on protein and gluten content, basically there are 3 types of flour which are :
  • Strong flour (made from hard grain with high protein contents that give elastic but inextensible gluten. The protein contents of strong flour is usually in the range 10.5-14.5%. This kind of flour is perfect for making bread)
  • Medium flour (made from wheat with medium protein contents or mixed from hard and soft wheat. The protein content of medium flour is usually in range 8.5-10.5%.)
  • Weak flour (made from wheat with lower protein contents that give more extensible but less elastic gluten. The protein contents of soft flour is usually less than 8.5%. This flour is perfect for biscuit productions)
As you know, nowadays there're a lot of type of flour in the market. Not only soft, medium and hard flour anymore. We can find self rising flour, cake flour, all purpose flour, semolina, durum, pastry flour, whole wheat flour, bread flour, gluten flour, bleached flour, and instant flour. The most common flour that i can find in the store nearby are all purpose flour, self raising flour, whole wheat flour, and instant flour for cake and for bread. I don't want to talk about self raising and instant flour. They already contained some raising agent such as baking powder or yeast. Let's talk about all purpose flour and whole wheat flour. Nowadays, they are the most common type of flour. What are they?

All purpose flour

All purpose flour is the most widely used flour. It comes from the finely ground part of the wheat kernel called the endosperm. The endosperms were separated from the bran and germ during milling process.

All purpose flour is made from blend of high gluten wheat and low gluten wheat so it has protein content in range 9-12% (depend on the brand). That's why all purpose flour can be categorized as medium-strong flour. All purpose flour can be used universally for a wide range of food products such as yeast bread, cakes, cookies, biscuit, pastry, doughnut, and many thing else.

Is all purpose flour the same with regular plain wheat flour? The answer is yes, it is. Regular plain wheat flour have protein content in range between 9-12% like all purpose flour. In here, Netherlands, I won't be able to find flour with "All purpose flour" written on its package. I only can find patent tarwebloem (fine wheat flour) or volkoren tarwebloem (whole wheat flour). Or self rising flour, bread flour, and cake flour. But i always buy patent tarwebloem which i consider it as all purpose flour because it is regular plain flour with protein content 11 grams/100 grams flour. I will use it for making any kind of food such as cake, cookies, doughnut, bread, even for thickening agent in cream soup.

Whole Wheat Flour

Whole wheat flour is one type of wheat flour which is composed of 99% wheat grain. It is made by grinding the whole grain of wheat including the bran and the germ. That's why it is called whole wheat flour. Because whole wheat flour contains all part of the grain, its color is darker and more brownish than regular plain flour.

I tried to take a picture of both type of flour. The left one is all purpose flour, and the right one is whole wheat flour.  As we can see, whole wheat flour has some brownish particle mixed in the flour. That stuff are wheat bran. The bran can not be grained as well as the endosperm. That's why it gives whole wheat flour a rougher texture than all purpose flour. 

What's the difference between all purpose and whole wheat flour?

Based on USDA Nutrient Standard Reference Database, whole wheat flour has higher protein content than all purpose flour. It has 13.21 grams protein/ 100 grams flour meanwhile all purpose flour only has 10.33 grams protein/ 100 grams flour. So, does it mean that whole wheat flour has higher gluten than all purpose flour? The answer is NO. Whole wheat flour has lower gluten than all purpose flour. Hey, how come?? 

Back to the definition and the raw material of each flour. Whole wheat flour is made from whole grain including the bran and the germ. The bran and the germ itself contain some protein. But all purpose flour is made only from the endosperm.  Let's consider that about 3 grams protein content difference are from the bran and the germ. So basically, the endosperm has the same protein content, which can be assumed they both has same gluten content. But why whole wheat flour product can not form gluten as well as all purpose flour product? Once again, it is because of the bran and germ. 

Before we're talking about bran, let's back to how gluten formed for a while. Gluten is formed from 2 proteins which is gliadin and glutenin which will interact with presence of water during stirring or kneading process. There are some factor which can affect gluten formation. One of them is the presence of bran and germ. The bran can do some physical disruption of expanded gluten matrix. Bran can cut trough gluten matrix during the kneading or mixing and thus will weaken the gluten structure formed. Beside that, it is possible that there is a competition between bran and gluten protein to absorb water during the process. It will decrease the gluten that formed because gluten formation definitely need water. 

Meanwhile, wheat germ contains a substance called glutathione. In world of baked product, glutathion is common called as a gluten inhibitor because it can limit the development of gluten. That's why,  it is always suggested to add bread flour or gluten flour to make whole wheat bread to keep the texture of the bread. 

I did a small experiment on my kitchen using all purpose and whole wheat flour. I made 2 recipes of orange muffins. One was using all purpose flour and the other was using whole wheat flour (I was using whole wheat flour only 3/4 part of total flour and using all purpose flour for the rest). I was using the exact same recipe for both muffins except the type of flour. 

This is the result. The muffin on left side on both pictures is made using all purpose flour (let's call it muffin A) and the other is made using whole wheat flour (let's call it muffin B). The texture of muffin A is softer than muffin B. Inside and outside. The color of muffin A is lighter than muffin B. The most interesting is the difference of their shape. Muffin A is more compact than muffin B. As we can see in the picture, the top part of muffin B is wider than muffin A. It seems that the batter spreading too much during the baking process. I think it is because the gluten that formed in muffin B is not strong enough to hold the shape of the muffin like in muffin A. Muffin B is crumbly a lot as well even though it is heavier and more dense than muffin A.

I did some preference test as well. I asked my friends and my family to try them and compare which one is they like more. Most of them choose muffin A because it is softer than muffin B. I personally prefer muffin B than muffin A because for me the bran that presence in muffin B give a unique taste and texture in my mouth. But overall they are edible, acceptable, and taste great. 

So, answering the very first question. Can we substitute all purpose flour with whole wheat flour? Yes we can. But it would be better if we do not substitute the whole part of flour with whole wheat flour. It is needed in order to keep the texture and shape of the product. Some reference said substitute 70% and add the rest with all purpose flour or gluten flour. Meanwhile, other reference said 50:50 is good. And it is depend on the type of baked product. Too bad i do not have time and material to do all those experiment. I was thinking to do the experiment with dinner roll and playing with the amount of whole wheat flour for my muffin. But this is good enough to satisfy my curiosity. :)

Why  does whole wheat flour exist? What is the advantage adding bran and germ into the flour?

See you on part 2 with the answer :)

References : 

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1 comment :

  1. Hi,

    What do they call "Whole wheat flour" in the Netherlands? I am now sure that it is not Volkoren tarwebloem or Volkoren tarwemeel.