Flour – Why is there malted barley flour in all purpose flour

Bread is basically just flour, water, and yeast, so it's pretty hard to make it inedible unless you burn it to a crisp in the oven.

The difference between all-purpose flour and bread flour is gluten strength; if you substitute all-purpose flour then your bread won't rise as high or be as strong; this is a desirable quality in, say, cake, but not bread.

However, AP flour isn't that far off from bread flour in terms of gluten; while cake flour may be as low as 6% and bread flour can be as high as 14%, AP flour tends to weigh in at around 10% or more, which is why it's called "all-purpose". As Michael says, yeast bread is actually not as sensitive to the exact quantities as (for example) most pastries, but it's still better to use a recipe that was actually built around AP flour instead of just trying to substitute it for bread flour.

If you are determined to make the substitution, then I would suggest you try to find some wheat gluten and add a small amount of that to the AP flour. Mathematically, if you assume that you're lacking some 3% protein, then you'd want to add about 1 tbsp of gluten for every 2 cups of flour. It's really not much, though, and if you don't have or can't find wheat gluten then your bread would probably survive anyway with AP flour, it just might be a little denser than you expect.

Maida is wheat flour similar to what is sold in the US as cake flour. Like cake flour, maida is finely milled, and it has less protein than all purpose flour. You can use it for bread and cakes, as well as chapatis, parathas and puris.

To achieve a flour more like all purpose or other flour types, you can add gluten to maita. According to The Fresh Loaf, maida typically contains 7.5% gluten (if anyone can find a more authoritative source, please edit accordingly).

Cooking for Geeks has a good article about the gluten content of other flours:

High gluten flour and bread flour is produced from hard wheat. High gluten flour has a gluten percentage of about 12-14% while bread flour contains about 10-13% gluten. Both flours are almost completely made of hard wheat, but some high gluten flours are treated to reduce starch content, raising the gluten content to around 14%. These flours are generally used for making breads. High gluten flour is reserved for breads that are extra elastic such as bagels and pizza.

Cake flour is produced from soft wheat and is low in gluten content (8-10%). This flour is used for making delicate cakes. Baked goods made with cake flour has a tendency to crumble because of the low gluten content.

All purpose flour is made from a mixture of hard and soft wheats. The gluten content ranges from 9-12%. This is the most versatile flour because it can be used to make both cakes and breads. However, breads won't be as chewy and cakes won't be as tender as if you used bread or cake flour.

Pastry flour is also a mix of hard and soft wheat flours with an emphasis on soft. Generally, the gluten content is 9-10% and is often recommended for pie crusts.

So, again according to The Fresh Loaf:

Then if you're interested in the details of the math, start out with a formula like (100parts/100parts * 7.5%) + (Nparts/100parts * 75%) = 10.5% [or 9.5% or 12.5% or whatever your desired result is], then solve for N. Skipping intermediate steps, simplification gives N = ((end-percentage-goal * 100) - 750) / 75 (Even this math is actually an oversimplification that's not quite right. It takes the not-quite-correct shortcut of directly adding percentages without accounting for the total being more than 100 grams. Hopefully though it's "good enough" ...) The bottom line is: for every 100 grams Maida, add somewhere between 2.6 and 6.6 grams GlutenPowder. Adding 2.6 grams GlutenPowder will give a result with about 9.5% gluten, adding 4 grams GlutenPowder will give a result with about 10.5% gluten, and adding 6.6 grams GlutenPowder will give a result with about 12.5% gluten.

According to the original author of this answer, "You might find that bread and cakes made with maida don't keep as well as the same things made with all-purpose flour, but home baking never stays around for more than a day in my experience."