He mentioned that he has had a hard time figuring out baking gluten free and that you cannot substitute one flour straight across for wheat flour, and he asked about using gums.
Well, these are valid points. It really doesnt work to sub just say, rice flour for wheat flour and expect to have the same results as you would with the wheat flour. This is because the flours don't have the same components as wheat flour that give it the elasticity or starch or proteins. So to compensate, you need to make a blend of at least 3 flours, and depending on what you are making would you need to add a gum or agar or flax, etc. to get your elasticity and cohesion.
I have found that for some cakes if you don't use eggs, you would need some gum for the cohesion and sponge texture. Same for breads, you can forgo gum if you plan to eat or consume it all right away, but by day two it becomes crumbly and loses cohesion.
Usually cookies, scones, some muffins (like my oatmeal muffins) do not require gum at all in them. Pie crusts dont need the gum either, you want them flaky and to melt in your mouth.
On to flour components. Its good to have a base flour, the main one that has your protein components like brown rice, amaranth, quinoa, buckwheat, etc., then you want a starchy sweet type flour like tapioca, sorghum, white rice flour, etc., then you need a stach flour which provides the chew and thickens and makes your baked goods lighter and fluffier, like potato starch, corn starch, or arrowroot. However, when baking cakes, if you are wanting the light airy cake textures, you want to keep it fairly stachy flours, the blends I have had the most success with, that keeps people raving over taste and texture are white rice, tapioca or sorghum and arrowroot or potato flour. I have found that Bob's Red Mill's All Purpose GF Mix is fab for cookies as its base is a blend of bean flours and for some reason seems to make an awesome base for cookies. For my breads I like a mix of protein rich flours, quinoa, almond, amaranth, etc., mixed with tapioca and a starch. those are my preferences, and I think they work well for crusty crusts and soft chewy interiors.
When converting a traditional recipe to gluten free, weight is the key to success. All flours have different weights and how you measure a cup is going to be different everytime. Weighing your flours is the most consistent and will ensure your success. using a base weight of 140 grams equaling 1 cup of traditional flour will ensure you get the right amount of flour for your recipe. Look back at my Lemon Tea Cakes recipe, that was converted straight across.
So assuming 140 grams equals one cup, if your traditional recipe says 1 1/2 cups of flour, you would weigh out 210 grams of your flour mix, and proceed from there.
I would strongly recommend you go buy a digital scale that weighs both in ounces and grams. doesnt have to be expensive. Trust me that it will become the most important tool in your kitchen for baking. You will have consistency in your cakes and cookies everytime.
The other thing I will recommend to you is to get a copy of Michael Ruhlman's book, Ratios. It is invaluable in understanding how to make the basics and you can create many wonderful things from there.
No difference in quantities for baked goods when converting flour wise, as long as you weigh. Breads are different, when converting a bread recipe you will need at least half again as much liquid as what is called for in the original recipe. If the original recipe calls for 1 cup of liquid, you will add at least 1/2 to 1 cup more. You want the bread dough more like a thick shiny pancake batter. the amount of the water or liquid will also depend on your flours you are using.
And when mixing your breads, the last step is to beat the dough on high for 3 minutes to activate the gum acting as the gluten. This also serves to help beat air into your dough and helps it rise better.
When you have things you need to roll out like pie crusts, some cookies, etc., a little flour on the surface can help, but rolling between two sheets of parchment paper or cling wrap (the clear stuff) works best and your rolling pin won't stick to the dough. Some doughs need to be chilled and firm before rolling out, like pie crusts.
Otherwise, the basics are the same for creating any delicious baked treat.
These are my observations and techniques that give me amazing results time after time, and suprise everyone who tastes them. They always get an amazed look of sheer surprise and pleasure, and the question always is, "This is gluten free???" That is success in my book, and I get a lot of pleasure in making and sharing a superb goodie for my friends and loved ones. Which may explain why my nephews always want me to make their birthday cakes.
Have questions? Not sure of yourself? Ask away, and don't be afraid to jump in and try it. If it fails, oh well huh? You learned what not to do, and probably still have something tasty you can remake into something else, like cake crumbs in ice cream, or a trifle, in yogurt.... oh the list is endless. Dive in and enjoy baking again! Its not that scary or complicated!