Hello and welcome to the forum
How wonderful you bake with your grandson. Such time together are the making of cherished memories for the both of you.
Regarding pre-mixing:
Yes you can pre-mix your dry ingredients in advance. You can mix the flour, sugar, baking powder, baking soda and salt.
Store your mix in an dry airtight container. It’s important the container will be airtight to prevent any moisture from getting in.
The mix should hold at room temperature for one month. If you wish to store it longer, place it in the freezer. It should hold for approximately three months.
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Regarding adding the leavening:
You are correct leavening must be evenly distributed. Sifting is one step that should never be skipped or abbreviated.
The proper way to mix flour and leavening is to thoroughly whisk to combine. Then sift with a fine mesh sieve (see pic below). Depending on how fine the mesh sieve, the sugar and salt granules may be too large to go through it. If that is the case, then sift the flour and leavening. Then whisk in the sugar and salt.
I was taught to sift three times. Most professional pastry chefs that I have taken classes with sift three times as well. But I’ve noticed an aversion to sifting by younger bakers. Don’t quite understand it because it only takes a couple minutes to sift. They want to bake, but they just don’t want to do the work involved in baking—go figure.
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Saved your question about using just one leavening for last given it’s a complex question...
Yes, you can change the leavening to just one. BUT, it’s not advisable for several reasons.
Baking soda (sodium bicarbonate) is an alkaline. As an alkaline it requires an acid to activate. The minute it comes in contact with moisture and an acid, it will activate. So the activation happens before the batter is in the oven. Baking soda packs it punch fast and at the beginning of the baking process.
So if using baking soda only, enough must be added to ensure the leavening process is long enough to allow the batter to rise and set. And for a cake, the leavening process needs to continue for a good 25 minutes or longer.
But using baking soda only can be a problem. If too much baking soda is used and there’s not enough acid in the batter to activate all of it, the residual baking soda will leave a bitter aftertaste.
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Baking powder is mixed with an acid. Since an acid is already in baking powder you don’t need additional acid in the batter. This extends the leavening process. If you look at your can of baking powder it’s probably labeled “double acting.”
Since baking powder activates slower and longer, it doesn’t pack a big initial punch. So it may produce a slightly lower rise.
Common acids used in baking powder are sodium aluminum sulfate and sodium aluminum phosphate. There are some health concerns about aluminum. In addition the aluminum can produce a metallic taste.
I am also convinced that the aluminum is responsible for bitter gritty granules that sometimes develop in baked goods. It’s purely an adorable but every time I’ve talk to someone who has experienced this problem, The one constant is baking powder with aluminum.
I’ve never had those granules develop in any of my baked goods.
I only use aluminum free baking powder. And would encourage you to use aluminum free baking powder.
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Baking powder or baking soda alone can produce different textures in some applications.
In cookies using just baking soda produces that nice crisp edge and chewy bite. Baking powder alone in cookies produces a puffy, cake like texture.
So just keep that in mind that if you decide to use just one type of leavening it may change the texture.
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Baking soda and baking powder are NOT 1:1.
Baking soda is four times stronger than baking soda. If substituting one for the other you have to calculate the difference between them.
1 teaspoon baking powder = 1/4 teaspoon baking soda.
By weight:
Baking soda: 6 grams = 1 teaspoon
Baking powder: 4 grams = 1 teaspoon
Reminder: 1 teaspoon of baking soda produces the leavening power of 4 teaspoons of baking powder.
Leavening per cup of flour:
Baking powder: 1 teaspoon (4 grams) per 1 cup of flour
Baking soda: 1/4 teaspoon (1.5 grams) per 1 cup of flour
These are general guidelines, so a recipe may use more or less. I’ve noticed there’s a tendency among recipe developers to use more leavening than necessary. But most are excessive. But if you see a recipe with 3 or 4 teaspoons of baking powder, to two cups of flour, be a bit wary.
Any fine mesh sieve will work as a sifter.
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