Hello Jordan. Nostalgic family recipes like those bran muffins are truly special, and I completely understand wanting to ensure they turn out with the proper texture and rise.
To replace baking powder, the standard proportion is:
For every 1 teaspoon of baking powder required, use 1/4 teaspoon of baking soda combined with 1/2 teaspoon of vinegar.
White vinegar or apple cider vinegar will both work nicely here without altering the flavor profile of hearty bran muffins.
Because bran batters are naturally dense and heavy, here are a few key tips to ensure you get the maximum amount of lift:
1. Sift or thoroughly whisk the baking soda into your dry ingredients (flour, bran, spices, salt) so it distributes evenly.
2. Stir the vinegar into your wet ingredients (eggs, milk, oil, sweeteners) before combining.
3. The chemical reaction between baking soda and vinegar begins immediately upon contact, creating carbon dioxide bubbles. For this reason, gently fold the wet and dry ingredients together just until combined, portion the batter into your muffin tin, and place them directly into your preheated oven without delay.
If you follow these steps, your muffins should have plenty of lift and a wonderfully tender crumb. Best of luck with your bake!