The Difference Between Dark and Light Brown Sugar

If you have ever been in the middle of a baking project only to realize you don't have the right kind of brown sugar, you are definitely not alone. Your recipe for sweet potato casserole calls for dark brown sugar, and you only have light. Or you need light for your favorite Christmas cookies, and you wonder how much the recipe will be altered if you use dark, instead. Honestly, there are many times I have used whichever brown sugar I had on hand–dark or light–and didn't flinch; it never seemed to impact the outcome of my baked item. So just what is the difference between dark brown sugar and light brown sugar, and why should it matter?

Most brown sugar available at the grocery store is actually refined white sugar that has been mixed with that classic Southern sweetener, molasses. The darker the brown sugar, the more molasses it contains. For light brown sugar, that usually means 3.5% molasses. For dark brown sugar, that amount is nearly doubled—6.5% molasses. This helps dark brown sugar have a deeper, more complex flavor that's closer to toffee or caramel.

You can even prepare your own brown sugar. To make the equivalent of 1 cup of dark brown sugar, add 2 Tablespoons of molasses to 1 cup of granulated sugar and pulse three or four times in a food processor. To make light brown sugar, add 1 tablespoon of molasses to 1 cup of granulated sugar and pulse.

Does this mean that now you need to keep two types of brown sugar on hand? Not really. For the most part, dark and light brown sugars can be used interchangeably in recipes, since dark brown sugar simply has a slighter higher molasses content. More molasses, however, means dark brown sugar has slightly higher levels of acidity and moisture which might cause a batch of cookies to rise a bit higher and taste more caramel-y than those made with light brown sugar. Still, the difference is very minor and should not keep you from carrying through with your baking project. Many recipes simply call for "brown sugar" in the ingredient list, so pick one type of brown sugar to keep in your pantry and bake freely.