Don't Throw Out That Sour Milk! How Vintage Recipes Used The Ingredient For Delectable Chocolate Cake

Although unintentional, not getting through a gallon of milk before it starts to sour can happen, no matter how rare. It was more common before refrigerators became standard appliances in homes, which didn't happen until the late 1920s. Rather than throw out and waste expired milk in those days, people found a use for sour milk as an ingredient in cake batter.

Published in 1878 (only about 13 years after the Civil War), the book "Housekeeping in Old Virginia" is a collection of vintage recipes from 250 women edited by Marion Cabell Tyree. The recipe for Sour Milk Cakes on page 54 calls for 1 pint of sour milk. While you might never have heard of sour milk cake before, similar recipes today call for buttermilk instead.

The interesting thing is that sour milk is one of several substitutes you can use when you don't have buttermilk because they're virtually the same thing: milk that has started to ferment. Because of that, it's easy to swap the ½ cup of buttermilk in Daily Meal's two-layer chocolate cake recipe for ½ cup of milk that has gone sour in your fridge. The best part is that you don't have to purchase an entire carton of buttermilk for just one recipe.

Like buttermilk, sour cream, and yogurt — all products of soured milk — sour milk is a fantastic upgrade to chocolate cake batter because of how the higher acidity reacts with the other ingredients. One of these reactions occurs with the baking soda, producing carbon dioxide bubbles that incorporate more air pockets into the batter as it cooks. The result is a fluffier, lighter cake.

Also, the higher acidity reacts with the gluten in all-purpose flour, breaking down the long and fibrous molecules of this protein. The result is smaller protein pieces that give the cake a more tender texture while helping it maintain moisture as the batter bakes, putting it in the list of ingredients that will make your cake extra moist. It's also the same reason why adding sour cream to chocolate cake batter works so well.

On top of that, using pasteurized sour milk is safe in baked goods. Dana Gunders of the Natural Resources Defense Council told NPR's The Salt that it's unlikely to cause illness because the higher acidity creates an unfriendly environment for illness-inducing microbes.

There's one caveat to using sour milk as an ingredient in your chocolate cake recipe: Don't confuse it with spoiled milk. Although the terms are used interchangeably, sour and spoiled milk are not the same thing. Sour milk is milk that has begun fermenting, but it also isn't so bad or beyond expired that it has developed a nasty smell. So, if you have a container of milk in the fridge that has been open for a while but doesn't smell foul, you can taste it to see if it has soured: It will have a tang similar to buttermilk and plain yogurt.

Spoiled milk, on the other hand, will have a foul odor that's hard to ignore and gets worse the longer that the milk ages. It might start to turn yellow in color and develop a chunky texture, at which point it's best to avoid using it in baking (or anything else for that matter!).

Generally, how long milk lasts before going bad depends on whether or not it's open. Sealed milk can stay good up to seven days beyond the "use by" or "sell by" date, while opened milk can last up to three days after the date. However, raw milk could go bad a little faster than pasteurized milk. It's still safe even if it has soured, but you wouldn't want to use it in your coffee or cereal unless you like the imposing flavor. Like with buttermilk — the sour flavor isn't as imposing when used in baked goods and may only add a hint of tanginess.