Liquid Fat in Muffins

Many muffin and quick bread recipes use oil for a moist, tender crumb. But butter has a superior flavor, and it can melt into an easy substitute for oil. Although both butter and oil are fats, they differ at the molecular level, so a direct substitution won’t create the same exact bake. To learn more about the effects of substituting oil with melted butter, we compared the texture and taste of muffins made with both types of fat.

Experiment Overview

Goal: To taste differences in muffins made with oil and melted butter
Recipe: Best Ever Muffins from AllRecipes
Method: Mix and divide the dry ingredients and the wet ingredients except for the fat. Add oil or melted butter to each batch of wet ingredients. Add the wet ingredients to the dry ingredients. Bake, cool, and taste.
Results: Between the two types of fat, we noticed differences in
– Importance of temperature control
– Batter thickness
– Tenderness
– Taste
Conclusions: Oil makes a more tender muffin, and the batter is easier to prepare. But butter adds a rich taste that is especially noticeable in bakes that don’t have additional flavorings or mix-ins.

Testing Method

Ingredients and Equipment

  • 250g (2 c) Baker’s Corner bleached all-purpose flour
  • 1 Tbsp Baker’s Corner double-acting baking powder
  • 1/2 tsp Stonemill iodized salt
  • 150g (3/4 c) Baker’s Corner sugar
  • 242g (1 c) Friendly Farms Vitamin D whole milk
  • 1 Goldhen large egg
  • 28g (2 Tbsp) Carlini vegetable oil
  • 28g (2 Tbsp) Friendly Farms unsalted butter, melted
  • Whisk
  • Rubber spatula
  • 12-cup muffin pan lined with cupcake liners

Baking the muffins

  1. Preheat oven to 400°F.
  2. Whisk the flour, baking powder, salt, and sugar together in a large bowl (414g total). Divide in half (207g each).
  3. In a separate bowl, whisk the milk and egg together (300g total). Divide in half (150g each). To each portion, add either 28g vegetable oil or melted butter. Add the wet ingredients into the dry ingredients, and fold until just combined.
  4. Divide each portion of batter into six muffin cups.
  5. Bake for 20 minutes. Cool on a wire rack for 5 minutes, then remove muffins from pan to cool completely.


To better understand some of these results, I suggest reviewing the introduction to the structure and melting behavior of fats, and the post on how fats add tenderness to baked goods.

Importance of temperature control

As I added the fat into the rest of the wet ingredients, the most salient difference between oil and butter was the importance of temperature. Because fat does not mix with water, and milk is mostly water, neither fat blended well into the milk. But when I poured the melted butter into the milk and egg, it solidified into tiny chunks—the milk was too cold. Chunks of butter will form holes in a baked muffin as they melt away in the oven. Usually, we only want this to happen in puff pastry. So before moving on with the experiment, I had to microwave the wet ingredients to melt the butter while making sure I didn’t cook the egg.

Adding fat to the wet ingredients

The difference in the melting behaviors of oil and butter stems from their unique fat composition. Oil contains more unsaturated fat than butter. Remember that the shape of unsaturated fats prevents them from organizing into a neat, solid crystal, so oil will not solidify in cold milk. Butter, on the other hand, contains enough saturated fat to melt and solidify right around room temperature. So to prevent the butter from solidifying, it’s crucial that the milk and egg are at room temperature, not cold from the fridge.

Saturated fats (left) pack together neatly into solid crystals. Unsaturated fats (right) cannot form organized structures, so they remain liquid.

Batter thickness

After I combined the wet and dry ingredients for each batter, the oil batter felt thinner than the butter batter. Fats lubricate solid particles so that they slide past each other and flow more—we also see this when we use oil to thin chocolate—and in these batters, oil provided more lubrication than butter.

The oil batter (left) was thinner than the butter batter (right).

Although both the oil and butter were liquid, oil is 100% fat, while butter contains only about 80% fat. The remaining 20% is mostly water. Because butter contains less fat than oil, it contributes less lubrication to the solid flour particles, and the resulting batter is thicker.

As we’ve seen in castella cake, the consistency of a batter affects the rise of a bake because it determines how quickly gas moves through the batter. Although there weren’t dramatic differences in height or shape between the two types of muffins in this experiment, the batter thickness could affect features such as the pointiness of the muffin tops.

The two types of muffins were similar in shape and size.


As we discussed in detail here, oil theoretically creates a more tender, moist cake than butter for three reasons. First, as a liquid, oil can flow to coat flour more thoroughly. The better coated the flour, the less water it absorbs, the less gluten forms, and the more water remains in the final bake. Less gluten means tenderness, and more water means more moisture. Second, oil is 100% fat, which means that, gram for gram, there is more fat available to coat flour. And finally, oil is liquid at room temperature, whereas butter is more solid. The liquid oil in a cooled bake gives us the perception of moistness.

In these muffins, the difference was slight, but one of my two testers and I found that the oil muffins were softer and more tender than the butter muffins. (The other tester couldn’t detect any differences.) Although liquid butter coats flour more effectively than solid butter, it still contains less fat than oil, and it still solidifies when it cools. Even melted butter cannot fully duplicate the texture of oil.

The oil muffins were slightly more tender than the butter ones.


Although oil created a more tender muffin, butter was the clear winner when it came to taste. Neither of my testers detected a difference in flavor between the oil and butter muffins, but for me, the butter muffins were a league away. I had gotten tired of eating these muffins with all my experiments, but the butter ones seemed like a completely new recipe. The taste was richer and more flavorful. The difference was especially noticeable in these muffins because they didn’t contain any other flavorings, extracts, or mix-ins.


In muffin and quick bread recipes where the wet and dry ingredients are combined separately, oil creates a more moist, tender bake than butter. It’s also easier to work with because it won’t solidify. However, if you’re looking to add more flavor to a recipe, you can substitute the oil with an equal volume or weight of melted butter. Just make sure the rest of the wet ingredients are at room temperature or slightly warmer before adding the butter.


Corriher, S. O. Bakewise; Scribner: New York, 2008.

Figoni, P. How Baking Works, 3rd ed.; John Wiley & Sons, Inc.: Hoboken, 2011.

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