"Why can't you just reduce the fat in a recipe?"

"Reducing fat in baking changes the physics of the entire system. Less fat means more gluten development, which means chewier texture. It also means less moisture retention and potentially more spread in cookies. Some fat reduction is possible, but it changes the product. Low-fat baked goods compensate by adding other moisture-retaining ingredients like applesauce or yogurt, which change the structure differently."

"Why does butter make baked goods taste better than shortening?"

"Butter contains milk proteins and lactose that participate in the Maillard reaction during baking, producing complex flavors. It also contains diacetyl and other flavor compounds from the original cream. Shortening is nearly pure fat with no flavor-producing components. The texture shortening produces is often more tender than butter, but the flavor is flat."

"What does oil do differently than butter in muffins?"

"Oil is 100% fat with no water. Butter is about 80% fat and 16-18% water. In a muffin, oil coats gluten proteins completely and stays liquid at room temperature, keeping the crumb moist longer than butter, which solidifies as the muffin cools. Oil-based muffins are typically more moist on day two than butter-based muffins. They're also denser because there's no air incorporation and no flaky layering."

"What is the creaming method and why does it matter?"

"Creaming means beating softened butter with sugar until light and fluffy. During this process, sugar crystals cut tiny air pockets into the fat. When the batter bakes, those air pockets expand with heat and CO2 from leaveners, creating lift. This is the primary leavening mechanism in many cakes. It only works with butter or shortening, not with liquid oil, which can't hold air bubbles."

What Fat Does in Baking: Tenderness, Layers, and Moisture

Quick Answer

Fat coats flour proteins and prevents them from fully hydrating and linking into gluten networks. Shorter gluten means a more tender, less chewy texture. The shortening effect. Beyond tenderness, solid fats create distinct layers in pastry, fats retain moisture by slowing evaporation, and fat coats the palate to extend flavor perception. Solid and liquid fats behave very differently in the same recipe.

The Science

A pie crust with shortening and a pie crust with butter use the same basic recipe. The ratio of fat to flour to water is nearly identical. But one is flakier and the other is more tender. That result comes from the physical state of the fat and what it does to flour at a molecular level.

The Shortening Effect

Fat’s primary job in most baked goods is to shorten gluten. “Shortening” in this context isn’t a brand name: it’s a description of what fat does to gluten strands. It makes them shorter.

Gluten forms when the proteins glutenin and gliadin in wheat flour absorb water and link together into long, elastic networks. More water contact, more gluten. More mixing, longer and stronger gluten networks. Read the full mechanism in gluten development.

Fat intercepts this process. When fat coats flour particles before water is added, it creates a hydrophobic barrier that slows water absorption and reduces the contact surface between proteins. Less contact means shorter, less connected gluten strands. The result is a tender, crumbly, or short texture, depending on how much fat is present.

A high-fat pastry dough (pate sable, shortbread) has so much fat that gluten development is nearly eliminated. The texture is crumbly, almost powdery. A lower-fat dough (pie crust, brioche) has enough gluten for structure but the fat breaks it into shorter segments that make the crumb tender rather than chewy.

This is opposite to bread baking, where you want maximum gluten and deliberately avoid adding fat until after initial gluten development.

Solid Fat Creates Layers

Flakiness comes from solid fat, not liquid fat. A cold piece of butter or shortening, cut into flour, remains as distinct pieces coated in flour. Those fat pieces don’t dissolve into the dough during mixing. They stay separate.

During baking, two things happen. First, the water in butter turns to steam and the air trapped between fat and dough layers expands. This puffs the layers apart. Second, as the fat melts at baking temperature, it flows slightly and leaves voids in the dough structure that get filled with steam.

The result is the layered, flaky texture in pie crust and croissants. The “layers” you see in flaky pastry are the spaces where solid fat once was.

Liquid oil doesn’t create layers. It distributes evenly through the dough, coating all flour particles uniformly. No distinct fat pieces, no distinct layers, no flakiness. Oil-based doughs are tender but never flaky. For croissants and pie crust, this is why the fat crystallization state of the butter matters enormously.

Moisture Retention

Fat slows moisture loss from baked goods in two ways.

During baking, fat surrounds water molecules partially, slowing their evaporation from the crumb. A higher-fat cake or quick bread loses less moisture in the oven than a low-fat equivalent, though the effect is moderate.

After baking, fat in the crumb creates a barrier that slows moisture migration from the crumb to the crust and from the baked good to the surrounding air. This is why high-fat baked goods (pound cake, brownies) stay moist for days, while low-fat baked goods (angel food cake, most biscuits) stale faster.

Oil-based baked goods often stay moist longer than butter-based equivalents because oil is liquid at room temperature and continues to coat crumb proteins more completely than solidified butterfat.

Creaming: Air as Leavening

The creaming method (beating softened butter with sugar) is a fat-specific technique that doesn’t work with liquid oil. During creaming, sugar crystals mechanically cut air pockets into the semi-solid fat. These tiny air cells are stabilized by the fat’s structure.

When the batter bakes, the air pockets expand with heat and receive additional CO2 from chemical leaveners. The fat-stabilized air cells provide a starting structure for bubble expansion. The result is a cake with good volume and an even, fine crumb.

Butter needs to be at the right temperature for this. Too cold (below 60°F) and it’s too stiff to incorporate air well. Too warm (above 75°F) and it’s soft enough that air cells collapse. The ideal temperature for creaming butter is 65-70°F, where it’s pliable but still holds its structure.

Shortening, which has a higher melting point and different crystal structure, is better at holding air during creaming. Shortening-creamed cakes can be slightly lighter in texture than butter-creamed cakes, though significantly less flavorful.

Butter vs. Shortening vs. Oil: The Matrix

Butter is about 80% fat, 16-18% water, and 2-4% milk solids. The water creates steam for lift and the milk solids participate in the Maillard reaction for flavor. The fat content provides tenderness and flakiness. The flavor is complex.

Shortening is nearly 100% fat, no water, no flavor compounds. It produces the most tender texture because there’s no water to develop gluten and no steam mechanism. In pastry applications, it produces a shorter (more crumbly) texture than butter. In cakes, the air-holding capacity is slightly better. Flavor is absent.

Oil is 100% fat, liquid. Distributes evenly, no flaky layers, excellent moisture retention, stays liquid after cooling which extends moist texture. Best for quick breads, muffins, and applications where moistness is the priority and flakiness isn’t wanted.

No single fat is superior in all applications. The question is always what result you need, and the answer determines which fat serves that result.

What This Means for You

Use cold butter for flaky pastry. Use softened butter for creamed-fat cakes where you want lightness from air incorporation. Use liquid oil for quick breads and muffins where you want moist, tender crumb without any flakiness. Never substitute oil for butter in pastry recipes expecting the same result, the physics are completely different. Shortening produces the most tender texture but the least flavor.