In the last couple posts, we explored the chemical structure of fats, learned why fats repel water, and discussed how they melt. Moving forward, we’ll focus on how these properties affect our baked goods. As we’ll see, fats are crucial for the texture, flavor, and sensory properties of our food. Let’s start with a closer look at the molecular interactions that create tender textures in our bakes.
One of fats’ most important functions is tenderizing. Tender foods, like a perfectly cooked steak, are easy to bite through. In baked goods, the crumbly, melt-in-your-mouth textures of cornbread (versus a baguette) or shortbread (versus a chewy chocolate chip cookie) are also described as tender. The difference between tender and tough foods often comes down to the proteins. In steak, excess heat removes water and squeezes the proteins into large clumps that are hard to separate, so overcooked meat is difficult to chew. Similarly, if we overmix muffin batter or overwork pie crust, we form large, strong gluten networks that have a tough texture. To minimize gluten development and create a tender product, we should minimize mixing. But we can also develop recipes that use tenderizers like fat and sugar to reduce structure from tougheners such as gluten and starch.
Fats inhibit gluten formation.
One way fats (and emulsifiers) tenderize is by preventing gluten formation. You may remember that gluten is a protein that forms when flour is hydrated, and it becomes stronger and tougher with mixing or kneading. So if we block the flour from water, we prevent gluten from forming, and we are one step closer to a more tender baked good.
As we discussed in the context of gluten, fat prevents gluten formation by forming a barrier between flour and water. Think of a bowl of flour. If we add oil to the flour, the flour becomes coated in oil. The oil now repels any water we might add to the mixture. Without access to water, the gluten proteins in the flour cannot hydrate, so they cannot link together to form structure.
Cake recipes often use fat to minimize gluten development. After we cream the butter and sugar together, we add the dry ingredients. The flour gets coated in butter, and only then do we add the watery milk. Since the flour is greased, it absorbs less water and develops less gluten. Notice that order matters. If we add the milk to the butter first, then the flour, more gluten will form before the fat has a chance to coat the flour and seal it off from the water. Read more about my experiment on mixing order in cupcakes here.
However, combining flour with water first is a common strategy for bread doughs that contain a lot of fat, like brioche and milk bread, which need to develop a strong gluten structure to hold gas created by yeast. When we leave the fat for last, we develop gluten before the fat can interfere. In fact, with this mixing order, the bread actually rises higher. The fat lubricates strands of gluten and helps them stretch further to hold a greater volume of air. Even fermenting the dough in a greased bowl can contribute to volume.
Shortbread cookie recipes also contain a lot of fat. Many of these doughs are crumbly and difficult to work with, especially if they also contain nuts. To create a dough that’s easier to roll and shape, we can first add some water to the flour to develop gluten, and then add the butter. The resulting cookie still melts in the mouth, but the dough is more manageable.
Recipes for other bakes such as muffins, quick breads, choux pastry, and yeast breads add watery and fatty ingredients to the flour at the same time. In this case, fat tenderizes by coating some of the flour and preventing a portion of the gluten from absorbing water.
Liquid oils and soft fats coat flour better than hard fats.
Not all fats are equal tenderizers, though. Oils are liquid, so they can flow to coat flour more completely than solid fats like butter. Fats that are softer, such as shortening or warm butter, also coat flour more effectively than harder fats. The more thoroughly the flour is coated, the less water reaches it, the less gluten forms. Many muffins and quick breads are made with oil for texture. The oil reduces gluten formation, so oil muffins are often more tender than muffins made from other fats.
Some fats contain water.
Oils are also more effective tenderizers because they are 100% fat. Every single molecule in oil is a fat molecule. The same is true for lard and shortening. Butter and margarine, on the other hand, are only about 80% fat. So in the same volume of butter or margarine, there is less fat available to grease flour and prevent gluten formation. In fact, 16–18% of the molecules in butter and margarine are water molecules that contribute to gluten formation!
Coated flour absorbs less water.
Oil muffins and quick breads are also more moist than ones made from solid fat. Since oil is liquid at room temperature, we perceive more moistness in oil muffins. Furthermore, since oil coats flour so effectively, the flour absorbs less water. This leaves more water free in the batter, which translates into more moisture in the baked muffin.
As we discussed in the context of gluten, the difference in water absorption due to fat can be dramatic. Shirley Corriher has two “Ultimate Brioche” recipes: one where the flour is mixed with water then butter, and another where it’s mixed with butter then water. The recipe that combines the flour with butter first contains 25% less water.
In fact, fat can effectively waterproof pie crusts. If we incorporate miniscule pieces of fat into the flour, the fat quickly melts in the oven, coats the flour, and prevents it from absorbing water and becoming soggy. As we’ll see in the next post, however, this type of crust will not be flaky.
Fats prevent starch gelatinization.
Fats also tenderize by preventing starch from setting. Starch, like gluten, provides structure, especially in bakes that contain a lot of water. And like gluten, starch needs water to create that structure. Fats and emulsifiers inhibit starch gelatinization the same way they prevent gluten formation: by coating the starch and preventing water from reaching it. By limiting the amount of water available to the starch, the fat increases the temperature at which the starch gelatinizes, so the starch sets later and the baked good is more tender. Fat functions the same way in starch-based sauces and custards.
Fats slow staling.
Fats and emulsifiers also interfere with starches after baking. Remember that one cause of staling is retrogradation, where cooked starches reorganize into hard, dry crystals over time. Fats bond to cooked starches and prevent them from recrystallizing, ultimately delaying staling and increasing the shelf life of baked goods.
Solid fats contribute to leavening.
Another crucial way that fats contribute to tenderness is through leavening. When air bubbles in our doughs and batters expand in the oven, they stretch the surrounding batter thin to create a more tender product. In recipes where fat and sugar are creamed together, like in cake and cookies, the air comes from the fat. Creaming creates tons of tiny air bubbles, which later expand (with the help of heat, baking soda, and baking powder) to produce a high-volume, tender bake with a fine crumb.
Remember that fats do not like water, but they don’t mind air. When we cream air into solid fats like butter, crystals of fat molecules surround the air pockets and hold them within the fat. (Fat in whipping cream holds air the same way.) However, only solid, saturated fats form the crystals that stabilize air bubbles. Any air we beat into liquid oils (or melted fats) would quickly rise out of the oil without contributing leavening. This is the reason butter should be creamed at a cool room temperature. Any warmer, and it will start to melt, reducing the amount of air it can hold. If the butter is too cold, it’s not soft enough to create air pockets.
Butter does not contain air, so it’s crucial to cream it until it’s light and fluffy to create a light, fine-textured cake or cookie with high volume. The rough edges of sugar help to carry air into the butter, so butter and sugar are usually creamed together. Shortening, on the other hand, already contains about 12% air, so it is more forgiving. Some recipes don’t cream it at all!
Emulsifiers create finer texture.
We can often skip the creaming step with shortening because it contains emulsifiers. Butter naturally contains about 2–3% emulsifiers, but shortenings like Crisco can contain much more. Remember that emulsifiers help to combine fat and air with water. In cake batter and cookie dough, the air is held in the fat, so emulsifiers distribute the fat and air more evenly throughout the batter. This ultimately creates an even finer crumb in the baked good. Some liquid shortenings used in commercial bakeries have so many emulsifiers that you can directly combine all of the cake ingredients, then whip air into the batter. The emulsifiers (and some solid fat crystals) from the liquid shortening hold the air. The emulsifiers in liquid shortening are also so effective at coating flour that manufacturers typically recommend reducing the fat content by about 20% when substituting it for another fat.
One of fats’ most important roles in baking is tenderizing. In cookies, breads, and cakes alike, fat reduces structure by preventing water from reaching tough structural molecules. But fat can do much more. In the next post, we’ll take a closer look at laminated dough: scallion pancakes, baklava, puff pastry, and pie crusts, which require layers of fat to create flaky sheets of dough.
Brooker, B. E. The Stabilisation of Air in Cake Batters – The Role of Fat. Food Structure, 12(3), 285–296, 1993.
Corriher, S. O. Bakewise; Scribner: New York, 2008.
Figoni, P. How Baking Works, 3rd ed.; John Wiley & Sons, Inc.: Hoboken, 2011.
Nelson, D. L.; Cox, M. M. Lehninger Principles of Biochemistry, 6th ed.; Freeman, W. H. & Company: New York, 2012.
Yamaguchi, Y.; Okawa, Y.; Ninomiya, K.; Kumagai, H.; Kumagai, H. Evaluation and Suppression of Retrogradation of Gelatinized Rice Starch. Journal of Nutritional Science and Vitaminology, 65, S134–S138, 2019.