Fats in the Kitchen: Flavor

Over the last few posts, we’ve discussed some different textures fats can create, such as tenderness and flakiness. But we haven’t yet explored one of the most important functions of fat. As my grandmother told me, “有油才會香!” You need fat for flavor! Fats like butter and olive oil have a unique taste, but more importantly, all fats carry flavor in our food. They’re also responsible for textures such as creaminess and moistness. And of course, we can’t forget the distinctive taste of fried foods. Today, we’re going to break down the many flavors of fat.

Fats concentrate flavor.

In stir-fries, once we heat up the oil, we add the aromatics: ginger, garlic, chilies, and onions. In cookies and cakes, we add extracts and flavorings to the butter. And in a butcher shop, the best cuts of meat are marbled with fat. Fat is a vehicle for flavor.

Fat molecules repel water.

Fat elevates food because it holds flavor. To better understand why flavor compounds dissolve more readily in fat than in water, let’s first review why water and fat don’t mix. Water molecules are structured so that they attract each other like magnets. Fat molecules, on the other hand, don’t form these attractions. They’re like wood blocks.

If we imagine a mixture of magnets and wood blocks, we expect all the magnets to stick together. In a glass of water and oil then, the water molecules stick together and form their own layer of liquid, and the oil floats separately on top.

Fat molecules (left) do not attract each other, but water molecules (right) do. The black lines indicate attractive forces between water molecules.

Flavor compounds tend to repel water.

Flavors are chemical compounds, too. Our tongues sense them and tell our brains what we taste. And just like water and fat, every flavor compound can be characterized on a spectrum from wood-like to magnet-like based on its structure. (Scientists call this property polarity.) Magnet-like compounds, including salt, sugar, baking soda, and vinegar, stick to other magnet molecules, like water. And because they attract water at the molecular level, they dissolve. (Remember our detailed discussion about how sugar dissolves?) Scientists describe any magnet-like compound as hydrophilic, or water-loving.

Sugar (or sucrose) is an example of a magnet-like, hydrophilic molecule. It dissolves in water because it attracts water molecules, as indicated by the dashed blue lines.

Wood-like compounds, on the other hand, including fats and the flavor molecules of citrus, onion, or ginger, repel water. We call them hydrophobic, or water-fearing. They don’t dissolve in water, but these molecules do dissolve in fats because the wood-like molecules don’t repel each other.

(Remember, we’ve also discussed the terms hydrophilic and hydrophobic in the context of proteins!)

“Aromatics” are likely to dissolve in fat.

Most flavor compounds are wood-like or hydrophobic, so they dissolve more readily in fat. As a result, fats carry higher concentrations of these flavors to our tongues. Furthermore, fats (along with anything dissolved in them) coat our tongues and linger on our taste buds, so they can change our perception of certain flavors.

When we bake, we typically add flavorings like vanilla extract, grated ginger, or lemon zest to the fat. Because fat holds onto the flavor compounds in these ingredients more strongly, it prevents them from vaporizing in the heat of the oven. As a result, the flavors are stronger within the bake.

In these gingersnaps, fresh grated ginger is creamed with the butter and sugar to give the cookies a strong ginger flavor.

The words we use to describe flavors, like “fragrant” or “aromatic,” are themselves a clue to the molecules’ hydrophobic nature. If something is aromatic, we can smell it. And in order to smell something, our nose detected the molecule in the air. For the molecule to be in the air, it must have evaporated at room temperature. This suggests it wasn’t very strongly attracted to the water inside the food. So the molecule is more wood-like than magnet-like, and it dissolves readily in fat.

Some vitamins are also fat-soluble.

In addition to flavor compounds, some vitamins (specifically A, D, E, and K) dissolve in fat, not water, because they are hydrophobic. (That’s why they’re called the “fat-soluble” vitamins.) Our bodies need fat to store, transport, and use these vitamins, which is one reason fats are crucial to a healthy diet. In food, these vitamins are concentrated in fat as well.

Fats have their own flavor.

Of course, some fats have tastes of their own. Olive oil, coconut oil, and some lards are distinctively flavored, so if you choose to use them, make sure they complement the bake. In most cases, though, butter is king of flavor. Although shortenings and margarines can be butter-flavored, they do not match the subtlety and complexity of real butter. Neutral-flavored oils such as vegetable oil and canola oil don’t have much flavor (unless they’ve gone rancid), but they still add richness to food.

Fats add creaminess

Many desserts, like custards, mousses, and ice creams, are both rich and creamy. Richness can come from any fat, but creamy desserts often contain a lot of dairy products like milk, cream, or yogurt. The unique fat distribution in these ingredients gives us the perception of creaminess.

Dairy products contain fat.

All dairy products start with fresh milk. Milk is mostly water, but it also contains fats and proteins. As we discussed, water and fat repel each other and we expect them to separate, yet they’re evenly combined in milk. Any homogenous mixture of water and fat, like milk, mayonnaise, or vinaigrette, is an emulsion.

Emulsions are possible with the help of emulsifiers, which blend the water and fat together. As we described a couple posts back, emulsifiers surround tiny droplets of fat, shield them from water, and help them dissolve. If we return to our analogy of water molecules as magnets and fat molecules as wood, adding an emulsifier is like disguising the wood blocks as magnets. With the help of this magnetic coating, the wood blocks attract water molecules and dissolve.

Emulsifiers (the red and yellow molecules) coat small droplets of oil and dissolve them into water.

In mayonnaise, emulsifiers come from the egg yolk. Without the yolk (or an emulsifier substitute), the mayonnaise would never form. In milk, the emulsifiers are specific proteins and lipids. As in any emulsion, these emulsifiers surround tiny spheres of milkfat and dissolve them into the water.

Milkfat tastes creamy.

Dairy products, including cream, butter, and yogurt, retain the small fat globules from milk. They taste creamy because the little bubbles of fat roll over our tongues. When we use these ingredients in our desserts, we add their fat globules and their creaminess. The higher the fat content, the creamier the final product. So a heavy cream custard is creamier than a whole milk custard. In my home state of Pennsylvania, the ice cream at Penn State Berkey Creamery is famous for its high milkfat percentage, which makes an exceptionally rich and creamy treat.

Ice cream tastes creamy because it contains tiny bubbles of fat that roll over our tongues. The higher the fat content, the richer and creamier the ice cream.

When we work with dairy products, there’s always a risk of separating the fat from the water and breaking the emulsion. Overwhipped cream, for example, splits into butter and water because the milkfat sticks together to hold air. Frozen cream will also split because ice crystals destroy the protective layer of emulsifiers around the fat. We’ll discuss best practices for working with cream in a future dairy series!

Fats can taste moist or waxy.

As we discussed in the post about tenderness, fats and emulsifiers prevent flour from absorbing water and thereby keep more water free in our bakes. More significantly, oils, which are liquid at room temperature, add moistness to baked goods. The more fluid the fat at body temperature, the wetter it tastes, and the more moistness we perceive. This is one reason oils create moister cakes than solid fats.

Oil muffins taste moister than butter muffins because oil is liquid at room temperature.

When it comes to solid fats, mouthfeel is dependent on how quickly the fat melts in our mouth. The longer the fat remains solid, the waxier it tastes. Melting behavior is a combination of two factors: temperature and speed.

Puff pastry margarine, for example, is designed to remain solid at warm temperatures. This gives bakers more time to fold and roll it in laminated dough, but the high melting point also means that the margarine needs more time to melt in our mouths. Margarines and shortenings also tend to melt more slowly than butter. A wide melt curve means that we don’t have to worry as much about the temperature of these fats when we cream them, but the fat tastes waxier because it melts more slowly.

Of the solid fats, butter has the best mouthfeel. It melts right at body temperature, and it melts quickly. Although its melting behavior makes butter the most finicky solid fat, its superior mouthfeel and flavor make it a popular choice for home and professional bakers alike.

Fried foods have a distinctive flavor.

In the oven, choux pastry becomes a cream puff, but in the fryer, it becomes an indulgent beignet or churro. Baked doughnuts may be a more health-conscious choice, but they cannot match the flavor of fried doughnuts. Why are fried foods so tasty?

One characteristic of fried foods is their texture. We get the signature crisp exterior and soft, fluffy interior when the food gets very hot, very quickly in the fryer. We’ll discuss this process in much more detail in a future series about cooking methods.

Fried foods also have a unique flavor that results from the breakdown of fat molecules. In the heat of the fryer, fats react with oxygen in the air and with water from the food to produce many different chemical compounds. Some of the smaller compounds vaporize as gas, which creates the scent of frying food. Other compounds are responsible for the taste of fried foods, and they’re absorbed by the food as it cooks.

Liquid oils are especially prone to these chemical reactions because they’re high in unsaturated fats. In the introduction to fats, we described what unsaturated fats are and why they’re so reactive. Remember that their reactivity also makes them prone to spoilage, which occurs when air, light, and heat break down the fat and make it rancid.

With air, light, or heat, fat molecules break down into smaller fragments. Depending on the molecule, these fragments may make the oil rancid, or they may contribute desirable fried-food flavor.

Fats contribute to flavor and mouthfeel.

Fats are indispensable in the kitchen. Their chemical structure allows them to concentrate flavor compounds in both savory and sweet dishes. They add richness to our food, and they make creamy custards and moist cakes. Fats can also contribute their own distinctive flavors to complement other ingredients in our bakes.



References

Choe, E.; Min, D. B. Chemistry of Deep-Fat Frying Oils. Journal of Food Science, 72(5), R77-R86, 2007.

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

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

McGee, H. On Food and Cooking; Scribner: New York, 2004.

Nelson, D. L.; Cox, M. M. Lehninger Principles of Biochemistry, 6th ed.; Freeman, W. H. & Company: New York, 2012.

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