The following essay is reproduced with permission from The conversationan online publication covering the latest research.
My mother loves butter. It’s the main fat I ate growing up. She spread it on any type of bread, potatoes, nut rolls or coffee cakes. She cooked exclusively with it.
When I was studying nutrition in college, I had a teaching assistant who recommended margarine over butter. I was shocked – and wondered about the difference between the two. It was one of the things that sparked my interest in food science. Today I I’m a food scientistand study how foods such as butter and margarine can have subtle chemical differences, with a big impact on their action in foods.
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Chemical structures
Butter and margarine are emulsions mixtures of tiny water droplets spread everywherea continuous fatty matrix. This matrix is made mainly triglyceridesthe main form of fat in our diet.
Fatty acids are long carbon chains surrounded by hydrogen atoms. In a triglyceride, there are three fatty acids, each connected to the same three-carbon glycerol molecule, which acts as the backbone of the molecule. Although the structure is always the same, the number of carbons contained in fatty acids can vary. In cream, triglycerides are packaged in globules or crystals.
Butter and margarine have a combination of saturated and unsaturated fatty acids. However, butters are mostly saturated, which makes them fit together and stack compactly to form a nice straight chain, because they don’t have double bonds between the carbons.
The fatty acids in margarine are primarily unsaturated and come from a mixture of vegetable oils. Unsaturated fats give them an irregular shape at the molecular level. The double bonds between the carbons twist the molecule so they can’t be so carefully arranged. This difference affects how they melt.
There are many forms of fat crystals in butter and they have different melting points. These crystals make the butter very firm when cold and allow it to gradually soften at room or body temperature. They also trap air easily when creamed with crystal sugar, which adds lightness and porosity to baked goods.
Butter and margarine are at least 80% fateven if some butters are closer to 85% fat. Their water content hovers around 16% and butter is composed of 1 to 4% vitamins, minerals, lactose and proteins.
Butter has a official identity standard set by the U.S. government, meaning manufacturers must meet specific guidelines for their product to be considered butter. This food standard is one of the oldest in the United States.
Make butter
When you shake or churn the cream, the fat globules break up. The fat escapes and forms semi-solid grains of butter. With more shaking or churning, these grains grow and separate from the watery, naturally low-fat buttermilk.
You then collect, knead and press the mass and, voilà, you have butter. Some butter is cultured by adding lactic acid bacteria. These bacteria ferment milk sugaror lactose, in aromatic compounds and organic acids, which give butter a smooth and complex flavor.
Sweet butter is easy to make at home if you add cold, heavy cream with a fat content of at least 36% to a standing mixer fitted with a whisk attachment. Turn it on and move away a little, and when you hear the sound of watery buttermilk, you know you have butter ready to press.
Make margarine
Margarine sticks start as plant-based liquid oils and are transformed into a solid. Producers chemically rearrange the fatty acids on the glycerol molecule in a modification process called Interesterificationwhich makes solid oil and fats more evenly distributed.
This process rearranges the triglycerides in the margarine without adding saturated fats or creating trans fats. Trans fats have been banned in many countries due to their association with cardiovascular disease And higher cholesterol levels.
Interesterification allows margarine to stay solid longer when cooking, with a more precise melting point.
Spreadable or squeezed margarines do not go through this process and instead rely on higher ratios of water and air compared to solid oils, which keeps them soft and spreadable. These spreadable types are less fatso they don’t work well for baking. The higher water content changes the texture and most baking recipes are formulated assuming a higher percentage of fat.
Processors are not required to indicate on the label whether the margarine has passed through interesterification.
Flavor and color
Butter gets its golden color from beta-carotenean orange pigment found in grass. Cows eat grass but do not metabolize beta-carotene efficiently, so it is expressed in their milk. Margarine is naturally colorless, but producers add synthetic beta-carotene to imitate the color of butter.
Margarine producers also add flavors like diacetyl, a distinctive butter-flavored molecule, and mixtures of whey components and preservatives to reproduce the flavor of butter. They may add emulsifiers such as lecithin or monoglycerides to prevent water and fat from separating. The exact proportions of ingredients vary between producers.
Chemical differences can translate into subtle differences in health. Although both are primarily made up of triglycerides, the fats in butter are naturally occurring, while the fats in margarine are industrially modified. This difference makes margarine an ultra-processed food, but it also means it contains less saturated fat. While you may have health reasons for choosing one over the other, be aware that the chemistry behind how these fats are made can also influence how they behave in the kitchen.
Cooking differences
When you heat butter, the proteins and lactose in it combine, creating that signature brown color and a delicious, nutty, toasted, caramelized flavor. Because margarine does not contain lactose, it will not brown as well as butter nor will it yield the same level of aromatics.
When cooked in a very hot oven, butter contains enough water to form steam that separates the dough into layers of flaky pastry. The water content varies in margarine, and while it will steam, it won’t work as well as butter.
However, margarine has some advantages over butter. It’s very consistent and melts in a controlled manner. Its shelf life is also longer. Yes, you can use them interchangeably, but knowing the functional differences between the two can help you determine when to use which.
This article was originally published on The conversation. Read the original article.