Both butter and margarine are at minimum 80 per cent fat, though some butters are closer to 85 per cent fat. Their water content hovers around 16 per cent, and butter is made up of 1-4 per cent vitamins, minerals, lactose and protein.
Making butter
When you shake or churn cream, fat globules rupture. The fat leaks out 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, voila, you have butter. Some butter is cultured by adding lactic acid bacteria. These bacteria ferment milk sugar, or lactose, into flavour compounds and organic acids, which give the butter a mild tang and complex flavour.
Churning butter disrupts fat chunks and separates solids from buttermilk. Photo: Churncraft
Sweet butter is easy to make at home if you add cold, heavy cream with a fat content of at least 36 per cent to a standing mixer with a whisk attachment. Turn it on and walk away for a bit, and when you hear the sloshing sound of watery buttermilk, you know you have butter ready for pressing.
It’s surprisingly simple to make your own butter at home.
Making margarine
Margarine starts as liquid, plant-based oils and are made into a solid. Producers chemically rearrange fatty acids on the glycerol molecule in a modification process called interesterification, which makes the oil solid and the fats more uniformly distributed.
This process rearranges the triglycerides in margarine without adding saturated fats or creating trans fats. Trans fats have been banned in many countries because of their association with cardiovascular disease and higher cholesterol.
Interesterification allows margarine to stay solid longer when baking, with a more precise melting point.
Spreads or squeeze-style margarines do not go through this process and instead rely on higher ratios of water and air to solid oils, which keep them soft and spreadable.
These spreadable types are lower in fat, so they don’t work well for baking. The higher water content alters the texture, and most baking recipes are formulated assuming a higher percentage of fat.
Processors are not required to state on the label whether margarine has gone through interesterification.
Flavour and colour
Butter gets its golden colour from beta-carotene, an orange pigment present in grass. Cows eat the grass but do not metabolise beta-carotene efficiently, so it is expressed in their milk.
Margarine is naturally colourless, but producers add synthetic beta-carotene to it to mimic the colour of butter.
Margarine producers also add flavours such as diacetyl, a distinctive butter-flavour molecule, and blends of whey components and preservatives to replicate the flavour of butter.
They may add emulsifiers such as lecithin or monoglycerides to keep the water and fat from separating. The exact ratios of ingredients vary between producers.
Chemical differences can translate into subtle health differences. While both are mainly made of triglycerides, the fats in butter are naturally occurring, while fats in margarine are industrially modified.
This difference makes margarine an ultraprocessed food, but it also means it has fewer saturated fats. While you might have health reasons for choosing one over another, take note that the chemistry behind how these fats are made also can influence how they behave in the kitchen.
Baking differences
When you heat butter, the proteins and lactose in it combine, creating that signature brown colour and a delicious nutty, toasty, caramelised flavour. Because margarine doesn’t contain lactose, it won’t brown as well as butter, nor will it impart the same level of aromatics.
When baked in a very hot oven, butter contains enough water to form steam, which separates doughs into layers of flaky pastry. Water content varies in margarine, and while it forms some steam, it will not perform as well as butter.
However, margarine has some advantages over butter. It’s very consistent and melts in controlled way. It also has a longer shelf life. Yes, you can use them interchangeably, but knowing functional differences between the two can help you determine when to use which.
Rosemary Trout is Associate Clinical Professor of Culinary Arts & Food Science at Drexel University
