Learn the science behind:
We eat our freshly baked bread with a spread of butter (or margarine).
Use lard (or shortening) in a pie crust.
Yet they’re all fats and even not that different. Without fat there would be no butter, lard, margarine, shortening or ghee. But what really are the differences between all of these?
The basis: triglycerides
The key to understanding why and how fats are different lies in the chemistry of these different fats. The major components of all of them are triglycerides. These triglycerides are a large group of molecules with a similar basic structure. They have a glycerol backbone and attached to it, three (hence tri) fatty acid chains.
Since the backbone is the same in all cases, differences in behaviour come from differences in the fatty acid chains. The length of these chains is important as well as the level of saturation. Saturated fats are more linear whereas unsaturated fats contain some bends and crooks.
Melting point of fats
Aside from effects on health, the main difference between triglycerides is their melting point. The temperature at which they change from solid to liquid. In a solid the molecules are kept in place and don’t move around whereas in a liquid can move more freely.
The more easily molecules can stack together in a solid form, the higher the temperatures should be for them to start moving. It’s easier to stack small rectangular blocks than it is to stack crooked shapes of all different shapes. This is why, fats with shorter fatty acids as well as more unsaturated ones, have a lower melting point.
We dive into the details in more detail in our chemistry course!
Apart from the types of fat present in our fats, we need to look at the other ingredients present in our delicious ingredients. More specifically, we need to look at the moisture (water) and protein content as well as the presence of flavour molecules.
Even though all of our aforementioned fats look like just solid fats, they are not. Some of them (e.g. butter) contain a decent amount of water. This water is caught within the fat, hiding the water. The presence of water will impact the behaviour of the fat.
Unlike fats, water evaporates easily especially at increased temperatures. So, if you use these fats in a food that goes into the oven, this water will evaporate. Whether or not this is desirable depends on the food!
Proteins are a separate, important, group of molecules in food. Proteins react well in various chemical reactions, the most important one for this application being the Maillard reaction. In this reaction sugars and proteins react together to form a nice brown colour and a wide range of flavours. It is what makes your bread turn brown in the oven. If there’s some protein present in your fat, it might contribute to this browning reaction.
The presence of flavour molecules will not impact the behaviour of the fat in your food. But, it will impact the final flavour! Generally a wide range of flavour molecules make up the flavour in a specific food. Even though the will be a very small number of flavour molecules compared to fat molecules in your fat, you will be able to pick up on them.
Comparing our fats
Now that we know all this, let’s have a look at the previously mentioned fats: ghee, butter, lard, shortening and margarine.
Butter & Ghee
Butter and ghee are very similar. Both start out as cow’s milk. However, whereas butter still contains some of that moisture after it’s been churned, ghee does not contain any moisture at all. Ghee can be made from butter by gently simmering the butter to evaporate all the water.
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Since they are both made up of milk fats, the composition of the fats is the same. As such, ghee and butter have a similar melting point. Do keep in mind that even within ghee and butter varieties melting point can vary considerably! Milk varies naturally due to differences between cows, living conditions, food, etc.
Both ghee and butter are liquid at our body temperature. They literally melt in the mouth.
Whereas ghee and butter start with a cow, lard starts with a pig. Lard is the fat of a pig. It is made by gently heating the skins and other fats rich parts of a pig to extract the fat out. The final product is purely fat.
The fat of a pig is not identical throughout the whole pig. As a result, the melting point of lard will depend on where in the pig the lard comes from.
Lard is very similar to tallow. Lard is made from pig’s fat and tallow from that of a cow.
Shortening & margarine
Lard, ghee and butter all have in common that they can only be tuned in their behaviour to some extent. Since they come from animals and aren’t modified in any way, the chemical composition is fixed. This is not the case for shortening and margarine at all. On the contrary, these two products are man-made and can be tuned to those properties a user might be looking for.
Both shortening and margarine start out as plant oils. Oils are also made up of triglycerides, but they have a larger number of unsaturated fatty acids. This makes them more liquid like. However, processors can get rid of these unsaturated bonds through a process called hydrogenation. By controlling just exactly how much is hydrogenated, the properties of these fats can be modified quite precisely.
Manufacturers process the plant oils well before they are transformed into shortening or margarine. For one thing, they remove all odours and flavours from the oil. As such, shortening and margarine should be flavourless.
Margarine was developed to imitate butter? As such, it also contains water, just like butter. Shortening on the other hand does not contain any water.
A note on margarine
The initial margarine was developed to replace butter. However, since margarine can be tweaked by manufacturers in a lot of different ways, by now there exist a lot of different margarines. Some contain less fat than the 80% mentioned above.
|Fat||Contains water?||Contains protein?||Melting point*|
* These are average values, as mentioned above, they can vary quite considerably on processing conditions or on natural variation.
So how do you go about substituting one for the other? The best substitution depends on your application so we’ll discussing those one by one.
All of the fats work perfectly fine here. Just be sure not to choose a margarine with a lower than normal fat content or you’re just baking in water. The others may have slightly different flavours, but they all work pretty much the same.
When it comes to deep frying you want to look at the smoke point of the different fats. A higher smoke point will make it more stable and better suited for deep frying. Also, the presence of water is detrimental. Your best choice here is ghee, or using an oil (which is a liquid fat).
You can go a lot of different ways with pie crust and all of our five fats will work. When looking for a substitute for your recipe, ideally use one with the same moisture content. So butter and margarine can be exchanged with very little problems and so can shortening, ghee and lard. Due to the differences in melting point the final texture may be somewhat different and so may flavour, but it won’t ruin your crust for sure.
You want your cake to be soft and silky and easily melt in your mouth. Shortening and lard for that reason aren’t your best bet. Butter and margarine can be replaced for one another quite easily again. If you want to replace butter for ghee keep in mind that ghee doesn’t contain any water. As such, reduce the amount of ghee (by a factor of 4/5) and increase the amount of moisture (add 1/5 of the weight of butter).
Have you ever made a cookies with shortening or lard? They aren’t the most common, but because of their higher melting points they do give nice firm cookies. Cookies are probably your most flexible of any baked good so you can substitute most fats for one another. For most similar results substitute margarine and butter for one another and shortening for lard.
If you need to firm up your cookies in the fridge keep in mind that shortening and lard might come out a little harder, making it slightly harder to roll. By cooling them for a longer period of time or just leaving them to warm up a bit more, you can overcome that problem though!
Cook’s Illustrated, Clarified Butter: A Substitute for Shortening?, link
Cooking for geeks, 85°F / 30°C: Average Melting Point of Fats, 2015, link