The Magic of Magic Shell
Have you stopped to wonder what’s so magic about Magic Shell? Why does it harden into a delicious chocolatey shell when you pour it on your ice cream, while regular chocolate syrup doesn’t? Ask Science explores the mystery.
Lee Falin, PhD
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The Magic of Magic Shell
Last week, we talked about the science behind blowing on your hot chocolate to cool it off. This week we head to the opposite end of the dessert temperature spectrum, and sit 
down for nice cold bowl of ice cream.
As you might imagine, my family of 7 has wide and varied tastes when it comes to ice cream toppings. Some of us like whipped cream, others like nuts, some don’t care for sprinkles, and I’m the only one enlightened enough to appreciate cherries. However there’s one topping that is universally loved in our home: Magic Shell.
But have you stopped to wonder what’s so magic about magic shell? Why does it harden into a delicious chocolatey shell when you pour it on your ice cream, while regular chocolate syrup doesn’t?
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I’ve Got a Lovely Bunch of Coconuts
The key ingredient behind the magic of Magic Shell is coconut oil. Coconut oil allows the chocolatey goo to harden on contact with ice cream (or anything else cold) thanks to its relatively high melting point.
Coconut oil has a melting point of around 25o Celsius (or 770 Fahrenheit). This means that as long as it’s at least that warm, coconut oil will stay in liquid form. However if you were to cool it down (by pouring it on ice cream for example), it freezes into a solid.
By comparison, olive oil has a melting point of -6o Celsius (or 21o Fahrenheit). So there’s a much smaller chance of it freezing if you were to pour it on your ice cream.
Remember: All Magic Has a Price…
The difference between the melting points of these two oils all comes down to the simplest element in the universe: hydrogen.
91% of the fat in coconut oil is saturated fat, while only 14% of the fat in olive oil is saturated fat. Aside from making coconut oil much less healthy for you, the high percentage of saturated fat is responsible for coconut oil’s high melting point.
The reason that saturated fats make it easier for an oil to freeze is because of their shape. Fatty acid molecules consist of a carboxyl group (a carbon atom, a pair of oxygen atoms, and a hydrogen atom) with a long hydrocarbon chain.
The hydrocarbon chain consists of a long series of carbon atoms bonded together with either single or double bonds. Carbon atoms that are connected by single bonds also have a hydrogen atom attached. Those that are connected by double bonds don’t have enough valence electrons to support a hydrogen atom, so they just have to content themselves with being bonded to the other carbon atoms in the chain.
Aside from depriving a carbon atom of the ability to have a hydrogen pal, the double bonds in unsaturated fats also alter the shape of the molecule, causing it to bend slightly.
Just like it’s easier to stack boxes of the same size and shape than it is to stack a pile of oddly shaped items, it’s easier for the straight saturated fats to stack up together than it is for those bent up unsaturated fats.
In fact, the reason saturated fats are called “saturated” is because they are saturated with hydrogen atoms, preventing the carbon atoms from forming double bonds.
We Need More Power
As handy as it is to have coconut oil melt at 25o Celsius (or 77o Fahrenheit), some food manufacturers want to boost that melting point up a little higher to make sure it stays solid even in relatively hot climates. As you might have guessed, this requires increasing the percentage of saturated fats; a feat accomplished through hydrogenation.
As you might infer from the name, when we hydrogenate something, we’re adding more hydrogen to it. By tearing apart the double bonds between carbon molecules in the fatty acid hydrocarbon chain, we can free up more valence electrons, allowing those carbon atoms to bond to hydrogen.
By converting the unsaturated fats to saturated fats, manufacturers can increase the percentage of saturated fat in coconut oil, raising its melting temperature as high as 40o Celsius (or 104o Fahrenheit).
Beware The Trans Fats
Some kinds of hydrogenation (called incompleted hydrogentation) can lead to the creation of partially hydrogenated oils, which are high in trans fatty acids (usually just called trans fats).
Trans fats are unsaturated fats whose double bonds have been twisted around in a way that make them look a lot like saturated fats, but for reasons we don’t fully understand yet, seem to be particularly bad for your health.
The Nutrition Diva has more on trans fats and their badness.
Conclusion
So now you know a little more about the magic behind Magic Shell, what makes a saturated fat saturated, and how manufacturers can modify fatty acid molecules with both good and bad consequences.
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Chocolate Magic Shell image courtesy of Foodista at Flickr. CC BY 2.0.
