One Ingredient Caramel: The Science Behind Condensed Milk

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Did you know you can make caramel with only one ingredient? Well, two if you include salt. You can make this One Ingredient Caramel in your slow cooker. Drop a can in, cover it with water, and walk away. How easy is that?

The Science Behind Condensed Milk

Making condensed milk is an oddly tricky process.  Patents for preserving milk date back to the early 1800s, but the method was revolutionized by Gail Borden in 1856.  Now the story (probably rather folksy) goes something like this: when Borden sailed from London to the United States the cows got seasick, stopped producing milk, and the infants starved to death.  I’m not clear why it was the cows’ responsibilities to feed the infants and not the mothers’, but let’s roll with it. Maybe the mothers felt seasick too.

At any rate, Borden wanted to find a way to preserve milk in a sterile, safe fashion.  He discovered that milk is predominantly water. This is where the tricky part comes in.  You cannot simply boil milk to reduce it to a condensed form. The heat causes permanent changes to the protein and fat, which works wonderfully well for puddings and caramel, but not so well for keeping the milk intact.

The answer lies in the realms of physics and chemistry.  Water boils at approximately 212°F at sea level. In case you’ve forgotten your high school chemistry, water is made up of hydrogen and oxygen molecules, which move around.  When you apply heat to these molecules, they begin to wiggle and squirm faster, like a bunch of toddlers eating sugar.

Now imagine that these toddlers start arm wrestling.  When they first start the game, they are evenly matched.  They apply the same amount of pressure to each other and their arms don’t move.  As the sugar high starts to kick in for one of the kids, he gets more energy, applies more pressure, and pushes the other kid’s arm down.

You can think of the boiling point of water as the point when one toddler wins the arm wrestling match.  (I know, it’s a weird analogy but bear with me). Water molecules “fight” with the surrounding air molecules, each applying equal pressure to the other.  Adding heat to water gives the molecules energy, which causes them to move faster and apply pressure to the air molecules. Water becomes steam when the water pressure is greater than the atmospheric pressure.

Now I told you that, so you’ll understand this:  Borden discovered the secret to condensing milk. He boiled the milk in a vacuum.  Vacuums lack atmospheric pressure. The milk does not need nearly as much energy (aka heat) for the water content to boil.  Since the water boils off at a lower temperature, the protein and fat content of the milk remains unchanged.

Nifty, huh?

How to Make Caramel from Condensed Milk

Since condensed milk uses sugar as a preservative, it actually makes a lovely dulce de leche, or caramel.  And it’s incredibly easy to make. Take the label off of the can and boil the can for a few hours. This works for condensed milk made with dairy or coconut milk.

While you absolutely can do this on the stove, I’d highly recommend using a crock pot.  Either way, you need to make sure the can is completely covered with water at all times.  Remember that pressure thing we were talking about earlier? It really comes into play here.  If you don’t keep the can covered, it will explode.

Fortunately, my caramel did not explode but I can only assume that hot flying caramel hurts when it hits you.

If you use a crock pot, you don’t have to worry about the water evaporating quite as rapidly.  For a soft caramel sauce, cook on low for 10-12 hours. For a firmer caramel, cook on low for 20-24 hours.

When it’s ready, take it out of the crockpot, let it cool, open it and enjoy.  I have a few ideas for how you can use your caramel. Each of the following recipes uses one can of condensed milk, a bag of chocolate chips, sea salt, plus a few added ingredients.

What to do with One Ingredient Caramel

First up, we have Chocolate Caramel Sandwich Cookies.  Any very thin cookie will work, but I chose rice thins.  Spread melted chocolate on one cookie, caramel on another, smush them together.  Drizzle chocolate on top and dust with sea salt. Simple but good.

Next up, we have Peanut Butter Caramel Pretzel Cups.  Silicone muffin liners are super helpful here, but traditional paper ones might work as well.  Place a dab of melted chocolate into each liner, top with a pretzel, peanut butter/powdered sugar mixture, and caramel.  Fill it the rest of the way up with chocolate. Top the cups off with sea salt.

They remind me a bit of Take 5 candy bars, but in Reese’s form.

How about a simple chocolate bark?  Spread melted chocolate chips onto parchment paper, cover it with broken pretzels, drizzle caramel over the top, and of course, sprinkle it with sea salt.  Place the bark in the fridge to cool, then break it into pieces.

Are you seeing a pattern yet?

I saved the most involved recipe for last.  For Chocolate Caramel Candies, you really need a chocolate mold like this one.  Place a very small amount of melted chocolate into each mold, add a cube of caramel, some salt, then top off with chocolate.

You can always drizzle caramel over any of your favorite foods. Go on, I won’t judge. Try it over some Black Bean Brownie Truffles!

Each of the One Ingredient Caramel recipes is listed below, but you can also download my PDF, which has each of the candy recipes on one page.

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References

• The Surprisingly Complicated Physics of Condensed Milk by Esther Inglis-Arkell
• Evaporated and Condensed Milk by How Products Are Made
• Condensed Milk by Science Direct