Frozen Yogurt

I get frozen yogurt cravings all the time. Sometimes, the particularly serious cravings will even prompt me to sing my frozen yogurt theme song. The song is only about 5 words repeated over and over, but I think it gets my point across (any guesses what the lyrics are?) While I absolutely 100% love the true frozen yogurt that actually tastes like yogurt, I’m not a fan of the variety that tries to taste like ice cream. If I want ice cream, an imitation where that yogurty taste has been masked with loads of different flavours just isn’t going to cut it. Good frozen yogurt, on the other hand, is  the perfect blend of sweet and tangy that leaves you desperate for more once you realize your cup is empty. That last spoonful is always a sad moment for me.

There are no frozen yogurt shops near me so I’ve had to start making my own. It is such a simple recipe, as little as two ingredients, but oh so satisfying. Frozen yogurt is also one of those situations where less is more; this recipe is great with no toppings or just a bit of fruit. Not only is frozen yogurt very simple to make, but it is a guilt-free treat. For one 3/4 cup serving of this recipe, you are looking at 165 – 230 calories, 18 g of protein, and zero fat. You can also reduce the amount of sugar you add, or use different sweeteners to suit your taste and lower the calories.

Ingredients

1 container of PLAIN Greek-style fat-free yogurt (500 g)*
1/4 cup- 1/2 cup sugar (50-100 g)**
Optional: 1 tsp. vanilla or other flavouring

*Stay tuned for a post I am currently writing that will talk about making your own yogurt at home

**I tried with 1/2 cup of sugar and it tasted overly sweet before putting it in the ice cream maker. Once it was churned, however, it tasted better. If you are like me and love that tangy taste of yogurt, use less sugar.

Directions

Mix ingredients and chill in fridge for 1 hour.

Process in ice cream maker according to manufacturer’s instructions.

Serve alone or with fruit. It is best served right out of the ice cream maker for that soft-serve texture. You can freeze any leftover yogurt, although it will harden up a bit too much. If you do freeze it, allow it to thaw slightly and stir it up before eating.

The Science of Ice Cream Makers

One of the main things an ice cream maker does is churn the cream, or in this case, yogurt, to incorporate air into the mixture. When you make ice cream at home you will notice that it increases considerably in volume. This is because the churning process forces air bubbles into the cream. Without these air bubbles, ice cream would be dense and hard. This is why you cannot just stick cream in the freezer and expect to get ice cream. Some ice cream recipes will call for eggs, which help retain the air bubbles that are incorporated during whipping. The fat found in cream also helps retain the incorporated air (and gives it a creamy taste!)

The other role of ice cream makers is to freeze the cream (whaaaat?)

The process of melting ice requires energy, in the form of heat. When ice melts, it will take heat from its surroundings, causing the surroundings to get colder. When ice melts in the outer chamber of an ice cream maker, it steals heat from the cream, or yogurt, resulting in the frozen dessert we were going for. When the salt is added to the ice cubes in the outer chamber of the ice cream maker, the freezing point of the water-salt solution is lowered, resulting in the need for more energy to melt the ice. This extra heat transfer is what ultimately freezes the cream or yogurt. Without the salt, the cream would just get really cold but wouldn’t freeze.

Many of you already know that salt melts ice by lowering water’s freezing point (i.e. ice’s melting point), but do you know why salt does this?

When ice is at its freezing point, some of the molecules are actually melting; however, there is an equilibrium between ice that is melting and water that is re-freezing. When salt is added, it dissolves in the water and gets in the way of this water re-freezing into ice (the water molecules can no longer pack together as tightly.) Now there are still ice molecules that are melting but fewer water molecules freezing back into ice. In order to freeze these water molecules, the temperature must be lowered even further.

The higher the concentration of salt, the lower the temperature needs to be to freeze salt water. We can use this to control the texture of frozen yogurt and ice cream. The more salt that is added to the outer chamber of the ice cream maker, the faster the cream freezes. However, the faster the cream freezes, the less smooth the texture of the final product. Thus, to obtain the smoothest possible texture, you must wait longer.

There is one really cool way to make ice cream almost instantly: using liquid nitrogen. Liquid nitrogen boils at -196 C so when it comes into contact with anything warmer than -196 C, it begins to boil. As you can imagine, when something such as milk, comes into contact with liquid nitrogen, it freezes as the nitrogen boils. To make liquid nitrogen ice cream, you mix milk, vanilla, and sugar in a bowl and pour in some liquid nitrogen while stirring like crazy. All the nitrogen gets boiled off and you are almost instantly left with ice cream. It tastes like normal ice cream, although not surprisingly, the texture isn’t as smooth as ice cream that has been churned. I hope to get my hands on some liquid nitrogen at some point to do a demo for you; I used to have access to it at my old job, but sadly no more :(. If any of my readers have access to liquid nitrogen and would like to share, let me know!

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