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Frozen Strawberries Become Sweet Smoothies

strawberries in a freezer bag

I love getting the first strawberries of the season because they are always the sweetest and most flavorful. To enjoy the seductive perfume of the season's first berries for more than a week or two, I like to freeze them.

How do you freeze a strawberry the right way? Well, before I get into that, let's talk about the science of freezing. Food "freezes" when the water molecules inside the food, drops below 32 degrees F. At this point the water molecules stop moving and form a solid crystalline structure.

The structure and how large the crystals are depend on how quickly the water is frozen. The longer it takes to freeze, the larger the crystals grow. When large crystals form, they rupture the cell walls of the strawberry. When the ice melts, the gaping voids the ice crystals created collapse, and the water, along with the contents of the cells leak out all over the place.

Small crystals on the other hand do not damage the cells as much and so when a strawberry that's been quickly frozen is defrosted, it retains much of the original characteristics of the fresh strawberry.

In large commercial operations such as manufactures of frozen foods, they have special freezers that freeze food in minutes or even seconds. Unfortunately, your average home freezer will take hours to freeze a bag of food.

One option available to the daring is to use liquid nitrogen. Since liquid nitrogen boils at -321 degrees F, it will freeze strawberries almost instantly. That's also why ice cream made with liquid nitrogen is so smooth in texture. The danger here is that it will freeze your fingers almost as fast as the strawberries, so you need to be wearing proper gloves and eye protection when working with liquid nitrogen.

Since most of us don't have a Dewar of liquid nitrogen sitting around, the next best thing is to freeze the berries as quickly as possible in your home freezer. Here are a few tips to get your strawberries frozen in the shortest time possible:

  1. Smaller is better – It takes less time to freeze smaller objects, so cutting your strawberries into quarters will make them freeze faster.
  2. Give them space – If your strawberries are crammed together it's the same as having one giant strawberry, so arrange them in a single layer. Aluminum is a great thermal conductor, so arranging them in a single layer on an aluminum baking-sheet is a good way to freeze them, once they're frozen you can transfer them to a freezer bag. If you don't have room for a baking sheet, you can arrange the strawberries in a single layer in a freezer bag, then sandwich the bag between ice packs.
  3. Go to the source – figure out where the cooling elements are in your freezer and put your strawberries near them (this is usually the back of the freezer).


To illustrate the difference you can make by freezing quickly vs. slowly, I cut a strawberry in half, wrapped one in plastic wrap and stuck it between two ice packs. The other half got wrapped in plastic and thrown in with a larger bag of whole fresh strawberries.

While the strawberry on the right still leaked some liquid, it was far less than the one on the left. It's even more apparent in the photo below where I sliced the berries in half. The one that took a long time to freeze was mushy, so when I cut into it, the red color on the outside bled into the white center. The quickly frozen strawberry on the right maintained its shape much better.

One of my favorite uses for frozen strawberries is to turn them into smoothies. The beauty here is that since the strawberries are frozen, there's no need to add ice, which prevents your smoothie from getting watered down.

I like using maple syrup to sweeten strawberries because the earthy flavor is a nice pairing with the bright strawberries, but it also has the added benefit of being vegan friendly. Make this with tofu and soy milk instead of yogurt and milk and you'll have a vegan smoothie.

This recipe was originally posted on PBS Food.

Strawberry Smoothie

Ingredients

  • 9 ounces frozen strawberries
  • 1/2 cup yogurt (or silken tofu)
  • 1/2 cup milk (or soy milk)
  • 2 tablespoons maple syrup

Instructions

  1. Add all the ingredients to a blender. Unless you have a very high-powered blender it will struggle with whole frozen strawberries, so be sure you use Marc's technique for freezing strawberries and cutting them up before you use them.
  2. Blend until smooth.
https://indianapublicmedia.org/eartheats/turn-frozen-strawberries-sweet-smoothies/


This recipe was originally posted on PBS Food.

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