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Raspberry Sorbet and Some Chemistry!

9 February 2012

We got an ice cream maker attachment for our KitchenAid mixer a while back, but have yet to put it to good use. We had some frozen raspberries so sorbet seemed like a good idea. I was looking up recipes to find the correct ratio of sugar and water to use when I stumbled upon something that piqued my interest. It was called invert sugar. It’s made from regular sugar and supposedly it could make desserts sweeter and have a smoother texture. I had never come across it before and, upon further investigation, I discovered that it is created by a very simple chemical reaction. Being a biochemist, I found it quite cool that I could easily understand what’s going on.

*For those of you who aren’t really into chemistry, you can just skip to the recipe below*

Sucrose, or table sugar, is a disaccharide (2 sugar units) composed of glucose and fructose. To produce invert sugar, you dissolve it in water and heat it with some sort of acid. In this case I used cream of tartar (tartaric acid), but you could also use lemon juice (citric acid). The acid (H+ in the diagram below) catalyzes the hydrolysis (‘break up’) of sucrose into its component sugars, glucose and fructose. The resulting syrup is known as invert sugar (glucose and fructose dissolved in water). Fructose is naturally sweeter than glucose and sucrose and the invert sugar also gives a smoother texture to desserts (smaller crystals).

Isn't chemistry fun?

Maybe that was too much explanation…oh well. I am definitely channeling my internal chemistry geek in this post. The science of cooking is some pretty cool stuff. I feel like the more I know about the science behind certain foods, the more interesting it is to eat them. Is it just me?

Anyways, I used invert sugar as the sweetening component of the sorbet and it definitely did result in a ‘creamier’ texture (due to freezing point depression for the chemists out there). It is still winter, but I feel that frozen desserts taste good all year round. Next I’m going to try making some gelato!

Here’s what you’re gonna need:

Invert Sugar:

  • 1 cup sugar
  • 1 cup water
  • 1/4 tsp. cream of tartar
Raspberry Sorbet:
  • 4 cups raspberries (fresh or frozen)
  • 1 cup water
  • 1 recipe invert sugar (above)
  • splash of lemon/lime juice

Here’s how to make it:

Invert Sugar:

1. Heat small saucepan over medium heat and add sugar, water and cream of tartar. Allow sugar to dissolve and solution to reach a mild boil. Allow to boil at medium-low heat for 30 minutes. Cool to room temperature (syrup can be stored at this point).

Sorbet:

1. Heat water in a medium saucepan over medium heat and dissolve invert sugar syrup. Add raspberries. Cook for 15 minutes while maintaining a light boil.

2. Remove from heat. Purée mixture with a blender or immersion blender.

3. Strain mixture with a fine sieve into a bowl. Discard solids. Add lemon juice. Refrigerate for at least 4 hours to completely cool.

4. Make sorbet according to your ice cream maker’s instructions. Freeze for at least 4 hours to harden. Enjoy!

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