It was an unusually hot summer in Denmark this year but as usual I was struggling with my equipment in the lab all through summer. I use a scanning tunneling microscope to ‘image’ molecules on a surface. To make sure that the molecules don’t move around too much, I cool the molecules with liquid nitrogen. Liquid nitrogen has a boiling point of -195.79 °C at atmospheric pressure so that as soon as you pour it out it boils and evaporates by taking away heat from whichever object it comes into contact with thereby cooling it rapidly. Liquid nitrogen is usually stored in a vacuum flask or Dewar and kept at a temperature of -196.15 °C so that it boils slowly. This means that the Dewar will be empty a few days after filling it.

The liquid nitrogen dewar we get for the lab

I had some problems with the STM so I couldn’t use it for a few days. Instead of wasting the liquid nitrogen that I had already brought from the workshop, a colleague suggested that we use it to make ice cream instead! While pitching ideas for the flavour, we concluded that it would be easier to make sorbet instead considering the limited kitchenware we had. After a long discussion over lunch break, we decided to make lemon sorbet with rosemary garnish the next day.

It’s really easy to make sorbet! Take sugar syrup, a flavoured concentrate of your choice in a large bowl and then pour liquid nitrogen in and whisk away with all the strength you can muster. We used Jamie Oliver’s recipe. We weren’t too sure how much liquid nitrogen to add at first so we ended up pouring too little and the mixture was only getting cold but not crystalline. Gradually we got the amount of liquid nitrogen right and after taking turns to whisk vigorously, we finally had a sorbet!

Georgios and I trying to get as much juice as possible from the lemons while Andrew is making the sugar syrup on a hot plate

Not sure if it actually tasted good or we were just too excited to give it a thought.

Lemon sorbet garnished with rosemary

You can find the recipe we followed here: https://www.jamieoliver.com/recipes/fruit-recipes/lemon-sorbet/

We made raspberry sorbet the next week. The plan is to keep it going, a new flavour every week. Hawthorne, coffee… leave a comment if you have an interesting flavour suggestion.

Collage of photos taken at each stage of making Raspberry sorbet

Be careful with liquid nitrogen! Read this document before you use liquid nitrogen. https://www.ars.usda.gov/ARSUserFiles/80000000/SHE/LN%20safety.docx

This post was written by Rijutha Jaganathan. She works in the Surface Dynamics Lab at Aarhus University. Georgios and Andrew Cassidy are in the same research group too. Georgios Pantazidis is an ESR while Andrew is the Project Manager for EUROPAH.

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