Science puzzle: why did my fridge set at 3°C freeze fresh carrot juice, and has never done it to anything else?

I made fresh carrot juice last night with a new juicer for the first time. I left an uncovered cup of leftover juice on the top shelf of my fridge, which is set to 3°C. Today I took it out and was astonished to see a layer of ice on top. It was unmistakably ice. Multiple irregularly shaped sheets of ice between 1-4 cm² and about 1-2mm thick.

There was a cup of freshly squeezed orange juice next to the carrot juice, which was made at the same time. It did not freeze. Also, the carrot juice felt really cold when I put my fingers into it, colder than the orange juice (I do not have a thermometer to take a measurement).

No liquid – water, shop-bought juice, milk, alcoholic drinks – ever behaved as this freshly squeezed OJ! How did it become super cooled and form ice? I understand that my fridge's temperature setting is not scientifically accurate but it can't be 0°C, and no liquids ever formed ice in the many years I've had it.

Weirdly, while trying to Google about it, I came across people complaining that the fridge was freezing their carrots but not other things!

Hoping to harness the science hive mind (tried posting on AskScience but apparently questions based on "personal anecdotes" are not allowed).