Frozen fruit aggregates in hot porridge!

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I noticed something when making my breakfast that seems totally counterintuitive. If I add frozen berries that are separate in the pack to my porridge, as I'm heating it, the berries instantly form a solid, icy mass that I can lift out as one block.

I can't understand why the berries all aggregate together in a hot medium - any ideas?
 

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  • #2
anorlunda
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Wow! That's an unusual question. I'll try a guess.

The berries are cold enough to cool a bit of the hot porridge and freeze it. If a bit of liquid is sandwiched between two or more berries, that happens even faster. That forms a clump. Then when the clump meets another berry, it freezes the liquid between them, making a bigger clump. ...

But the freezing will not move berries from the far edges of the bowl into the middle. There must be something else providing motion to bring the berries near each other.
 
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But the freezing will not move berries from the far edges of the bowl into the middle. There must be something else providing motion to bring the berries near each other.
Thanks for the reply. To be clear I'm pouring the berries into the middle of hot porridge so it naturally forms a sort of berry "hill". I think you're right though, there must be liquid from the porridge seeeping into the interstices in the berry hill and they must be cold enough to freeze that liquid even though it must be quite hot and the hill is surrounded by hot porridge. Actually it seems sort of obvious now that you've pointed it out to me.
 
  • #4
256bits
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I agree. The berries are likely around -30C, so water on the surface is freezing into ice, and upon contact the berries freeze together in the pot. The hot medium ie porridge being cooked will have a drop in temperature in the vicinity of the berries.
 
  • #5
sophiecentaur
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I would suggest that the outsides of the berries gets above 0C and the surrounding ice layer melts due to nearby hot porridge. After some time, this water freezes again due to heat loss to the insides of the berries.
The only solution is to mix in the berries initially or sprinkle, I think.
 

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