Eli5: freeze drying. I just can’t wrap my head around how it gives different results even tho both take out water out of say fruit. And also how they evaporate in freezing environment
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As others have said here, the basic principle is “sublimation”, which is where water changes from a solid to a gas (or vice-versa) without passing through the liquid phase.
Have you got ice cubes in your freezer? Ever notice that, if you leave them frozen for weeks and weeks, they get a bit smaller? That’s sublimation in action. Same thing if you get ice crystals growing inside a freezer.
At an industrial level, the main approach seems to be to freeze the food in a sealed container, and then lower the atmospheric pressure, such that the water molecules are drawn off. Then, raise back the pressure, but keep the food frozen, at least until you want to consume it.
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