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Table of Contents
The Beginnings
The Plan
I would like to make vacuum freeze-dried food at home for fun.
Ben at Applied Science made it look easy.
The Shopping
- Strawberries,
- Raspberries,
- Mangoes,
- Kiwi fruit,
- Rainbow ice cream.
The Assembly
The vacuum pump pulls a low vacuum, about 50 mbar. The cold trap is filled with methylated spirits and dry ice. This brings it to around -75°C. The water ice in the food sublimates directly to a gas without disturbing the macro-scale structure of the food. I.E. The ice cream doesn't melt - it maintains its structure and becomes dry. The gaseous water travels along the tube and condenses in the cold trap.
Ideally the food should be at or below -35°C when it goes into the vacuum chamber. My freezer only goes to -20°C, so I have boxed and bagged portions of the food separately so I can superchill them in the cold trap before putting them into the food chamber. I have a temperature-controlled hotplate on standby to put some heat into the system to kick off the sublimation. I will pre-chill the food chamber too, so the ice cream doesn't start to melt as soon as it hits the stainless steel.