I've been considering buying a food dehydrator, mostly for fruit, maybe some jerky. I know that a conventional food dehydrator can take a while, 12-24 hours. I'm curious, can I use a vacuum chamber to dehydrate the fruit instead? Will it take less time? I imagine that making raisins may be problematic as they have a sealed skin and would explode, but I don't think that would happen with banana or apple slices.
You can certain lyophilize fruit. It's done commercially and there's no insurmountable barrier to doing it at home. Since water basically 'boils til it freezes' in a vacuum, then slowly sublimes, you're not likely to get much improvement on a dehydrator's 12-24 hour cycle. For some fruits however, product can be much better when freeze dried. Here's some examples of what you can get: Bananas, peas, tomato slices, carrot slices, spinach, beans, mango, whole berrys etc.
Any vacume chamber and really the size you choose to have.will determine it. make or buy. Most of them "WILL NOT' need a way to separate water. most water vapor will be in a gas state just being boiled off your product will now just be compressed and vented from the high side of the compressor..I'm not saying that 100% of the water vapor won't condense in the oil in the compressor. but most won't . you should change the oil in the compressor after each use any way. Vacuum pumps to my knowledge still get there lubricant by way of mineral oil on the low or suction side of the system.with say dehydrating Vegetables the water vapor will be Semi minute ..any water vapor comming back to the compressor a great deal of it will leave the system by way of the high side of the system after being compressed...after say dehydrating your batch of vegetables you just need a valve on the suction line to close once your product is finnished close the valve let the compressor keep running say for the same amount of time it took you to dehydrate your product by doing so any extra water that's in the mineral oil will just boil off and leave the system by way of the high side of the system water vapor will always condense is the coldest part of the system.. this is not the mineral oil because it's hot from lubricanting the piston and cooling the piston of the vacume pump..building your oun vacume chamber would be a very easy task..1. refrigeration vacuum pump from harbor freight.. 2. A very thick glass jar say a cookie jar or better yet a thick glass water holding jar .. because you can remove the despencing Handel and place your service port for low side where the dispensing Handel was. This way you don't need to try and drill a hole in the glass your hole is already there . 3.epoxy puddy for the hole to be sealed with your service port . 4. Wire. Make your shelving inside the jar with wire and epoxy to hold it in place. 5. ,s refrigeration man's tools a manifold & hoses would be nice for you to have. You can pick up used one's on eBay for $30. After putting it all together. Pull a vacume say 29 inches vacume on your chamber turn off the low side valve on you refrigeration man's tools manifold. Test it now to make sure you have no leaks by it holding 29 inches in a vacume..if not reseal all the areas it could be leaking..depending where your at sea level absolute vac is 29 inches if your on a mountain at 6000 ft above sea level absolute vacum will be about 26 inches vacuum.. at absolute vacuum any water vapor in your vegetable will boil off them at 70 ° F you won't see it actually boil it's just a term we use it will probably take 24 hrs to dehydrate your product.