dehydrating
I just bought a nesco dehydrator. Used it a few times with good results. Yesterday I sliced up some fresh pineapple and placed it over 4 racks. I let it run at 140-145 for 6 hours. The thinner slices were dehydrated but still moist.
My question is, how does the temperatures affect how food is dried? One would assume that the higher the temperature, the faster the drying. Obviously that isn't the case…or is it?
Sounds like it's working for you. As long as the dough doesn't form a skin, inhibiting rising, then looks like it ain't drying out.
Very even heating too, I imagine; that's critical: with the hot and cold patches of some big ovens, uneven fermentation and rising could ruin a loaf especially the final proofing. Cracks in the sides of the crust can be blamed on this.
The temperature varies not by how long you want to keep the item, but by what you are dehydrating. Consider a carrot. A raw carrot will keep for literally months. A cooked one at room temperature will not even keep for days. So, when you're dehydrating carrots (for example to reduce the weight of the food you take camping) you want to be sure not to cook them in the process. Now, consider raw meat such as jerky. This has a LOT of water in it. If you dry it at too low a temperature, it will spoil before you have reduced the water content enough. Same for a fruit puree. But herbs, if you have it too hot you will draw out the flavours and just keep dehydrated dust.
My dehydrator came with a book telling me what temperatures to use for what products. There are also words on the temperature dial. This is a cropped shot of my model on the manufacturer's website:
While you can't read the words, they say "fruit", "vegetables" etc. The coolest temps are for herbs, then it goes raising bread, making yogurt, then dehydrating veg, then fruit, and finally jerky.
And just as you can't choose one temperature to use for dehydrating any and all food, nor can you assume one keeping time for any and all food. My book also tells me which things keep for months, and which for years. I don't think there's anything that will let your dried meat keep for years, but you should do ok with legumes and some vegetables.
Best Answer
The higher the temperature the faster the drying but also the more damage will be done to the food. As high as 140 and it is being cooked. For something like pineapple this is fine but for delicate things like basil that is not ok.
If you live in a dry climate the heater might not be necessary at all but it will save time.
I don't know exactly why your pineapple didn't turn out but here are a couple notes:
1- Things that are thick or very moist take much longer than usual. 6 hours is not a long time. Obviously pineapple is both. Try letting it go overnight.
2- Really really sugary things are so hygroscopic that they have a hard time drying completely and staying dried.
3- Commercial dried fruits are usually candied and chemically altered before being dried in equipment that I can't reproduce. This shouldn't discourage you by any means but don't expect your product to always be exactly like commercial dried fruit.