I had a bunch of asian pears on the dehydrator that I had sliced too thick for the season and weather. So most of them had started fermenting and were likely going to rot before drying. I took them off and am cooking them now, after which I might spread them more thinly on the dehydrator to make a leather.
I've had berries ferment in the dehydrator and then end up drying, and they became very tart/zingy and less sweet (less calories), but still worth eating I thought.
My understanding is fermenting is converting sugars into alcohol. When I dry it, the alcohol will evaporate out? But I'm sure there's a lot more going on there too.
I'm guessing there's no obvious probiotic benefit to fermented-then-dried - if the drying kills the microbes. But maybe some of them go dormant and are still there?
My understanding is that some fermented foods are good for you because of the probiotic addition to your body but some fermented foods are better for you simply because they have been “predigested” (like sourdough bread). I imagine that at the very least, slightly fermented fruit that’s been dehydrated falls under the second category.
I’ve always been curious about how much and what kinds of microbiota survives the dehydration process, if any.
There’s way more to fermentation than sugar -> alcohol -> acid and probiotic microbes.
Less sugar is good for starters.
And then there’s the gazillion other organic compounds - enzymes, fatty acids, etc. many of which will survive drying.
If it smells good and tastes good, then it probably is good.
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The asian pear experiment went well. I took the fermenting pear slices off the dehydrator, threw them all in a pot and boiled it to kill the fermentation/rotting process and evaporate some more of the moisture, and then put half of them back on the dehydrator and canned the other half. Both the canned and dried fermented asian pears taste amazing - they have a unique flavor compared to the ones that dried properly from fresh slices and will be a special sort of candy.
I just read a book on Japanese country cooking where the daikon radishes were dried then fermented. I've never tried this and am not sure about how you can ferment if something has no moisture to support microbes. Possibly they were just dried to reduce but not eliminate moisture.
But it sounds like you hit on a simultaneous drying and fermentation process. This is pretty interesting. I'm glad it turned out well.
I don't think drying kills the microbes. I have successfully dehydrated and rehydrated my sourdough starter for moving cities. I assume this is what "sourdough starter" kits are at the supermarket (i.e. a sham given how absurdly easy starting a sourdough is!). Yoghurt "starters" are sold as powders. You can buy LAB as powders. You buy yeasts as powders. Koji rice is often sold dried. I presume these are also dehydrated. I've seen people dehydrate water kefir grains.
So my guess is that drying simply slows their metabolism of the micro-organisms to a much much slower rate, but doesn't kill them. I had a quick scour through the excellent The Art of Fermentation and surprisingly didnt find an index reference for dehydration - so I extrapolating from the patterns I see around me.
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