Tuesday, September 8, 2009

Dehydration station


That's my place these days, partly because my deep freezer is temporarily too full to pack any tomatoes in there, partly because dehydrated vegetables are really tasty and neat. I can eat them straight off the tray. They even look pretty. Right now the dehydrating process is all about tomatoes (and a little bit about zucchini) because zucchini freezes badly, and tomatoes only freeze for sauce—there will be plenty of sauce too, in time.




Our dehydrator is probably 30 years old. It's electric, with a heating coil at the bottom, but nothing about it is adjustable except for the number of trays you stack up, and the size of the holes at the top for letting out moist air. It runs on the principle of convection—the air at the bottom heated by the coil rises, taking with it incidental moisture being expelled by the vegetables, and drawing fresh dry air in. The instruction booklet is long gone, so every time I get the thing out, I have to re-learn several lessons, which I repeat here for my future self and any readers finding themselves in the same predicament.

Don't fill the dehydrator too full, or the vegetables will take too long to dehydrate. How long is too long? In my case, if the tomato slices are still damp 24 hours after they've been put in, they'll develop mould. What does mould look like? On tomatoes, like sprinklings of white dots or powder, which, in a super macro closeup, resolve themselves into this:

This photograph was a real relief to me because when I first caught sight of the sprinkles I thought they were bug eggs. Insects don't go near the dehydrator, though; maybe its 140F temperature is too hot for them, or maybe they don't like to fly against the convection current.

Interestingly, the mould at this stage has no taste at all. However, I didn't want to take chances of it being somehow deadly poison (even though I ate some as an experiment with no ill effects) or an allergen (sending a guest to the emergency ward or the morgue isn't an experience any cook enjoys), so I threw out two batches before determining that, for tomatoes, four shelves at a time is the maximum. In the composter, the mould developed further into a beautiful pure white fuzz. Fruit flies seem to love it.

Slice the tomatoes no more than ¼ inch thick. Romas are great because they are less juicy than other kinds of tomato so they'll dry into slices thicker than a sheet of paper. Sheets of paper are fine too; they're just harder to get off the tray.

Rotate the shelves a few times during the next 16-24 hours to allow everybody to get some bottom time, where it's hotter, and then peel them off the trays and put them into a bowl or on a plate until they're completely cool:
I'm keeping my dried tomatoes in the freezer or I'll pack them in olive oil, so I'm not paranoid about getting every last molecule of water out, but of course if you're planning to store them in jars or bags or take them on hiking trips as part of a soup mix, you want them totally, crackably, shatterably dry.

Once I got over the distress of losing my mouldy batches, the process became really fun and it certainly isn't time consuming (for me personally with preparation and the like) or messy, so I think I'll keep the dehydrator out and try a few other things, maybe even some molecular cuisine. That's…oh…months in the future though, once the tomatoes are gone.

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