[Syzygies]

Tom Colicchio, Thomas Keller, Paul Bertoli and many other chefs have their version of "precious tomatoes", a tomato confit. None of these recipes scale. After many years of struggling with home dehydrators, I bought one of those full sheet pan carts you see in bakeries, enclosed it in nice plywood, added a 1500W wall heater, brewery temperature regulator, and a crawl space fan that looks like it belongs in a stereo rack. The top and bottom sheet pans serve as buffers and spares, but the middle six sheet pans (lined with silpat) can process 60 lbs of heirloom garden tomatoes at a time. We often grow twenty plants and supply family and friends, so this scale is necessary.

We skin, slice, spread onto oiled silpat, salt, and partially dry tomatoes till "gooshy", about 25% of original wet weight. We then vacuum pack 220g or so to a pouch, and store in a chest freezer till needed.

This equipment also makes great southern Italian concentrated tomato paste, "estrattu". My favorite tomatoes for these are dry-farmed Santa Cruz Early Girls, which I'm put up in a blind taste test against any tomato grown in Italy.

Cleanup is pretty easy, on the lawn with an electric pressure washer. This is a good time to give one's molcajete a cleaning too, if the coarse stone has been trapping food.

I can't eat canned tomatoes; I have to avoid tomato dishes in even the fanciest Italian restaurants. It baffles me why no one is doing what I do on a commercial scale to supply their restaurants, selling the extra through Eataly.

[WaxProlix]

Oh my god, not sure if they were specifically that variety but we used to get dry farmed tomatoes from the farmers market in Santa Cruz and they were incredible. Too expensive for me to make a sauce out of at the time, so they just went on bread or with cheeses usually. Really great tomatoes out there. I wonder if I could get a crate shipped...

[magneticnorth]

Can you grow your own tomatoes?

I've also had Californian dry-farmed early girls, and those are definitely the best tomatoes I've ever paid for.

That said, I think home-grown early girls or other small flavorful varieties are equally good even if you can't properly dry-farm them, so long as you can let them stay on the vine until fully ripe.

[WaxProlix]

Not in my current situation, no, but it's a priority if/when that changes.

[nkurz]

I'd be interested to hear more about your technique. What were the issues with the dehydrators you tried? Are you pre-boiling to peel skins or do you have some other way? Are you scooping and discarding the "guts" or are your tomatoes dry enough to do whole? Are you blowing air through the heater on the way in to the plywood box, or do you have the heater in the box? What temperature are you drying at, and where are you measuring it?

[Syzygies]

I've been planning to put up a web site with plans, as most DIY plans out there are rather sketchy. For most DIY engineering projects I have a pretty good idea of the practical physics, but this challenged me and involved some false steps on the way to a working design. What heat and airflow did I need? That was an empirical question, I couldn't find equations that were relevant to practice in this instance.

I have to go to work shortly, I'll try to update this if you check back.

My heat source is a Cadet Com-Pak 1500-Watt 120-Volt Fan Heater, suspended by metal angle irons in a cradle underneath the unit, intake filtered by a generic 12" air filter. I convinced myself that the wood never got hot because of the gap and airflow, but the auto shutoff in the heater itself was too sensitive for me to drive the dehydrator hard. I shorted its thermostat and added my own from Digikey. This allows me to aim for temps up to 145 F without the heater cutting out.

I regulate the temperature using a Ranco Electronic Temperature Control from a beer making supply company.

I regulate airflow using a AIRTITAN T8-N, CRAWL SPACE AND BASEMENT VENTILATOR FAN. Expensive but slick.

The dehydrator operates very effectively if one has outdoor barbecue experience. While I managed to weave the airflow tray to tray, one needs to tend the trays every few hours, and there can be front or back edge effects from a leaky airflow. This is nothing new to anyone comfortable with fires, but frustrating if one expects a perfect abstraction. Believe me, I've thought about redesigns with perfect air mixing, and they all double the size of the unit, which already looks like a washing machine.

The Italian grandmothers making estrattu on tables in the Sicilian sun have to worry about which tables first get afternoon shade. Nothing new here, the issues just take a different form.

This relates to your temperature measurement question. I choose middle locations for both thermostat probes, and I also have two TelTrue analog thermometers. Like BBQ, the idea of a single temperature is misleading. One flies this ship somehow, with better results than I know how to obtain any other way.

[nkurz]

Thanks, sounds like a great project. Please add a link here to your web site if you ever make it. I try to check my old comments occasionally, so will probably notice eventually.