Necessity is the mother of invention. Sometimes you hit a roadblock; something knocks your plans horribly askew. So it was for me this week, when I planned to reduce a half-bushel (25-26 pounds) of tomatoes to thick tomato paste.
We had washed, quartered, squished and strained the entire basket, and put the sauce into two large flat hotel-style pans. The pans went into the oven at 425˚F for what was intended to be 4 to 5 hours of reducing.
But the oven stopped working, and wouldn’t start again. (It turns out the electronic board that controls operation just crashed. Crashed hard. I never crashed a stove before.)
Faced with 10-11 quarts of hot tomato pulp and no working oven, I decided to try to make tomato paste in my two large slow cookers. I filled them quite nearly to the brim and set them on HIGH. I laid two chopsticks across the ends of both these long ovals, and rested the lids on top, so there was about a half-inch gap, which I hoped would provide opportunity for evaporation. After an hour or two, I checked the pots, and found moderate bubbling around the edges, but no active boiling. I decided to let them work. It had to be better than stirring a big pot on the stovetop for hours and hours!
24 hours later, I was pleased that there had been no browning or scorching, and the tomatoes had reduced by nearly half. I was able to combine the pulp into just one pot: my largest 6-quart slow cooker. I set the lid on the chopsticks again, and let it continue.
In another 8 hours, the tomato pulp was reduced almost by half again, and was clearly becoming thick. I didn’t like the rough texture, though, so I took my immersion blender, and blitzed the tomato glop into silky smoothness: progress! I tested it: I dropped a spoonful on a saucer, and tilted the saucer. Darn, clear liquid drained, so it’s still not thick enough!
It was 4 hours later when the tomato paste showed thick enough that a spoonful dropped on a saucer wouldn’t separate at all, and would retain its shape. It took 30 full hours in the slow-cooker on HIGH, with the lid(s) propped up to permit evaporation. I continued as in my original recipe, putting the paste in 4-ounce jars, adding a bit of citric acid, and sealing in a waterbath for 45 minutes.
Good news: you don’t need an oven to make tomato paste. You don’t need to stand over a hot pot and stir so that the tomatoes won’t scorch. You do need patience, though, and a large slow cooker or two. Flat large cookers will work faster than tall ones for this purpose; the more surface area, the better. I wish I had taken photos all throughout this process. Next time, I promise I will.
Result: from a half-bushel of Roma tomatoes, 24 4-ounce jars of slow cooker tomato paste, and the satisfaction of establishing a new easier cooking method to use in the future.
Link to recipe: oven-roasted tomato paste