Tomato harvest day at the cottage came on September 19. All summer we have taken what we needed as we needed it from the garden but with the passing of the halfway mark in September frost is a possibility and the determinate tomatoes are ripe and a couple are showing possible signs of blight. It has been easy to find delicious uses for the six to ten tomatoes we have gleaned over the past few weekends but this time I brought home about sixteen pounds of tomatoes. Roughly a third of this haul was not quite as ripe as I’d like so they’ve been wrapped in newspaper and stashed in a warm, dark room to ripen. The other two thirds needed to be preserved before they spoiled.
Last summer I made a simple tomato sauce with the extra garden tomatoes and froze it. This was a good sauce and it made for a meal in February (with some homemade pasta) that did an excellent job of reminding us of summer. The downside was that while we kept a large brick (about the size of medium-size cookbook) of tomato sauce in our freezer for months we only got to enjoy it with one meal. This year I wanted to find a way to spread the flavours of August over more time. Paul Bertolli’s Cooking by Hand–a well-respected cookbook that along with the works of Hugh Fearnley-Whittingstall and Michael Ruhlman are often referenced on my favourite food blogs–has an extensive tomato section that includes a recipe for tomato conserva. It is tough to describe the difference between tomato paste and conserva–they can be used in much the same way to enrich tomato or meat dishes–except to say that they deserve their individual names. Tomato paste tastes like something that should be called “paste” while conserva earns its more exotic Italian name.
This process is one of those somewhat advanced cooking techniques that, like bread making without a machine, has a relatively long inactive prep time where not much is required from the cook other than the occassional moment of attention. The liquid extraction process starts by chopping the tomatoes into a rough dice and then quickly cooking them in a large saute pan or skillet.
A food mill is used to separate the seeds and the skin from the rest of the tomato and the resulting thick tomato juice is spread out on a half sheet pan. I hope it is obvious to everyone that the food mill should be set over a bowl and not held directly over the sheet pan (you may feel like you’re saving yourself a bowl to clean but it will be very messy and difficult to keep the food mill stable).
Bertolli gives times for cooking the conserva in a conventional oven and goes on to say that they can be shortened if using a convection oven but fails to say by how much. (I guess it is assumed that if you have a convection oven you’ll know how to make these conversions.) The times, without convection, are five hours at 350°F and an additional two hours at 250°F. It is tough to know for sure but I found that two hours at the higher temperature plus two hours at the lower temperature worked fine.
Sterilising the jars that the conserva is going into is an absolutely essential step. There is no processing step after the jars are filled so to make sure they were totally clean I put them through a cycle in the dishwasher and then scalded them in boiling water. In the jars the conserva is topped with olive oil so this is essentially a confit technique wherein a layer of fat is used to separate the food being preserved from the air and its harmful microbes. I wonder about how I am going to get the conserva out of the jar without taking all of the olive oil with it especially since the jars are refrigerated and this causes the oil to solidify.
The consensus seems to be that my best bet is to remove the jar from the fridge a couple hours before it is needed to let the oil re-liquiefy and then carefully tip the jar to expose the conserva, take what is needed, let the oil re-settle and then top wtih more oil if any of the conserva is exposed to the air.
Also, I recommend storing the jars in the coldest part of your refrigerator. The one that I had on the door of the refrigerator doesn’t have a solid layer of olive oil on top and I worry that either because of the greater agitation or the warmer temperature in this part of the fridge the conserva will absorb some of the oil.
I used the recipe as adapated here in the Los Angeles Times. Mine was a double batch using ten pounds of tomatoes and yielding roughly two and a half cups that I spread over three jars.