Once a year I buy 20 to 40 kg of end-of-season tomatoes for real cheap and make passata.
The jars of sauce last 1 to 2 years in the refrigerator, and I use them for pizza bases, pasta sauces, eggs in tomato sauce, and ragu.
The traditional method is time-consuming because the Italians remove the seeds and skins. I devised a way to skip that – blend whole tomatoes in a Vitamix. The skins and seeds disintegrate into the liquid and have no negative effects on the sauce, from my experience.
The liquid is then cooked over a stove – it dehydrates/thickens, intensifies in flavour, and undergoes the Maillard reaction (to some extent), which increases the sweetness and reduces sourness.
These are from the farmer’s market; 20kg for $30. The Roma variety is the one traditionally used, although my favourite batches over the years have been with some other ugly variety I don’t know the name of.
Wash, cut, blend.
Whole tomatoes in the blend cause them to get stuck, so I chop most of them in half.
The Vitamix does a great job of pulverising the seeds and skin; you can’t even tell after the blend that the skins and seeds were included. Well, not true, if you look closely, you can see some speckles of skin, on the edge of the blender “glass”, but that’s because I only blend for 15 seconds or so.
I then cook them for about 3 hours. I’m looking for the liquid to halve in volume (approximately) and for the boiling bubbles to become thick. At that point, sauce starts spurting out and onto the stove surface. I cover it with a lid but leave it ajar to allow steam to escape and dehydrate further, but not too much.
Don’t put too much salt, you can do that later when you’re using it.
Also, I put salt near the end. Salt causes the boiling point of water to go higher, and it seems like a waste to do that. I boil 50% of the liquid out, THEN I add salt.
Then I put the sauce into jars through a funnel. I used to keep large jars but that became inconvenient when using, as I’d break the seal, and may only use half the jar. If I had no plans to use the other half soon, it goes mouldy in the fridge after a while.
Some of the jars have a surface of olive oil. I was in the process of finishing that job; they all will be covered.
I don’t do any sterilisation techniques (canning). My jars 2 years at least (I usually finish them in a year, depending on how much I made). The last because of:
- The sauce has been cooking for a long time and is nearly sterile, meaning the pathogen load is very low.
- The jars are clean (not sterile)
- Tomatoes are acidic which inhibits most pathogen growth
- A seal of olive oil on the surface
- Once used, the contents of the jar are used quickly. Mould on the surface is removed, and the contents beneath are still good to eat.
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