Although we associate tomato purée sauce or passata with pizza and spaghetti, its origin, in actual fact, was far nobler. This sauce came about as a real dish, in eighteen century South America, where it was served as a sort of hot or cold soup, in which slices of bread were dipped.
Whatever its use, the fact remains that tomato purée sauce owes its success to simplicity, but we would be wrong to think of it as being easy to prepare.
Have you noticed, for example, how difficult it is to make a good tomato purée sauce at home? This is because behind a few kilos of tomatoes there is a multitude of chemical and physical parameters that need to be considered. Otherwise, our preserve will have a bad taste or, in the worst case, we will find it has gone moldy after a few weeks, while we would like to preserve its aroma for the cold winter months.
How to prepare tomato purée sauce
For avoiding such problems and for enjoying a great tomato purée sauce, the only thing to do is to approach its preparation in a scientific way. To make an excellent purée sauce, you will need tomatoes, let's say a couple of kilos of San Marzano and basil.
The first trick is to check every single tomato very well and eliminate any rotten parts. The tomato, in fact, is a climacteric fruit, that is, it continues to mature even once it is detached from the plant and this is because it releases ethylene. In the case of tomatoes, this substance acts as a maturation hormone and it is therefore responsible for the perishability of the tomato. Therefore, if rotten parts are present, even if very small, we risk accelerating the decomposition of our tomato purée sauce: Heaven forbid!
Based on a similar rule, once our tomatoes have been cleaned, they must also be washed with care, to remove other small impurities that risk compromising preserving the sauce.
How to cook tomato purée sauce
At this point, the small fruits should be cut, seeded and placed in a large pot where they should be cooked over a low heat, keeping the pot covered. The use of a lid and low temperature is a must to avoid burning the product and because we need a long cooking time to reduce the tomatoes to pulp, but, in actual fact, there is also a biological reason: the cooking process, for all intents and purposes, ensures sterilization, which has the purpose of destroying the micro-organisms naturally present in our produce, which could modify the organoleptic features of the tomato purée sauce.
This cooking step is often underestimated: we tend to pour the tomatoes into the pot and "leave" them there to cook, according to the mantra "the longer they cook the better". Wrong: leaving them covered to cook in so much water will dilute the flavour. And this is why there are those who, before cooking in a pot, place the tomatoes to dry in the sun. Which is very romantic, for heaven's sake, but you will obtain the same result by putting the tomatoes in the oven at about 120°C, for a couple of hours. In this way, the cooking phase in the pot can be reduced to around 30-40 minutes.
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The mixture obtained is then sieved using a so-called vegetable mouli: avoid the blender, because it takes in too much air, while for proper preservation of the tomato purée sauce, we need to remove as much air as possible. There are those who add lemon or vinegar, to increase acidity and improve preservation, but the truth is that the tomato is already quite acidic and there is no need to spoil its taste.
How to preserve tomato purée sauce
Once this is done, boil the well-washed preserving jars in boiling water. Here the secret is to then remove them from the pot, drain them and fill them immediately with the purée sauce and a few basil leaves while they are still warm, leaving a couple of centimeters of air from the cap. Once the jars are closed, they need to be reimmersed in water and boiled again for half an hour, so that a "vacuum" is formed. And now, all that remains is to keep the jars in a cool, dry place and enjoy the taste of summer even during the coldest of winters.