Passata making with a passata machine

Back to September diary

San Marzano are a paste tomato, which means they have relatively few seeds and are quite dry. You don´t get a juicy squirt when you cut one! They are hollow where most seeds would be on a non-paste tomato. The seeds are also large, so easy to sieve out.
Passata means to pass through, as this is what happens to the tomatoes and a sieve (or other grid, like a passata machine or mouli.)

 

I use a passata machine from Seeds of Italy, which is easy to use, easy to clean and works very well. Tomatoes get put in the hopper, and you crank the handle and out comes passata from the main chute into the bowl, and pips and skin come out of the side chute into another bowl. The tomatoes do tend to need helping down the crusher in the first instance - a wooden spoon handle or fingers work well here! The skin and seeds don´t give up all the pulp after just one passing through: you can reduce their bulk by about half by repeatedly returning it to the hopper several times. The San Marzano pips don´t tend to go through the 1mm mesh of the machine.

More affected fruits, though with intact outer skins.

Processing the passata
If you want to keep it for any length of time, and you don´t want to use a freezer, it´s best to bottle the passata. The AFRC book "Home Preservation of Fruit and Vegetables" is my reference here, as it was originally a government-sanctioned book for housewives in the 1920s.
Fill up jars/bottles with the passata, adding ¼ teaspoon of citric acid per pound (454g) of pulp. (I found 18 fl oz weighed a pound.) This helps the preserving, and doesn´t spoil the taste. You can also add salt and basil if you want. (The bottle pictured has torn basil leaves added.) Bring the passata to the boil and simmer for 5-10 minutes, which reduces the water a bit too, as well as heating it to kill any bugs. Then fill sterilised jars (wash thoroughly in hot soapy water, rinse with hot water, and then put in a cool oven to dry and warm up. Best to put them in when you start the whole process!) and put on the lids as advised by the manufacturer. The jars I used are passata bottles, again from Seeds of Italy, and have screw top lids. I tighten them on, then release by a quarter turn. This allows steam to escape from inside while it´s being boiled, and stops pressure building up. Bottling fruit and veg is dangerous when the pressure builds up as jars can explode. The seeds of Italy leaflet just says to tighten the lids immediately but I personally don´t want to risk having a redecorated ceiling (or no eyesight).
Put the jars in a large pan of boiling water, with a trivet or rack to prevent the bottles from directly touching the heated surface of the pan. (Folded newspaper works if you don´t have a trivet.). The water should completely cover the jars, but if there´s a bit uncovered, make sure it´s covered by a lid or bowl so the steam can cook the top bit. Boil for 10 minutes for a small jar, 20 for large (I take the 1 litre passata bottle to be a large!) then cool.
The AFRC book says fish out, tighten lids immediately and leave to cool. This is because at the end of cooking, the contents of the bottles will have expanded in the heat. As they cool, they will contract, and if the seal is still not tightened, it can suck cooking water back in to the pulp and contaminate it. If the lids are immediately tightened once the pan is off the boil, the pressure will start to drop and the seal is formed but without contamination.
The Seeds of Italy sheet says leave in the water to cool (which takes hours) and which continues the cooking process - the lids are on tight so that´s fine, no danger of contamination of the pulp by water being sucked back in through a non-tight lid as it cools.

I use a combination of techniques - I fish out the jar, tighten the lid, then put it back in!

The finished, cooling product. The white film on the jar is limescale, which shows how bad our water is...