Perhaps not a subject we should talk about on hot days but here we go.
Heat processing is an integral part and process of preparing food for long term storage. Indeed the Americans way of processing is more time consuming but a lot more thorough than the Brtish way although not infallible.
Certainly when it comes to canning type processing under extreme pressure they seem to know what they are doing. In reality any air remaining in the bottles or jars expands and is released during the heating process and a vacuum forms on cooling which is what you want for long term storage. Canners are a different entity altogether and the two processes are very much separate and apart and not the subject of this particular article.
Heat processing falls into a couple of categories in this country. Either by processing in the oven or in a hot/or cold water bath method.
Using your sterilised jars fill them with your chosen preserve according to manufacturers instructions. Fruit is often bottled in a sugar syrup - the degree of the syrup can be of different strengths either light medium or heavy. Basically you gently heat 1 pint of water with either 4oz, 6oz or 10oz of sugar until the sugar has dissolved which forms the syrup. I tend to make this in advance so that it is ready for popping over the fruit at the point of popping it into the jars.
Cut your fruit into halves or quarters and pack into warm sterilised jars. Add the syrup making sure that it comes to the brim of the lid.
I always use a skewer to dab around the jar to release any air pockets before putting the lid on the jar.
For rubber band style jars like Le Parfait or indeed older Kilner jars with a rubber seal fit a new gasket on a jar after it has been soaked into some boiling water and then lock the jar down with the screw ring tightening it and then taking it back a quarter turn or with the spring clip lids provided.
For Kilner and Ball type jars soak the seal in boiling water and dry with tissue then pop on to the jar as you are ready to use them. Then pop on the screw lid tightening it without forcing it and then take it back a quarter turn. I have found that in reality the standard Kilner jar rings and seals interchange with the Ball ones and that the Kilner seals and rings also fit the Quattro Staggioni jars. I bought a quantity of these jars a few years ago for my pasta sauce and then was unable to get replacement seals so I did the next best thing. Having this piece of information gives you a little more freedom in which seals and rings you go for. You are not tied to one particular manufacturer.
For the Hot Water Bath Method of Preserving
In a large pan put the jars to be processed on a folded tea towel in the base of the pan or on a trivet. The idea of the cloth is so that the jars do not touch each other and the soft cloth keeps the jars apart. Fill the pan with enough hot water to cover the jars completely at least by 1 inch of water. Cover the pan and bring very slowly to a simmer and then heat for the required time (following any good bottling chart for the times required for specific fruit which are in good modern books like "The Preserving Book by Dorling Kindersley or a Little Course in Preserving by Dorling Kindersley".
Remove the jars from the pan with some tongs or jar lifter and tighten the screw bands down immediately. Leave until cold.
To test that you have a seal wait until the jars are cold. If a seal is there the seal lid will be very hard and there will be no give in it if there is any movement the seal will not be there and the best thing to do is use the product there and then or pop it into the fridge until you can use it.
Using a baking tray add some newspaper to the bottom of the tray and pop the tray in the middle of the oven for the required processing time. Remove the jars and tighten clips or screw bands immediately.
And that basically is Hot Water Bath Heat processing which is typically used for bottling fruit in this country. "Bottling" is the English term for Hot Water Bath processing. This technique is used to preserve cordials and sauces and gives the preserve a longer storage time.
I make pasta sauce using the Hot Water Bath method of processing the sauce but I add a teaspoon of lemon juice to each of the jars to increase the acidity. Low Acidity with vegetables can cause serious problems if the food is not processed correctly which allows botulism to get into the preserve. However all my tomatoes are roasted and cooked in the oven first with onion, garlic and herbs and whizzed to a smooth sauce in the food processor and then heat processed.
Hopefully soon I will have my canner for my vegetable produce particularly as I want to make various different soups using a lot of vegetables.
There is a general rule of thumb when it comes to using preserves. If you don't like the look of them or something appears to be going on in the jar that you do not like the look of - like air bubbles.
Catch you later.