Bottling is extremely useful for whole fruit, purees, and tomatoes, and has the benefit of freeing up some of the space in your freezer for other things. While I would always try and use the fruit in its fresh state, in times of glut, bottling could be the answer. The special Bottling jars, “Le Parfait”, with wide tops with rubber sealing rings, can be found in season, at John Lewis and Lakeland. They come in different sizes but the ones that I find most useful are the 1 litre size, as they fit into my Prestige Hi-Top pressure cooker. Yes, I know that it is no longer made, but your Granny may still have one or you may find one at a car-boot sale, and the replacement sealing rings and valves are still available. Most pressure cookers now available seem to be very small in comparison.
Bottling works by sterilising the bottle and all the contents, thus killing all organisms such as yeasts and moulds, and inactivate the enzymes, that could lead to spoilage of the bottle contents. You must follow the instructions for bottling given by the manufacturer of your pressure cooker.
You must be extremely careful to thoroughly heat all the contents of the bottle right through for sufficient time, as recommended by the pressure cooker manufacturer, to prevent any toxins forming in the bottle while it is stored.
Bottling fruits. As fruit are usually sufficiently acidic to prevent the growth of bacteria, they are most suitable for bottling. It goes without saying, that you must throw away the contents of any bottles that have not sealed properly, or are fermenting with rising gas or smell bad or are “off” in some way.
The fruit should always be good quality, with all unsound fruit removed. Top and tail as necessary, if bottling the fruit whole.
Whole fruit such as Blackcurrants, Plums, should be ripe, but use unripe Gooseberries to help retain texture. Pack into clean bottles, filled up to the marked filling line (this allows for the expansion of the liquid ) with a light sugar syrup. This consists of 150 gm of sugar, dissolved in 600 ml of hot water. Pressure cook for the time recommended by the manufacturer.
Sieved or pureed fruit. This can be used for the storage of Blackcurrants, Raspberries, and Tayberry purees, which can be used later for jellies or ice cream. Bring the fruit to the boil and simmer for some 10 minutes till soft. Sieve or strain into stainless steel pan (to prevent corrosion from the concentrated fruit acids), before adding 150 gm sugar to each 600 ml of fruit liquid. Fill the bottles to the marked filling line while the liquid is still very hot, and pressure cook for the time recommended by the manufacturer.
Pureed Tomatoes. This is useful for times of a tomato glut, and can be used for the base of a homemade Winter Tomato soup. Wash and quarter the tomatoes (do not bother skinning or de-seeding as life is too short! ), bring to the boil and simmer for 5 minutes. As some Tomatoes can have a relatively low level of acidity, depending on the variety, it is usual to add lemon juice to provide additional acidity.
For details of method including increased pressure cooking times, see http://www.ext.vt.edu/pubs/foods/348-027/348-027.html#L5
Other vegetables. Because most vegetables have very low levels of natural acidity, special precautions have to be taken to prevent the growth of dangerous bacteria such as clostridium botulinum. Vastly increased pressure cooking times are required.
For details of methods and pressure cooking times for many vegetables see http://www.ext.vt.edu/pubs/foods/348-027/348-027.html#L5
Opening of bottles before use. This can be easier said than done, and strangely, this is not covered by the books!! My method is to heat up the sealed bottles with the clip undone, in a pan or depressurized pressure cooker, with water. This causes the bottle contents to expand, and reduce the vacuum, thus enabling the lid to be opened. Simple if you know how!