Canning and seasonal preserves

Canning is treating food so that it keeps a long time without spoiling; thanks to it, fruit and vegetables that are plentiful in season can be used all year round and carried to distant places. The textbook groups canning methods into three: physical (heating, cooling, freezing, drying), chemical (adding substances such as sugar, salt or vinegar) and microbiological (for example, pickling by fermentation with useful bacteria). The main kinds of preserves are: juice, squeezed from fruit and made safe by heating; murabbo, in which fruit keeps its shape while cooked in sugar syrup; jem, in which the fruit softens in the syrup and does not keep its shape; marinade, in which vegetables or fruit are kept in a solution with acetic acid and pasteurised; and ikra, a mixture of chopped, fried vegetables and spices. In a medium with a lot of sugar or salt, micro-organisms lose water and cannot multiply. Freezing is also convenient: no sugar or salt has to be added and vitamins are well kept, but refreezing thawed fruit is not recommended. For home preserves to be safe, jars and lids must be clean and undamaged and the sterilisation and pasteurisation in the recipe must be done fully; only adults handle hot jars and pots. Never eat a preserve with a swollen lid, cloudy contents or a changed smell; tell an adult.