Preserving and chak-chak

The main cause of food spoiling is micro-organisms: moulds, bacteria and yeasts. To keep food for a long time we freeze, dry, salt, pickle in vinegar or heat it (sterilisation). The simplest reliable home method is sterilisation: food goes into glass jars, is covered with lids and boiled in water. Jars hold 0.2 to 3 litres; a special hand machine seals them. Jars are washed and steamed first. Fruit is packed leaving 2–3 cm below the rim, syrup is poured on, and the lid is put on loosely. Jars stand on a rack in a deep pan; the water volume is close to the volume of the jars. Once the water boils the sterilising time is counted: the book gives 15–18 minutes for a one-litre apricot compote. When time is up the jars are lifted with special tongs and sealed tightly with the machine, then cooled upside down. Marinating uses salt, sugar, vinegar (6–8 %) and spices. Food in a tight jar that lets in no air or water keeps. Safety: boiling water, steam and hot glass burn, so this work is done only by the teacher or an adult. Pupils sort and wash the fruit, plan on paper and write labels. Never touch a hot jar without tongs, and never use a cracked jar. If a lid bulges or the contents are cloudy, do not drink or eat it; give it to an adult. Vinegar is sharp and strongly smelling: keep it out of your eyes. Tell the teacher about any fruit allergy.