Prunes

Botany and history
The plum we know today is a white-flowering tree up to 5 metres tall from the rose family and a hybrid of the blackthorn and the cherry plum, which originally comes from Persia. The plum was cultivated in Greece over 2,500 years ago and was brought to France and Germany by the Romans.
Plums come in many different varieties, some of which are difficult to distinguish. Plums also include damsons, mirabelle plums and plum varieties. They are often interbred, so that there are now more than 2,000 varieties worldwide. 
In earlier times, dried fruit was in demand as a source of energy and vitamins for desert crossings, long sea voyages or for the time between fruit harvests. The fruit is preserved by extracting moisture: Naturally dried plums only have a residual moisture content of 18-23%, while plums processed with sorbate have a moisture content of around 28%.
Plums flourished during the Middle Ages and the Renaissance. Monasteries and aristocratic courts played a central role in the distribution and grafting of various types of plums. In addition, the plum was also highly valued as a remedy in those days and was considered helpful for digestive problems, fever and even melancholy.
 

Main cultivation countries
The annual harvest of prunes worldwide is around 210,000 tonnes. The main producers are the USA (California) with an average harvest volume of approx. 75,000 tonnes per year, followed by Chile with approx. 65,000 tonnes, France with approx. 35,000 tonnes and Argentina with 30,000 tonnes.
Only fruits of varieties that do not tend to ferment are suitable for prunes. A distinction is made between sour ‘Italian prunes’ and sweet ‘French prunes’. Italian prunes and French prunes have a dark purple skin when fully ripe, which can be easily removed from the flesh. The best-known French variety is the ‘Prune d'Agent’. Prunes are a particularly fine dried fruit: skinned, pitted and dried plums, which are mainly produced in the south of France.

Processing and use
The degree of ripeness of the fresh fruit is decisive for the quality of the dried plum. The trees are shaken, with only the really ripe fruit falling to the ground. The plums are collected in nets and immediately transported in large wooden crates for further processing.
The first processing step is to remove the moisture using hot air. Around three kilograms of fresh plums are then turned into one kilo of dried plums. The plums are then sorted by size using punched vibrating plates. The plums are then pitted using either the ‘Ashlock method’, in which the stone is removed using a bolt, or the ‘Elliot method’, in which the stone is squeezed out using rollers. For a longer shelf life, the plums are sprayed with sorbate after coring.
Prunes are rich in fibre and nutrients, making them a healthy, aromatic snack. They are used in the bakery and confectionery industry, for example, as an ingredient in fruit bread and chocolates as well as in fruit mixes and muesli.