ITDG 
Interdev Agroalimentaire  

Small-scale processing of sun-dried tomatoes

	Type de fiche	Techniques/Technologies
	Mise en œuvre	ITDG(Royaume Uni)
	
	Zone géographique	Global; 
	Mots clés	TOMATE; SECHAGE

	Echelle d’action	Groupe
	Public(s) cible(s)	Small- and medium-scale food processors

Contexte
The demand for tomato processing usually arises from a need to preserve the product for cooking purposes out of season, or to add value for extra income.  Traditionally the most important methods used are concentration to a paste or puree and drying either fruit pieces or to a powder.  These methods are the most suitable for small-scale processors, although it is possible to produce other products such as sauces and chutneys.  These require the addition of further ingredients, equipment and packaging materials, which increases the production costs. 

The production of sun dried tomatoes and dried tomato powder is described in this fiche.  A separate fiche (ref _ link) describes the production of tomato pulp which can be made into puree, paste, juice, ketchup and chutney. 

Problématique / Objectifs
High quality salad tomatoes have the highest value when sold fresh and in good condition.  These would not normally be used for processing (as they fetch a premium price) unless for hoe use to save excess at the height of the season.

When producing dried tomatoes, it is essential that the raw material is of top quality.  The tomatoes should be ripe, red, firm to soft, free from all mould growth and free of stems, leaves, dirt and other soils.  It is less important if the tomatoes have surface blemishes as these can be cut out or are removed.  Salad or eating tomatoes are often rejected if they have any surface blemishes, cuts or cracks, but provided they are not infected, they are perfectly fine for eating and processing and may be available at a cut price.  Under no circumstances should mouldy or over-ripe fruit be used as this will spoil the final product.

Description/Mise en oeuvre
Sun drying 
Sun drying is a traditional method of preservation that takes place in hot dry regions.  At the most basic level, the tomato halves are placed in the sun on a clean flat surface (eg a roof) with the cut side facing up, or threaded onto strings that are hung in the sun from a branch or beam.  If climatic conditions are favourable _ ie it is hot and humidity is low - drying is very rapid. However, there may be some contamination of the product by insects, dirt and dust. This can be reduced by covering the tomatoes with fine muslin cloth or mosquito netting.  The end product is dark red, leathery pieces with a strong tomato flavour that will keep for several months provided that the humidity is low.  Re-hydration of the tomatoes is slow, but this is probably unimportant when used in cooking applications.  If the humidity rises the dried tomatoes will need some protective packaging to prevent them from going mouldy.  The best form of packaging is sealed plastic bags, preferably polypropylene or thick polythene, or sealed pottery jars.

If humidity increases, the tomatoes can be dried over a fire to a low moisture content.  The tomatoes should be far enough from the fire to prevent cooking.  They are fully dried when they become hard and brittle.

Tomato powder
When tomatoes are dried to a low moisture content so that they are hard (eg about 5% water), they can be pounded or milled to a powder. This is more convenient to use and store, but does require airtight, moisture proof packaging for storage.  The dried powder is very hygroscopic, that is it will readily pick up moisture from the air, and this will decrease the storage life of the powder.

Résultats/Eléments chiffrés
Sun drying 
Sun drying is a traditional method of preservation that takes place in hot dry regions.  At the most basic level, the tomato halves are placed in the sun on a clean flat surface (eg a roof) with the cut side facing up, or threaded onto strings that are hung in the sun from a branch or beam.  If climatic conditions are favourable _ ie it is hot and humidity is low - drying is very rapid. However, there may be some contamination of the product by insects, dirt and dust. This can be reduced by covering the tomatoes with fine muslin cloth or mosquito netting.  The end product is dark red, leathery pieces with a strong tomato flavour that will keep for several months provided that the humidity is low.  Re-hydration of the tomatoes is slow, but this is probably unimportant when used in cooking applications.  If the humidity rises the dried tomatoes will need some protective packaging to prevent them from going mouldy.  The best form of packaging is sealed plastic bags, preferably polypropylene or thick polythene, or sealed pottery jars.

If humidity increases, the tomatoes can be dried over a fire to a low moisture content.  The tomatoes should be far enough from the fire to prevent cooking.  They are fully dried when they become hard and brittle.

Tomato powder
When tomatoes are dried to a low moisture content so that they are hard (eg about 5% water), they can be pounded or milled to a powder. This is more convenient to use and store, but does require airtight, moisture proof packaging for storage.  The dried powder is very hygroscopic, that is it will readily pick up moisture from the air, and this will decrease the storage life of the powder.

Enseignements
If the climate is not hot and dry, an artificial drier could be used.  However, the cost of the drier and the fuel need to be carefully calculated before embarking on this option as the dried tomato is a relatively low value food.  It may be uneconomical to invest in a drier solely for dried tomatoes.

Auteur : Sue Azam Ali
Saisie le : 06/12/2001 

		Pour aller plus loin

	Contact	ITDG, Intermediate Technology Development Group Ltd
Bourton Hall, CV 23 9QZ, Rugby
Tel.:(44) 1788 661 100, Fax: (44) 1788 661 101, E-mail: itdg@itdg.org.uk
Site web: http://www.oneworld.org/itdg/