ITDG 
Interdev Agroalimentaire  

Small-scale processing of tomatoes

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

	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, 

This fiche describes the production of a tomato pulp that can be made into various products such as tomato paste, puree, juice, ketchup and chutney.  There is a separate fiche available (ref - link) that describes the production of sun dried tomatoes.

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 home use to save excess at the height of the season.

When producing the following products 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
Production of tomato pulp
Tomatoes are sorted and cleaned.  All damaged and bruised parts should be discarded.  A pulp is prepared by crushing the tomato flesh and juice, while removing the inedible parts such as seeds, skins and stalks.  The pulp can be prepared in a number of ways, depending upon the scale of production.  At the simplest level a mortar and pestle can be used to crush the fruit.  The inedible fraction is then removed by sieving through a medium mesh (eg 1-2mm holes).  Some mills are also suitable for macerating the tomato flesh and small pulping machines are also available.  Again, the seeds and skin must be removed by sieving the pulp. At a larger scale some pulping machines have an integral sieve or separator which separates out the various fractions.

The pulp (ie the crushed flesh mixed with the tomato juice) can then be used for the preparation of a number of products - juice or squash, puree and sauces.

Tomato juice and squash
Tomato juice can be separated out from the pulp by filtering, but it is more common to make a thick juice from the entire pulp.  The pulp is transferred to sealed, sterile bottles where it is pasteurised at 90-100 C for at least 10 minutes.  This is achieved by standing the filled bottles in a large vat of water, which is then brought to the boil.  Alternatively, the juice can be pasteurised in a stainless steel pan by heating to 90-100 C for at least 10 minutes, then hot filled into clean, sterile bottles.  With this method, care must be taken to prevent localised heating and burning of the juice.  It is better if the juice is indirectly heated in a jacketed container.  With the first method, care must be taken to ensure that the sealed bottles are heated for long enough to allow pasteurisation to be complete.  Since the bottles are sealed, the internal temperature of the contents cannot be measured.  Sample bottles should be removed from the batch and the temperature tested on these.  Remember that it will take longer for the heat to penetrate to the centre of the bottles, therefore this is where the final temperature should be measured.  Bottles should not be too large and all bottles in one batch should be of the same size.  The pasteurisation times will vary for bottles of different sizes and diameters and processors will need to establish the time taken to achieve pasteurisation with their own particular bottles.

During storage, there is a certain amount of separation of the pulp and the juice.  This is inevitable and is acceptable.  Consumers need to shake the bottle before use.  However, if the contents totally separate out into a pale liquid and a solid pulp layer, this indicates that the product is under-pasteurised.  Some processors add a small amount (0.3%) of stabiliser or thickener such as sodium alginate to the juice to prevent separation. This is a permitted additive in most countries, but may be expensive and is not really necessary.

Tomato squash
Tomato squash is tomato pulp with added sugar syrup that has a final concentration of 30-50% total solids ( Brix) as measured by a refractometer.  It is not a widespread product as people generally prefer fruit squashes made from other fruits, but it may be worth investigating the potential for the product in your own area.

Tomato squash is prepared in a similar way to other fruit juices (refer to fruit juice fiche - link).

Concentrated tomato pulp
Tomato pulp can be boiled to evaporate the water and then used in the preparation of a range of products.  The different products vary in the amount of water removed and the type of other ingredients added.  Different examples are listed below:

Product	Solids content (%)*	Temperature at sea level	Other ingredients
Paste	40	101	none
Puree	34	100	none
Jam	68-70	106	Pectin, sugar, acid
Chutney	42	101	Vinegar, salt, spices
Ketchup	35	100	Vinegar, salt, spices

*.	Solids content is usually measured by refractometer and expressed as  Brix. The temperatures shown are the final temperature of the product of boiling at sea level. This is an alternative way of measuring solids content. However, at higher elevations, the boiling point it progressively reduced so this does method becomes unreliable for determining solids. Separate technical advice is needed at approximately 2000m above sea level.

The basic principle behind all these products is to remove water by boiling. This has two purposes - to heat the product and destroy enzymes and micro-organisms that denature and spoil the product.  Also, to reduce the active water content so that it is too low to support the growth of further micro-organisms.

The concentration can be carried out by heating the pulp in an open pan over a fire. It is necessary to heat the pulp slowly, especially when the product is more concentrated, to prevent it burning onto the pan. It should also be stirred continuously to prevent burning, which is very labour intensive and hot work.  The final product will be a dark red paste with a strong taste of tomatoes.

A better method is to use a steam jacketed boiling pan with steam from a boiler.  This is more expensive in terms of the equipment that is needed, but it is faster and produces a brighter coloured product.  The bright red colour of imported tomato purees and pastes can only be achieved using a vacuum evaporator, which is too costly for a small-scale processor.

The pulp is boiled until it reaches the desired total solids content (this is measured by a refractometer).  It is then hot-filled into clean sterile jars and allowed to cool to room temperature.

When making jam, chutney and ketchup, the ingredients are added to the pulp and the same process followed.

There is a flow sheet for tomato juice production (link)

Résultats/Eléments chiffrés
Recipes for various tomato products:

Tomato jam
1kg tomato pulp
1kg sugar
(pectin and citric acid are not usually necessary, but 0.1% pectin and adjustment to a pH of 3.3 with citric acid may be needed if the jam will not set)

Tomato ketchup
420g tomato puree
150g sugar
300g vinegar (10% acetic acid)
30g salt
70g onion pulp
30g garlic puree and other spices to taste
(in some countries a hotter ketchup is made by adding chilli powder or ground chillies to taste)

The following equipment is required:

For preparation of tomato pulp
Mortar and pestle or small mill or pulping machine
Medium mesh (1-2mm) sieve

For preparation of products
Stainless steel pan or steam jacketed pan
Glass bottles, bottle washer and sterilising facilities
Weighing scales
Refractometer
Thermometer

Enseignements
  Only fresh, fully ripe tomatoes should be used.  Over-ripe or mouldy fruit should be discarded. However, fruit with skin blemishes or cracks can be used so long as the flesh is not contaminated.
  Particular attention should be paid to the quality of re-useable glass bottles. Check for cracks, chips etc and wash thoroughly before use.  Always use new caps or lids.
  Tomato juice, puree and paste are very simple to make at the small-scale and do not require expensive equipment. However, before starting to make these products, it is essential to carry out a market survey to determine demand for the products.  It is not sufficient to start production based on a seasonal glut of tomatoes.
  There are several different recipes for tomato ketchup - ie the addition of different amounts of ingredients.  The one chosen will reflect local tastes.  It is important that the total solids is about 35%, to ensure a sauce of a good consistency and with good keeping properties.

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