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Tomato semi-processing (Practical Action Technical Brief)
Semi-processing of tomatoes refers to the production of a partially processed stable tomato pulp which can be stored for further processing later in the season, or sold onto processors for further processing into a number of tomato-based products. The technical brief on tomato processing includes ideas and recipes for the use of tomato pulp. The advantages of semi-processing tomatoes are as follows:
• The pulp can be produced when there is a glut of tomatoes and processed later in the season, thus spreading the processing season throughout the year
• If tomato pulp is sold on for further processing, it cuts out the need for packaging materials such as glass bottles and jars and for bottling equipment.
The details in this technical brief are based on the experience of a farmers group in Sri Lanka who process the tomato pulp and sell it on to a processor for further processing (contact Practical Action Sri Lanka for further details). The procedure can be varied to suit local conditions, but the quality control points must be adhered to to ensure a high quality product.
Quality Assurance guidance notes
Farmers deliver the tomatoes to the processing unit between 3.00 and 5.00pm on a daily basis. Processing takes place up to about 12.00 midnight everyday during the season. If there are messages that need to be conveyed (minimum, maximum of supply, changes in working hours etc.) to the farmers (suppliers) these messages are put up on a notice board at the delivery point, so that the person who delivers tomatoes can take the message back. Farmers are not allowed inside the processing area.
The farmers are asked to supply fully ripe tomatoes which cannot be sold as fresh tomatoes. Tomatoes of any shape, size and variety and without split skins are accepted. Bruised tomatoes are accepted provided that the skin is fully intact. The farmers, who are members of the society, have been given thorough instructions and they have agreed upon the quality of the raw material. Farmers understand that bringing unsuitable fruit will increase the production cost. They bring the tomatoes packed in boxes.
The tomatoes are accepted through a half door, weighed and a receipt given to the farmer which indicates the weight of the tomatoes (minus the individual rejects of the previous day). The farmers have requested that the seeds extracted from a previous days production are returned to them for preservation for use in next season.
Sorting is done by putting tomatoes onto a sorting table which has a slight gradient at one end. The good quality tomatoes gently roll into a basin of water and the rejected tomatoes (spoilt, damaged with broken skins) are collected and weighed. Each delivery is sorted separately to identify accepts/rejects for each farmer.
The good quality tomatoes are thoroughly washed in clean water to ensure they are free of soil and other foreign matter.
The clean tomatoes are fed into an electrically driven mechanical pulper with a 1-1.5 HP motor. This separates the juice from seeds and skins. The tomatoes are rubbed against a perforated drum by two brushes which are fixed to the central shaft driven directly by the motor. The juice passes through the perforated drum into the outer stationary drum and is collected through an outlet. The remaining seeds and skins are pushed out through an outlet connected to the inner perforated drum.
The acidity of the juice is checked to ensure that it is below pH 4.5. If it is higher than pH 4.5, citric acid is added until the desired acidity is achieved.
The total soluble solids content (TSS) of the juice is measured. It should be a minimum of 5°Brix and is usually about 6-7°Brix. If it is lower than 5°Brix, the juice can be mixed with juice recovered from tomato which has a higher Brix value. It should be noted that the refractometer should only be used with juice at ambient temperature. Juice at high temperatures will give an incorrect reading.
The juice is heated in a large stainless steel pan to 90ºC, for about 45 minutes, using an industrial gas stove.
The hot juice is poured into clean, food grade, plastic drums. Just before use the drums should be thoroughly washed with clean water. It is recommended to use boiling water or, ideally, 35% hydrogen peroxide solution for the final rinse. Cleaned, empty drums should be stored upside down on racks.
Preservative (700ppm) of either sodium or potassium metabisulphite is added to the drum of pulp and the drum is quickly sealed. The metabisulphite is mixed by shaking the barrels after sealing.
The drums should be sealed as quickly as possible to minimise the loss of the preservative. As the juice cools down, if there is a good seal, a slight vacuum will be formed. This helps with preservation of the pulp.
The sealed drums must be carefully moved and stored in a clean space at ambient temperature (25-30ºC). Care should be taken not to damage the seal while moving the drums. If the seal is broken the levels of sulphur dioxide will start to decrease and there will be no vacuum. This will cause the juice to ferment and be unacceptable for the consumer and for further processing.
The price per litre of tomato juice is negotiated with the buyers. The drums are transported in a lorry from the processing unit. Members are paid for the supply of tomatoes. The profits left after covering the costs are divided according to the quantity of tomatoes supplied by each member. These are then deposited into individual bank accounts at the Regional Rural Bank in Matale.
For further information, please write to:
Practical Action South Asia
5 Lionel Edirisinghe Mawatha
Sri Lanka Tel: +94 11 2829412
Fax: +94 11 2856188
References and further reading
• Tomato Processing, (Practical Action Technical Brief)
• How to grow tomato and peppers: Agrodok 17: M. Amati et al, Agromisa, 1989
• Small-scale Food Processing: A Directory of Equipment & Methods, S. Azam-Ali et al, ITDG Publishing, 2003.
• Tomato and Fruit Processing, Preserving and Packaging: An example of a village Factory, G. Klein, CIEPAC/TOOL, 1993.
Note: This is a selective list of suppliers and does not imply endorsement Practical Action.
Pulpers and juicers
Bombay Industrial Engineers
430 Hind Rajasthan Chambers
D S Phalke Road, Dadar (C Rly)
Mumbai 400 014
Tel: +91 22 2411 3999/2411 4275
Eastend Engineering Company
173/1 Gopal Lal Thakur Road
Calcutta 700 035
Tel: +91 33 2577 3416/6324
Fax: +91 33 2556 6710/160
158 Golf Links
New Delhi 110003
Tel: +91 11 23344287/23363640
Fax: +91 11 23717179
Geeta Food Engineering
Plot No C-7/1 TTC Area
Pawana MIDC, Thane Belapur Road
Behind Savita Chemicals Ltd
Navi Mumbai – 400 705
Tel: +91 22 2782 6626/2766 2098
Fax: +91 22 2782 6337
Kaps Engineers 831, G.I.D.C.
Vadodara - 390 010
Tel: +91 265 644692/ 640785/ 644407
Fax: +91 265 643178/ 642185
P-25 Connaught Place
New Delhi 110 001
Tel: +91 11 2336 3547
Fax: +91 11 2374 6705
1st Floor, 31 Parekh Street
Mumbai – 400 004
Tel: +91 22 2385 1258
Tel: +94 8 420482
Uda Aludeniya, Welligalla
Tel: +94 8 388586
Fax: +94 8 388909
Mark Industries (Pvt) Ltd
348/1 Dilu Road
Tel: +880 2 9331778/835629/835578
Fax: +880 2 842048
12 Avenue Gal Leclerc
Tel: +33 3 85588080/85586666
JR Albert Aberd
No 400 Urb Miguel Gau (Ex Pinote)
San Martin de Porres
Tel/Fax: +51 14 4811967
Lehman Hardware and Appliances Inc.
P.O. Box 41
Tel orders: +1 877 438 5346
Tel enquiries: +1 888 438 5346
DISEG (Diseno Industrial y Servicios Generales)
Av. Jose Carlos Mariategui 1256
Villa Maria del Triunfo
Tel: +51 14 283 1417
Tel: +44 1666 577333
Fax: +44 1666 577339
Tel: +44 (0) 23 9247 6000
Fax: +44 (0) 23 9239 2400
Refractometers and pH meters
Fisher Scientific UK Ltd
Bishop Meadow Road
Tel: +44 1509 231166
Fax: +44 1509 231893
International Ripening Company
1185 Pnieridge Road
Tel: +1 757 855 3094
Fax: +1 757 855 4155
India (see above)
The Schumacher Centre for Technology and Development Bourton-on-Dunsmore Rugby, Warwickshire, CV23 9QZ United Kingdom Tel: +44 (0)1926 634400 Fax: +44 (0)1926 634401 E-mail: firstname.lastname@example.org Website: http://www.practicalaction.org/ This document was produced by Dr. S Azam Ali for Practical Action in March 2008. Dr. S Azam-Ali is a consultant in food processing and nutrition with over 15 years experience of working with small-scale processors in developing countries.