As rains pound different parts of the country, tomatoes are one of the crops whose production is suffering.
Heavy rains lead to diseases like blight which affect supply making the commodity scarce.
But being a common vegetable, tomatoes can easily be transformed into various products to diversify use in the food industry.
They include ketchup, sauce, pickle, chutney, juice, puree and soup.
It is a healthy beverage with a good taste and aroma and a vitamin content close to that of raw tomatoes. A high quality tomato juice contains 0.4 percent acid (citric acid), 0.5 percent salt and 0.1 percent sugar.
Preparation: Select deep red ripe tomatoes, wash and trim to remove tops, green or yellow portions. Cut the tomatoes in small pieces and cook until soft.
This takes approximately 10 minutes. Salt, sugar and citric acid are then added and mixed well with soft crushed tomatoes.
To collect the juice, pass the lot through a stainless steel sieve.
The juice is then pasteurised at 130OC–150OC for 8-12 seconds then cooled to 90OC and filled in sterile containers (bottles), which are then closed and inverted for 5-7 minutes to further sterilise them after which they are allowed to cool to room temperature.
Ketchup is commonly used with snacks and ready-to-eat foods. Compared to tomato sauce, it is thicker and has more spices.
In home-scale production, the ingredients required are tomatoes (3kg), starch (5g), sugar (400g), salt (20g), cumin powder (5g), red chili powder (10g), cloves (10g), black pepper (15g), crushed ginger (25g), chopped onions (100g), crushed garlic (5 cloves), sodium benzoate (2g) and 15ml of glacial acetic acid.
Procedure: Ripe tomatoes are chopped into pieces and then mixed with the onion, ginger and garlic. The mixture is then boiled in a pressure cooker or a covered pan to a soft mix.
The mix is then passed through a strainer to obtain the pulp (juice). The extracted juice is allowed to further cook while starch is added while mixing is thoroughly done to prevent pulp formation.
Sugar is then added and cooking continues until the total soluble solids reaches 28 per cent (refractometer can be used to monitor the total soluble solid). Salt is then added.
The remaining spices are added after which the pulp is removed from the heating source.
Sodium benzoate and glacial acetic acid are finally added before the ketchup is transferred to sterile dry containers where it is allowed to cool.
Home-scale production requires 1kg ripe tomatoes, grated onions 100g, crushed garlic 10g, red chili powder 10g, black pepper 5g, cardamom 5g, cinnamon 5g, cloves 5g, sugar 250g, salt 20g, starch powder 1g, sodium benzoate 0.5g and glacial acetic acid 10ml.
Procedure: The tomato pulp is extracted just as explained in the ketchup procedure. The pulp is then boiled with chopped onion and garlic.
Sugar and starch are added to the mixture until the total solids reach 28 per cent. Salt and sodium benzoate are then added while mixing continues.
The sauce is removed from fire then glacial acetic acid is finally added. The sauce is packed in sterile dry containers tightly covered and allowed to cool to room temperature.
Tomato pickle and chutney are appetising products that are commonly used with rice and snacks. They are highly recommended for children because they improve appetite.
To make tomato pickles, ingredients include tomatoes 10kg, chopped onions 1kg, chopped ginger 25g, garlic (optional) 50g and edible oil 50g.
Cumin, cardamom, cloves, black pepper and cinnamon in equal quantities of 200g, red chili 400g (optional), turmeric powder 200g, sugar/jaggery 1kg (optional), glacial acetic acid 120ml and sodium benzoate 10g.
Procedure: Tomatoes are cut in either quarters or eight pieces and then cooked with onion, ginger and garlic. Jaggery or sugar is added after about 10 minutes of cooking and mixed well.
The tomato mixture is then removed from fire. Half the oil is heated to fry the remaining spices and the tomato mixture is added and fried together.
Finally, salt, sodium benzoate and glacial acetic acid are added in that order while mixing well. The pickle is then filled in dry sterile glass jars and covered with a cloth.
The remaining oil is heated in a separate pan until it fumes and then it is allowed to cool. The oil is then added to the pickle in jars to prevent air contact with the product. The jars are then sealed tightly.
Ingredients are tomatoes 10kg, sugar/jaggery 4kg, salt 200g, chopped onion 300g, grated ginger 200g, crushed garlic 50g (optional), broken cashew nuts 50g, raisins 100g, cumin, cardamom, cloves, black pepper, cinnamon in equal proportions of 200g, edible oil 250g and glacial acetic acid 150 ml.
Procedure: Same as explained for tomato pickle.
Edible oil is used for frying the spices and to act as an air lock covering the top surface of the final product in the jar.
This is a concentrated tomato juice with total solids of between 9 and 12 per cent.
The tomato pulp is extracted as in the procedure of tomato juice preparation.
The pulp is then concentrated in an open cooker or a vacuum pan. The concentration is stopped when the total solid is attained.
The concentrated puree is then sterilised at 92OC for five minutes after which it is hot filled into sterile bottles.
This is a concentrate of tomato juice but it has higher total solids of not less than 25 per cent.
The tomato paste with the required total solids is also hot filled into containers just as explained in tomato puree.
Alternatively, if pasteurisation is not done, preservation can be done by addition of sodium benzoate at 0.75 per cent of the finished product.
Dehydrated tomato slices
Drying is the most common way of food preservation. Dehydration of tomatoes involves the slow removal of water from the tomatoes to improve their shelf-life.
Time taken to dry tomatoes depends on many factors that include the variety of the tomato, temperature, humidity of air during the drying, thickness of the slices and efficiency of the dehydrator or oven.
The tomatoes to be dried should be firm, ripe and meaty. The best varieties for drying include Roma, Plum and Pear since they have a good pulp and few seeds.
Properly dried tomatoes should be dark red, lathery, not brittle and non-sticky.
Drying can be done in the sun, oven or by use of a dehydrator.
Dehydrator products are usually of high quality than sun dried products. Dehydrators, however, limit the amount to be dried compared to sun drying.
In a dehydrator, heated air is circulated and drying may take less than six hours depending on the tomato variety. Most dehydrators are fitted with a thermostat and hence more control is possible.
It is important to turn the slices during drying. Packaging and storage is done in air tight jars or food grade plastic bags.
When stored at room temperature, the dried slices can go for 200 days.
Tomato powder is derived from dehydrated tomato slices through crushing. Packaging and storage methods are the same as those of dried slices.
Rehydration can be done by addition into stews, or soaked in water or vegetable juice. Complete rehydration takes an hour or two.
Apart for extending the shelf-life, dehydration reduces space in packaging, shipping, storage and transportation.
The writer is based at the Department of Dairy Food science and Technology, Egerton University.