Diced tomatoes, canned (chopped, raw?, organic?)

Tomatoes are available diced (chopped) and canned. They can also be in organic quality. Diced canned tomatoes are used in sauces, soups and stews.

Culinary uses of diced tomatoes

Tomatoes can be processed in many ways. In addition to tomato paste, diced tomatoes are also available preserved in cans or jars. These are available in different versions. The consistency depends on the respective product. Some are soft and watery, others are a bit firmer and mixed with tomato paste. The content of some cans is similar to that of tomato sauce. The more tomato paste you add, the stronger the flavor.

Canned tomatoes are boiled down to preserve them, and therefore last much longer than fresh ones and are a popular "stock item". They are also tastier than fresh tomatoes outside the tomato season, as the canned tomatoes have been able to ripen in the sun for a long time.

Diced tomatoes are mostly used in the preparation of sauces for whole wheat pasta, salsa or dips or soups. You can also use them for stews (e.g., chilli sin carne, African stew with kidney beans and peanut butter) and casseroles. You can also use diced canned tomatoes for tomato risotto, shakshuka and Indian tomato curries with chickpeas.

In addition to onions and garlic, fresh or dried herbs such as oregano, thyme, basil or parsley are popular spices for refining tomato sauces. A dash of white wine, red wine or balsamic vinegar gives tomato sauces a special touch.

Diced canned tomatoes are pre-cooked and therefore not raw.

Can you eat canned tomatoes raw? Even if canned tomatoes are always cooked, it is advisable to reheat the contents well before consumption.

How to make diced tomatoes

Tomatoes are easy to preserve yourself - whole, chopped, with or without the skin. If you want to preserve the tomatoes without the skin, cut the skin at the bottom of the tomato in a cross shape. Put the tomatoes in boiling water for max. 30 seconds so that the tomato skin bursts open. Then put the tomatoes in ice-cold water so that the red color remains, and the skin comes off easily. Remove the tomatoes and carefully peel off the skin with a paring knife. Then place the peeled tomatoes whole or chopped into pieces in sterile jars. Close the well-filled jars and place them in a large saucepan lined with newspaper. Fill the pot with water until all glasses are covered. Bring the water to a boil and cook for about 30 minutes. Then take out the glasses and let them cool down. Check that the snap closure on the lid is bent inwards after it has cooled.

Depending on your needs, you can also refine the preserved tomatoes with herbs.

Vegan recipe for Shakshuka with Diced Canned Tomatoes

Ingredients (for 4 people): 1 onion, 1 clove of garlic, ¼-½ chili pepper, 2 red sweet peppers, 2 tsp cumin (ground), 1 tsp paprika powder (sweet), 2 tbsp tomato paste, 800 g diced tomatoes (2 cans), 1 tbsp rapeseed oil, some salt and pepper.

Additionally: 200 g vegan feta (e.g., from tofu), 15 g parsley, flatbread.

Preparation: Peel and finely chop the onion and garlic clove. Rinse the chili pepper and cut into fine rings. Wash the sweet peppers and cut into strips. Heat the oil in a pan and briefly sauté the onion, garlic and spices (cumin, paprika). Add tomato paste and sauté for 2–3 minutes. Add the peppers and diced tomatoes and simmer for at least 20 minutes, until the tomato juice has evaporated. Season the creamy shakshuka with salt and pepper. If you like, crumble the vegan feta in a bowl. Rinse the parsley, shake dry and roughly chop. Remove the vegan shakshuka from the heat, top with vegan feta and parsley and serve with fresh flatbread.

To find vegan recipes with diced tomatoes follow the reference: "Recipes that have the most of this ingredient".

Purchasing - storage

Canned diced tomatoes can be bought in all supermarkets such as Walmart, Costco, Whole Foods Markets, Kroger, Target, Albertsons and Safeway (United States); Asda, Sainsbury’s, Tesco, Morrisons, Aldi, Lidl, and Holland & Barret (Great Britain); Metro, Extra Foods, Real Canadian Superstore and Goodness Me (Canada); and Coles, Woolworths, and Harris Farm (Australia). Organic supermarkets also have diced organic tomatoes.

Canned tomatoes are sold commercially as polpa (or polpa di pomodoro in pezzi), chopped or whole peeled tomatoes (pomodori pelati). Some products also describe the content as "tomato pulp"; usually tomato juice is added extra. Occasionally, one finds it refined with basil or other herbs. Please read the list of ingredients, as salt or preservatives (acidity regulator citric acid E330) are often included.

Storage tips

Canned food should be stored at a temperature of 8 °C to 19 °C. The minimum shelf life of canned diced tomatoes is usually one to two years. If you don't need the whole can of chopped tomatoes at once, you should pour the leftovers into a well-sealed storage container and store them in the fridge. The leftovers must be used up within three days.

If a can shows external changes, such as rust, a curved lid or bottom, the product should no longer be used and disposed off unopened. If canned food smells or tastes metallic, putrid or fermented, it is no longer edible. With canned goods in jars, the "click" when opening is a sure sign that the vacuum has broken.

Ingredients - nutritional values - calories

100 g of diced and canned tomatoes contains 7.3 g of carbohydrates and has an energy content of 32 kcal. With 1.6 g protein per 100 g, preserved tomatoes are rather low in protein and have a low proportion of fat (0.28 g/100g).¹

Canned tomatoes contain 293 mg/100g of potassium – which is 15% of the daily requirement. A similar amount can be found in fresh carrot juice and raw, unpasteurized sauerkraut. Kombu algae with 6100 mg/100g or dried tomatoes (3427 mg/100g) have significantly more potassium.¹

100 g of preserved tomatoes (diced) contain 9.2 mg of vitamin C (ascorbic acid) (12% of the daily requirement). Plums and pumpkins have similar levels. The vitamin C content of fresh tomatoes is slightly higher, at 14 mg/100g (17% of the daily requirement). The yellow sweet pepper has an even higher value with 184 mg/100g.¹

100 g of tomatoes (diced, canned) contains 0.15 mg of vitamin B6 (pyridoxine) which is 11% of the daily requirement. This content can be compared to that of kohlrabi and carrots. At 1.7 mg/100g, pistachios contain around 11 times the amount of vitamin B6.¹

You can find the total ingredients of diced tomato, the coverage of the daily requirement and comparison values ​​with other ingredients in our nutrient tables above.

Health effects

Are canned tomatoes healthy? Tomato is a rich source of nutrients such as flavonoids and phenolic acids and is the main source of lycopene, which has been linked to many health benefits such as: anticancer and cardiovascular protective effects.⁵ Although fresh, ripe tomatoes usually contain more nutrients than canned tomatoes, the lycopene content in canned tomatoes is usually higher due to the long ripening period of the tomatoes used and the processing and heating.

The consumption of tomatoes and products made from them can support the absorption of bioactive substances.⁵ Read more about the health aspects of tomatoes under the ingredient "Tomato (red, raw, organic?)".

Dangers - intolerances - side effects

Are canned tomatoes bad for your health? Bisphenol A (BPA) is a plasticizer for plastics. It is used as an internal coating for metal cans so that the contents of the can do not come into direct contact with the metal.² BPA is an endocrine disruptor. In high doses, it is toxic to the liver and kidneys and causes changes in the structure of mammary glands (at least in rodents).³ A 2019 study looked at BPA levels in urine and found that it increased after eating canned foods. However, a one-day washout period is said to be effective in limiting BPA exposure.⁴

According to the Swiss Federal Office of Public Health, the effects of BPA at low concentrations are unclear. According to the current state of knowledge, BPA does not pose a health risk because the level of exposure is too low. However, the statement is controversial.³

In 2018, Kassensturz and Saldo (Swiss consumer magazine) tested 14 canned tomato products in the laboratory and were unable to find BPA in any of the tested products.

In food botulism, bacteria (including Clostridium botulinum) form neurotoxins due to insufficient heating. These are highly toxic metabolic products. Spores of the bacterium germinate under anaerobic conditions, which manifests itself in canned goods with bloated lids or cans. The neurotoxins are heat-labile and can be destroyed by subsequent heating. However, it is advisable to stop using canned food that is bloated, obviously damaged or foul.¹³

Ecological footprint - animal welfare

Fresh tomatoes should only be bought during the season, ideally from outdoor cultivation. These tomatoes have the best eco-balance because emissions from heating greenhouses with fossil fuels are avoided.⁸ In the off-season, it makes good environmental sense to buy canned tomatoes instead of fresh tomatoes grown in greenhouses. In addition, it is best to use organic products, as they are produced without the use of chemical pesticides and fertilizers.

Preserved tomato products such as diced tomatoes or tomato paste can be found in cans, jars or in composite boxes (consisting of paper and aluminum or plastic). The packs have different ecological footprints. The German Nature Conservation Union (NABU) requested the Institute for Energy and Environmental Research (ifeu) in Heidelberg to analyze the environmental impact of various types of packaging. In the case of processed tomatoes, they compared composite cartons, tin cans and disposable jars with tin lids. The composite carton turned out to be the most environmentally friendly packaging in this comparison. The reasons for this are that cardboard is lighter than tin or glass, and therefore reduces emissions during transport, and consists largely of renewable raw materials. One disadvantage of composite cardboard is that the production of paper contributes to aquatic eutrophication, i.e. the unnatural accumulation of nutrients in waters that are actually poor in nutrients. One-way glass and tin-plate both perform comparably poorly. Tin-plate is lighter than glass and therefore causes slightly fewer pollutant emissions during transport.⁹

However, the CO₂ footprint of canned tomatoes (only tomatoes that have been strained are mentioned here) are as follows - in the composite carton (1.6 kg CO₂eq/kg), the can (1.8 kg CO₂eq/kg) or in the jar (1.9 kg CO₂eq/kg) - higher than that of seasonal and regional tomatoes (0.8 kg CO₂eq/kg).¹¹

The water footprint for the production of 1 kg of fresh tomatoes is 214 liters, less than the water required for preserved, peeled tomatoes (267 L/kg), strained tomatoes (713 L/kg) or the water requirement for tomato paste (855 L/kg).¹²

Worldwide occurrence - cultivation

The countries that consume the most canned tomatoes, or are at least the main importers, are mostly within Europe. These include the UK, Germany and France. The most important non-European markets for canned tomatoes are in Japan and Canada.⁶

China is the largest tomato producer in the world. A large proportion of the tomatoes grown there end up in Italy, where they are processed into preserves.⁷

Possibility of confusion

What are diced tomatoes? Diced canned tomatoes are not the same as tomato paste (aka passata). For the paste, tomatoes are finely pureed so that no pieces or seeds can be found. Diced or chopped tomatoes, as the name suggests, are canned tomatoes cut into chunks.

Diced tomatoes are also not the same as tomato puree. Tomato puree consists of tomato pulp (without skin and seeds) that has been thickened under vacuum and heat to make it durable.

Industrial production

A typical commercial conservation operation employs the following processes:¹⁰

• Washing
• Sorting, classifying
• Preparation (peeling, cutting)
• Filling into containers
• Venting and closing of the containers
• Heat sterilization
• Cooling
• Packing and labelling, and storing for shipment

Additional information

The primary goal of food processing is to preserve perishable foods in a stable form so that they can be stored and used year-round.

Why preserve tomatoes? The goal of the preservation process is to kill all microorganisms in the food and prevent recontamination by microorganisms. Heat is usually used to kill microorganisms. Oxygen deprivation can be used with other methods to prevent the "growing" of aerobic microorganisms.¹⁰

Alternate names

Diced tomatoes are also known as chopped tomatoes.

Author: Sonali Mookerjee | 10 Jul 2023