Can Green Tomatoes Be Poisonous?

Last updated on October 23rd, 2023 at 08:32 pm

Ripe tomatoes not only taste better, but are also healthier than unripe specimens. Because green, unripe tomatoes usually not only have a bitter taste, but can lead to symptoms of poisoning if eaten in large quantities!

Except for some varieties, the green coloration of tomatoes is an indicator of the ripeness of the fruit. As long as the fruits are green in color, they are considered unripe and ideally still remain on the mother plant. This is because at this stage of ripeness, the tomatoes still contain a high amount of solanine, an active ingredient that is toxic to humans and animals. How harmful solanine really is and how you can reduce the solanine content, you can find out here!

Green tomatoes contain solanine

Before fully ripe tomatoes take on their variety-specific discoloration, they are basically green in color. This is primarily a natural protective mechanism of the plant, as it helps camouflage the green tomatoes. To further protect the fruit, the plant produces the chemical solanine, which is present in all green parts of the plant, including the unripe fruit. Also known as “tomatin”, this substance is toxic and thus protects the plant from animal enemies. However, the solanine content is reduced as ripening progresses, so that fully ripened tomatoes can be eaten without hesitation. However, a small amount of solanine remains in the green parts of the plant such as leaves and stems.

• Solanine is toxic
• it belongs to the group of alkaloids
• many nightshade plants contain solanine
• it is heat resistant and insoluble in fat
• but not carcinogenic

Solanine can have a toxic effect

The consumption of a large amount of solanine can lead to symptoms of poisoning and even death. However, it depends on the amount and the own body weight, because as a guideline: About 1 to 2 milligrams of solanine per kilogram of body weight can already cause symptoms of poisoning. For adults, the consumption of up to 200 milligrams of solanine is generally considered safe, but anything above this level has a toxic effect:

• from 200 mg solanine first symptoms of poisoning
• such as stomach complaints, diarrhea, dizziness
• larger quantities can damage the central nervous system
• this leads to paralysis and cramps
• from 400 mg solanine there is danger to life

Poisoning from green tomatoes unlikely

The solanine content is highest while tomatoes are green and unripe. This is because 100 grams of these fruits contain around 9 to 32 milligrams of solanine. Taking into account the maximum value, the conclusion is therefore that about 625 grams of the green tomatoes can be consumed before the first symptoms of poisoning appear. Life-threatening solanine poisoning from the consumption of green tomatoes is therefore extremely unlikely as a rule. Particularly as the solanine content continues to reduce with advancing ripeness, resulting in the following guide values:

• semi-ripe tomatoes contain about 2mg solanine/100g
• toxic when consumed at around 10 kg
• ripe tomatoes contain about 0.7m solanine/100g
• toxic when consuming about 29 kg

Note: These guideline values refer exclusively to adult humans, children should not consume green tomatoes in principle!

Process green tomatoes

In some regions, the green, unripe tomatoes are considered a specialty and are often made into jams or pickled sweet and sour. The advantage here is that the bitter taste is masked by sugar and other spices. However, this has only a minimal effect on the solanine content! To ensure that no symptoms of poisoning occur, no more than 100 to 150 grams of these specialties should be consumed. The processing of the green, unripe tomatoes has different effects on the solanine content of the fruit:

• pickled tomatoes: about 90% solanine content.
• Tomato jam: Sugar reduces solanine content by about 35%.
• lactic sour: solanine content is reduced by one third

Allow green tomatoes to ripen

Instead of processing the unripe fruits directly, it is worthwhile to let them ripen. The important thing here is that only healthy, intact tomatoes are suitable for post-ripening. Depending on how many green tomatoes are still on the mother plant, various methods are suitable for this. Small quantities can be easily wrapped in newspaper or ripened on the windowsill. For larger quantities, cardboard boxes or baskets are suitable for post-ripening. In order for the fruits to ripen without problems, the following conditions should be met:

• Temperature between 16-25 degrees.
• the warmer it is, the faster the fruits ripen
• relative humidity above 80%
• too humid: fruits rot
• too dry: Fruits dry out

Tip: If there are still many green tomatoes on the mother plant, these should be allowed to ripen on the plant. To do this, pull the plant out of the ground, including the roots, and hang it upside down from the ceiling in a cellar or laundry room.

Green tomato varieties

Although most tomato varieties produce red, yellow or orange fruits, there are still some exceptions: For there are now numerous tomato varieties whose fruits retain their green color even when fully ripe. Among the best-known green tomatoes are the following varieties:

• Green Zebra
• Green Grape
• Kumato
• Lime Green
• Furry Yellow Hog
• Green Bell Pepper
• White Furry Boar

Tip: Whether green tomato varieties are ripe can be determined with a simple pressure test, because the ripe fruits are somewhat softer. Visually, fully ripe green tomatoes can be identified by their size on the one hand and a slight yellow sheen on the other.

Green tomatoes: poisonous or delicacy?

Many people already know that green tomatoes are not yet ripe and contain toxic solanine. In some regions, however, they are still eaten – as a specialty. How digestible is the fruit vegetable?

Why green tomatoes are poisonous

Plants have special protective mechanisms with which they keep their predators away from them. Fruit-bearing plants in particular protect themselves with a certain sophistication. This works on the one hand by camouflage, on the other hand by resistance.

The tomato is no exception. To protect the fruits from predators, they remain green for as long as possible. Thus, they are very difficult to see between the leaves. The color remains unchanged until the tomatoes have matured to the point where the fruits are ready for reproduction. Only then do the tomatoes turn red or yellow, depending on the variety.

For a double protection, however, the tomato does not only camouflage its fruits. In addition, green tomatoes contain solanine. The poisonous alkaloid tastes particularly bitter. If an animal nevertheless does not let go of the plant, poisoning symptoms set in with excessive consumption. In the worst case, it can die from this.

Green tomatoes: What is solanine?

Solanine is an alkaloid. This term is used to name various substances that are often found in plants as defensive substances.

In addition to solanine, colchicine is also one of them, for example. This poison is contained in the meadow saffron. It can have a lethal effect even in small doses. Strychnine of the nux vomica also belongs to the alkaloids.

A little better known is capsaicin, which you can find in chilies and hot peppers, among other things. There, the substance provides the spiciness. And even the morphine of the opium poppy belongs to the alkaloids.

Some of these substances are also used in medicine in small doses. In this case, however, only a few milligrams are used. If you consume a larger quantity of alkaloids in your diet, for example, it can be dangerous.

How toxic are green tomatoes?

Solanine is found exclusively in the green parts of the tomato. If you eat a ripe fruit, there is no danger of poisoning.

Green tomatoes contain about 9 g to 32 mg of solanine per 100 g of vegetable. To cause the first severe symptoms of poisoning in humans, you would have to eat about 625 g of green tomatoes.

If the tomatoes are not quite ripe, but also no longer completely green, they contain only 2 mg of solanine per 100 g of fruit. Then you would have to eat a whole 10 kg of them to experience symptoms of poisoning.

If the tomatoes are really ripe and bright red, they still contain solanine. However, it is then only 0.7 mg per 100 g of vegetable. You would then have to eat a whole 29 kg of them before signs of poisoning appear.

If tomatoes glow bright red, they are ripe and ready to eat. However, varieties of green tomatoes do not change color even when ripe.

How likely is poisoning?

Because the solanine tastes unpleasantly bitter, it is unlikely that a person would eat so much of it that they would poison themselves with it. In addition, the amount of solanine in tomatoes is very small. As the vegetable ripens, the amount steadily decreases.

Therefore, the probability that symptoms of poisoning will actually occur is very low.

In certain regions, however, green tomatoes are pickled sweet and sour. Sometimes jam is also made from them. Here you should be careful, because solanine does not decompose with heat. So it is still present after cooking. At the same time, the bitter taste is masked by the ingredients. Sugar, vinegar and other spices then hide the fact that something poisonous is being eaten.

Pickled tomatoes in particular still contain a good 90% of the solanine. If you eat 100 g to 150 g of them, the first symptoms of poisoning can occur.

How do you recognize poisoning from green tomatoes?
Solanine poisoning is manifested by:

• drowsiness
• heavy breath
• stomach problems
• diarrhea

In severe cases, damage to the central nervous system leads to:

• convulsions
• Paralytic symptoms
• A dose of around 400 mg or more of solanine is considered fatal.

You can eat these green tomatoes

The variety “Green Zebra” belongs to the green tomatoes, which do not turn red even when ripe.

Basically, it is good if you only eat ripe tomatoes. Depending on the variety, these are usually bright red or orange or yellow.

However, if you also want to eat green tomatoes, it is best to choose one of the varieties that are still green when they have long since ripened. There are now several of these, which you can of course also grow yourself in a greenhouse. Among the non-toxic green tomato varieties are “Green Zebra”, “Limetto” or even “Green Grape”.

By the way, these particular varieties are not only green on the outside: they also show the color of hope on the inside. The flesh of the fruit is green, just like the skin of the vegetable.

But how do you tell when green tomatoes are ripe? It’s simple: press gently on the fruit. If they give slightly, they are ripe.

In the supermarket we see more and more exotic tomato varieties: from yellow to striped, some are green. But be careful with unripe tomatoes because of the solanine.

The difference between unripe and green tomatoes

Unripe tomatoes actually contain the toxin solanine. This is typically found in the green parts of nightshade plants. It is found in the sprouts and green parts of potatoes, as well as in the green, woody stem end of ripe tomatoes. This is why it is also cut off. In cherry tomatoes, however, it is so small that eating it is no problem.

Green tomatoes in the supermarket are ripe, although they are green. This is a green variety, so it is okay to eat them. Their ripeness can be recognized by the yellowish glow and the fact that they are no longer rock hard.

For amateur gardeners: ripening tomatoes is worth it.

In the case of unripe tomatoes, it is advisable to cut off the tomato plant completely and hang it up with the green tomatoes to ripen. You can also pick the last unripe tomatoes, put them in a paper bag and let them ripen there for a few days – at pleasantly warm temperatures of 18 to 20 degrees. In this way they will still turn red. It is important to let them ripen as long as possible. Because the tomato develops more flavor when it ripens on the bush, and then it also breaks down more solanine.

Use unripe tomatoes for green chutneys only with caution

On the other hand, it is not recommended to process unripe tomatoes into chutneys or tomato jam, because solanine is heat-stable. Processing does not break down the toxin at all.

Chutney recipes aim to eat only a little tomato at a time. An unripe vine tomato may well contain up to 30 milligrams of solanine. From one milligram per kilo of body weight, symptoms of poisoning can occur – these are headaches, stomach aches, nausea or vomiting about three quarters of an hour after eating. This is possible with not even three unripe, green vine tomatoes in an adult of about 80 kilos body weight.

Solanine is lethal only at eight to nine tomatoes – almost no one manages that and is therefore very rare. So in moderation, chutneys and jams made from unripe tomatoes are fine. However, caution is advised here with children!