The fact is that unripe tomatoes contain the alkaloid solanine, which occurs in many nightshade plants, including potatoes, for example. During the ripening process, the alkaloid is gradually broken down in the fruit. Only very small amounts are then detectable in the ripe tomato. In larger quantities, solanine causes symptoms of poisoning such as shortness of breath, dizziness, gastrointestinal complaints or vomiting and can even lead to kidney inflammation, paralysis and seizures.
Green tomatoes – a dangerous food
True, the green tomato fruit with bitter taste warns not to eat it. Thus, the plant is trying to protect itself from predators as long as the seeds inside the fruit are not yet ripe for dispersal. Nevertheless, there are delicacies made from unripe tomatoes. Pickled in sweet and sour marinade or as jam, green tomatoes are popular. Fried green tomato slices are a traditional dish in the Southern United States. The spices here mask the tart flavor, which is actually meant to draw attention to the harmfulness of the fruit. But this can be dangerous. That’s because unripe tomatoes contain between 9 and 32 milligrams of solanine per 100 grams of fruit. The amount that is dangerous for humans to consume is about 2.5 milligrams per kilogram of body weight. Above 3 milligrams per kilogram of body weight it becomes even life-threatening!
Solanine does not dissolve
Solanine is water-soluble, but insoluble in fat and is extremely temperature-resistant. Even when boiled or fried, the toxin is not broken down and can even pass into the cooking water. Reassuringly, to absorb harmful amounts of solanine, one would have to eat far more than half a kilo of green tomatoes. However, this is unlikely to happen in most cases, because green tomato products are not designed to be eaten in large quantities. In addition, the solanine content of newer varieties is significantly lower than that of old varieties. But beware: solanine has a long half-life and remains in the body for hours to days. The toxin is stored in the liver and accumulates with regular consumption of foods containing solanine.
Green cultivars are harmless
Some varieties like ‘Green Zebra’ remains green even when ripe. The fruit can be harvested when it yields slightly to light pressure
Green tomatoes are quite toxic and should not be consumed for fun. Anyone who wants to try a food made from green tomatoes should limit themselves to small amounts and rare occasions.
How to properly prepare green tomatoes
If you are eager to process green tomatoes because they are left over from the summer harvest, consider the following tips: If possible, let the tomatoes ripen indoors for a while. Even half-ripe tomatoes reduce their solanine content many times over. Most solanine is found in the stalk of the tomato as well as in its skin. If you want to prepare green tomatoes, you should rinse the tomatoes under hot water and peel off the skin and remove the stalk. Always pour away cooking water or juice drawn with salt and do not process further! It is best to make chutney or jam from green tomatoes, because here there is no danger of ingesting too large quantities. Children and pregnant women should not eat green tomatoes in principle!