John Myers
What to do if there is only a jumble of wrinkled specimens with green spots and long sprouts in the potato bucket? Can you still eat them?
While Frederick the Great in 1756 had to defy the peasant resistance with his so-called potato order and had to virtually impose potato cultivation, such persuasion is no longer necessary today – the advantages of the potato have long since got around: it is nutritious, tasty and healthy. However, there are a few things to consider when handling the potato, because as a nightshade plant it also contains substances that are not good for us at all: glycoalkaloids.
Glycoalkaloids – heat-resistant poisons
About 95 percent of these glycoalkaloids are found in the very outer skin of the potato, says Dr. Norbert Haase, who, as head of the Max Rubner Institute in Detmold, deals with the chemistry of food.
The scientist urgently advocates peeling or at least peeling the potato before eating it, because glycoalkaloids are toxic to us. Even cooking or even deep-frying doesn’t change anything, because these substances are extremely heat-resistant and only break down at temperatures well above 200 degrees.
The intoxication threshold is low
The intake of glycoalkaloids can lead to discomfort, stomach pain and diarrhea, and that from a concentration of one milligram per kilogram of body weight, says Norbert Haase.
So an adult weighing 70 kilograms could eat 300 to 350 grams of unpeeled potatoes before the intoxication threshold was reached, a child weighing 10 kilograms only 50 grams. That’s not much. However, peeled or peeled potatoes could safely be consumed more than five times as much.
Storage matters
The glycoalkaloid levels also depend on the storage of the potatoes, which should be kept at four to six degrees Celsius and in the dark. Because potatoes turn green when exposed to light: a sign of chlorophyll formation, which in itself is harmless, but at the same time leads to an increase in toxic glycoalkaloids. Isolated green areas should therefore be generously cut away, and completely green potatoes should be disposed of, advises Norbert Haase.
The germs are tough
If the storage conditions are not optimal, the potatoes will germinate sooner. A process in which, according to Norbert Haase, all valuable substances in the tuber are broken down, rearranged and sent to the potato sprouts. Among other things, extremely high glycoalkaloid concentrations can be found there, which are even 30 to 50 times higher than in the shell area.
The highly toxic potato sprouts should therefore not be eaten under any circumstances. The scientist warns that even the consumption of one to two grams can have serious consequences.
The toxins migrate back into the tuber
In the germination stage, the tuber itself should also be treated with caution. This is where the glycoalkaloids from the germs shift back to. From a germ length of three to five centimeters, there are also increased levels in the potato, i.e. levels that are harmful to health.
In other words, simply picking off the germs is useless. A common but risky practice, because with glycoalkaloids the transition from the intoxication threshold of one milligram per kilogram of body mass to the lethal dose of three to five grams is not large.
Fewer glycoalkaloids = more chemistry
How dangerous glycoalkaloids can be was shown in Sweden in the mid-1980s. A series of serious illnesses broke out there after a certain potato variety had produced an unusually large amount of glycoalkaloids due to the weather.
Although this is the exception, one wonders why these substances have not been bred out of the potato long ago. This has already been achieved in Israel, but only through genetic engineering – and that is unthinkable for us, says Norbert Haase, who also sees the breeders in a conflict:
the potato needs glycoalkaloids to defend itself against predators. If it is robbed of its own protective mechanisms, more chemicals are needed. And that would hardly be in the interest of consumers.
Enjoy potatoes (carefully)
Potatoes and glycoalkaloids somehow belong together. Is that why you’d rather do without the otherwise healthy tuber altogether? Absolutely not, says Norbert Haase, just be careful and take a few things to heart: store in a cool, dark place, don’t eat sprouts and clearly sprouted or poison-green potatoes, and to be on the safe side, always remove the skin.
And what else? Let the senses speak, says Norbert Haase: If the taste tends towards bitter, that is also a sign of an increased glycoalkaloid concentration in the potato. It is therefore not suitable for consumption.
