Q: Is the bitter eggplant juice harmful? When it is for cooking, I separate it by soaking it in cold salt water, but I have no idea how to do this before baking it and if I have to endeavor so much?
A: The eggplant is a controversial vegetable, contrast in every respect. It is glamorously purple from outside, bright from inside, with unique taste despite the usual bitterness, spongy and dry at the same time, perceived as a vegetable but actually a fruit – like tomatoes. It is available throughout the year, but features its best qualities in the period August – October when is its season. The “aubergine” as it is also called, comes from India and is cultivated 4000 years ago. Only 100 g of it give us more than 80 valuable nutritional substances. In these 100 g compared with the Guideline Daily Amounts (GDA) from the World Health Organization there are: fibers – 11% of GDA; manganese – 10%; molybdenum – 5%; potassium – 5%; folates – 5%; vitamin K – 3%; tryptophan – 3%; vitamin C – 3%; magnesium – 3%; copper – 3%; calories – 1%. In addition to the rich palette of vitamins and minerals, eggplants contain important phytonutrients which has proven anti-oxidant properties. Some of them are phenols such as caffeic and chlorogenic acids, and others are flavonoids – nasunin predominantly.
Nasunin is subject of extensive research recently. It is an anthocyane phytonutrient found mainly in the peel of the vegetable and in lower concentrations inside. As an active anti-oxidant, nasunin protects the cell membranes from numerous injuries and is also proven to be beneficial for the vascular system as it lowers cholesterol levels and acts as a vasodilator. Nasunin has also functions in regulation of iron metabolism in the body. It normalizes the immune response in allergic reactions and helps in collagen synthesis.
The bitter eggplant streak comes from the presence of the alkaloid solanine M, also known as melongene, and depending on its content, eggplants are darker and lighter. It is an alkaloid and is typical for other plants like tomatoes, potatoes, peppers, tobacco etc. Toxic in nature it is found in higher concentrations in the roots, leafs and fruits of the plants. Its aim is to protect them from vermin like insects, birds and herbivores. The intake of larger amounts of this alkaloid can prevent the transmission of the neurotransmitter acetylcholine which causes increased sense of thirst, dryness in the mouth, palpitations, hallucinations, delirium and even paralysis.
Another negative characteristic of solanine is the fact it is not soluble in water and cannot be destroyed with boiling or cooking, but with deep frying or baking, the last is preferable in dietetics.
The lethal dose for adults is 1mg per kilogram body mass. This means a man must eat four kilograms of eggplants to reach the critical values.
Concerning the concrete question, without being a cook, I share the popular opinion that the bitterness of eggplants is removed with cutting them to pieces, putting a lot of salt and leaving aside for around 30 minutes. Then they are washed thoroughly with cold water and dried with paper.
Being fully comprehensive from nutritional point of view, I cannot omit the increased amounts of oxalates in this vegetable. These are natural compounds found in almost all life forms, but the high concentration in the body fluids can lead to crystallization of substances and subsequent health problems. That is why people suffering from temporary or chronic diseases of kidneys, liver or gallbladder should avoid this otherwise valuable vegetable.