Unlike oranges or lemons, it's difficult to squeeze an eggplant by hand to get juice. Instead, you'll need a juicer or masher to extract liquid. Juicing the vegetable removes much of the natural fiber content found in the pulp. Nonetheless, eggplant juice contains valuable nutrients including vitamin C, folate, phosphorus and potassium. If you can stomach the taste, drink eggplant juice raw -- it retains more nutrients than boiled juice.
The easiest way to juice an eggplant is to use a juicing machine. When chopped into chunks, the vegetable will fit into the juicer hopper. The stem and hard crown at the top of the eggplant won't juice, so discard these. An eggplant won't produce high volumes of juice -- maybe less than one-fourth of a cup per eggplant. Of course, the larger the eggplant, the more juice you're likely to get.
If you don't have a juicer in your kitchen, mashing and straining an eggplant will do nearly as well. A heavy spoon or meat tenderizer will squash chopped eggplant, releasing the juice. Allowing the pulp to drip into a bowl through a fine mesh sieve gives you juice without the seeds. A large sieve lined with filter paper makes very thin eggplant juice.
For many people, eggplant juice may be too bitter or strange tasting. As with many vegetable juices, you can make the juice more palatable by mixing it with one or two juiced apples. Other options include pears, bananas, strawberries, oranges -- or any sweet and juicy fruit. Eggplant tends to produce a paste when mashed or ground. It's often easier to mix this with water to create a diluted juice rather than to try to squeeze every bit from a whole eggplant.
Like potatoes and tomatoes, eggplants are from the nightshade family of plants, which contain a toxin called solanine. However, you would need to eat at least 4 1/2 pounds of eggplant to experience toxic effects, according to Carol Ann Rinzler in "The New Complete Book of Food." If you do feel ill after drinking the juice, stop taking it. Alternatively, boil the eggplant juice and allow to cool before drinking. Boiling destroys the toxic compounds in the plant.