Some ingredients in recipes are nonnegotiable while others can be substituted with no adverse effects. Eggplant varieties are very similar, and it's easy to swap one kind for another when your preferred option is not available. There are just a few things to consider when using Asian eggplant in lieu of Italian eggplant, such as size and flavor.
There are many species of eggplant, from tiny grape-size Asian varieties to the huge globes characteristic of the European varieties. Colors vary just as much, from green and white to deep purple. Asian eggplant varieties tend to be slimmer and smaller than globe eggplants, which are the standard Italian variety found in most supermarkets.
The taste difference between the different types of eggplant in supermarkets is negligible. Asian varieties usually are milder with thinner skin and less seeds than Italian eggplant. The exception is the golf-ball like Thai eggplant, which is quite small and round. These often are green or white in color with a more bitter flavor than other varieties. Thai eggplant also tends to have more seeds, which should be removed prior to cooking.
The most important factor to consider when substituting one variety of eggplant for another is size. One Italian eggplant is roughly the same size as three Japanese eggplants. Alternatively, one Italian eggplant equals 4 cups peeled and cubed, so substitute freely with other varieties that add up to 4 cups.
Eggplant doesn't have to be peeled, but Italian eggplant generally has a thicker skin and more seeds, so some recipes ask for them peeled. Japanese varieties don't have the same tough skin, so you can leave it intact without hampering the final dish. Older eggplants of all varieties have larger seeds that can taste bitter, so look for smaller, firmer fruit when making your selection.