Shortening een aanduiding voor (plantaardig) vet met een hoog vetpercentage. Het kan eventueel worden vervangen door boter of margarine hoewel dit een lager vetgehalte heeft. Zie onderstaande referenties.

Shortening, in its most generic meaning, is any fat or oil that is used to make a short crust or dough (one that has a high ratio of fat to flour, and turns out tender, crumbly, and rich).
In general usage, when you see the word shortening as an ingredient in a recipe in this country, the author is referring to solid vegetable shortening, of which Crisco is the best-known brand.
http://www.ochef.com/401.htm

Many people also use butter or margarine in their crusts. Unlike lard and vegetable shortening, which are 100% fat, butter and margarine are around 80% fat, so you have to boost the amount of fat in your recipe by 20% to get the right ratio relative to the other ingredients. In using butter and margarine, you're also adding a certain amount of water to your crust, so you may need to cut back on another liquid specified in the recipe. A crust made with only butter or margarine will turn out less tender and flaky than one made with lard or vegetable shortening.

Lard and vegetable shortening are also used in pie crusts because they have a higher melting point than butter, so they are easier to work with and don't require you to be as obsessive about keeping the dough cold. Vegetable shortening, in particular, does nothing for the taste of your crust, however, so many bakers look for a happy compromise of taste and workability by using a mixture of butter and shortening.
http://www.ochef.com/908.htm