Shortening

Product detail:

Shortening is any fat that is solid at room temperature and used to make crumbly pastry. The reason it is called shortening is that it prevents cross-linkage between gluten molecules. Cross linking gives dough elasticity. In pastries such as cake, which should not be elastic, shortening is used.^[1] Although butter is solid at room temperature and is frequently used in making pastry, the term "shortening" seldom refers to butter but is more closely related to margarine.

 

http://www.macworldinc.com