Glycerol tristearate
White greasy solid.
Tristearin is the primary fat in beef. It is a triglyceride, a molecule of glycerine has reacted with three molecules of the fatty acid stearic acid.
It is a saturated fat. This means that every carbon has as many hydrogen atoms as it can hold (it is saturated with hydrogen), and there are no double bonds between any two carbons.
Carbon can form four bonds. If a carbon is attached to two other carbons in a chain, it has two bonds left that can attach to hydrogens.
Single bonds are flexible, and can bend and rotate easily. Double bonds are more rigid. A rigid bond does not allow the molecules to fit together easily, so they can't pack tightly into a solid.
Saturated fats are usually solids, while unsaturated fats or polyunsaturated fats (which have two or more double bonds) are usually liquids at room temperature.
stearic acid: InChI=1/C18H36O2/c1-2-3-4-5-6-7-8-9-10-11-12-13-14-15-16-17-18(19)20/h2-17H2,1H3,(H,19,20)/f/h19H
stearate: InChI=1/C18H36O2/c1-2-3-4-5-6-7-8-9-10-11-12-13-14-15-16-17-18(19)20/h2-17H2,1H3,(H,19,20)/p-1