White pepper is a ripe peppercorn with the dark wall removed. It is the volatile oil content which contributes the aroma and the non-volatile constituents, mostly piperine, which is the source of the pungency. The unique value of pepper lies in the combined effects of these two attributes. It is the balance between them that distinguishes peppers from different sources and of different grades or qualities. Pepper oil and pepper oleoresins are obtained from the black pepper.
Pepper oil is produced by steam distillation of whole or crushed fruits.
The oil is an almost colourless to bluish-green liquid with a characteristic odour, reminiscent of pepper, but without the pungency of the spice. Pepper oleoresin is produced by solvent extraction and, unlike the oil, contains the principal pungent compound, piperine, along with some essential oil.