Pumpkin seeds come from the fruits of the New World native Cucurbita pepo, are notable for being deep green with chlorophyll, and for containing no starch, as much as 50% oil, and 35% protein. Pumpkin seeds are eaten widely as a snack and in Mexico are used as a sauce thickener. There are “naked” varieties that lack the usual tough, adherent seed coat and are therefore much easier to work with.
Pumpkin seed oil is a prominent salad oil in central Europe. The oil, containing mainly polyunsaturated linoleic and monounsaturated oleic acids, is intriguingly changeable in color. Pumpkin seeds contain both yellow-orange carotenoid pigments, mainly lutein, and chlorophyll. Oil pressed from raw seeds is green; but when the seed meal is wetted and heated to increase the yield, more carotenoids are extracted than chlorophyll. The result is an oil that looks dark brown in the bottle or bowl from the combination of orange and green pigments; but in a thin layer, for example on a piece of bread dipped into the oil, there are fewer pigment molecules to absorb light, the chlorophyll dominates, and the oil becomes emerald green.