Must Find a Use

• When winemakers drain away the newly made wine from their fermentation tanks, the grape seeds in the fermented grape residue -- called "must" -- can be converted from waste to a commercial product. The seeds are crushed, to break down their cell walls, then flushed with solvent to extract their oils. The solvent in turn is separated, leaving a light and clean-tasting oil behind. Artisanal and organic grapeseed oils avoid the problematic solvent, but grapeseed doesn't lend itself to cold pressing. Instead, those producers use a heated version version of the expeller used for cold pressing other oil seeds.

The Bitter End

• It's a different case with olives, a bitter fruit that is packed to the brim with oils. Extra-virgin olive oil is extracted by simply pressing unheated olives, while ordinary olive oil is taken from ground and heated fruit. The relatively dry olive pulp remaining, and the crushed olive pits, are then treated with a solvent to extract the still-large quantity of residual oils. That final class of olive oil, called pomace or extra light olive oil, lacks the flavor that makes other olive oils distinctive. This oil still shares olive oil's healthy characteristics, and its neutral flavor and high temperature tolerance make it a more versatile cooking fat.

Head to Head

• Although grapeseed oil and extra light olive oil are both neutral-tasting, healthful oils, they're different under the hood. Grapeseed oil consists primarily of polyunsaturated oils, while extra light olive oil is made up primarily of monounsaturated fats. Both are considered better for heart health than saturated fats, and there is clinical evidence that both of these oils can reduce "bad" cholesterol. Long storage and exposure to light can cause either oil to break down and develop unpleasant flavors or odors -- especially the polyunsaturated grapeseed oil -- so buy them in small quantities and keep them in a dark place. Refrigerating your oils will extend their shelf life, though monounsaturated olive oil will become cloudy in the fridge. That doesn't affect its quality, and will go away as the oil warms.

In the Kitchen

• Both grapeseed oil and extra light olive oil are good for general-purpose cooking. Both are quite neutral -- the "extra light" in the olive oil's description refers to its flavor -- and won't compete with the flavors in your food. Grapeseed oil has a moderately high smoke point of approximately 420 degrees Fahrenheit, so it's suitable for all but the highest-temperature cooking. Extra light olive oil can tolerate temperatures of 460 F or higher, suitable for extreme applications, such as pan-searing or broiling. If you have the frugal habit of straining and saving your fry oil for later use, the olive oil is a better choice. Monounsaturated oils are more stable, and hold up better under repeated use.