Soybean Oil: The Most Common Oil or Fat
Oil Reserves

Soybean oil appeared 355 times in our tally of fast-food ingredients, but it wasn't the only oil we found. Cottonseed oil made 86 appearances, followed by canola oil with 62 appearances and corn oil with 38. Canola oil, by the way, comes from the canola plant, a crossbreeding experiment from the 1970s.

Drive around America long enough, and you're bound to see a soybean farm. According to the U.S. Department of Agriculture, nearly 75 million acres (30 million hectares) of farmland were used in 2008 to grow soybeans, resulting in 2.9 billion bushels of crop [source: U.S. Soybean Industry Statistics].

What happens to all of those soybeans? Many are crushed and mixed with solvents to extract soybean oil -- a fast-food staple used for deep-frying and as a key ingredient in margarine, pastries, cookies, crackers, soups and nondairy creamers. Some ingredient lists describe it as soybean oil, others as vegetable oil.

Soybean oil contains several unsaturated fatty acids, which means their component molecules have fewer hydrogen atoms. Unfortunately, unsaturated fats don't have long shelf lives. Hydrogenation, or forcing hydrogen gas into soybean oil under extremely high pressure, eliminates this undesirable characteristic. But it also leads to the creation of trans fatty acids, which have been linked to heart disease.

Scientists have recently developed varieties of soybeans that produce oils low in unsaturated fats. As a result, this new and improved oil doesn't require hydrogenation. Fast-food restaurants are slowly embracing trans-fat-free soybean oil, although hydrogenated oil is still widely used.

Food processors also use soybean oil as a starting point for other additives, including the two closely related ingredients we're about to cover.