The federal government has become serious about virginity -- at least when it comes to olive oil.

Propelled by complaints about slippery food purveyors selling low-end product as high-end goods, or olive oils being doctored with cheaper canola, safflower or peanut oils, the U.S. Department of Agriculture this fall will roll out new standards to help ensure that consumers buying "100 percent extra virgin" olive oil get what they pay for.

Demand for the greenish-gold oil is surging in American kitchens. Consumers here sopped up 79 million gallons in 2008 -- up from 47 million gallons a decade earlier. And according to a trade group, consumers annually spend about $720 million on the stuff at supermarkets.

But a lack of strict standards means the U.S. is awash in low-quality, adulterated and even dangerous oils that have made some consumers ill, according to experts. The new rules are voluntary -- not mandatory -- so the prospect of more slick shenanigans continues.

Connecticut investigators tested dozens of bottles of olive oil from store shelves a few years ago after local producers and consumers complained that there was something fishy -- or perhaps nutty -- going on. They were right.

"People were getting sick and thinking, 'It must be the poultry that I fried up in the olive oil last night,' or that it was a type of bread that had been exposed to nuts in the bakery," said Jerry Farrell Jr., commissioner of the Connecticut Department of Consumer Protection. Early this year, his team returned to the market aisles after hearing rumbles of more sly shortcuts.

"It took awhile for people to identify that the oil itself is the thing that was making them sick," Farrell said.

Many industry officials agree that "extra virgin" olive oil is essentially oil that is cold-processed to prevent degradation of aromatic compounds and has higher levels of healthy fats and antioxidants. It also has relatively low acidity levels, 0.8 grams per 100 grams or less, according to the International Olive Council in Madrid, whose product standards the USDA rules are generally based upon.

Federal law bars a company from not disclosing on the label that it is selling a blend of oils. But the practice of labeling lower-quality olive oil as top-end -- and charging a premium for it -- is technically legal in the U.S.

The reason is simple: There are no federal rules that define what is -- or is not -- "virgin" or "extra virgin" olive oil, said Vito S. Polito, professor of plant sciences at the University of California-Davis and co-chairman of the school's Olive Center, a research group.

As a result, Polito said, "the U.S. has been a dumping ground for cheap olive oil for years." Most olive oil consumed in the United States is imported from nations including Spain, Italy, Greece and Portugal. California, which dominates the domestic industry, produced 850,000 gallons of olive oil worth about $17 million during the 2009-10 season.

Although it's hardly the worst oil crisis facing the U.S. at present, the purity issue remains a serious one. People with health concerns or allergies often use olive oil for cooking. Extra virgin oil also is marketed as a premium consumer product and routinely commands an equally prime price: At the Pavilions grocery store in Seal Beach, Calif., a 750 milliliter bottle of Bertolli's extra virgin olive oil cost $14.29, while the same size bottle of Bertolli's extra light olive oil cost $7.99.

Making extra virgin oil can be labor-intensive, with some producers hand-picking the olives while others manually bottle the oil. Lower quality oils, or adulterated oils, are cheaper to produce.