Is it real or is it Memorex?

So goes the commercial about a brand of cassette tape, but the same could be said about extra-virgin olive.

Is it real, or is it a lower-grade product?

A group of University of California, Davis, students have built a palm-sized biosensor designed to quickly and easily evaluate the chemical profile of oil to ensure it's actually extra-virgin, according to a news release.

The undergraduate students—Lucas Murray, Brian Tamsut, James Lucas, Sarah Ritz, Aaron Cohen and Simon Staley—will present their biosensor at the International Genetically Engineered Machines this weekend in Boston.

Extra-virgin olive oil is the highest grade and is produced by crushing fresh olives and extracting the oil. True extra-virgin oil has a fruity flavor and no defects, such as rancidity.

Lower-grade oils, produced by using heat or solvents to extract the oil, lack the health benefits and flavor of the higher grade.

The electrochemical biosensor, shaped like an over-sized thermometer, comes with the computer hardware and software needed to read rancidity levels from a single drop of oil.

The sensor is best suited for producers, buyers and retailers because it's probably too complicated to test olive oil by home producers.