A team of UC Davis students built a bio-sensor machine that can detect rancid or fraudulent olive oil. From left are: James Lucas, Sarah Ritz, Simon Staley, Yeonju Song, Brian Tamsut and Lucas Murray. (Karin Higgins/UC Davis)
A team of UC Davis students built a bio-sensor machine that can detect rancid or fraudulent olive oil. From left are: James Lucas, Sarah Ritz, Simon Staley, Yeonju Song, Brian Tamsut and Lucas Murray. (Karin Higgins/UC Davis)

When Good Oil Goes Bad

  • by Diane Nelson

Team of UC Davis students that built rancid oil sensor shine during international competition

Extra-virgin olive oil is flavorful and healthy, which could explain why sales of high-quality olive oil have tripled in America in the last two decades. But when you buy a bottle of extra-virgin olive oil, can you be sure the oil inside is, indeed, “extra virgin”?

No. In fact, as much as two-thirds of the extra-virgin olive oil sold in the United States is actually much lower-grade oil, lacking the antioxidants, omega-3 fatty acids, and flavor found in true extra-virgin olive oil. What’s a consumer to do?

Don’t despair. A team of UC Davis students has built a biosensor designed to quickly and easily evaluate the chemical profile of oil, providing producers, distributors, retailers and ultimately consumers with an effective, inexpensive way to ensure olive oil quality.

The biosensor is UC Davis’ entry into an international science competition called iGEM (International Genetically Engineered Machines), which invites top students from around the world to spend their summer engineering solutions to real-world concerns.

The UC Davis team of undergraduate students — Lucas Murray, Brian Tamsut, James Lucas, Sarah Ritz, Aaron Cohen and Simon Staley — will present their biosensor at the iGEM convention this weekend, today through Nov. 3, in Boston.

“It’s a lot of work, but it’s rewarding,” said Tamsut, a sophomore majoring in biotechnology, surrounded by his teammates in the UC Davis Genome Center where their palm-sized biosensor was taking shape. “It’s especially rewarding knowing our project is practical and will solve a real, tangible problem.”

When good oil goes bad

Ensuring olive oil quality is, indeed, a real concern for consumers and people throughout the olive oil industry. Shoppers pay more for extra-virgin olive oil and want to get their money’s worth. Honest olive oil producers want to keep fraudsters from passing off sub-par olive oil as the real deal, and retailers, distributors and producers want a quick, easy way to ensure olive oil quality. And it’s not just a question of fraud.

“Even good oil can go bad,” explained Dan Flynn, executive director of the UC Davis Olive Center. “Extra-virgin olive oil has a shelf life.”

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

Rancidity is that stale taste and smell that you get when oil oxidizes over time or is exposed to too much light, heat or air. Lower-grade olive oils, produced using heat or solvents to extract the oil, lack the health benefits and flavor of high-grade olive oil.

There are olive oil standards set by the International Olive Council and the USDA, but they are voluntary. Importers, especially, can get away with mislabeling and selling a sub-par product because it’s hard to trace where and how imported olive oil is produced. (Most domestic extra-virgin olive oil is produced from olives grown in California.)

And most consumers aren’t savvy enough to know the difference between fresh and defective olive oil. Fun fact: UC Davis researchers discovered many consumers actually prefer a slightly rancid taste to their olive oil, probably because it’s so familiar.

Trained sensory scientists can distinguish fresh and high-quality from defective olive oil, but there’s no user-friendly machine that can quickly assess olive oil quality.

Enter team iGEM

What does rancid olive oil look like, chemically speaking, and how do you build a device that can quickly, easily and inexpensively test for those signature chemical compounds? That was the daunting task facing the six iGEM team members, the best and brightest of the hundreds who applied to be part of the 2014 UC Davis team.

“It’s extremely complicated,” said Selina Wang, research director for the UC Davis Olive Center and one of four advisers to the 2014 iGEM team. “The chemical methods we have available now are either too crude and don’t correlate with sensory traits, or are too time-consuming and require expensive instruments. The students’ goal was to generate an affordable device to detect a comprehensive profile of signature rancidity compounds that match what we smell.”

They’re really close. Their electrochemical biosensor — shaped liked an oversized thermometer — comes complete with the computer hardware and software necessary to read rancidity levels in a single drop of oil.

“It’s not perfect, but we’re getting there,” said Aaron Cohen, a junior majoring in biomedical engineering.

Their biosensor will be best suited for producers, buyers and retailers because it’s probably too complicated in its current form to easily test olive oil quality at home. But Wang sees a day when a future generation of this technology could be built into every bottle of extra-virgin olive oil to guarantee freshness.

“That way, consumers can see at a glance whether their olive oil is starting to turn rancid,” Wang said.

In the meantime, people throughout the olive oil industry, here and abroad, could benefit from the new biosensor, which the team predicts will retail for about $125.

“I think their project has great potential,” said David Garci-Aguirre, production manager at Corto Olive Co. in Lodi. “A biosensor that provides an easy, affordable way to help ensure the quality of our olive oil could prove an incredibly useful tool for us, for retailers and especially for consumers. I see this kind of innovation really helping to get good oils into the hands of those who are trying to buy good oils.”

In addition to Wang, the UC Davis iGEM advisers include Justin Siegel, chemical biology professor; Marc Facciotti, biomedical engineering professor; and Ilias Tagkopoulos, computer science professor. The team also includes two “shadow students,” Yeonju Song and Michaela Gobron, who are gaining iGEM experience and will likely compete on next year’s UC Davis iGEM team.

UC Davis has fielded an iGEM team for the last six years, consistently placing in the top 10 percent of the more than 200 entries from around the world. Winners compete for trophies and bragging rights. This is the first UC Davis iGEM entry relating to food and nutrition, which is a source of pride for the 2014 team.

“UC Davis provides world-class agricultural research,” said Simon Staley, a sophomore majoring in biosystems engineering. “So it’s fitting for us to seek solutions to food quality and safety concerns.”

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