Has that food in the fridge gone bad?

Ester Segal of Technion explains her  team’s creation of a sensor to detect  bacteria in food and water. Photos by Suzanne Pollak
Ester Segal of Technion explains her team’s creation of a sensor to detect bacteria in food and water.
Photos by Suzanne Pollak

Those expiration dates on the yogurt and salad dressing in the back of the refrigerator may one day be a thing of the past.

A team at Technion- Israel Institute of Technology has a developed an inexpensive and quick way to identify bacteria in food and water, with the invention currently in testing stages.

Ester Segal, associate professor at Technion, spoke Jan. 29 at Ohr Kodesh Congregation in Chevy Chase about her team’s design.

While thinking big, Segal worked on an incredibly small scale. Her team’s invention, called a biosensor, is designed to greatly reduce the amount of contaminated food available for consumption. Work was done using nanotechnology, which means her team’s measurements were done using the nanoscale. A nanometer is equal to one-billionth of a meter.


As any parent who has waited to learn results of a throat culture knows, it can take two days in a lab for bacteria to grow and for health care providers to obtain test results, she said.

But, if the results can be learned instantly, medicine can administered sooner.

Similarly, bacteria-infected food can be removed before it reaches stores.

“The challenge is to ID [the bacteria], ideally in real time and outside the lab [at the site of the contamination],” Segal said during her talk, which was sponsored by the Israel Solidarity Committee of Ohr Kodesh and the Washington Chapter of American Technion.

The biosensor has two elements.

One is a receptor, often an antibiotic, which recognizes bacteria. The other is a transducer, which enables a person using the biosensor to recognize the presence of bacteria. The person reading the results is alerted to bacteria by a light that changes color.

The machine uses a silicon wafer similar to the ones in cellular phones. However, this piece of silicon is perforated so that it has tiny holes throughout, Segal explained.

When water or food is tested, the bacteria present either fall down these holes or stay atop the wafer. Either way, the change disturbs the way light is reflected, sending off a different color.

Segal anticipates that her biosensor one day will be inexpensive enough for people to test the yogurt in their refrigerators, instead of relying on a printed expiration date.

Those dates are “intellectual guesses” and “assumptions,” she said.

She asked the 25 people gathered in the synagogue’s library how often they threw something away even though it had yet to expire or noticed that one piece of food had mold on it while another did not, although they both had the same expiration date.

The biosensor is licensed by Technion and is undergoing testing in a European lab.

A pilot program will be conducted in the Netherlands during this spring’s growing season. This is important, Segal said, because the Netherlands does not allow chlorine in its water, which permits bacteria to grow. Without chlorine, there is a “huge potential” for contamination, Segal said.

If everything is successful, Segal expects the biosensor to be approved for use. She is optimistic the new nanotechnology will greatly reduce the roughly 3,000 deaths and 45 million non-fatal illnesses annually in the United States due to bacteria-contaminated food and water.

Meanwhile, her team is trying to create better food packaging material using essential oils that will lengthen the shelf life of food and prevent bacteria from growing while food is being transported. Currently, plastics are used in a great deal of packaging materials, although fungi and mold grow in that environment, Segal said.

“Fungi and molds are very difficult to kill. You must know that from your shower curtains,” she said.
He team also is looking into detecting bacteria more quickly in illnesses, including urinary tract infections, and being able to determine more readily which antibiotics work on which bacteria.

Segal’s use of nanotechnology to improve food safety has been in the works since 2008.

That includes time spent raising funds and seeking grants, she said, as raising money for her work is part of her job. She said it took her about one year to obtain money from the Israel Science Foundation before she was able to begin her scientific work. As the biosensor progressed, Segal often found herself involved in applying for competitive grants to keep her work on track.

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