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STRONG QC &
STRONG QC & QAQA

New Technology offers Faster and

Cheaper Food Testing

Researchers at the Massachusetts Institute of Technology (MIT) have created a better
safety test for Escherichia coli O157 which causes more than 73,000 illnesses and 60
deaths every year in the United States alone.

MIT News Office explains that the new test is based on new Detecting bacteria
t y pe of liquid droplet that can bind to bacterial proteins. The Two years ago, Swager’s lab developed a way to easily make
interaction can be detected by the naked eye or a smartphone; complex droplets including droplets called Janus emulsions. These
offering a much faster and cheaper alternative to existing food safety Janus droplets consist of two equally sized hemispheres, one made
tests. of a fluorocarbon and one made of a hydrocarbon. Fluorocarbon is
The foodborne pathogen Escherichia coli O157 causes an denser than hydrocarbon, so when the droplets sit on a surface, the
estimated 73,000 illnesses and 60 deaths every year in the United fluorocarbon half is always at the bottom.
States. Better safety tests could help avoid some of the illnesses The researchers decided to explore using these droplets as
caused by this strain of E. coli and other harmful bacteria, according sensors because of their unique optical properties. In their natural
to MIT researchers who have come up with a possible new solution. state, the Janus droplets are transparent when viewed from above,
The new MIT test is based on a novel type of liquid droplet that but they appear opaque if viewed from the side, because of the way
can bind to bacterial proteins. This interaction, which can be detected that light bends as it travels through the droplets.
by either the naked eye or a smartphone, could offer a much faster To turn the droplets into sensors, the researchers designed a
and cheaper alternative to existing food safety tests. surfactant molecule containing mannose sugar to self-assemble at
“It’s a brand new way to do sensing,” says Timothy Swager, the the hydrocarbon–water interface, which makes up the top half of
John D. Mac Arthur Professor of Chemistry at MIT and the senior the droplet surface. These molecules can bind to a protein called
author of the study. “What we have here is something that can be lectin, which is found on the surface of some strains of E. coli. When
massively cheaper, with low entry costs.” E. coli is present, the droplets attach to the proteins and become
Qifan Zhang, an MIT graduate student, is the lead author of the clumped together. This knocks the particles off balance, so that light
paper, which appears in the journal ACS Central Science. Other hitting them scatters in many directions, and the droplets become
authors are Suchol Savagatrup, an MIT postdoc; Peter Seeberger, opaque when viewed from above.
director of the Max Planck Institute of Colloids and Interfaces in Researchers are using the native molecular recognition that
Germany; and Paulina Kaplonek, a graduate student at the Max these pathogens use. They recognize each other with these weak
Planck Institute. carbohydrate-lectin binding schemes. Researchers took advantage

44 FOOD FOCUS THAILAND SEP 2018