Early-warning system for milk supply contaminants

A 5-minute test that provides an early warning of contaminants in the milk supply chain has been developed by a team of European researchers. The test could also be used in beer or water processing applications.

Despite high standards of food safety and quality in the dairy industry, there is still the possibility that traces of impurities and contaminants could find their way into milk. For example, udder infections can lead to harmful organisms entering the milk, and chemical substances such as antibiotics or pesticides can contaminate the product via fodder or as a result of inadequate control of equipment and storage facilities.

As part of an EU-funded project called MOLOKO, Fraunhofer researchers have teamed up with 12 partners from seven countries to develop an optoplasmonic sensor designed to provide fast, on-site analysis of safety and quality parameters for milk.

The aim is to use the biosensor at various points along the value chain — both as a lab device and directly installed in dairy equipment. It could also be suitable for testing the quality of liquids other than milk, such as beer or water.

Taking just 5 minutes, the sensor is used to analyse the product for a total of six parameters relating to contaminants and proteins, thereby providing a supplementary check and an early-warning system within the supply chain, well before the milk is pumped into the tanker. The sensor is functionalised with receptors for specific antibodies that serve as indicators of various quality and safety parameters for milk.

The entire system consists of a re-usable microfluidic chip, organic light-emitting transistors (OLETs) or diodes (OLEDs), a sensor comprising organic photodetectors (OPDs), a nanostructured plasmonic grating and the specific antibodies. The organic photodetector is undergoing development at the Fraunhofer Institute for Organic Electronics, Electron Beam and Plasma Technology FEP, and the microfluidic chip at the Fraunhofer Institute for Electronic Nano Systems ENAS. The OLET, meanwhile, is being developed by CNR-ISMN in Bologna, and the photonic grating by the company Plasmore Srl in Pavia, both in Italy. Coordinator of the project is CNR-ISMN.

Image credit: © Fraunhofer FEP

“The unique thing about our chip is that it can be re-used,” explained Andreas Morschhauser, researcher at Fraunhofer ENAS. “The target molecules are stripped from the immobilised antibodies by a regenerating buffer. This means that the antibodies can be re-used for further tests.” In fact, the estimated life of the chip is 100 test cycles.

In addition to supplying information on milk safety and quality, the measured parameters also reveal details about the health and condition of each cow. This can help farmers spot infections in their cows at an early stage and begin treatment immediately.

How does it work?

Dr Michael Törker, a researcher at Fraunhofer FEP, explained: “Light emitted by the transistor falls onto a grating coated with antibodies specific to the various substances being tested for. When milk is flushed over the grating, any target molecules in the milk then bond with the antibodies. This alters the refractive index in the immediate vicinity of the grating, which in turn modifies how this light is reflected. The reflected light is registered by the photodetector, which measures minimal changes in the refractive index.” This basic phenomenon, which occurs on specially structured nanogratings, is known as surface plasmon resonance. It provides rapid and highly sensitive readings.

Initial results from the development of the optoplasmonic chip will be on show at CES 2020 in Las Vegas on 7–10 January 2020.

Image credit: ©stock.adobe.com/au/Thitiwut