Germs get around — testing must get mobile, too
Anybody who has gotten food poisoning knows how bad it is. It’s also rampant — according to the Centers for Disease Control (CDC), each year 1 in 6 Americans becomes sick from contaminated food or beverages, and 3,000 die from some foodborne illness. The U.S. Department of Agriculture (USDA) estimates that foodborne illnesses cost the nation more than $15 billion annually in medical expenses, lost business productivity, lawsuits, and compromised branding.
Time is vital in tracking down foodborne pathogens. Traditional approaches like culturing and plating are the most reliable techniques, using selective enrichment of food or environmental samples so the pathogenic cells multiply to detectable levels. Other benefits include ease of interpretation, recovery of live cells for further analysis, and minimal specialized equipment.
The drawback is how long it takes to obtain results — more than five days in some cases, which is problematic for the food industry and regulatory agencies that need to identify and control outbreaks. Products with short shelf lives also may spoil before results become available.
Portable testing is crucial. On-site tests ensure precision in critical situations, such as identifying water contamination or outbreaks of foodborne pathogens associated with processing plants, restaurants, or retail stores. The ability to conduct tests on the go ensures that results are promptly accessible and the location is geo-coded, leaving no room for doubt about the site.
Portability is especially valuable for food inspectors and border inspectors who analyze imported food or food products that are frequently misrepresented, mislabeled, or tampered with. In such circumstances, the ability to conduct tests on location can significantly enhance the accuracy of inspections and protect consumers.
An ideal platform for detecting pathogens should work for diverse food matrices, offer fast results, be user-friendly and cost-effective, and integrate with hand-held devices like cellphones. The goal is to reduce physical size by compacting all the components — easier to do with today’s newer-generation microelectronics, small lasers, power supplies, and batteries.
Several portability solutions
Our research team is focused on developing multiple portable approaches. For example, we have proposed a quartz crystal microbalance (QCM) system that combines a smartphone, an in-situ fluorescence imaging component, and a flow injection component. This system enables real-time frequency data to be received by a smartphone via Bluetooth, while the camera verifies the presence of bacteria on the quartz crystal surface via a fluorescence-tagged antibody.
We also employ a fluorescence-based, loop-mediated isothermal amplification (LAMP) assay to detect mycotoxins — harmful molecules produced by fungi that can cause health problems when consumed by humans and enter the food chain through food crops or animal feed.
Typically, mycotoxin detection is done after harvesting and processing, as concentrations can increase during these steps. If farmers could detect the fungi that produce toxins before harvesting, they could prevent cross-contamination, save resources, and improve food safety.
For example, the fungus Fusarium graminearum is a major problem for cereal crops, producing a mycotoxin called vomitoxin (also known as deoxynivalenol, or DON). We designed a low-cost, portable, microfluidic device to extract the fungal DNA from wheat samples and perform a LAMP assay. The prototype detects the fungus at concentrations relevant to U.S. limits for DON.
Combating food fraud
We also use portable devices for food authentication. While not strictly a contamination issue, food fraud often is associated with contamination or adulteration. The primary techniques we employ are laser-induced breakdown spectroscopy (LIBS) and Raman spectroscopy. We focused initially on products like European Alpine-style cheeses, balsamic vinegar, coffee, spices, and vanilla to demonstrate the technology.
LIBS is a promising analytical technique that uses high-energy laser pulses to create a plasma plume at the surface of a material and measure the optical emission of the elements, ions and molecules that comprise the sample. Our current efforts aim at combining Raman and LIBS into a single, portable, hand-held device to detect food fraud, adulteration and contamination. It would not only address the mislabeling and misattribution of product origin but also detect the presence of harmful substances, including pesticides, metals and microplastics.
Collaboration among experts in fields such as food science, chemistry, microbiology, statistics, data science, and engineering is essential for this interdisciplinary research. Our data science expertise has allowed us to develop predictive models to identify potential food fraud. Our studies also involve analytical chemistry techniques, molecular biology methods, and optoelectronic detection tools. In addition, we have developed immunoassays and biosensors that can detect specific toxins and pathogens in food matrices or cultures.
Making the smartphone an analytical tool
We want to transform the smartphone into an analytical instrument suitable for many use cases. So far, we’ve reported smartphone-based spectrometers, colorimetric devices, lateral-flow analysis devices, and bioluminescence detection — examples of numerous potential applications that smartphone-based instruments can provide. While these measurement modalities have been tested in food-related research to date, they are perfectly applicable to any life science area involving analysis of bacteria, viruses and/or toxins.
The majority of our research is sponsored by USDA Agricultural Research Service (ARS) programs; we also get funding from the Center of Food Safety Engineering at Purdue. In addition, we receive assistance from companies through their instruments and devices; for example, SciAps Inc. let us access its LIBS system until we could buy our own. We’re also working with the Purdue Research Foundation and seeking patents for several technologies.
We hope these ideas will be developed further by partnering companies. Our goal is to implement these technologies on the upstream side with producers and manufacturers so contamination can be detected earlier and dealt with before causing too many problems downstream in society.
J. Paul Robinson, PhD
Distinguished Professor of Cytometry and The SVM Professor of Cytomics, Department of Basic Medical Sciences, College of Veterinary Medicine
Professor of Biomedical Engineering, Weldon School of Biomedical Engineering, College of Engineering
Director, Purdue University Cytometry Laboratories (PUCL)
Purdue University
Fellow, National Academy of Inventors (NAI)
Fellow, American Association for the Advancement of Science (AAAS)
Fellow, American Institute for Medical and Biological Engineering
Honorary Fellow, Royal Microscopical Society
Euiwon Bae, PhD
Senior Research Scientist/Continuing Lecturer
School of Mechanical Engineering, College of Engineering, Purdue University
Bartek Rajwa, PhD
Research Professor of Computational Life Sciences
Bindley Bioscience Center, Purdue University
Kennedy Okeyo, PhD
Visiting Scholar, Purdue University
Xi Wu, Sharath Iyengar, Sungho Shin, Iyll-Joon Doh
Postdoctoral Research Scientists
Department of Basic Medical Sciences
College of Veterinary Medicine, Purdue University
