Scientists developing new, low-cost tool for detecting bacteria in food and water

January 23, 2018 by Janet Lathrop, University of Massachusetts Amherst
Credit: University of Massachusetts Amherst

Food scientist Lili He and colleagues at the University of Massachusetts Amherst report that they have developed a new, rapid and low-cost method for detecting bacteria in water or a food sample. Once commercially available, it should be useful to cooks using fresh fruits and vegetables, for example, and aid workers in the field responding to natural disasters, He says.

An analytical chemist and expert in detection methods for food contamination, He says, "Most people around the world cook their vegetables before eating, but here in the U.S. more and more people like to eat these foods raw. This gave us the idea that a quick test that can be done at home would be a good idea."

She adds, "Microbial contamination is an important research topic right now.  "It has been a problem for a long time, but it is now the number one concern for food safety in the U.S."

He, with fellow food science researcher Lynne McLandsborough and their students, in particular first author Brooke Pearson, reported on their new two-step - one optical, one chemical - in two papers this year, one in a recent early online issue of Food Microbiology scheduled for publication in 2018, and an earlier one in the Royal Society of Chemistry's journal, Analytical Methods.

For this work, they designed a sensitive and reliable bacteria-detecting chip that can test whether fresh spinach or apple juice, for example, carry a bacterial load. The chip, used with a light microscope for optical detection, relies on what He calls a "capture molecule," 3-mercaptophenylboronic acid (3-MBPA) that attracts and binds to any bacteria. The chemical detection method, "surface-enhanced Raman spectroscopy" (SERS), relies on silver nanoparticles. The techniques are now in the patenting process.

Over the past summer, the optical detection method was adapted for possible home use with a smart phone microscope adapter that is widely available online for about $30. The first step in the new test for bacteria detection is to collect a sample of water, juice or mashed vegetable leaf and place the chemical-based detection chip in with the sample. A summer high school student in He's food science laboratory developed a simple smart phone app that visually detects bacteria in samples that contain the chip. "This is just the beginning of the work," says He. She hopes to receive more funding to continue this practical application.

The standard method for culturing bacteria from food samples, known as an aerobic plate count (APC) takes two days, He explains. "There are some others that are faster, but they are not very sensitive or reliable because ingredients in the food can interfere with them. We show in our most recent paper that our method is both sensitive and reliable and it can give you results in less than two hours."

To address the food interference problem, the researchers designed the UMass Amherst chip to attract only bacteria but not sugars, fats and proteins in food or dirt. The food compounds can be washed away with a high-pH buffer, the food chemist says, leaving only bacteria for visual counting with the smart phone microscope and app. This method can detect as few as 100 cells per 1 milliliter of solution, compared to a sensitivity of 10,000 cells for other rapid methods.

In their recent study, He and colleagues explored "the advantages and constraints of this assay over the conventional APC method and further developed methods for detection in real environmental and food matrices," the authors explain. "This study advanced the SERS technique for real applications in environment and matrices," they point out.

Explore further: New 'sugar-glass' film uses viruses to kill harmful bacteria in food

More information: Brooke Pearson et al, Rationalizing and advancing the 3-MPBA SERS sandwich assay for rapid detection of bacteria in environmental and food matrices, Food Microbiology (2017). DOI: 10.1016/j.fm.2017.11.007

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8 comments

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Whatmaze
not rated yet Jan 23, 2018
We live in a sea of microorganisms, our air, our skin our kitchens. How is it possible that one would never detect bacteria? I also didn't see any claim that the analysis could differentiate between the good bacteria (they do exist) and those bacteria that can be fatal to humans (i.e. salmonella, E. coli). It also seems most unreasonable to expect a vegetable diet to arrive on ones kitchen counter perfectly sterile. Perhaps I missed something.
Thorium Boy
not rated yet Jan 24, 2018
What a load. We keep hearing it. Microchemistry on slides, pocket spectrometers, portable cheap microscopes, microchannel fluidic analysis products on the cheap.. NONE of it comes to fruition. You think these biochem manufacturers can survive making $30 products? Are they doing to sell hundreds of thousands of them? No.
mackita
not rated yet Jan 24, 2018
The problem is, this method will not save you against eggs or various parasites, which are adhering on food. You can get quote a lot of additional meal for example by eating raw sushi.
mackita
not rated yet Jan 24, 2018
antialias_physorg
5 / 5 (1) Jan 24, 2018
but here in the U.S. more and more people like to eat these foods raw.

Which strikes me as funny, because while raw food contains more vitamins (some get destroyed during cooking) it's also the case that our intestines aren't equipped to get at those vitamins from raw foods.

There's a reason why e.g. cows "chew the cud" and have incredibly long intestines. This is needed to break down the incredibly tough cell walls of raw foods to get at some of the vital ingredients. (We basically simulate this by 'external predigestion'...viz.: cooking)

So: chew your raw carrots all you want. Sure they're tasty and full of vitamin A - but you aren't getting any of it (most all of it leaves you next time you head to the bathroom. Not to mention that vitamins A, D, E and K are oil soluble - so will not be taken up by your intestines even if they are freed. That's why we use cooking fats/oils or oils oils on salads)
mackita
not rated yet Jan 24, 2018
it's also the case that our intestines aren't equipped to get at those vitamins from raw foods
In most cases the oily dressing would solve this problem. The ruminants rely on bacteria on food instead, because the plant food lacks essential aminoacids, which these bacteria produce.
mackita
not rated yet Jan 25, 2018
rrwillsj
1 / 5 (1) Jan 25, 2018
"If it don't eat me first? It's on the menu for my consumption!"

My concern is, that many (most?) of the foods we actually enjoy eating? Have to be processed by enzymes, bacteria and fungi before the foodstuffs have any notable flavor or chewability.

Aside of course, to our addiction to sugar and salt.

"Those who confused the 'Lite' swill with real beer? Indoottatably confuse tofu with beefsteak!"

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