Researchers develop fluorescence sensing platform for visual monitoring of food safety

CHINA – A research team led by Prof. Jiang Changlong from the Institute of Solid State, Hefei Institutes of Physical Science (HFIPS) of the Chinese Academy of Sciences (CAS) has designed a method that could aid in the development of food quality control evaluation systems for gallic acid.

The research team constructed a multi-emitting europium metal organic framework fluorophore for the visual detection of gallic acid (GA) through a portable sensing platform.

They designed and synthesized dual-emission Europium Metal-Organic Frameworks (Eu-MOF) fluorescent probes through the covalent binding and enrichment of GA in tea and fruit juice.

The study was published in the Chemical Engineering Journal.

GA is a phenolic compound found in plants especially fruits, nuts, wine and tea. It has various biological activities due to its reducing properties. It is also widely used in food and health-care products due to its strong antiradical activity and antioxidant effects.

The rapid and visual detection of GA is essential for human health and quality control in food, drugs and health-care products.

In this study, based on the polymerization of boronic acid-based ligands and europium metal ions, the researchers developed a multi-emission Eu-MOF under single-wavelength excitation for rapid visual detection of GA.

They used a color identifier (a smartphone application) to identify fluorescent probe solutions. The Red-Green-Blue (RGB) value of the color realized the visual detection of GA.

After the introduction of boronic acid groups, Eu-MOF had two emission centers under single-wavelength excitation. When GA was detected, the emission color of Eu-MOF changed from red to blue under a UV lamp, which was caused by a shift in energy transfer efficiency in Eu-MOF.

“This multi-emission Eu-MOF exhibited remarkable luminescence properties, high sensitivity, fast visual response to GA, good dispersion and low detection limit in detection, which could be used in practical samples such as tea and fruit juices,” said Pan Lei, first Author of the study.

The visual detection can be performed when combined with the fluorescence sensing platform prepared by smartphone.

“This designed method provided new ideas and approaches for the development of food quality control evaluation systems and was expected to expand the application of multi-emission Eu-MOFs in the fields of chemical and analytical sensing,” said Lei.

Antimicrobial potential of gallic acid

A 2019 study published in PubMed Central, developed an innovative light-enhanced antimicrobial treatment by exposing gallic acid to ultraviolet-C (UV-C) light. The sun gives off this type of invisible ultraviolet light, and it’s commonly used as a disinfectant, said the study.

"This designed method provided new ideas and approaches for the development of food quality control evaluation systems and was expected to expand the application of multi-emission Eu-MOFs in the fields of chemical and analytical sensing."

Pan Lei, first Author of the study Tweet

Due to the antimicrobial activity exhibited, the authors suggested that gallic acid exposed to UV-C light has potential as a new antimicrobial treatment in the food system.

Furthermore, a lab study found that gallic acid improved the shelf life of fresh black truffles. It did so by fighting a bacterial contaminant known as Pseudomonas.

Older and newer studies have equally found that gallic acid fights other foodborne pathogens like Campylobacter, Escherichia coli, Listeria monocytogenes, and Staphylococcus aureus, as well as a bacteria abundant in the mouth called Streptococcus mutans.

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