Sensing Exposure Time to Oxygen by Applying a Percolation-Induced Principle

Noa Afik,Naomi Fuchs,Amr Alatawna,Gal Yosefi,Omri Yadgar,Ronit Bitton,Anastasiya Volison-Klimentiev,Sivan Peretz-Damari,Oren Regev,Avia Ohayon-Lavi

doi:10.3390/s20164465

Abstract

The determination of food freshness along manufacturer-to-consumer transportation lines is a challenging problem that calls for cheap, simple, reliable, and nontoxic sensors inside food packaging. We present a novel approach for oxygen sensing in which the exposure time to oxygen—rather than the oxygen concentration per se—is monitored. We developed a nontoxic hybrid composite-based sensor consisting of graphite powder (conductive filler), clay (viscosity control filler) and linseed oil (the matrix). Upon exposure to oxygen, the insulating linseed oil is oxidized, leading to polymerization and shrinkage of the matrix and hence to an increase in the concentration of the electrically conductive graphite powder up to percolation, which serves as an indicator of food spoilage. In the developed sensor, the exposure time to oxygen (days to weeks) is obtained by measuring the electrical conductivity though the sensor. The sensor functionality could be tuned by changing the oil viscosity, the aspect ratio of the conductive filler, and/or the concentration of the clay, thereby adapting the sensor to monitoring the quality of food products with different sensitivities to oxygen exposure time (e.g., fish vs grain).

Highlights

Spoiled food is the cause of many health problems (e.g., Salmonella, Campylobacter) resulting in significant mortality [1,2,3,4,5]
We developed a novel hybrid composite-based sensor consisting of a linseed oil matrix loaded with graphite powder and clay fillers
Temporal electrical conductivity (EC) measurements of the composite-based sensor were carried out under air, and the duration of the sharp increase in the EC was expressed as a parameter that we defined as an 'indication of air-exposure time' (IAET)

Summary

Introduction

Spoiled food is the cause of many health problems (e.g., Salmonella, Campylobacter) resulting in significant mortality [1,2,3,4,5]. Lengthy manufacturer-to-consumer transportation lines increase the probability of food spoilage [11,12]. It is, essential that food manufacturers and suppliers should have at their disposal reliable real-time means for monitoring the freshness of food products [10]. One of the main factors contributing to food spoilage is the exposure to oxygen, resulting in growth of aerobic microorganisms (e.g., yeasts, molds and bacteria such as Aeromonas hydrophila, Yersinia enterocolitica) and quality degradation (change in the color, flavors and nutritional losses) [9,10,13,15,16,17,18,19]. Suitable parameters for in situ monitoring the freshness of packaged food would be exposure time to oxygen and its concentration

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