A Multi-Sensor System for Sea Water Iodide Monitoring and Seafood Quality Assurance: Proof-of-Concept Study

Abstract

Iodine is a trace chemical element fundamental for a healthy human organism. Iodine deficiency affects about 2 billion people worldwide causing from mild to severe neurological impairment, especially in children. Nevertheless, an adequate nutritional intake is considered the best approach to prevent such disorders. Iodine is present in seawater and seafood, and its common forms in the diet are iodide and iodate; most iodide in seawater is caused by the biological reduction of the thermodynamically stable iodate species. On this basis, a multisensor instrument which is able to perform a multidimensional assessment, evaluating iodide content in seawater and seafood (via an electrochemical sensor) and discriminating when the seafood is fresh or defrosted quality (via a Quartz Micro balance (QMB)-based volatile and gas sensor), is strategic for seafood quality assurance. Moreover, an electronic interface has been opportunely designed and simulated for a low-power portable release of the device, which should be able to identify seafood over or under an iodide threshold previously selected. The electrochemical sensor has been successfully calibrated in the range 10-640 μg/L, obtaining a root mean square error in cross validation (RMSECV) of only 1.6 μg/L. Fresh and defrosted samples of cod, sea bream and blue whiting fish have been correctly discriminated. This proof-of-concept work has demonstrated the feasibility of the proposed application which must be replicated in a real scenario.

Keywords: electrochemical sensors; gas sensors; iodide; iodine; sea water; seafood quality.

Figure 1

Schematic overview of a typical scenario of application of the method here tested. The multisensory instrument should be used for the evaluation of iodide content in seafood (only when fresh, meaning not defrosted); iodide content could be compared against a selected threshold; a report claiming quality assessment of seafood with respect to iodide content could be generated at the end of the process. The step labelled with numbers 1, 2 and 3 are the ones performed in this work.

Figure 2

Experimental set-up of the fish headspace measurement via BIONOTE-V.

Figure 3

Schematic of the circuit used to control the BIONOTE-L device in a threshold modality.

Figure 4

Voltammograms obtained as output current of the BIONOTE-L when calibrated with different concentration levels of iodide in the range 0–640 μg/L.

Figure 5

Measured vs. predicted (partial least square (PLS)-model) values of Iodide concentration. The root mean square error in cross validation (RMSECV) is 1.66 μg/L.

Figure 6

Fingerprints registered by the seven sensors of the BIONOTE-V; from left to right: codfish, sea bream, blue whiting. For each species two fingerprints are reported: (blue) fresh sample, (red) defrosted sample. Each of the 7 axes is relative to the response given by each of the QBM sensors. The response is in Hz, because it is a frequency shift with respect to the resonance frequency.

Figure 7

Boxplots of the olfactive intensity for each fish species (from up to down) blue whiting, codfish, sea bream, divided into two populations: fresh and defrosted. The boxes (green for defrost and orange for fresh) represents the 25–75% quartiles of each population. The median is shown with a horizontal line inside the box. The minimal and maximal values are shown with short horizontal lines (“whiskers”).

Figure 8

Scores plot of the first two principal components (PCs) of the PCA model elaborated on the dataset registered by the BIONOTE-V in the analysis of the samples of fishes pertaining the three species considered for the experiment: codfish, sea bream, blue whiting. For each of them a specific cluster has been defined on the PCs plane.

Figure 9

Scores plot of the first two principal components (PCs) of the PCA models elaborated on the dataset registered by the BIONOTE-V in the analysis of the samples of fishes pertaining the three species considered for the experiment: (A) codfish; (B) sea bream; (C) blue whiting. Along the most informative PC (the PC1) a clear discrimination can be observed among the fresh and defrosted samples of each species.

Figure 9

Scores plot of the first two principal components (PCs) of the PCA models elaborated on the dataset registered by the BIONOTE-V in the analysis of the samples of fishes pertaining the three species considered for the experiment: (A) codfish; (B) sea bream; (C) blue whiting. Along the most informative PC (the PC1) a clear discrimination can be observed among the fresh and defrosted samples of each species.