Histology as a Valid Tool To Differentiate Fresh from Frozen-Thawed Marinated Fish.

European Commission Regulation (EU) 1276/2011 requires that fishery products intended for raw consumption be frozen at -20°C for not less than 24 h or at -35°C for at least 15 h in order to kill viable parasites other than trematodes. But because marinating processes are not always effective in destroying nematode larvae, raw marinated fish preparations should be frozen before consumption. This study evaluated the performance of a standardized histological method to distinguish between fresh and frozen-thawed raw marinated fish. Sixty anchovy (Engraulis encrasicolus) fillets were sampled: 30 were marinated at +4°C for 24 h, and 30 were frozen at -20°C for 24 h before being marinated for 24 h. All 60 samples were fixed in formalin, processed for paraffin embedding, cut, and stained with hematoxylin and eosin. The slide preparations were examined microscopically by three independent histopathologists and classified as frozen-thawed or negative according to standard operating procedure criteria in use at our laboratory. Performance evaluation of the method showed 100% sensitivity (95% confidence interval [CI], 88.4 to 100%) and 100% specificity (95% CI, 88.4 to 100%), and the interrater agreement (Cohen's kappa) was 1 (95% CI, 0.85 to 1). Histology proved a valid and reliable tool to distinguish fresh from frozen-thawed marinated fish. It can be applied to deliver safe raw fishery products to consumers in order to minimize the risk of anisakidosis

Exploring common and distinct information among three different kinds of NIR instruments by means of chemometrics

Food fraud is an old but still common and widespread problem that affects almost any type of food commodity sold on the market. Products may be mislabelled or counterfeit and, in many cases, it can be very difficult to detect these illegal practices. For this reason, quick and reliable methods are needed for efficiently tackling this problem. Due to its ease of use and rapidity, near-infrared (NIR) spectroscopy is particularly suitable for the purpose. In this study, the subtle differences between fresh and thawed cephalopods were investigated using different NIR instruments to collect the data and different chemometric approaches to perform the data analysis. Fifty fresh cephalopod specimens of both cuttlefish (Sepia officinalis) and musky octopus (Eledone spp.) were collected directly at the food distribution warehouse and immediately analysed at refrigeration temperature (~5°C). Then, the specimens were kept frozen at –20°C for at least 48 hours and eventually thawed and analysed once again. Data collection was performed by measuring the same specimens using three different NIR spectrometers: one portable low-cost instrument (SCiO by Consumer Physics), one portable moderately highcost instrument (MicroNIR by Viavi), and one benchtop instrument (MPA by Bruker). The common and distinct information among the three data sources was investigated by means of a mid-level data fusion approach (Borràs et al., 2015) and by means of methods such as CovSel (Covariance Selection–Roger et al., 2011) and ComDim (Common Dimensions–Cariou et al., 2019). Differently from other traditional techniques employed for counteracting fraud, NIR spectroscopy coupled with chemometrics proves a robust approach for distinguishing between fresh and frozen cephalopods. Similarities and differences among the three NIR datasets, unravelled by the tested chemometric tools, reflect the building characteristics of each instrument and provide a complementary picture of the specimens’ evolution during the freeze-thaw process

Differentiation between Fresh and Thawed Cephalopods Using NIR Spectroscopy and Multivariate Data Analysis

The sale of frozen–thawed fish and fish products, labeled as fresh, is currently one of the most common and insidious commercial food frauds. For this reason, the demand of reliable tools to identify the storage conditions is increasing. The present study was performed on two species, commonly sold in large-scale distribution: Cuttlefish (Sepia officinalis) and musky octopus (Eledone spp.). Fifty fresh cephalopod specimens were analyzed at refrigeration temperature (2 ± 2°C), then frozen at −20°C for 10 days and finally thawed and analyzed again. The performance of three near-infrared (NIR) instruments in identifying storage conditions were compared: The benchtop NIR Multi Purpose Analyzer (MPA) by Bruker, the portable MicroNIR by VIAVI and the handheld NIR SCiO by Consumer Physics. All collected spectra were processed and analyzed with chemometric methods. The SCiO data were also analyzed using the analytical tools available in the online application provided by the manufacturer to evaluate its performance. NIR spectroscopy, coupled with chemometrics, allowed discriminating between fresh and thawed samples with high accuracy: Cuttlefish between 82.3–94.1%, musky octopus between 91.2–97.1%, global model between 86.8–95.6%. Results show how food frauds could be detected directly in the marketplace, through small, ultra-fast and simplified handheld devices, whereas official control laboratories could use benchtop analytical instruments, coupled with chemometric approaches, to develop accurate and validated methods, suitable for regulatory purposes

Identification of Illicit Conservation Treatments in Fresh Fish by Micro-Raman Spectroscopy and Chemometric Methods

In the field of food control for fresh products, the identification of foods subjected to illicit conservation treatments to extend their shelf life is fundamental. Fresh fish products are particularly subjected to this type of fraud due to their high commercial value and the fact that they often have to be transported over a long distance, keeping their organoleptic characteristics unaltered. Treatments of this type involve, e.g., the bleaching of the meat and/or the momentary abatement of the microbial load, while the degradation process continues. It is therefore important to find rapid methods that allow the identification of illicit treatments. The study presented here was performed on 24 sea bass samples divided into four groups: 12 controls (stored on ice in the fridge for 3 or 24 h), and 12 treated with a Cafodos-like solution for 3 or 24 h. Muscle and skin samples were then characterized using micro-Raman spectroscopy. The data were pre-processed by smoothing and taking the first derivative and then PLS-DA models were built to identify short- and long- term effects on the fish's muscle and skin. All the models provided the perfect classification of the samples both in fitting and cross-validation and an analysis of the bands responsible for the effects was also reported. To the best of the authors' knowledge, this is the first time Raman spectroscopy has been applied for the identification of a Cafodos-like illicit treatment, focusing on both fish muscle and skin evaluation. The procedure could pave the way for a future application directly on the market through the use of a portable device

Chemometric Differentiation of Sole and Plaice Fish Fillets Using Three Near-Infrared Instruments

Fish species substitution is one of the most common forms of fraud all over the world, as fish identification can be very challenging for both consumers and experienced inspectors in the case of fish sold as fillets. The difficulties in distinguishing among different species may generate a “grey area” in which mislabelling can occur. Thus, the development of fast and reliable tools able to detect such frauds in the field is of crucial importance. In this study, we focused on the distinction between two flatfish species largely available on the market, namely the Guinean sole (Synaptura cadenati) and European plaice (Pleuronectes platessa), which are very similar looking. Fifty fillets of each species were analysed using three near-infrared (NIR) instruments: the handheld SCiO (Consumer Physics), the portable MicroNIR (VIAVI), and the benchtop MPA (Bruker). PLS-DA classification models were built using the spectral datasets, and all three instruments provided very good results, showing high accuracy: 94.1% for the SCiO and MicroNIR portable instruments, and 90.1% for the MPA benchtop spectrometer. The good classification results of the approach combining NIR spectroscopy, and simple chemometric classification methods suggest great applicability directly in the context of real-world marketplaces, as well as in official control plans

Development of an innovative microcantilever-based biosensor for 17β-estradiol detection in bovine muscles: preliminary results

17β-estradiol is the most powerful substance with estrogenic effect, commonly used as illegal growth promoter in livestock production. To avoid health risks for consumers, sensitive, reliable and low-cost methods for quantification of extremely low concentrations of such carcinogenic residues in food are needed. Antibody-immobilised microcantilever resonators were proposed as innovative biosensors able to quantify an adsorbed target mass thanks to a shift in resonance frequency. Furthermore, the quantification of masses on the order of few picograms has recently shown to be successfully achievable with very high precision. In this study, we analysed the performance of our microcantilever sensors using extracted samples of bovine muscle from experimental animals, containing variable concentrations of 17β-estradiol (HPLC-MS/MS tested). Preliminary data showed that treated animals are correctly revealed, exhibiting large negative frequency shifts. More experiments, though, are needed to obtain a correct quantification of 17β-estradiol concentration