The use of stable isotopes for authentication of gadoid fish species

A synergistic solution for fighting fraudulent practices in squid using light stable isotope ratios and lanthanide tracers

To identify a novel optimized strategy for preventing fraudulent substitutions of squid species and origins, forty European squids (Loligo vulgaris) and forty flying squids (Todarodes sagittatus) from the Mediterranean Sea and Atlantic Ocean were analyzed for δ13C, δ15N, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Yb, and Lu using isotope ratio mass spectrometry and inductively coupled plasma-mass spectrometry. While δ13C and δ15N variations were mainly species-related, they alone could not reliably distinguish samples. To address this issue, decision rules were developed using Classification and Regression Tree analysis. Threshold values for δ13C (-19.91‰), δ15N (14.87‰), and Pr (0.49 μg kg-1) enabled successful discrimination among Mediterranean European squids, Atlantic European squids, Mediterranean flying squids, and Atlantic flying squids, achieving over 90% accuracy, 81% precision, 80% sensitivity, and 93% specificity. This method holds promise for enhancing traceability and safety in the seafood industry, ensuring product integrity and consumer trust.

Isotope Fingerprinting as a Backup for Modern Safety and Traceability Systems in the Animal-Derived Food Chain

In recent years, due to the globalization of food trade and certified agro-food products, the authenticity and traceability of food have received increasing attention. As a result, opportunities for fraudulent practices arise, highlighting the need to protect consumers from economic and health damages. In this regard, specific analytical techniques have been optimized and implemented to support the integrity of the food chain, such as those targeting different isotopes and their ratios. This review article explores the scientific progress of the last decade in the study of the isotopic identity card of food of animal origin, provides the reader with an overview of its application, and focuses on whether the combination of isotopes with other markers increases confidence and robustness in food authenticity testing. To this purpose, a total of 135 studies analyzing fish and seafood, meat, eggs, milk, and dairy products, and aiming to examine the relation between isotopic ratios and the geographical provenance, feeding regime, production method, and seasonality were reviewed. Current trends and major research achievements in the field were discussed and commented on in detail, pointing out advantages and drawbacks typically associated with this analytical approach and arguing future improvements and changes that need to be made to recognize it as a standard and validated method for fraud mitigation and safety control in the sector of food of animal origin.

The Use of Stable Isotope Ratio Analysis to Trace European Sea Bass (D. labrax) Originating from Different Farming Systems

Simple Summary

European sea bass is one of the most economically important fish species in the Mediterranean area. The potential effects of farming systems on the final quality of this product and the recent popular demand for labels to certify the animal rearing origin, which is increasingly used as a marketing tool, have raised the use of analytical techniques that make it possible to differentiate this fish product according to the rearing farming system and authenticate their geographical origin. The aim of this study was to determine whether isotopic ratio mass spectrometry (IRMS) can discriminate farmed European sea bass according to different farming systems (concrete tank inland, sea cages, and extensive methods in valleys or salt works) and geographic origins (different locations scattered throughout Italy). The results of this study showed the viability of δ¹³C and δ¹⁵N to discriminate cultured sea bass from different farming systems (extensive vs. intensive) reared at different geographical sites in Italy. Meanwhile, the measurement of δ¹⁸O and δ²H made it possible to distinguish the geographical origin of the sea bass farmed extensively and intensively (in cages).

Abstract

This study aimed to determine whether isotopic ratio mass spectrometry (IRMS) can discriminate farmed European sea bass according to different farming systems and geographic origins. Dicentrarchus labrax of commercial size from three different rearing systems (concrete tank inland, sea cages, and extensive methods in valleys or salt works) were collected at the trading period (autumn–winter). For each farming type, different locations spread over Italy were monitored. Once the fish were harvested, the muscle and feed were sampled. For both muscle and feed, δ¹³C and δ¹⁵N were measured by continuous flow elemental analyzer isotope ratio mass spectrometry (CF-EA-IRMS) with the goal of discriminating samples based on the rearing system. Additional δ²H and δ¹⁸O measurements of fish samples were performed by continuous flow total combustion elemental analyzer isotope ratio mass spectrometry (CF-TC/EA-IRMS) to track the geographical origin. The measurements of δ¹³C and δ¹⁵N made it possible to discriminate cultured sea bass from different farming systems (extensive vs. intensive) reared at different geographical sites in Italy. Additional information was obtained from δ¹⁸O and δ²H, which enabled the geographical areas of origin of the sea bass farmed extensively and intensively (in cages) to be distinguished.

Geographical origin traceability and species identification of three scallops (Patinopecten yessoensis, Chlamys farreri, and Argopecten irradians) using stable isotope analysis

Traceability and authenticity is crucial to the food safety of scallop. The present study investigated the possibility of using stable isotope analysis to identify the origins and species of scallops (Patinopecten yessoensis, Chlamys farreri, and Argopecten irradians) in the coastal areas of China. The δ¹³C and δ¹⁵N values of a total of 575 samples from seven sites around China were determined and additional 150 samples were tested by fisher linear discrimination analysis (LDA) to estimate the accuracy of origin identification and species prediction. The results show that the stable C and N isotope composition differed significantly depending on the origin, season and species of scallops. Meanwhile, the LDA shows that 92% of the samples were correctly classified for origin prediction, and an accuracy of 98.3% was obtained for species prediction. This study reveals that stable isotope ratio is an effective technique to trace the geographical origin and identify the species of scallops.

Discrimination of the species and authenticity of Rhizoma Coptidis based on stable isotope and multielement fingerprinting and multivariate statistical analysis

It is essential to be able to identify the source species and to determine the authenticity of traditional Chinese medicines (TCM) in order to prevent the use of false or inferior medicines. In this work, a stable and reliable method of discriminating among the three source species of Rhizoma Coptidis and checking the authenticity of Rhizoma Coptidis samples was established. The technique involved evaluating stable isotope ratios and the contents of multiple elements in samples along with the use of multivariate statistical techniques. The stable isotope ratios δ¹³C, δ¹⁵N, δ²H, and δ¹⁸O and the concentrations of various inorganic elements (Li, B, Na, Mg, Al, P, Si, K, Ca, Ti, Mn, Fe, Cu, Zn, Sr, and Ba) in authentic Rhizoma Coptidis samples from three source species (n = 56) and in counterfeit Rhizoma Coptidis samples (n = 39) were determined. The results showed that there were significant differences between the samples from different source species according to multivariate statistical analysis. The three species were clearly distinguished using hierarchical cluster analysis (HCA). Employing stepwise linear discriminant analysis (SLDA), a classification model for differentiating the three species was developed, and this model achieved 100% classification accuracy when applied to samples. In addition, authentic samples and counterfeit samples were successfully discriminated using stable isotope and multielement fingerprint analysis and orthogonal projections to latent structures discriminant analysis (OPLS-DA), and OPLS-DA models for checking the authenticity of Rhizoma Coptidis were established and verified. Therefore, stable isotope and multielement analysis combined with multivariate statistical analysis was shown to be a promising method of discriminating among the three source species of Rhizoma Coptidis and of establishing the authenticity of Rhizoma Coptidis samples. Graphical abstract.

Determination of the Geographical Origin of All Commercial Hake Species by Stable Isotope Ratio (SIR) Analysis

The determination of the geographical origin of food products is relevant to comply with the legal regulations of traceability, to avoid food fraud, and to guarantee food quality and safety to the consumers. For these reasons, stable isotope ratio (SIR) analysis using an isotope ratio mass spectrometry (IRMS) instrument is one of the most useful techniques for evaluating food traceability and authenticity. The present study was aimed to determine, for the first time, the geographical origin for all commercial fish species belonging to the Merlucciidae family using SIR analysis of carbon (δ¹³C) and nitrogen (δ¹⁵N). The specific results enabled their clear classification according to the FAO (Food and Agriculture Organization of the United Nations) fishing areas, latitude, and geographical origin in the following six different clusters: European, North African, South African, North American, South American, and Australian hake species.

Authentication of fishery and aquaculture products by multi-element and stable isotope analysis

The market of fishery and aquaculture products is globalized with increasing numbers of mislabeled products. This highlights the need for approaches to indentify the origin of these products. Among the measures used to identify the origin of other agro-products, multi-element and stable isotope analysis are promising approaches to identify the authenticity and traceability of fishery and aquaculture products. The present paper reviews the use of multi-element and stable isotope analysis to determine the origin of fishery and aquaculture products. Principles and limitations of each method will be illustrated and perspectives for traceability of fishery and aquaculture products will be discussed. The aim of this review is to mediate fundamental knowledge for the interpretation of experimental data on authentication of aquaculture products.

Comparing multiple criteria for species identification in two recently diverged seabirds

Correct species identification is a crucial issue in systematics with key implications for prioritising conservation effort. However, it can be particularly challenging in recently diverged species due to their strong similarity and relatedness. In such cases, species identification requires multiple and integrative approaches. In this study we used multiple criteria, namely plumage colouration, biometric measurements, geometric morphometrics, stable isotopes analysis (SIA) and genetics (mtDNA), to identify the species of 107 bycatch birds from two closely related seabird species, the Balearic (Puffinus mauretanicus) and Yelkouan (P. yelkouan) shearwaters. Biometric measurements, stable isotopes and genetic data produced two stable clusters of bycatch birds matching the two study species, as indicated by reference birds of known origin. Geometric morphometrics was excluded as a species identification criterion since the two clusters were not stable. The combination of plumage colouration, linear biometrics, stable isotope and genetic criteria was crucial to infer the species of 103 of the bycatch specimens. In the present study, particularly SIA emerged as a powerful criterion for species identification, but temporal stability of the isotopic values is critical for this purpose. Indeed, we found some variability in stable isotope values over the years within each species, but species differences explained most of the variance in the isotopic data. Yet this result pinpoints the importance of examining sources of variability in the isotopic data in a case-by-case basis prior to the cross-application of the SIA approach to other species. Our findings illustrate how the integration of several methodological approaches can help to correctly identify individuals from recently diverged species, as each criterion measures different biological phenomena and species divergence is not expressed simultaneously in all biological traits.

Naturally occurring stable isotopes reflect changes in protein turnover and growth in gilthead sea bream (Sparus aurata) juveniles under different dietary protein levels

Ideal nutritional conditions are crucial to sustainable aquaculture due to economic and environmental issues. Here we apply stable isotope analysis as an indicator of fish growth and feeding balance, to define the optimum diet for efficient growing conditions. Juveniles of gilthead sea bream were fed with six isoenergetic diets differing in protein to lipid proportion (from 41/26 to 57/20). As protein intake increased, δ¹⁵N and Δδ¹⁵N of muscle and Δδ¹⁵N and Δδ¹³C of its protein fraction decreased, indicating lower protein turnover and higher protein deposition in muscle. This is reflected in the inverse relationship found between Δδ¹⁵N and growth rate, although no differences were observed in either parameter beyond the protein/lipid proportion 47/23. Principal component analysis (PCA) also signaled 47/23 diet as the pivotal point with the highest growing efficiency, with isotopic parameters having the highest discrimination load. Thus, muscle isotope composition, especially ¹⁵N, can be used to evaluate nutritional status in farmed fish.

DNA barcoding for detecting market substitution in salted cod fillets and battered cod chunks

The Italian Ministry of Agricultural, Food and Forestry Policies (MiPAAF) Decree dated 31 January 2008, which reports the Italian name for fish species of commercial interest, establishes that baccalà can be obtained exclusively from G. macrocephalus (Pacific cod) and G. morhua (Atlantic cod). This paper describes the COI-based DNA identification system to verify the substitution or misbranding of gadoid fish species and, consequently, its concordance with the labels on salted cod fillets shown as baccalà and on battered cod chunks labelled as bocconcini di baccalà. The analysis of interpretable sequences revealed that 55/65 dried salted cod fillet samples were detected as belonging to the family Gadidae, while 10/65 samples appeared to belong to the Lotidae family, while among battered cod chunks labelled as bocconcini di baccalà, the post-sequencing data analysis shows that the labels were completely wrong, with 28/40 samples from Pollachius virens and 12/40 samples from Brosme brosme. The substitution rate for products labelled on the market as baccalà in this study raises significant issues relating to food safety and consumer protection.