Seafood Testing

Tian, Ye, et al. Spectrochimica Acta Part B: Atomic Spectroscopy 175 (2021): 106027.

Phosphates are widely used as food additives in seafood, serving legitimate functions such as retaining natural moisture, inhibiting flavor and lipid oxidation, aiding emulsification, removing shellfish shells, and providing freeze protection. However, concerns arise regarding the excessive use of phosphates to retain "added water," which can increase the size and weight of seafood products. This may lead to unfair trade practices and economic fraud.

Therefore, the quantitative determination of phosphates or total phosphorus in seafood is crucial for fraud detection and food safety issues. In this work, Laser-Induced Breakdown Spectroscopy (LIBS) was utilized as a rapid method for measuring phosphorus in three types of seafood: cod, scallops, and shrimp. Univariate and multivariate regression models were established, with special attention to correcting matrix effects to enhance the analytical performance of LIBS.

The results indicated that, compared to traditional univariate models and linear PLS models, the nonlinear SVM model provided the best performance coefficients, with an R² of 0.9904, RMSEC, RMSEP, and ARE of 1.68 g/kg, 1.42 g/kg, and 3.70%, respectively. The average RSD predicted by SVM was 5.18%, significantly lower than the value for PLS (9.40%) and comparable to the value for the univariate model (4.11%). This suggests that SVM may be more suitable for addressing nonlinear behavior in LIBS spectra caused by matrix effects, leading to a more robust calibration model.

Cao, Yunrui, et al. Food Chemistry 390 (2022): 133194.

Histamine is a non-volatile heterocyclic amine formed by the decarboxylation of L-histidine (His) through the action of histidine decarboxylase. It features an imidazole ring and an aliphatic amine linked by a two-carbon chain. Although histamine is ubiquitous and plays a key role in various pathophysiological functions, it is more widely recognized as a primary culprit in food poisoning associated with the consumption of fish.

Traditional detection methods are inadequate to meet the current demand for rapid histamine analysis. A novel ratio fluorescence nanosystem based on upconversion nanoparticles (UCNPs) and the inner filter effect (IFE) has been developed for the efficient detection of histamine. Through solid-phase extraction (SPE) pretreatment and a colorimetric azo coupling reaction, the fluorescence of UCNPs at 548 nm is quenched, while the fluorescence at 664 nm remains unchanged.

As a result, the ratio of fluorescence I548/I664 is inversely proportional to histamine concentration in the range of 10–200 mg/L, with a detection limit of 7.34 mg/L, which is an order of magnitude lower than that of traditional colorimetric methods (25 mg/L). Furthermore, this convenient and environmentally friendly detection system can also be used to quantify histamine in fish, shrimp, and shellfish samples, demonstrating promising application potential in seafood safety testing.

Bitencourt, Gustavo R., et al. Science of the Total Environment 749 (2020): 142301.

Plastic fragments smaller than 5 millimeters are typically classified as microplastics (MP). The ingestion of MPs can lead to gastrointestinal blockages. Given the potential sources of human exposure to MPs, it is well-known that consuming fish is a major source. Measuring the substances that humans may come into contact with through MP contamination in fish is very important.

A method for determining the microplastic (MP) content in seafood has been proposed, based on selective digestion of seafood without degrading the MPs. A simple method using dilute acid and microwave-assisted wet digestion was developed. The following parameters were evaluated: nitric acid concentration (0.5 to 14.4 mol L^-1), digestion temperature (180 to 220 °C), radiation program hold time (10 to 30 minutes), MP particle size (0.3 to 5 millimeters), and seafood mass (0.5 to 2 grams).

To develop a reliable method for measuring MP content, up to 2 grams of natural seafood samples were mixed with a known amount of MP (100 mg of mixed MPs). Suitable conditions were obtained at 200 °C (holding for 10 minutes) using 1 mol L^-1 HNO₃. The digested samples were filtered, and the plastic content was measured gravimetrically. The heating program lasted for 20 minutes, significantly reducing the analysis time typically reported in the literature for MP (which can range from several hours to 3 days).

The proposed method allows for the gravimetric determination of eight types of plastics with particle sizes ≥0.3 millimeters (polyethylene terephthalate, polystyrene, expanded polystyrene, polypropylene, high-density and low-density polyethylene, polycarbonate, and polyvinyl chloride). Up to 2 grams of natural seafood samples (shark, black bass, tuna, tilapia, and pink shrimp) were effectively digested, providing the potential to use the proposed digestion method for determining elemental contaminants (aluminum, arsenic, calcium, cadmium, cobalt, chromium, copper, iron, mercury, lanthanum, magnesium, manganese, molybdenum, nickel, lead, and zinc).