Carbamoylase-based impedimetric electronic tongue for rapid detection of paralytic shellfish toxins.

Phytotoxins produced by marine microalgae, such as paralytic shellfish toxins (PSTs), can accumulate in bivalve molluscs, representing a human health concern due to the life-threatening symptoms they cause. To avoid the commercialization of contaminated bivalves, monitoring programs were established in the EU. The purpose of this work is the implementation of a PST transforming enzyme-carbamoylase-in an impedimetric test for rapid simultaneous detection of several carbamate and N-sulfocarbamoyl PSTs. Carbamoylase hydrolyses carbamate and sulfocarbamoyl toxins, which may account for up to 90% of bivalve toxicity related to PSTs. Conformational changes of carbamoylase accompanying enzymatic reactions were probed by Fourier transform mid-infrared spectroscopy (FT-MIR) and electrochemical impedance spectroscopy (EIS). Furthermore, a combination of EIS with a metal electrode and a carbamoylase-based assay was employed to harness changes in the enzyme conformation and adsorption on the electrode surface during the enzymatic reaction as an analytical signal. After optimization of the working conditions, the developed impedimetric e-tongue could quantify N-sulfocarbamoyl toxins with a detection limit of 0.1 µM. The developed e-tongue allows the detection of these toxins at concentration levels observed in bivalves with PST toxicity close to the regulatory limit. The quantification of a sum of N-sulfocarbamoyl PSTs in naturally contaminated mussel extracts using the developed impedimetric e-tongue has been demonstrated.

Microplastics in marine mussels, biological effects and human risk of intake: A case study in a multi-stressor environment.

This study documented seasonal levels of microplastics (MPs) and biomarkers (condition index, neurotoxicity, energy, oxidative stress) in mussels (Mytilus galloprovincialis), and water physico-chemical parameters in the Douro estuary (NE Atlantic coast), and estimated the human risk of MP intake (HRI) through mussels. Mussel stress was determined through the Integrated Biomarker Response (IBR). HRI was estimated from mussel MP concentrations and consumer habits. MPs were mainly micro-fibres (72 %) with varied chemical composition. Seasonal MP means (±SEM) in mussels ranged from 0.111 ± 0.044 (spring) to 0.312 ± 0.092 MPs/g (summer). Seasonal variations of mussel stress (IBR: 1.4 spring to 9.7 summer) and MP concentrations were not related. MeO-BDEs, PBDEs, temperature, salinity and other factors likely contributed to mussel stress variation. HRI ranged from 2438 to 2650 MPs/year. Compared to the literature, MP contamination in mussels is low, as well as the human risk of MP intake through their consumption.

Volatile Composition of Fortification Grape Spirit and Port Wine: Where Do We Stand?

Port wine's prominence worldwide is unequivocal and the grape spirit, which comprises roughly one fifth of the total volume of this fortified wine, is also a contributor to the recognized quality of this beverage. Nonetheless, information about the influence of the grape spirit on the final aroma of Port wine, as well as its volatile composition, is extremely limited. Moreover, the aroma characteristics of Port wines are modulated mainly by their volatile profiles. Hence, this review presents a detailed overview of the volatile composition of the fortification spirit and Port wine, along with the methodologies employed for their characterization. Moreover, it gives a general overview of the Douro Demarcated Region (Portugal) and the relevance of fortification spirit to the production of Port wine. As far as we know, this review contains the most extensive database on the volatile composition of grape spirit and Port wine, corresponding to 23 and 208 compounds, respectively. To conclude, the global outlook and future challenges are addressed, with the position of the analytical coverage of the chemical data on volatile components discussed as crucial for the innovation centered on consumer preferences.

HS-SPME Gas Chromatography Approach for Underivatized Acrylamide Determination in Biscuits.

Acrylamide (AA) is a food contaminant in thermally processed products that is object of tight control. A simple and easy-to-apply methodology for routine monitoring of AA levels in food products could allow producers to be players in the control of their own products. In this work, a simple methodology for AA quantification without derivatization was developed for biscuits, for which the benchmark levels recommended by EFSA are 350 µg/kg, and 150 µg/kg for biscuits for infants and young children. Headspace-solid phase microextraction (HS-SPME) was used in 120 mL screwed-cap vials with a carboxen/polydimetylsiloxane fiber, 4 g of biscuits, and 10 mL of water during 15 min at room temperature under stirring. The addition of 30 mL of propanol under stirring during 15 min at room temperature and 15 min at 60 °C was used to promote AA transfer to the headspace. The fiber exposure was 45 min. A gas chromatography-mass spectrometry analysis allowed to obtain an external calibration curve at m/z 71, with linearity R2 > 0.99 and precision RSD < 9%. The detection and quantification limits were 27.4 µg/kg and 91.5 µg/kg, respectively. The methodology was successfully used in biscuits with lower AA amount, where mitigation strategies (asparaginase or pectate) were applied.

Lignosulfonate-Based Conducting Flexible Polymeric Membranes for Liquid Sensing Applications.

In this study, lignosulfonate (LS) from the acid sulfite pulping of eucalypt wood was used to synthesize LS-based polyurethanes (PUs) doped with multiwalled carbon nanotubes (MWCNTs) within the range of 0.1-1.4% w/w, yielding a unique conducting copolymer composite, which was employed as a sensitive material for all-solid-state potentiometric chemical sensors. LS-based PUs doped with 1.0% w/w MWCNTs exhibited relevant electrical conductivity suitable for sensor applications. The LS-based potentiometric sensor displayed a near-Nernstian or super-Nernstian response to a wide range of transition metals, including Cu(II), Zn(II), Cd(II), Cr(III), Cr(VI), Hg(II), and Ag(I) at pH 7 and Cr(VI) at pH 2. It also exhibited a redox response to the Fe(II)/(III) redox pair at pH 2. Unlike other lignin-based potentiometric sensors in similar composite materials, this LS-based flexible polymeric membrane did not show irreversible complexation with Hg(II). Only a weak response toward ionic liquids, [C2mim]Cl and ChCl, was registered. Unlike LS-based composites comprising MWCNTs, those doped with graphene oxide (GO), reduced GO (rGO), and graphite (Gr) did not reveal the same electrical conductivity, even with loads up to 10% (w/w), in the polymer composite. This fact is associated, at least partially, with the different filler dispersion abilities within the polymeric matrix.

Major characteristics of microplastics in mussels from the Portuguese coast.

The present study reports the quantity, shape, colour and chemical properties of microplastics (MP) and MP-like in whole soft tissues of the mussel Mytilus spp. collected in January and February 2019 from four natural banks in the Portuguese coast. Three sites are located in estuarine areas influenced by anthropogenic pressures and freshwater discharges, and one in the coast far from urbanised areas. An alkaline digestion (KOH) of biological tissues was used and a polymeric identification of 20% of the visually sorted particles was achieved using the Fourier-transform mid-infrared spectroscopy (FT-MIR). MP and MP-like concentrations ranged from 0.54 to 3.0 items g-1 without significant differences among the sites. Particle size varied from 36 to 4439 µm, being fibers the most abundant shape (50%) followed by films (22%) and spherules (18%). FT-MIR revealed that 69% of the analysed particles were plastic, being identified six polymers and two polymeric blends, and 32% were cellulose-based materials. Fibers identified in mussel tissues were mainly composed of cotton and viscose (77%). This study emphasizes the importance of the polymer's spectroscopic identification after microscopic observation to recognise MP.

Sustainable Valorization of Sambucus nigra L. Berries: From Crop Biodiversity to Nutritional Value of Juice and Pomace.

Improvement of dietary and ecological biodiversity, namely by exploring autochthonous varieties, is a key point to the construction of a more sustainable food system and planetary health. However, the environmental sustainability continues to face huge challenges, reflecting the importance of achieving a better understanding about the functional role of biodiversity in ecosystems. Thus, the main objective of this research is to contribute to the sustainable valorization of Sambucus nigra L. berries through a comprehensive approach to evaluate the effects of elderberry's cultivar, harvest year, and plantation field on the physicochemical berry composition. Moreover, the nutritional value of elderberry juice and respective dried pomace was determined. This complementary information is of huge utility for the rational and, as much as possible, integral use of elderberries. The harvest year, followed by field and the interaction of harvest × field, accounted for the highest impact on the berry's physicochemical parameters, indicating the importance of the combined impact of the macro- and mesoclimate conditions on plant metabolism. Elderberry juice and dried pomace are a good source of carbohydrates (ca. 12 and 82%, respectively) and have low amounts of fat (≤2.5%), making them low-energy foods. Dried pomace may also represent a potential alternative source of vegetal protein (ca. 6%).

Sorption of okadaic acid lipophilic toxin onto plastics in seawater.

The present study tested under laboratorial conditions the sorption of okadaic acid (OA), a lipophilic toxin produced by marine phytoplankton, onto 6-mm plastic circular fragments. Fragments (4 g L-1) of polyethylene terephthalate (PET), polypropylene (PP), expanded polystyrene (EPS) and non-expanded polystyrene (PS) were exposed for 96 h to seawater spiked with 10 ng mL-1 of OA. Results of the experiments showed a broad percentage of OA removed from the water by plastics after 48 h of exposure: 30 ± 5.1% (PET), 37 ± 9.5% (PP), 62 ± 7.1% (EPS) and 83 ± 1.9% (PS). Sorption appears to be highly influenced by polymer's characteristics, such as polarity and degree of crystallinity. Further studies are needed to clarify the effect of the contact area on sorption by expanded plastics. These results point to the plausible interaction of OA and plastics in coastal waters.

Paralytic Shellfish Toxins (PST)-Transforming Enzymes: A Review.

Paralytic shellfish toxins (PSTs) are a group of toxins that cause paralytic shellfish poisoning through blockage of voltage-gated sodium channels. PSTs are produced by prokaryotic freshwater cyanobacteria and eukaryotic marine dinoflagellates. Proliferation of toxic algae species can lead to harmful algal blooms, during which seafood accumulate high levels of PSTs, posing a health threat to consumers. The existence of PST-transforming enzymes was first remarked due to the divergence of PST profiles and concentrations between contaminated bivalves and toxigenic organisms. Later, several enzymes involved in PST transformation, synthesis and elimination have been identified. The knowledge of PST-transforming enzymes is necessary for understanding the processes of toxin accumulation and depuration in mollusk bivalves. Furthermore, PST-transforming enzymes facilitate the obtainment of pure analogues of toxins as in natural sources they are present in a mixture. Pure compounds are of interest for the development of drug candidates and as analytical reference materials. PST-transforming enzymes can also be employed for the development of analytical tools for toxin detection. This review summarizes the PST-transforming enzymes identified so far in living organisms from bacteria to humans, with special emphasis on bivalves, cyanobacteria and dinoflagellates, and discusses enzymes' biological functions and potential practical applications.

Nanocomposite Polymeric Materials Based on Eucalyptus Lignoboost® Kraft Lignin for Liquid Sensing Applications.

This study reports the synthesis of polyurethane-lignin copolymer blended with carbon multilayer nanotubes to be used in all-solid-state potentiometric chemical sensors. Known applicability of lignin-based polyurethanes doped with carbon nanotubes for chemical sensing was extended to eucalyptus LignoBoost® kraft lignin containing increased amounts of polyphenolic groups from concomitant tannins that were expected to impart specificity and sensitivity to the sensing material. Synthesized polymers were characterized using FT-MIR spectroscopy, electrical impedance spectroscopy, scanning electron microscopy, thermogravimetric analysis, and differential scanning calorimetry and are used for manufacturing of all solid-state potentiometric sensors. Potentiometric sensor with LignoBoost® kraft lignin-based polyurethane membrane displayed theoretical response and high selectivity to Cu (II) ions, as well as long-term stability.

A Carbamoylase-Based Bioassay for the Detection of Paralytic Shellfish Poisoning Toxins.

Out of control proliferation of toxic phytoplankton, called harmful algal blooms (HABs), have a significant economic impact on bivalve aquaculture and harvesting in coastal waters. Some phytotoxins, such as paralytic shellfish toxins (PSTs), are of concern due to the life-threatening symptoms they can cause. Development of rapid and low-cost screening tools would be a welcome addition to the laboratory methodologies employed in routine monitoring programs. However, most of the assays and biosensors for the screening of PSTs, are restricted to a single target, saxitoxin (STX), which is the most potent PST. The present study aimed at developing an assay for the detection of N-sulfocarbamoyl PST-GTX5, which is one of the most abundant toxins in bivalves during G. catenatum blooms as found on the Portuguese coast. Enzymatic assay employing PSTs' transforming enzyme-carbamoylase-was proposed. Carbamoylase was extracted and purified from the surf clam S. solida. Carbamoylase displayed similar specificity to both carbamate (STX) and N-sulfocarbamate toxins (GTX5 and C1+2) converting them into decarbamoyl saxitoxin (dcSTX) and decarbamoyl gonyautoxins 2+3 (dcGTX2+3), respectively. The enzymatic assay involved hydrolysis of GTX5 by carbamoylase and quantification of the product of enzymatic reaction, dcSTX, using a potentiometric chemical sensor. A potentiometric sensor with plasticized PVC membrane that displayed sensitivity to dcSTX and selectivity in the presence of GTX5 was employed. Enzymatic assay allowed determination of GTX5 in the concentration range from 0.43 to 3.30 µmolL-1, which encompasses levels of GTX5 in contaminated bivalve extracts with toxicities above PSTs regulatory limits. The feasibility of the carbamoylase-based potentiometric assay for detection of GTX5 was demonstrated.

Molecularly Imprinted Polymer Thin-Film Electrochemical Sensors.

Preparation of potentiometric and amperometric sensors with thin-film membranes based on molecularly imprinted polymers (MIP) is described. Spherical MIP microparticles with diameter below 1 µm are suitable for incorporation into the sensing membrane by the deposition of a conducting polymer on the electrode surface. This is achieved through electropolymerization from the suspension of MIP particles in monomer solution. Procedures of the synthesis of MIP particles, preparation of sensing membranes, and analytical application of potentiometric and amperometric sensors with MIP-modified membranes are described.

D-Shaped POF Sensors for Refractive Index Sensing-The Importance of Surface Roughness.

In this study the influence of the surface roughness on the transmission capacities of D-shaped plastic optical fibers (POFs) and sensors performance was investigated. Five D-shaped POF sensors were produced and characterized for refractive index sensing between 1.33 and 1.41. The sensors were characterized using a low-cost optical sensing system based on the variation of the transmitted light though the POF with refractive index changes (RI). Higher surface roughness increases the scattering losses through the POF and influences the sensors' performance; therefore, a balance must be attained. Generally, the best performance was achieved when the sensing region was polished with P600 sandpaper as a final polishing step. Polishing with sandpapers of lower grit size resulted in lower scattering, higher linearity of the sensor response and generally lower performance for RI sensing. A sensor resolution of 10-3-10-4 RIU, dependent on the value of the external refractive index, was obtained through simple and low-cost manufacturing procedures. The obtained results show the importance of surface roughness in the development of POF sensors which can be used in several applications, such as for water quality assessment.

Data on yields, sugars and glycosidic-linkage analyses of coffee arabinogalactan and galactomannan mixtures and optimization of their microwave assisted extraction from spent coffee grounds.

The data presented here are related to the research paper entitled "Structural features of spent coffee grounds water-soluble polysaccharides: towards tailor-made microwave assisted extractions" [1]. Microwave assisted extraction conditions were applied to spent coffee grounds for recovery of polysaccharides, namely arabinogalactans and galactomannans. Following an experimental design testing temperature, time, and alkali conditions as influence factors during microwave assisted extraction, this article reports the response data for the total extracted mass, sugars yield (including arabinogalactans and galactomannans total content, and mass ratio), and structural features (including degree of polymerization and degree of branching) for each set of operating conditions. In addition, it provides gas chromatography-mass spectrometry (GC-MS) chromatograms (and respective GC-MS spectra) of arabinogalactan and galactomannan mixtures with different structural features corresponding to representative microwave treatment conditions.

Structural features of spent coffee grounds water-soluble polysaccharides: Towards tailor-made microwave assisted extractions.

This work studies the microwave-assisted extraction conditions for recovery of polysaccharides from spent coffee grounds, including their effect on arabinogalactans and galactomannans polymerization and branching structural features. Temperature (140, 170, and 200 °C) has the most significant impact on total extracted mass (ηtotal soluble solids) and sugars yield (ηsugars), arabinogalactans (ηAG) and galactomannans (ηGM), and polysaccharide mass ratio (ηAG/ηGM). Time (2, 5, and 10 min) and alkali (diluted 0.1 M NaOH) treatments have less influence. Alkali treatment and shorter time (2 min) provided a protective effect against polysaccharides degradation. At 170 °C, the yield of arabinogalactans was found to be significantly higher than that of galactomannans (ηAG/ηGM >1). Increasing temperature to 200 °C leads to decrease the polymerization of polysaccharides, promoting the formation of debranched polysaccharides and oligosaccharides. This study shows that the optimum conditions for polysaccharides extraction cannot be selected only by mass yield but need to be defined according to the desired structural features for the specific applications.

A comprehensive look into the volatile exometabolome of enteroxic and non-enterotoxic Staphylococcus aureus strains.

Staphylococcal food poisoning is a disease that originates significant health and economic losses and is caused by Staphylococcus aureus strains able to produce enterotoxins. The aim of this work is to go further on the study of the volatile exometabolome of S. aureus using an advanced gas chromatographic technique. Enterotoxic and non-enterotoxic strains were assessed. The volatile exometabolome profile comprised 240 volatiles belonging to ten chemical families. This volatiles were mainly by-products of branched-chain amino acids and methionine degradation, pyruvate metabolism, diacetyl pathway, oxidative stress and carotenoid cleavage. Metabolites released by the first two pathways were produced in higher contents by the enterotoxic strains. This study add further insights to S. aureus volatile exometabolome, and also shows that by applying it, it is possible to distinguish strains of S. aureus by the number of produced enterotoxins, which is especially important from the food safety point of view.

The impact of exercise training on the lipid peroxidation metabolomic profile and respiratory infection risk in older adults.

Aging is associated with oxidative stress that may increase susceptibility to respiratory infections (RIs). We aimed to assess the impact of exercise training on the risk of RIs in older adults and on a targeted metabolomic profile of stress oxidative lipid peroxidation-related metabolites. METHODS: In an 8-month clinical trial, 38 participants over 60 years of age were allocated to an exercise group (EG), in which participants underwent 90-min training sessions three times/week(n = 20), or a control group (CG), in which participants maintained daily physical activities(n = 18). Daily respiratory symptoms and RIs number and severity were collected. Serum by-products were assessed by comprehensive two-dimensional gas chromatography coupled to mass spectrometry with time of flight analyzer. Serum metabolomic profiling comprised 76 metabolites (alcohols, aldehydes, alkanes, and ketones). Principal components analysis and ANOVA-simultaneous component analysis were used to evaluate the metabolomic profile change. RESULTS: The odds ratio of RIs for the EG was 2.0 CI 95% [0.2;25]. The incidence of RIs was 47% [23;70] in the EG vs. 44%[12;77] in the CG. The metabolomic profiling showed that alkanes and aldehydes classes differed between the EG and the CG before and after intervention. A calibration model showed a relation between the metabolites from four main classes (ketones, alcohols, alkanes and aldehydes) and the prediction of the number of RIs. CONCLUSION: Moderate exercise training, in older adults, compared with no exercise in controls, did not show a difference in the risk of RIs. A pattern of lipid peroxidation was associated with the number of RIs.

Calibration Update and Drift Correction for Electronic Noses and Tongues.

One of the obstacles to the wider practical use of the multisensor systems for gas and liquid analysis-electronic noses and tongues, is the limited temporal validity of the multivariate calibration models. Frequent recalibration of multisensor systems is often excessively costly and time consuming due to the large number of necessary reference sample and their limited availability. There are several circumstances that can invalidate multivariate calibration model. The most common problem in the case of sensor systems is temporarily drift or gradual change of sensor characteristics occurring during sensor exploitation. Another common situation is a change in the composition of the analyzed samples that also alters sensor response due to the matrix effects. Finally, a necessity to replace sensors in the array or to transfer calibration model from one sensor set or one type of sensors to the other can arise. As an alternative to the recalibration of the sensor system using full set of calibration samples, drift correction and calibration update has been proposed. The main approaches can be summarized as follows: Drift correction that consists in modeling sensor temporarily drift or drift direction using a series of measurements and then using it for correcting new data.Calibration standardization that aims to correct new measured data by eliminating new variation. For this purpose, a relationship between two experimental conditions is established using a reduced set of samples measured at both conditions (standardization subset).Calibration update that consists in incorporation of new sources of variance in the calibration model by recalculating it using initial calibration samples and reduced set of samples measured at new conditions. The latter can be either standard or unknown samples. This paper presents an overview of different methods reported for the drift correction and calibration update of the electronic noses and tongue and discussion of the practical aspects of their implementation.

Cheeses Made from Raw and Pasteurized Cow's Milk Analysed by an Electronic Nose and an Electronic Tongue.

Cheese prepared from whole milk, raw and pasteurized, were analysed by an electronic nose based on piezoelectric quartz crystals and an electronic tongue based on potentiometric sensors, immediately after their preparation and along ripening (after 7 and 21 days). Whey was also analysed by the potentiometric electronic tongue. Results obtained by the electronic nose and tongue were found to be complementary, with the electronic nose being more sensitive to differences in the milk and the electronic tongue being more sensitive to milk pasteurization. Electronic tongue was able to distinguish cheeses made from raw and pasteurized milk, both analysing the whey or the curd, with correct classification rate of 96% and 84%, respectively. Besides, the electronic nose was more sensitive than the electronic tongue to the ripening process, with large differences between samples after 7 and 21 days, while the electronic tongue was only sensitive to the initial maturation stages, with large difference between freshly prepared cheese and with seven days of maturation.