Paulo Vaz-Pires

The volatile amines trimethylamine (TMA) and dimethylamine (DMA) could be used as important spoilage indices for seafood products, assisting in the determination of the rejection period. In the present study, a systematic analytical duality-by-design (AQbD) approach was used as a powerful strategy to optimize the most important experimental parameters of headspace solid-phase microextraction (HS-SPME) and gas chromatography-mass spectrometry (GC-MS) conditions for the quantification of TMA and DMA in Sparus aurata. This optimization enabled the selection of the best points in the method operable design region for HS-SPME extraction (30 min; 35 °C; NaOH 15 M and NaCl 35%, w/v) and GC-MS analysis (80 °C; gradient 50 °C/min; flow rate 1 mL/min and splitless mode). The rejection day, estimated through the TMA concentration (>12 mg/100 g, at days 9–10), was compared with sensory (quality index method: day 7–8), physical (Torrymeter: day 8–9), and microbial (day 9–10) analysis, corrobo...

Freshness is considered one of the most important parameters to judge the quality of most fish products. In the current study, the seasonality effect on the freshness profile of different economic fish species was evaluated for the first time, using three different approaches (sensory: Quality Index Method (QIM) and European (EC) Scheme; physical: Torrymeter (TRM) values; and microbiological analyses: Total Viable Counts (TVC) and degradative bacteria). Over a year, individuals of farmed fish Sparus aurata and Dicentrarchus labrax, as well as the wild fish Trachurus trachurus, Scomber colias, and Sardina pilchardus, were sampled seasonally for the evaluation of their freshness profile over 10 days on ice. In general, data showed an increase in QIM values, a decline in TRM, and an increase of spoilage bacteria throughout the storage time, revealing a clear temporal degradation of the quality of the fish. Additionally, some signs of seasonality effect could only be observed for some s...

The current study evaluated the microalgae replacement by dry macroalgae () in the reproductive success and biochemical composition of the Pacific oyster () during broodstock conditioning. Five nutritional regimes were tested: 100% macroalgae (diet 1), 50% macroalgae+50% microalgae (diet 2), 25% macroalgae+75% microalgae (diet 3) and 100% microalgae (diet 4). An unfed group was used as a negative control. The microalgae blend was composed of 33% and 67% diatoms (75% +25% ). Gonadal maturation was reflected in the physiological condition of the individuals. All treatments, except diet 1, showed an increase in condition index and were fully matured at the end of the trial, with the best physiological condition observed in oysters fed diet 3 and diet 4. Protein and total lipid content increased during the conditioning period, whereas glycogen content decreased. Oysters conditioned with diet 3 had higher protein and total lipid content and lower glycogen content than the other treatment...

Salting and drying of cod has been dated back to the fifteenth century. Dried and/or salted cod has a long shelf life (from months to years) without any special packaging needs but it requires storage with controlled relative humidity and temperature. For the countries where this product is most appreciated, the objective of salting and drying fresh cod is no longer aimed at producing a shelf-stable product but to promote essential sensory characteristics that remain throughout desalting and cooking. This chapter describes the raw material characteristics and processing steps until its use by the consumer.

Abstract The blue jack mackerel, Trachurus picturatus, is an economically important fishery resource of the NE Atlantic, commonly captured around the Macaronesian islands of Azores, Madeira and Canaries, but also along coastal Portugal mainland. Despite its importance for the fisheries industry, information regarding stock delineation for management and conservation purposes is still scarce. This study examines whether otolith shape is efficient to infer about the population structure of the species and if the obtained data is consistent over time. Individuals of T. picturatus were collected in 2013 and 2016 from six important fishery regions in the NE Atlantic: Azores, Madeira, Canaries and Portugal mainland – Matosinhos, Peniche and Portimao. Otolith shape indices and elliptic Fourier descriptors were investigated by uni and multivariate statistical analyses. Data showed regional differences in the otolith shape analysis, with differences between the years. Fish sampled in 2013 showed an overall low re-classification rate (43%) with a high overlap of individuals within sampling locations, suggesting a single population unit. However, samples from 2016 allowed the discrimination of three distinct spatial groups with a moderate overall correct re-classification (62%) - group 1 with samples from the Azores; group 2 with samples from the Canaries; and group 3 with samples from Madeira and Portugal mainland. The hereby data suggests that fish population structure could be dynamic over time, recommends a year-classes follow-up of the population units in the main fishing areas and stresses the need of holistic methodological approaches to study fish stocks. Furthermore the hereby observed complex spatial dynamic structure of the species demands region-specific requirement actions to ensure a rational management of the fishery.

Sensory methods are the most interesting methods to estimate fish quality. Among these, the recently developed Quality Index Method (QIM) has gained popularity, as shown by the multiple publications of QIM schemes in the last years. The objective of this study was to create a new Quality Index Method scheme (QIM sensory table and corresponding point system) for the common carp (Cyprinus carpio), basing the definition of the rejection point on sensory, physicochemical (thiobarbituric acid reactive substances, total volatile basic nitrogen, pH, and color measurements), and microbiological criteria (counts of mesophiles, psychrotrophs, and Pseudomonas spp.). A new QIM scheme was developed and is proposed for use in the future; it will be useful for practical evaluations of carp freshness in all steps of the production chain, and it will contribute to a more effective use of the species as an alternative for human food supply.

The objective of this study was to determine the prevalence of antimicrobial resistance (AMR) exhibited by enterococci isolated from faeces of pets and its underlying risk factors. From September 2009 to May 2012, rectal swabs were collected from 74 dogs and 17 cats, selected from the population of animals visiting the Veterinary Hospital of University of Porto, UPVet, through a systematic random procedure. Animal owners answered a questionnaire about the risk factors that could influence the presence of AMR in faecal enterococci. Enterococci isolation, identification and antimicrobial (AM) susceptibility testing were performed. Data analyses of multilevel, univariable and multivariable generalised linear mixed models were conducted. From all enterococci isolated (n=315), 61 per cent were considered multidrug-resistant, whereas only 9.2 per cent were susceptible to all AMs tested. Highest resistance was found to tetracycline (67.0 per cent), rifampicin (60.3 per cent), azithromycin (58.4 per cent), quinupristin/dalfopristin (54.0 per cent) and erythromycin (53.0 per cent). Previous fluoroquinolone treatments and coprophagic habits were the features more consistently associated with the presence of AMR for three (chloramphenicol, ciprofloxacin and azithromycin) and seven (tetracycline, rifampicin, gentamicin, chloramphenicol, ciprofloxacin, erythromycin and azithromycin), respectively, out of nine AMs assessed. Evaluating risk factors that determine the presence of drug-resistant bacteria in pets, a possible source of resistance determinants to human beings, is crucial for the selection of appropriate treatment guidelines by veterinary practitioners.

ABSTRACT This study was conducted to evaluate the effects of dietary probiotic supplementation on growth performance, fish welfare, sensory evaluation, freshness during ice storage and changes in intestinal microbiota of rainbow trout (Oncorhynchus mykiss). The 9-week feeding trial was conducted in cages under commercial conditions during the winter season, when water temperature decreased from 14°C to 7°C. Fish were fed either a diet without probiotic supplementation (control) or with 0.2% (2 × 109 CFU kg−1 diet) of multi-strain probiotic bacteria (Bacillus sp., Pediococcus sp., Enterococcus sp., Lactobacillus sp.). Fish weight was recorded at 0, 2, 4, 6 and 9 weeks. Growth performance was not affected by dietary probiotic supplementation. Alternative complement activity (ACH50) was significantly higher in fish fed the diet with probiotic (58.4 ± 3.7 units mL−1) than in the control group (46.9 ± 3.1 units mL−1) (P = 0.03). Several biochemical markers were altered by the dietary treatment. 7-ethoxyresorufin-O-deethylase (EROD) (P < 0.01), glutathione S-transferase (GST) (P < 0.001), glutathione peroxidase (GPx) (P < 0.05) increased and lipid peroxidation (LP) (P < 0.01) decreased with dietary probiotic supplementation. Flesh quality and shelf-life of fish stored on ice was not affected by dietary probiotic supplementation. Probiotic supplementation had a limited effect on the intestinal microbiota. Signal strength of the observed operational taxonomic units (OTUs) differed between the control and treatment samples and could indicate variations in the abundance of certain OTUs. Microbiota adhering to the intestinal mucus varied between sampling points, indicating that changes were associated with water temperature.

The Food Technology Laboratory of ICBAS published some of the last QIM (Quality Index Method) tables dedicated to locally relevant species, namely: common octopus (Octopus vulgaris), cuttlefish (Sepia officinalis) and broadtail shortfin squid (Illex coindetii), and ...

Fish and fish-based products are easily perishable foods due to different factors, including fragile organization, abundant endo-enzymes, psychrophilic bacteria, and impact of pre-harvest operations, that contribute to reducing its value. Therefore, a timely effective method for fish freshness and shelf-life evaluation is important. In this context, this study aimed to develop a sensory scheme based on the Quality Index Method (QIM) (sensory table and point system) for freshness monitorization and shelf-life prediction for Seriola dumerili from aquaculture in Madeira Island. Evaluation of appearance, texture, eyes, and gills was performed during 20 days of storage on ice (0 ± 1 °C). The shelf-life prediction was supported by the analysis of microorganisms (total viable colonies, TVC, counts), texture (Torrymeter), and production of trimethylamine (TMA), evaluated by HS-SPME–GC–MS and validated according to Association of Official Analytical Chemists AOAC guidelines. The result is a ...

Antimicrobial resistance is a phenomenon of increasing importance. Sewage treatment processes are a vehicle for dissemination of resistant bacteria in both aquatic and terrestrial environments. To assess the number of antimicrobial resistant E. coli present in the wastewater inflow, effluent and sludge from urban sewage treatment plants in Portugal, 42 samples of crude inflow, treated effluent and sludge were collected

The aim of this study was to analyse the influence of desalting temperature, fish thickness and desalting time on the mass transfer kinetics during the cod desalting process by physicochemical analyses. Both water uptake and salt loss increased with increasing temperature (15 °C>10 °C>5 °C) up to 24 h in "thicker" pieces. The equilibrium achievement was faster in "thinner" pieces and also with increasing temperature. Longer desalting times at 10 °C can be a good practice to be used during cod desalting at an industrial scale in order to obtain commercial products with higher yields. The faster mass transfer during desalting of "thinner" pieces appears to follow 3 periods as a result of diffusion of the components (water, NaCl, and soluble proteins) because of the concentration differences, and pressure gradients due to expansion/shrinkage of the protein matrix, which is dependent on the NaCl content. The refractive index can be used by industry as...

The presence of multidrug-resistant (MDR) Escherichia coli has recently been reported in wild birds (gulls and birds of prey) that had no apparent exposure to antimicrobials. Little work has been done to assess the role of the food chain in the emergence and spread of MDR E. coli . In this study, we evaluated the presence of MDR E. coli in 29 fecal samples collected from wild birds living in a rehabilitation center (the center receives injured animals found in their natural habitat) and in eight feed samples. In total, 166 E. coli isolates were obtained: 129 from cloacal swabs and 37 from raw feed samples. The antimicrobial resistance profile of these isolates was determined, and we found that 75 isolates showed resistance to five or more drugs, resulting in a total of 38 different antimicrobial resistance patterns. Subsequently, the molecular characterization of 36 isolates, performed by pulsed-field gel electrophoresis, revealed a great similarity between isolates collected from v...

To advise consumers and manufacturers regarding decreasing the time needed to desalt salted cod (a time-consuming process), there is a need to develop knowledge about quality changes at different desalting temperatures. The objective of this work was to evaluate the physico-chemical, microbiological and sensory quality changes and their causes during cod desalting at 5, 10 and 15 °C, using a cod/water ratio of 1:9 without water changes. The influence of slices with different thickness and different desalting times was also evaluated. Desalting promoted a decrease in the levels of total volatile basic nitrogen, thiobarbituric acid reactive substances and free amino acids nitrogen (FAA-N). The highest FAA-N values were found in 'thicker' samples desalted at 15 °C due to the higher proteolytic bacteria number observed in these samples, which activity compensated the leaching of soluble components to the desalting solution. The water uptake and the salt leaching out of the muscle found during the processes created conditions for the bacterial growth, contributing to the spoilage at 15 °C. Based on fresh odour and 'off'-flavours results,…

The effects of graded levels (0 %, 0·5 %, 0·75 and 1 %) of dietary conjugated linoleic acid (CLA) were assessed on 97 g rainbow trout. Fish were fed to satiation twice a day for 12 weeks. At the end of the experiment, all groups of fish weighed more than 250 g and no significant differences were detected in growth performance, feed conversion, nutrient or energy utilisation or body composition between treatments. A decrease in liver lipid content resulted from including CLA and was accompanied by a reduction in malic enzyme activity. The muscle saturated acid and PUFA content did not vary between dietary treatments, despite the increasing concentration of stearic acid and CLA. In the liver, however, both fractions increased significantly with dietary CLA. Moreover, the MUFA decreased significantly in both muscle and liver. CLA was incorporated into tissue lipids, with levels in flesh (2·1–4·2 %) being 2-fold higher than in liver (0·8–1·9 %). In muscle, the percentage of cis-9, trans...

The authors investigated the antimicrobial resistance of Escherichia coli isolates in 22 samples of crude inflow, treated effluent, and sludge collected at the wastewater treatment plants of eight poultry slaughterhouses in Portugal. A total of 549 E. coli strains were recovered and tested for resistance to 12 antimicrobial agents. Multidrug resistance was present in 55.7 percent of the isolates. Resistance to tetracycline, ampicillin, trimethoprim/sulfamethoxazole, streptomycin, and enrofloxacin was found in 80.7 percent, 56.5 percent, 47.5 percent, 39.2 percent, and 18.4 percent of the isolates, respectively. Resistance rates of E. coli to nearly all of the tested antibiotics were higher in the strains obtained from the six slaughterhouses that handled conventional broilers than in the two slaughterhouses that handled free-range broilers. Wastewater treatment resulted in an E. coli decrease of between 0.5 log and 3 log; nevertheless, an average of 5.2 x 10(5) CFUs/100 mL were pres...

Analysis of post mortem lesions is a common means for assessing poultry welfare during rearing and pre-slaughter handling. The aim of this study was to determine the influence of: age, sex, rearing system, total number of birds on-farm, period between catch and slaughter and distance from poultry house to processing plant on the incidence of: foot-pad dermatitis (FPD), breast blisters (BB), bruises and scratches. Rearing systems consisted of extensive indoor (EI) and traditional free-range (TFR). Accordingly, birds were reared under non-intensive conditions (< 12 broilers m-2). In TFR, the maximum flock size was 4,800, birds had continuous daytime access to open-air runs from at least the age of six weeks, and the minimum slaughter age was 81 days; whereas EI rearing was exclusively indoor and birds were slaughtered at 56 days or later. Observations occurred daily after plucking and each bird was examined for: haematomas, scratches, FPD and BB. Logistic regressions were applied t...

A controlled environment poultry house (1600m(2)) was divided into two separated compartments. Three hundred twenty chick containers (each containing 100 chicks) were randomly allocated to each compartment. Antimicrobial products were provided (via drinking water) to one broiler group in three different growth phases for prophylactic purposes: lincomycin associated with spectinomycin from day 1 to day 3, trimethoprim associated with sulfamethoxazole from day 19 to day 21, and tylosin from day 26 to day 28. Feed and faecal samples from both groups were obtained on days 0, 4, 9, 14, 18, 22, 25, 29 and 33. One sample of the drinking water and samples from the broiler house environment were obtained one day before bird placement. A maximum of 16 enterococci isolated from Kanamycin Aesculin Azide Agar were tested for resistance using the disk diffusion method. A high prevalence of resistance to drugs such as tetracycline, erythromycin and nitrofurantoin was detected in enterococcal isolates from medicated and unmedicated flocks. Resistance occurrence in the non-medicated group revealed a shift in resistance profiles with the gradual change of the initial strains, isolated from the day-old chicks' cloacal swabs, by others displaying a different phenotype. Resistance phenotypes obtained from faecal strains were correlated with those isolated from the farm environment and feeds.

Under field conditions, three commercial antimicrobials were sequentially prescribed to 16,000 broiler chickens during their rearing period, via drinking water using subtherapeutic levels for 3 days. A control group of 16,000 broilers was placed in the same controlled environment poultry house. Feed diet and fecal samples from both groups were collected periodically. One sample of the drinking water along with samples from the broiler house environment was also collected 1 day before bird placement. Samples were plated onto Tergitol BCIG Agar media; a maximum of 26 Escherichia coli were isolated per sample, and their susceptibility was tested to 12 antimicrobials by disk diffusion agar method. We have observed that day-old chicks were rapidly colonized by new antibiotic-resistant patterns shortly after treatment with lincomycin associated with spectinomycin. After medication with the second (sulfadiazine with trimethoprim) and third (tylosin) antimicrobials, a more radical displacement was observed, and, concurrently, antimicrobial resistance phenotypes have become more complex. In contrast, more than 70% of the strains isolated in control group during the experiment displayed exactly the same resistance pattern found in the day-old chicks. This study provides clear evidence that a sequential medication of a broiler flock, with different antimicrobial classes during short periods of time for prophylactic objectives, was accompanied by a dramatic increase in both antimicrobial resistance rates and phenotype diversity of E. coli strains.

The effects of MTGase (5 g/kg, w/w) and dietary fibre (inner pea fibre, 40 g/kg, w/w, carrageenan, 10 g/kg, w/w, carrageenan + konjac flour, 10 + 10 g/kg, w/w) on heat-induced gels from sea bass (Dicentrarchus labrax) trimmings were studied. MTGase incorporation had a positive effect on texture: gel strength and force at rupture increased. MTGase reduced protein solubility, meaning greater protein aggregation, according to electropherograms. Pea fibre

A new concept was applied to fish products. Chemical reagents targeting specific chemical bonds were incorporated in to gel products for assessing the importance of non-covalent (sodium dodecylsulphate, 1.0%, w/w), disulphide (dithiothreitol, 0.2%, w/w) or transglutaminase-catalyzed (N-ethylmaleimide, 0.2%, w/w) bonding. These reagents acting as chemical probes were applied to the study of sea bass and hake protein gels and the

The objective of this study was to collect general data about octopus as seafood and to clarify the validity of the methods for quality evaluation designed normally for other species. Sensory, microbiological and physical analyses were used to characterize whole raw ...

The effects of microbial transglutaminase (MTGase; 0.5%, w/w) and high hydrostatic pressure (HHP) on the quality of protein gels from unwashed mince of hake (Merluccius capensis) trimmings were studied. MTGase incorporation improved texture. Protein solubility was lower for those gels containing MTGase, as a result of myosin heavy chain cross-linking. HHP improved texture. Pressure level was the most important HHP

The effects of microbial transglutaminase (MTGase, 0.5%, w/w), dietary fiber (konjac flour, Kjc, 1. 0%, w/w) and ultraviolet irradiation, UV (254 nm, 3300 µW/cm(2) and 40 min), on heat-induced gels from gilthead seabream mince (Sparus aurata) were studied. MTGase addition improved texture, force at rupture increased from 44.3±18.1 to 131.9 ± 56.7 N, and increased pH and water-holding capacity. Moreover, MTGase reduced the elastic modulus E(1) and darkened the gels; protein solubility declined, meaning greater protein aggregation, according to electropherograms. Evidence was found that disulfide bonding has a role in textural improvement by MTGase. Kjc increased the hardness from 15.1±3.1 to 20.6 ± 4.7 N, the elastic modulus and WHC. Kjc itself and not its effect upon proteins may explain the hardening effect. However, gels containing Kjc were less deformable and Kjc reduced the extractable protein in the various selective bond media. UV did not present advantages as a gelation-promoting technology. MTGase and Kjc were texturally advantageous, although without synergies for gel strength: it fell from 56.9±7.1 to 24.6±5.9 N mm as a result of adding Kjc to gels containing MTGase. Nevertheless, the hardening effect of Kjc and MTGase combined surpassed the sum of the individual effects, thereby indicating the existence of a mutual reinforcement of the hardness through MTGase and konjac. Additionally, this study showed that gilthead seabream may be used to produce good quality (concerning texture, color and WHC) heat-induced gels.

The effect of seasonal changes (summer versus winter) upon the quality of heat-induced gel products from farmed sea bass (Dicentrarchus labrax) was studied. Moreover, the effect of microbial transglutaminase addition (0.5%, w/w) on the quality was assessed. Fat content of gel products attained from sea bass grown during summer was higher (12.0% versus 7.6%). Textural properties of the gels from the summer fish were higher. Protein of gels from winter fish was less soluble in SDS + DTT (sodium dodecyl sulphate, SDS; dithiothreitol, DTT). Contrary to some literature, higher fat level may have played a protective role during processing. Accordingly, season via fat content variation had a strong effect on the gelling ability of heat-induced gels prepared from sea bass.