Analysis of an edible coating of chitosan as an alternative to glazing of frozen salmon

Dissertação de mestrado integrado em Engenharia Biológica (área de especialização em Tecnologia Química e Alimentar)A natureza perecível do peixe, aliada ao aumento no seu consumo, tem levado à necessidade de melhoria das técnicas de preservação. A utilização de revestimentos de quitosano oferece vantagens em relação às técnicas tradicionais de conservação, no entanto existe a necessidade de avaliar o seu efeito nas propriedades sensoriais do salmão. Neste trabalho as propriedades protetoras de uma solução de quitosano a 1.5 % foram estudadas e comparadas com as de amostras vidradas com água, e sem revestimento, sob stress térmico, com temperaturas a variar entre -15 ⁰C e -5 ⁰C, durante 70 dias; os parâmetros avaliados incluem os valores de pH, contagem de microrganismos a 30⁰ C, Azoto Volátil Total, assim como cor e perda de revestimento. O efeito da solução de quitosano nas propriedades sensoriais, de salmão Atlântico (Salmo salar) também foi estudado, recorrendo a um colorímetro, um texturómetro e um painel sensorial treinado ao longo de seis meses. Os resultados mostram que sob stress térmico as amostras revestidas com quitosano obtiveram valores semelhantes aos obtidos com as amostras vidradas com água no que diz respeito a cor, valores de pH e Azoto Volátil Total, ao passo que oferecem melhores resultados em valores de contagem de microrganismos a 30 ⁰C e de perda de revestimento, mostrando que o quitosano pode ser uma melhor opção protetora que a vidragem. Realizou-se uma análise sensorial para estudar e comparar os efeitos dos diferentes revestimentos nas propriedades organoléticas de amostras de salmão e os resultados mostraram que não existiram diferenças significativas entre os diferentes revestimentos no que diz respeito à cor e à textura. A análise sensorial realizada por um painel treinado demonstrou que o quitosano é uma melhor escolha após seis meses de conservação em amostras congeladas, enquanto para amostras descongeladas e cozidas não se verificaram diferenças significativas entre amostras vidradas com água e revestidas com quitosano, sendo que ambas apresentaram melhores resultados do que amostras sem revestimento. Houve um particular cuidado em determinar se teria ocorrido difusão de sabor dos revestimentos para as amostras de salmão, tendo a análise estatística dos resultados do painel treinado mostrado que não existiu nenhuma relação entre o tipo de revestimento e o sabor da amostra, indiciando que nenhuma difusão de sabor ocorreu.The perishable nature of fish, coupled with an increase in fish consumption in recent years, has led to the improvement of fish preservation techniques. Chitosan coatings offer several advantages over more traditional freezing techniques, however there is a need to assess their effect on the sensory properties of salmon. In this work the protective properties of a chitosan solution at 1.5 % (w/v) were studied and compared to those of uncoated and water glazed samples, under thermal stress conditions, with temperature varying between -15 ⁰C and -5 ⁰C, during 70 days. Assessed parameters included pH, Total Volatile Basic Nitrogen (TVB-N), Total Viable Count (TVC) values, as well as coating loss and color parameters. The effect of the chitosan solution on the sensory properties, especially flavor, of Atlantic salmon (Salmo salar) was also studied through the use of a colorimeter, a texturometer and a trained sensory panel over six months of storage. Results show that under thermal stress conditions the chitosan coated samples presented similar values regarding color, pH and TVB-N values while offering better results in terms of TVC and coating loss values, proving chitosan a better protective option than water glazing. Sensory analysis was conducted to study and compare the effects of different coatings, and the results show that no significant differences were found between different coatings regarding color and texture. Sensory analysis by a trained panel of judges demonstrated that chitosan was a better choice after six months in frozen samples, while in thawed and cooked samples no significant differences were present between chitosan coated and water glazed samples, while both were better than uncoated samples, after six months of storage. In particular flavor was assessed in order to determine if flavor diffusion from the chitosan coating had occurred, and statistical analysis of the results of the trained panel of judges showed no relation between coating type and sample flavor, indicating that no flavor diffusion had occurred

Application of chitosan-based coatings on frozen salmon - Sensory assessment and retail simulation approach

GLUPOR 12 - 12nd International Meeting of the Portuguese Carbohydrate Chemistry GroupDue to an increase in fish consumption over the past years , in comb ination with the perishable nature of fish , the fish industry has given an added focus on the improvement of the currently used fish preservation techniques. Chitosan coatings may add improvements to the traditional water glazing , name ly in physical and ant i- microbial protection , allowing for shelf life extension. Nevertheless , during retail storage , frozen fish products can suffer temperature variations that lead to a decrease in quality. These temperature var iations can be caused by a multitude of reasons , some of which are easy to control , while others are due to unforeseen circumstances . In either case , thermal stress can often affect frozen fish products and this effect is of considerable importance . This work was meant to determ ine the influence of chitosan coatings in the organoleptic characteristics of salmon as well as report a strategy to help mitigate the effects of thermal stress of frozen fish samples .A 15 g/L chitosan solution was applied on frozen salmon samples through dipping at a temperature of 8 °C, wi th a dipping time of 10 s; water glazing was applied as blank treatment at 0.5 °C, with a dipping time of 40 s. Some of the samples were submitted to retail- simulated thermal stress conditions (i. e. a temperature variation of -15 °C to -5 °C was enforced ), and studied during a 70-days long experiment , while others were used to assess the sensory properties of chitosan coat ings on Atlantic salmon (Sa/mo salar) and were compared with uncoated and water glazed samples over a six-month storage period at -18 °C. Retail simulation samples were tested for variations in pH , coat i ng loss and color , while samples used for sensory analys is were evaluated by a sensory panel (frozen , frozen+thawed and frozen +thawed+cooked samples were assessed ,) regarding its organolept ic properties , and textural analysis , by means of a TPA (texture profile analys is ). Samples analys is common to both exper iments were microbiological stabi lity, assessed through TVC (ISO 4833-1 :2013 standard) , and chemical stability , determined as TVB-N (N P 2930 :2009 standard ). Through coating loss, it was possible to verify that chitosan coatings offer better protect ion, with water glazed samples becoming virtually unprotected after the evaluation period, with losses of more than 80 % of its glazing , while chitosan coated samples maintained 50 % of its coating. Extrapolat i ng this data to complete loss of water glazing shows an increase in shel f life of at le ast 26 % in chitosan coated samples. No significant changes between samples were obtained in the other parameters assessed . The anti-m icrobial effect of chitosan was confirmed through TVC which showed a reduction in microbial counts in chitosan coated samp les , whi le while TVB-N results showed to remain stable , for both experiments . The proven anti - microbial effect of chitosan coated samples in conjunction with a slower coating loss leads to an expected increase in shelf life , even in unforeseen circumstances of temperature change in retail transportation. Textural results from the TPA analysis showed no significant differences between different coatings. Results of the trained panel indicated that for frozen samples ch itosan was the preferred choice , while no significant differences existed between chitosan -coated and glazed samples in thawed and cooked samples. Flavor diffu sion from the chitosan coating to the samples was assessed by Principal Component Analysis and no correlation between coating type and sample flavor could be established , meaning that no chitosan flavor was detected by the panellists.Portuguese Foundation for Science and Technology (FCT) under the scope of the strategic funding of UID/BIO/044691/2013 unit and COMPETE 2020 (POCl-01-0145-FEDER-006684) and BioTecNorte operation (NORTE-01-0145-FEDER-000004) funded by the European Regional Development Fund under the scope of Norte2020 - Programa Operacional Regional do Norteinfo:eu-repo/semantics/publishedVersio

Comparing the effects of glazing and chitosan-based coating applied on frozen salmon on its organoleptic and physicochemical characteristics over six-months storage

The perishable nature of fish, with an increase in fish consumption in recent years, led to the improvement of fish preservation techniques. Chitosan coatings adds to the traditional water glazing. The effect of a chitosan solution of 1.5% on the sensory properties of Atlantic salmon (Salmo salar) was studied over six months of storage. The sensory properties of the salmon were assessed through the use of a texturometer and a trained panel of judges. Microbiological parameters were studied in the form of Total Volatile Base Nitrogen (TVB-N) and Total Viable Count (TVC) tests. Microbiological analysis showed that chitosan had an anti-microbiological effect on the salmon samples, reducing the number of microorganisms present, while TVB-N values were maitained stable during experiment. Textural Profile Analysis (TPA) was performed and the results showed no significant differences between different coatings regarding texture. Sensory analysis by a trained panel showed that chitosan was a better choice in frozen samples, while in thawed and cooked samples no significant differences existed between chitosan-coated and glazed samples. Flavor diffusion from the chitosan coating was assessed, and analysis of the results showed no correlation between coating type and sample flavor, indicating that no flavor diffusion had occurred.The contribution of VANIBRU, Lda. regarding the PhD scholarship of Nuno Soares and the use of industrial facilities are gratefully acknowledged

Analysis of sensory effects of chitosan-based coatings applied on frozen salmon over six-months storage

The 19th Gums & Stabilisers for the Food Industry Conference: Hydrocolloid MultifunctionalityDue to an increase in fish consumption over the past years, in combination with the perishable nature of fish, the fish industry has given an added focus on the improvement of the currently used fish preservation techniques. Chitosan coatings may add improvements to the traditional water glazing, namely in physical and anti-microbial protection, allowing for shelf life extension. This work was meant to determine the influence of chitosan coatings in the organoleptic characteristics of salmon. The effects of chitosan coatings on microbiological (Total Viable Count – TVC) and chemical (Total Volatile Base Nitrogen – TVB-N) parameters were also assessed. A 15 g/L solution of chitosan was used to coat frozen salmon samples, and its effect on the sensory properties of Atlantic salmon (Salmo salar) was compared with uncoated and water glazed samples, and was studied over six months of storage at -18 °C. Samples were dipped in the chitosan solution at 8 °C during 10 s; water glazing was applied at 0.5 °C, with a dipping time of 40 s. Textural properties were evaluated through Texture Profile Analysis (TPA), while sensory properties of frozen, frozen+thawed and frozen+thawed+cooked samples were assessed by a trained panel of judges. Microbiological stability was assessed through TVC (ISO 4833-1:2013 standard), and chemical stability was determined as TVB-N (NP 2930:2009 standard). TVC analysis showed an anti-microbial effect of chitosan in the coated samples (reduction of the number of microorganisms), while TVB-N results showed to remain stable during the experiment. Textural results from the TPA analysis showed no significant differences between different coatings. Results of the trained panel indicated that for frozen samples chitosan was the preferred choice, while no significant differences existed between chitosan-coated and glazed samples in thawed and cooked samples. Flavor diffusion from the chitosan coating to the samples was assessed by Principal Component Analysis and no correlation between coating type and sample flavor could be established, meaning that no chitosan flavor was detected by the panellists.info:eu-repo/semantics/publishedVersio

Hybrid gels: influence of water and oil phase on textural and rheological properties

The 19th Gums & Stabilisers for the Food Industry Conference: Hydrocolloid MultifunctionalityHybrid gels are biphasic systems formed by conjugating hydrogels and oleogels. The mixture of water-based and oil-based gels provides distinct and unique characteristics to hybrid gels, and based on the structurant molecules and mixture ratio used during their production, different textural and rheological properties can be obtained. Hybrid gels remain a very recent topic concerning pharmaceutical and food applications and despite recent studies on the use of hybrid gels for controlled delivery of compounds (pharmaceutical applications) these structures are still under-studied in regard to their food application possibilities [1, 2]. To improve knowledge and expanding ways to use these systems, it is important to understand how these gels behave regarding textural and rheological properties. Also, the knowledge on their micro and nanostructure allows tailoring their properties and thus maximizing their applicability in foodstuffs. We report on how the combination of a beeswaxbased oleogel and a sodium alginate-based hydrogel influences the gel structural properties at macroscopic (rheological and textural), microscopic (optical microscopy) and molecular (Xray diffraction) levels. Different ratios of both hydrogel and oleogel were used in order to evaluate the hybrid gels’ behaviour in terms of morphological, textural, rheological and polymorphic properties. Differences regarding oleogel particles distribution in the hydrogel matrix were noticed with the increase of oleogel fraction. A more disarranged distribution of oleogel particles was observable for the 50:50 ratios of hydrogel and oleogel. X-ray diffraction data unveiled that once polycrystallinity is reached (in hybrid gels) these patterns remain persistent for all tested ratios. Oleogel showed d-spacings in the range of 3.74 to 8.04 Å. Hybrid gel samples (and hydrogel control) are semi-crystalline, displaying spacings ranging in intervals of d (001) 6.99 – 7.18 Å; d (002) 3.09 – 3.23 Å and d (003) 2.45 – 2.46 Å, respectively. The samples with increasing oleogel ratio revealed a firmness decrease and a consequent reduction of spreadability values. Consequently, is observed less adhesivity for these samples, due to a more pronounced disaggregated structure. For all hybrid gels a gellike behaviour (G´ > G´´) was observed. Results showed that it is possible to modify the hybrid gels’ rheological and textural behaviour by a controlled mixture ratio of oleogels and hydrogels. This opens the possibilities of food applications for this kind of systems.info:eu-repo/semantics/publishedVersio

The effect of alginate in the protection of probiotics from the harsh conditions of digestion

BioTech 2017 and 7th Czech-Swiss Symposium with Exhibition[Excerpt] Introduction: Probiotics are live microorganisms that when administered in adequate amounts confer a health benefit to the host. However, to accomplish this positive influence on Human health, probiotics should survive to the passage through the upper digestive tract in large numbers to unsure a desired beneficial effects in the host. Several encapsulation methods have been used to protect probiotics. Alginate is the most used biopolymer in the production of these systems, although its performance is totally dependent of its characteristics. In this work, alginates with different molecular weights and different M/G ratio were used in the encapsulation of Lactococcus lactis spp. cremoris (LLC) aiming the protection of this probiotic bacteria against the harsh conditions of digestion. In the first set of experiments, variables such as flow rate, needle-CaCl2 solution distance and the stirring speed, CaCl2 concentration, alginate type, alginate concentration and needle diameter were studied in order to understand how they affect the formation of alginate beads. [...]Portuguese Foundation for Science and Technology (FCT) under the scope of the strategic funding of UID/BIO/04469/2013 unit and COMPETE 2020(POCI-01-0145-FEDER-006684) and BioTecNorte operation (NORTE-01-0145-FEDER-000004) funded by the European Regional Development Fund under the scope of Norte 2020 - Programa Operacional Regional do Norteinfo:eu-repo/semantics/publishedVersio

Observation of Higgs boson production in association with a top quark pair at the LHC with the ATLAS detector

The observation of Higgs boson production in association with a top quark pair ( tt¯H ), based on the analysis of proton–proton collision data at a centre-of-mass energy of 13 TeV recorded with the ATLAS detector at the Large Hadron Collider, is presented. Using data corresponding to integrated luminosities of up to 79.8 fb −1 , and considering Higgs boson decays into bb¯ , WW⁎ , τ+τ− , γγ , and ZZ⁎ , the observed significance is 5.8 standard deviations, compared to an expectation of 4.9 standard deviations. Combined with the tt¯H searches using a dataset corresponding to integrated luminosities of 4.5 fb −1 at 7 TeV and 20.3 fb −1 at 8 TeV, the observed (expected) significance is 6.3 (5.1) standard deviations. Assuming Standard Model branching fractions, the total tt¯H production cross section at 13 TeV is measured to be 670 ± 90 (stat.) −100+110 (syst.) fb, in agreement with the Standard Model prediction.Peer Reviewe

Measurement of photon–jet transverse momentum correlations in 5.02 TeV Pb + Pb and pppp collisions with ATLAS

Jets created in association with a photon can be used as a calibrated probe to study energy loss in the medium created in nuclear collisions. Measurements of the transverse momentum balance between isolated photons and inclusive jets are presented using integrated luminosities of 0.49 nb$^{-1}$ of Pb+Pb collision data at $\sqrt{s_\mathrm{NN}}=5.02$ TeV and 25 pb$^{-1}$ of $pp$ collision data at $\sqrt{s}=5.02$ TeV recorded with the ATLAS detector at the LHC. Photons with transverse momentum $63.1 31.6$ GeV and pseudorapidity $\left|\eta^\mathrm{jet}\right| 7\pi/8$. Distributions of the per-photon jet yield as a function of $x_\mathrm{J\gamma}$, $(1/N_\gamma)(\mathrm{d}N/\mathrm{d}x_\mathrm{J\gamma})$, are corrected for detector effects via a two-dimensional unfolding procedure and reported at the particle level. In $pp$ collisions, the distributions are well described by Monte Carlo event generators. In Pb+Pb collisions, the $x_\mathrm{J\gamma}$ distribution is modified from that observed in $pp$ collisions with increasing centrality, consistent with the picture of parton energy loss in the hot nuclear medium. The data are compared with a suite of energy-loss models and calculations.Peer Reviewe

Pervasive gaps in Amazonian ecological research

Biodiversity loss is one of the main challenges of our time,1,2 and attempts to address it require a clear un derstanding of how ecological communities respond to environmental change across time and space.3,4 While the increasing availability of global databases on ecological communities has advanced our knowledge of biodiversity sensitivity to environmental changes,5–7 vast areas of the tropics remain understudied.8–11 In the American tropics, Amazonia stands out as the world’s most diverse rainforest and the primary source of Neotropical biodiversity,12 but it remains among the least known forests in America and is often underrepre sented in biodiversity databases.13–15 To worsen this situation, human-induced modifications16,17 may elim inate pieces of the Amazon’s biodiversity puzzle before we can use them to understand how ecological com munities are responding. To increase generalization and applicability of biodiversity knowledge,18,19 it is thus crucial to reduce biases in ecological research, particularly in regions projected to face the most pronounced environmental changes. We integrate ecological community metadata of 7,694 sampling sites for multiple or ganism groups in a machine learning model framework to map the research probability across the Brazilian Amazonia, while identifying the region’s vulnerability to environmental change. 15%–18% of the most ne glected areas in ecological research are expected to experience severe climate or land use changes by 2050. This means that unless we take immediate action, we will not be able to establish their current status, much less monitor how it is changing and what is being lostinfo:eu-repo/semantics/publishedVersio