71 research outputs found
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 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 of Pb+Pb collision data at TeV and 25 pb of collision data at TeV recorded with the ATLAS detector at the LHC. Photons with transverse momentum GeV and pseudorapidity . Distributions of the per-photon jet yield as a function of , , are corrected for detector effects via a two-dimensional unfolding procedure and reported at the particle level. In collisions, the distributions are well described by Monte Carlo event generators. In Pb+Pb collisions, the distribution is modified from that observed in 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
- …