276 research outputs found
Mechanical tests and definition of new indexes of grape berry firmness. Evolution of berry skin hardness during alcoholic fermentation
The mechanical strength or firmness of a fruit is considered an important parameter to characterise its state of ripeness or conservation, as well as other parameters such as sugar level or color. The mechanical hardness of grapes influences the integrity and sanitary quality of the harvest. In this study, the mechanical characteristics of grapevine berries were studied at harvest time in order to determine their rheological properties (firmness and hardness of the berry skin) during alcoholic fermentation. Special indexes were defined measuring the energy needed to crush the berries to 50 % of their initial diameter, and applied successively to two different varieties. The entire berry firmness and the skin hardness were both different. Mechanical indexes linked to grape firmness were defined. Using these indexes, a significant effect on the firmness behavior due to variety was recorded: the skin of 'Grenache Noir' was found firmer and harder than 'Carignan Noir'. Furthermore, during the alcoholic fermentation, no change in skin hardness was observed for both varieties, despite changes in the composition of the must. These results give new information on mechanical properties of berries and could be used as an aid in the winemaking process. Indeed, they would probably help the winemaker to better choose the type of fermentation and maceration adapted to his grapes according to the type of wine he wishes to produce
Colloidal stability of tannins: astringency, wine tasting and beyond
Tannin-tannin and tannin-protein interactions in water-ethanol solvent
mixtures are studied in the context of red wine tasting. While tannin
self-aggregation is relevant for visual aspect of wine tasting (limpidity and
related colloidal phenomena), tannin affinities for salivary proline-rich
proteins is fundamental for a wide spectrum of organoleptic properties related
to astringency. Tannin-tannin interactions are analyzed in water-ethanol
wine-like solvents and the precipitation map is constructed for a typical grape
tannin. The interaction between tannins and human salivary proline-rich
proteins (PRP) are investigated in the framework of the shell model for
micellization, known for describing tannin-induced aggregation of beta-casein.
Tannin-assisted micellization and compaction of proteins observed by SAXS are
described quantitatively and discussed in the case of astringency
Interactions between wine phenolic compounds and human saliva in astringency perception
[EN] Astringency is a complex perceptual phenomenon involving several sensations that are perceived simultaneously. The mechanism leading to these sensations has been thoroughly and controversially discussed in the literature and it is still not well understood since there are many contributing factors. Although we are still far from elucidating the mechanisms whereby astringency develops, the interaction between phenolic compounds and proteins (from saliva, oral mucosa or cells) seems to be most important. This review summarizes the recent trends in the protein–phenol interaction, focusing on the effect of the structure of the phenolic compound on the interaction with salivary proteins and on methodologies based on these interactions to determine astringency
Recommended from our members
Identification of structural features of condensed tannins that affect protein aggregation
A diverse panel of condensed tannins was used to resolve the confounding effects of size and subunit composition seen previously in tannin-protein interactions. Turbidimetry revealed that size in terms of mean degree of polymerisation (mDP) or average molecular weight (amw) was the most important tannin parameter. The smallest tannin with the relatively largest effect on protein aggregation had an mDP of ~7. The average size was significantly correlated with aggregation of bovine serum albumin, BSA (mDP: r=-0.916; amw: r=-0.925; p<0.01; df=27), and gelatin (mDP: r=-0.961; amw: r=-0.981; p<0.01; df=12). The procyanidin/prodelphinidin and cis-/trans-flavan-3-ol ratios gave no significant correlations. Tryptophan fluorescence quenching indicated that procyanidins and cis-flavan-3-ol units contributed most to the tannin interactions on the BSA surface and in the hydrophobic binding pocket (r=0.677; p<0.05; df=9 and r=0.887; p<0.01; df=9, respectively). Circular dichroism revealed that higher proportions of prodelphinidins decreased the apparent α-helix content (r=-0.941; p<0.01; df=5) and increased the apparent β-sheet content (r=0.916; p<0.05; df=5) of BSA
Study of the interactions between a proline-rich protein and a flavan-3-ol by NMR: Residual structures in the natively unfolded protein provides anchorage points for the ligands
Euclid preparation. TBD. The effect of linear redshift-space distortions in photometric galaxy clustering and its cross-correlation with cosmic shear
Cosmological surveys planned for the current decade will provide us with
unparalleled observations of the distribution of galaxies on cosmic scales, by
means of which we can probe the underlying large-scale structure (LSS) of the
Universe. This will allow us to test the concordance cosmological model and its
extensions. However, precision pushes us to high levels of accuracy in the
theoretical modelling of the LSS observables, in order not to introduce biases
in the estimation of cosmological parameters. In particular, effects such as
redshift-space distortions (RSD) can become relevant in the computation of
harmonic-space power spectra even for the clustering of the photometrically
selected galaxies, as it has been previously shown in literature studies. In
this work, we investigate the contribution of linear RSD, as formulated in the
Limber approximation by arXiv:1902.07226, in forecast cosmological analyses
with the photometric galaxy sample of the Euclid survey, in order to assess
their impact and quantify the bias on the measurement of cosmological
parameters that neglecting such an effect would cause. We perform this task by
producing mock power spectra for photometric galaxy clustering and weak
lensing, as expected to be obtained from the Euclid survey. We then use a
Markov chain Monte Carlo approach to obtain the posterior distributions of
cosmological parameters from such simulated observations. We find that
neglecting the linear RSD leads to significant biases both when using galaxy
correlations alone and when these are combined with cosmic shear, in the
so-called 32pt approach. Such biases can be as large as
-equivalent when assuming an underlying CDM cosmology. When
extending the cosmological model to include the equation-of-state parameters of
dark energy, we find that the extension parameters can be shifted by more than
.Comment: 15 pages, 5 figures. To be submitted in A&
Euclid preparation: XV. Forecasting cosmological constraints for the Euclid and CMB joint analysis
The combination and cross-correlation of the upcoming Euclid data with cosmic microwave background (CMB) measurements is a source of great expectation since it will provide the largest lever arm of epochs, ranging from recombination to structure formation across the entire past light cone. In this work, we present forecasts for the joint analysis of Euclid and CMB data on the cosmological parameters of the standard cosmological model and some of its extensions. This work expands and complements the recently published forecasts based on Euclid-specific probes, namely galaxy clustering, weak lensing, and their cross-correlation. With some assumptions on the specifications of current and future CMB experiments, the predicted constraints are obtained from both a standard Fisher formalism and a posterior-fitting approach based on actual CMB data. Compared to a Euclid-only analysis, the addition of CMB data leads to a substantial impact on constraints for all cosmological parameters of the standard Λ-cold-dark-matter model, with improvements reaching up to a factor of ten. For the parameters of extended models, which include a redshift-dependent dark energy equation of state, non-zero curvature, and a phenomenological modification of gravity, improvements can be of the order of two to three, reaching higher than ten in some cases. The results highlight the crucial importance for cosmological constraints of the combination and cross-correlation of Euclid probes with CMB data
Euclid preparation XXVIII. Forecasts for ten different higher-order weak lensing statistics
Recent cosmic shear studies have shown that higher-order statistics (HOS) developed by independent teams now outperform standard two-point estimators in terms of statistical precision thanks to their sensitivity to the non-Gaussian features of large-scale structure. The aim of the Higher-Order Weak Lensing Statistics (HOWLS) project is to assess, compare, and combine the constraining power of ten different HOS on a common set of Euclid-like mocks, derived from N-body simulations. In this first paper of the HOWLS series, we computed the nontomographic (Ωm, σ8) Fisher information for the one-point probability distribution function, peak counts, Minkowski functionals, Betti numbers, persistent homology Betti numbers and heatmap, and scattering transform coefficients, and we compare them to the shear and convergence two-point correlation functions in the absence of any systematic bias. We also include forecasts for three implementations of higher-order moments, but these cannot be robustly interpreted as the Gaussian likelihood assumption breaks down for these statistics. Taken individually, we find that each HOS outperforms the two-point statistics by a factor of around two in the precision of the forecasts with some variations across statistics and cosmological parameters. When combining all the HOS, this increases to a 4.5 times improvement, highlighting the immense potential of HOS for cosmic shear cosmological analyses with Euclid. The data used in this analysis are publicly released with the paper
Euclid Preparation. XXVIII. Forecasts for ten different higher-order weak lensing statistics
Recent cosmic shear studies have shown that higher-order statistics (HOS)
developed by independent teams now outperform standard two-point estimators in
terms of statistical precision thanks to their sensitivity to the non-Gaussian
features of large-scale structure. The aim of the Higher-Order Weak Lensing
Statistics (HOWLS) project is to assess, compare, and combine the constraining
power of ten different HOS on a common set of -like mocks, derived from
N-body simulations. In this first paper of the HOWLS series, we computed the
nontomographic (, ) Fisher information for the
one-point probability distribution function, peak counts, Minkowski
functionals, Betti numbers, persistent homology Betti numbers and heatmap, and
scattering transform coefficients, and we compare them to the shear and
convergence two-point correlation functions in the absence of any systematic
bias. We also include forecasts for three implementations of higher-order
moments, but these cannot be robustly interpreted as the Gaussian likelihood
assumption breaks down for these statistics. Taken individually, we find that
each HOS outperforms the two-point statistics by a factor of around two in the
precision of the forecasts with some variations across statistics and
cosmological parameters. When combining all the HOS, this increases to a
times improvement, highlighting the immense potential of HOS for cosmic shear
cosmological analyses with . The data used in this analysis are
publicly released with the paper.Comment: 33 pages, 24 figures, main results in Fig. 19 & Table 5, version
published in A&
Euclid preparation. XXIX. Water ice in spacecraft part I: The physics of ice formation and contamination
Molecular contamination is a well-known problem in space flight. Water is the
most common contaminant and alters numerous properties of a cryogenic optical
system. Too much ice means that Euclid's calibration requirements and science
goals cannot be met. Euclid must then be thermally decontaminated, a long and
risky process. We need to understand how iced optics affect the data and when a
decontamination is required. This is essential to build adequate calibration
and survey plans, yet a comprehensive analysis in the context of an
astrophysical space survey has not been done before.
In this paper we look at other spacecraft with well-documented outgassing
records, and we review the formation of thin ice films. A mix of amorphous and
crystalline ices is expected for Euclid. Their surface topography depends on
the competing energetic needs of the substrate-water and the water-water
interfaces, and is hard to predict with current theories. We illustrate that
with scanning-tunnelling and atomic-force microscope images.
Industrial tools exist to estimate contamination, and we must understand
their uncertainties. We find considerable knowledge errors on the diffusion and
sublimation coefficients, limiting the accuracy of these tools. We developed a
water transport model to compute contamination rates in Euclid, and find
general agreement with industry estimates. Tests of the Euclid flight hardware
in space simulators did not pick up contamination signals; our in-flight
calibrations observations will be much more sensitive.
We must understand the link between the amount of ice on the optics and its
effect on Euclid's data. Little research is available about this link, possibly
because other spacecraft can decontaminate easily, quenching the need for a
deeper understanding. In our second paper we quantify the various effects of
iced optics on spectrophotometric data.Comment: 35 pages, 22 figures, A&A in press. Changes to previous version:
language edits, added Z. Bolag as author in the arxiv PDF (was listed in the
ASCII author list and in the journal PDF, but not in the arxiv PDF). This
version is identical to the journal versio
- …