Ksenia Morozova | Free University of Bozen-Bolzano (original) (raw)

Papers by Ksenia Morozova

Electroanalysis, 2016

A flow injection system with amperometric detection at potentials poised at +0.4 and +0.9 V was u... more A flow injection system with amperometric detection at potentials poised at +0.4 and +0.9 V was used to evaluate intensity of the bitter taste in monovarietal Extra Virgin Olive Oils (EVOO). Results from the proposed method were based on the extraction of the bitter constituents of the virgin olive oil samples in methanol‐water, followed by the direct amperometric measurement. These potentials were selected according to the hydrodynamic voltammogram of oleuropein, one of the most prominent and bitter phenolic compound found in EVOO. The amperometric detection was applied on 32 monovariatal EVOO samples. Results were correlated with the phenolic profile measured by high performance liquid chromatography (HPLC). The amperometric signal at +0.9 V mainly correlated with the total phenols of the samples (R2=0.81), whereas the signal at +0.4 V mainly correlated with oleuropein aglycone (3,4 DHPEA‐EDA, R2=0.79). Bitterness intensity of the samples was evaluated by a trained sensory panel of experts and the results compared to those obtained by the amperometric flow system. The best correlation with the bitter taste was achieved by the sensor at +0.4 V (R2=0.72). A calibration model based on partial least squares was built with three variables, namely the sensors set at +0.4 and +0.9 V and the total phenol content of the EVOO extracts. The model showed a moderate capacity to predict the bitterness of the EVOO samples using leave one out method, (R2=0.75) and in prediction of a test set of samples (R2=0.7). Such approach is very promising for future studies.

Journal of Agricultural and Food Chemistry, 2017

This work describes a new approach based on multiple light scattering to study red wine clarifica... more This work describes a new approach based on multiple light scattering to study red wine clarification processes. 7 The whole spectral signal (1933 backscattering points along the length of each sample vial) were fitted by a multivariate kinetic 8 model that was built with a three-step mechanism, implying (1) adsorption of wine colloids to fining agents, (2) aggregation into 9 larger particles, and (3) sedimentation. Each step is characterized by a reaction rate constant. According to the first reaction, the 10 results showed that gelatin was the most efficient fining agent, concerning the main objective, which was the clarification of the 11 wine, and consequently the increase in its limpidity. Such a trend was also discussed in relation to the results achieved by 12 nephelometry, total phenols, ζ-potential, color, sensory, and electronic nose analyses. Also, higher concentrations of the fining 13 agent (from 5 to 30 g/100 L) or higher temperatures (from 10 to 20 °C) sped up the process. Finally, the advantage of using the 14 whole spectral signal vs classical univariate approaches was demonstrated by comparing the uncertainty associated with the rate 15 constants of the proposed kinetic model. Overall, multiple light scattering technique showed a great potential for studying fining 16 processes compared to classical univariate approaches. 17 KEYWORDS: multivariate analysis, fining, red wine, multiple light scattering 18 ■ INTRODUCTION 19 Among the quality characteristic of wine, limpidity is one of the 20 most important. A limpid wine requires not only the removal of 21 the large insoluble matters, such as dead yeast cells, pieces of 22 grape skin, gums or pectins but also of those fine impurities, 23 which are the most difficult to eliminate, like tannins and other 24 phenolic compounds. Although the large particles can be easily 25 and naturally removed by leaving the wine undisturbed in 26 storage vessels, the fine colloidal particles may preclude the 27 achievement of a sufficient clarity even after several months of 28 aging. 1 Even worse, a clear wine, if not stabilized, can become 29 suddenly hazy again, as result of a well-known defect called 30 casse. 31 From a practical standpoint, fining is a well-known operation 32 in winemaking that is intended to remove the turbidity caused 33 by such unstable compounds. In details, fining aims at speeding 34 up the settling of the suspended organic impurities by adding 35 fining agents to the wine. A number of fining agents are 36 commercially used. These include inorganic clays (i.e., 37 bentonite), animal proteins (i.e., gelatin, isinglass, and caseins), 2 38 synthetic polymers (i.e., polyvinyl polypyrrolidone (PVPP)), 3 39 or plant based protein. 4,5 Fining is often used to improve the 40 sensory quality of wine. Previous works have shown positive 41 effects of fining with protein agents and polyvinylpolypyrroli-42 done on the sensory profile of red wines. 6 43 Concerning the factors affecting wines fining, it has been 44 often reported that the mechanism linked to the interaction 45 between proteins and polyphenolic compounds is responsible 46 for the expected flocculation and clarification. 7 Limiting the 47 discussion to gelatin, one of the most widespread used fining 48 agents, some reliable evidence report the possible formation of 49 cross-links between the wine colloids, such as proteins, pectins, 50 and polymerized phenolic pigments, and how such aggregates 51 can contribute to the overall sedimentation phenomena. 8 52 By the way, winery companies have a keen interest to deepen 53 their knowledge on the potential effects of fining agents, as a 54 better understanding of the mechanism of fining agent 55 adsorption would provide an outstanding opportunity to 56 winemakers to comprehend the effect of fining treatments on 57 the resulting quality of their wines. At this purpose, cellars are 58 routinely involved in the measurement of the limpidity degree 59 of wine through a visual inspection of a sample under daylight 60 and lamps or performing simple objective nephelometric 61 measurements. 8 However, these methods offer only a limited 62 picture of the aggregates phenomena occurring during fining 63 and none of them is able to monitor the clarification 64 phenomena in a simple and nondestructive way and more 65 important online during the time of fining. 66 Nowadays, one of the most interesting techniques able to 67 predict the physical stability and follow online the destabiliza-68 tion phenomena of a colloidal system is represented by multiple 69 light scattering. Its principle is straightforward and based on the 70 measurement of the scattered radiation caused by the particles 71 in suspension. Recently, it has been used to examine the 72 aggregation behavior of model wine systems 9 and to follow 73 sedimentation. 10 74 In this work, a novel approach based on multiple light 75 scattering was used to describe the fining process of red wines 76 and determine the short-term efficiency of different fining 77 agents. At this purpose, a kinetic model accounting for (1)

Food Research International, 2017

Chemical compounds studied in this article: Dehydroergosterol (PubMed CID: 6436660) Glutathione (... more Chemical compounds studied in this article: Dehydroergosterol (PubMed CID: 6436660) Glutathione (PubMed CID: 124886) Adenine (PubMed CID: 190) S-Adenosyl-homocysteine (PubMed CID: 439155) Acetyl-carnitine (PubMed CID: 7045767) Keywords: Black truffle Antioxidant power High resolution mass spectrometry Storage Modified atmosphere packaging Reduced atmospheric pressure packaging A B S T R A C T Freshly harvested Tuber melanosporum samples were packed and stored at 4 °C under reduced atmospheric pressure or modified atmosphere for four weeks. Multivariate analysis was employed to correlate the antioxidant power of the ethanolic extracts of the samples with the chemical composition determined by high resolution mass spectrometry. High performance liquid chromatography coupled with a coularray detector was applied to select the chemical species associated with the antioxidant power. Four classes of chemical compounds were investigated in more detail by a targeted approach: derivatives of glutathione, adenine (such as S-adenosyl-homocysteine), oxidized linoleic acid and ergosterol. Adducts containing glutathione and adenine with oxidized linoleic acid were observed in TM for the first time and can be considered markers of freshness of the product. S-adenosyl-homocysteine, the acetyl-carnitine adduct with cysteinyl-glycine and several oxidized linoleic acid derivatives were among the markers of degradation.

LWT, 2018

Nylon-6 nanofibrous membranes (NFM) prepared by electrospinning have been used as solid state sup... more Nylon-6 nanofibrous membranes (NFM) prepared by electrospinning have been used as solid state support for the immobilization of the yeast Saccharomyces cerevisiae and then applied for the fermentation of grape juice. The membranes were characterized by scanning electron microscopy. The resulting metabolic activity was characterized by microcalorimetry. Sugar and ethanol changes during fermentation were monitored by HPLC. The results showed that the fermentation performance of immobilized yeasts on NFM is equal or even superior to the traditional fermentation process with yeasts freely dispersed in the medium. From calorimetry, free and immobilized yeasts showed the same enthalpy value in model solution, regardless to the amount of yeast loaded (52.2 ± 5.9 kJ mol −1 of glucose). Instead, immobilization of yeasts resulted in shorter lag time. Moreover, the maximum growth rate of immobilized yeasts was the same as with free yeasts in model solutions. However, the growth rate of immobilized yeasts was even higher, when performed in grape juice. In addition, the im-mobilization of yeasts on NFM exhibits the evident possibility of multiple reuse. Three consecutive fermentations were performed without significant loss of the overall performance. These findings support the development of nanostructured solid support for biocatalytic processes like fermentation of alcoholic beverages.

Journal of Thermal Analysis and Calorimetry, 2019

Isothermal microcalorimetry is often used to monitor microbiological activity and growth in vario... more Isothermal microcalorimetry is often used to monitor microbiological activity and growth in various types of biological
samples. Usually, it is useful to convert the isothermal microcalorimetry data into biologically meaningful data such as
growth rate, lag phase or maximum growth. In this work, isothermal calorimetry was applied for monitoring of grape juice
fermentation by Saccharomyces cerevisiae immobilized in nylon-6 nanofibrous membranes (NFM) prepared by electrospinning in comparison with freely dispersed yeasts. The resulting heat flow can be fitted using various approaches
applying graphical, exponential, Gompertz, modified logistic and Michaelis–Menten models. Advantages and drawbacks
of each approach for monitoring of the immobilized yeasts have been discussed in relation to the S. cerevisiae yeasts.
Analysis of the fitting parameters showed that immobilized yeasts had the highest growth rate and maximum growth in
comparison with freely dispersed yeasts. Parallel measurements of sugar and oxygen consumption rates for immobilized
and free yeasts cells confirmed the calorimetric data. The results of this work demonstrate practical approach to analysis
and modeling of calorimetric data in food analysis and advantages of application of NFM as solid support for yeast
immobilization.

A flow injection system with amperometric detection at potentials poised at +0.4 and +0.9 V was u... more A flow injection system with amperometric detection at potentials poised at +0.4 and +0.9 V was used to evaluate intensity of the bitter taste in monovarietal Extra Virgin Olive Oils (EVOO). Results were based on the extraction of the bitter constituents of the virgin olive oil samples in methanol-water, followed by the direct amperometric measurement. These potentials were selected according to the hydrodynamic voltammogram of oleuropein, one of the most prominent and bitter phenolic compound found in EVOO. The amperometric detection was applied on 32 monovariatal EVOO samples. Results were correlated with the phenolic profile measured by high performance liquid chromatography (HPLC). The amperometric signal at +0.9 V mainly correlated with the total phenols of the samples (R2 = 0.81), whereas the signal at +0.4 V mainly correlated with oleuropein aglycone (3,4 DHPEA-EDA, R2 = 0.79). Bitterness intensity of the samples was evaluated by a trained sensory panel and the results compared to those obtained by the amperometric flow system. The best correlation with the bitter taste was achieved by the sensor at +0.4 V (R2 = 0.72). A calibration PLS model based was built with three variables, namely the sensors (+0.4 and +0.9V) and the total phenol content of the EVOO extracts. The model showed moderate capacity to predict the bitterness of the EVOO samples using leave one out method, (R2 = 0.75) and in prediction of a test set of samples (R2 = 0.7). The measurements at different potentials were done separately with oleuropein concentrations of 18.5 µM and 185 µM, respectively (n=3). The injections were made when a stable baseline was achieved. The resulting run times were not synchronized. In order to overlay the peaks for the figure 1 (A) we needed to cut and reduce the data. As a matter of fact, while reducing the data, we lost the peak at 0.4V. Now the mistake was found and we modified again the figure 1, which is now consistent with the figures 2 and 3. We appologize for the inconvenience and time loss due to our mistake. In order to prove that we used the original data for figure 1, we attach the Excel file with chronoamperometric measurements at all potentials.

Oxygen ingress at bottling is crucial for the wine development during storage. Iron and copper ar... more Oxygen ingress at bottling is crucial for the wine development during storage. Iron and copper are known to catalyse the oxidation processes in wines. The aim of the present study was to evaluate the impact of oxygen, and iron and copper addition on changes in analytical and sensory parameters during storage. A Riesling wine was bottled with various oxygen concentrations determined by the headspace volume in the bottle (0, 10 and 20 mL) full with ambient air. Iron (1 mg/L) and copper (0.5 mg/L) were added to 50 % of the bottles. Headspace and dissolved oxygen, free and total SO2 and colour were monitored during 3 months post-bottling. Descriptive sensory evaluation took place in the end of the observation period. Fe and Cu addition had significant influence on the oxygen consumption rate, on the loss of SO2 during storage, and on the sensory changes in wine. Initial headspace volume additionally made significant impact on the evolution of the sulphur dioxide and on the sensory profile of bottled wines.

White wine spoilage due to oxidation is a major concern during post-fermentation treatments and b... more White wine spoilage due to oxidation is a major concern during post-fermentation treatments and bottling. In this study, we explored the effects of different oxygen and free SO2 levels and ascorbic acid addition on the development of white wine. Riesling wine was bottled in 500-mL bottles under screw caps with four different headspace volumes (0, 10, 20 and 30 mL), two levels of free SO2 (45 and 70 mg/L) and with and without ascorbic acid (250 mg/L) addition giving 16 wines for analysis. Cold stored (at 5 °C) control was used as reference for data analysis and sensory evaluation. Dissolved oxygen and the oxygen in headspace were measured in the resulting 17 wines. Free and total SO2 concentrations, ascorbic acid concentration, colour, redox potential and antioxidative capacity were measured regularly in wine samples. After 6 months of storage, the wines were evaluated using descriptive sensory analysis. Both sensory and analytical results showed significant differences among the wines. Intensive wine exposure to oxygen (headspace volume) affected colour, free and total SO2 rate, and the overall sensory quality of wine. Ascorbic acid addition had positive effect on the sensory evaluation of wines and on SO2 levels, whereas combined with large headspace volumes, provoked intensive browning in wine samples.

Studies conducted with a model solution and a Riesling wine showed that oxygen concentration at b... more Studies conducted with a model solution and a Riesling wine showed that oxygen concentration at bottling had a great impact on the evolution of the total consumed oxygen (TCO), free SO2, and the colour of model solution and wine. In the model solution, the addition of 0.1 mg/l of iron and/or 0.05 mg/l of copper influenced the oxygen consumption, in the real wine, however, this effect was not observed. Sensory evaluation (triangle tests and descriptive analysis) showed significant differences between wines bottled with different headspace volumes (0, 20 and 40 ml). The presence of iron and copper had no significant impact on the sensory characteristics and colour of wines.

Th e main aim of this study was to compare several instruments for carbon dioxide and oxygen meas... more Th e main aim of this study was to compare several instruments for carbon dioxide and oxygen measurement in wine.
For carbon dioxide determination CarboQC, Orbisphere 3568 and Agitation Cylinder were used. Oxygen measurements
were performed with PreSens, OxyQC and Orbisphere 3650. Sample bottles equally treated to have the same
carbon dioxide or oxygen content were used for the measurements. Measurements were undertaken in the range from
0 to 2200 mg/l for carbon dioxide and in the range from 0 to 12 mg/l for oxygen. Developing correlation graphics and
regression coeffi cients it was demonstrated that CarboQC and Orbisphere 3658 were eff ective for carbon dioxide measurement
in the whole measurement range. Agitation Cylinder can also be used for this purpose at normal atmospheric
pressure. Oxygen measurement with PreSens, OxyQC and Orbisphere 3650 showed good reliable results. Results
obtained with all three instruments showed good correlation against each other and the initial pressure. So any of these
devices can be used for oxygen determination in wine. However, more research should be made taking in consideration
limitations of the proposed method for sample preparation. Counter pressure fi llers should be used to obtain wine samples
with gas concentration higher than saturation level.

This work aimed at monitoring the metabolic activity of grapes during withering by microcalorimet... more This work aimed at monitoring the metabolic activity of grapes during withering by microcalorimetry. Samples of Corvina grapes, a cultivar used in the production of Amarone wine, were dehydrated for about 120 days at an industrial scale plants (fruttaia). Single berries, sampled in the course of the withering process, were closed in ampoules and maintained at constant temperature. As biochemical events (i.e. berry respiration, microbial growth, etc.) are always accompanied by the production of heat (q), the heat-flow (dq/dt) emitted by berries enclosed in the ampoules was used to monitor their metabolic activity during withering, i.e. respiration. For each sampling time, the heat rate production of the berries at 298 K was monitored till a steady state signal was achieved (within 60 h). Such heat flow value was used as marker during the entire withering process (120 days). Its trend allowed to characterize the changes in the metabolic activity of the grape berries along the withering process. To understand the origin of such changes, the emission of volatile organic compounds (VOCs) were also measured by proton transfer mass spectrometry (PTR-MS). The use of microcalorimetry associated with the analysis of specific VOCs fragments offered a valuable information to describe the withering process.

Electroanalysis, 2016

Journal of Agricultural and Food Chemistry, 2017

Food Research International, 2017

LWT, 2018

Journal of Thermal Analysis and Calorimetry, 2019

A flow injection system with amperometric detection at potentials poised at +0.4 and +0.9 V was u... more A flow injection system with amperometric detection at potentials poised at +0.4 and +0.9 V was used to evaluate intensity of the bitter taste in monovarietal Extra Virgin Olive Oils (EVOO). Results were based on the extraction of the bitter constituents of the virgin olive oil samples in methanol-water, followed by the direct amperometric measurement. These potentials were selected according to the hydrodynamic voltammogram of oleuropein, one of the most prominent and bitter phenolic compound found in EVOO. The amperometric detection was applied on 32 monovariatal EVOO samples. Results were correlated with the phenolic profile measured by high performance liquid chromatography (HPLC). The amperometric signal at +0.9 V mainly correlated with the total phenols of the samples (R2 = 0.81), whereas the signal at +0.4 V mainly correlated with oleuropein aglycone (3,4 DHPEA-EDA, R2 = 0.79). Bitterness intensity of the samples was evaluated by a trained sensory panel and the results compared to those obtained by the amperometric flow system. The best correlation with the bitter taste was achieved by the sensor at +0.4 V (R2 = 0.72). A calibration PLS model based was built with three variables, namely the sensors (+0.4 and +0.9V) and the total phenol content of the EVOO extracts. The model showed moderate capacity to predict the bitterness of the EVOO samples using leave one out method, (R2 = 0.75) and in prediction of a test set of samples (R2 = 0.7). The measurements at different potentials were done separately with oleuropein concentrations of 18.5 µM and 185 µM, respectively (n=3). The injections were made when a stable baseline was achieved. The resulting run times were not synchronized. In order to overlay the peaks for the figure 1 (A) we needed to cut and reduce the data. As a matter of fact, while reducing the data, we lost the peak at 0.4V. Now the mistake was found and we modified again the figure 1, which is now consistent with the figures 2 and 3. We appologize for the inconvenience and time loss due to our mistake. In order to prove that we used the original data for figure 1, we attach the Excel file with chronoamperometric measurements at all potentials.