Stefania Vichi - Academia.edu (original) (raw)

Papers by Stefania Vichi

Food Chemistry, 2009

The potential significance as odorants and markers of olive fruits degradation has been recently ... more The potential significance as odorants and markers of olive fruits degradation has been recently pointed out for volatile phenols in virgin olive oil (VOO) and related to the appearance of VOO sensory defects. The few studies carried out in order to elucidate the factors affecting their formation in olive fruits or VOOs, indicated that they could be considered as analytical indices of olive fruits degradation during storage, likely reflecting the microbiological activity. In the present study, the effect of the olive variety ('Arbequina', 'Arbosana' and 'Leccino') on the production of volatile phenols during twelve days of storage in closed plastic bags was evaluated. The different resistance of each variety to the microbiological attach was observed during olive fruit storage, and it was reflected by the evolution of guaiacol, 4-ethylphenol and 4-ethylguaiacol, and related to free acidity values. On the contrary, a scarce dependence on the microbial growth or varietal factors was observed for 4-vinyl derivatives, which appeared more directly related to the time of olives storage. The evolution of volatile phenols found certain correspondence in the sensory characteristics of the resulting VOOs, while the rest of VOO chemical quality indices did not show major variations during fruits storage.

International Journal of Food Microbiology, 2010

Given the importance of the interactions between wine and lees cell surface during sparkling wine... more Given the importance of the interactions between wine and lees cell surface during sparkling wine aging, and in view of recent results proving the antioxidant potential of yeast cell wall biomolecules, the antioxidant capacity of lees cell surface was investigated to establish its possible role in the antioxidative effect of lees. The surface antioxidant activity of lees from wines with different aging periods was determined on the whole cell by two widely used methods (DPPH and FRAP assays), obtaining maximum values of 24.5 μmol Trolox/g cells (fresh weight) by the DPPH assay, and 21.3 μmol Trolox/g cells (fresh weight) by the FRAP assay. Lees surface antioxidant activity was influenced by base wine characteristics and inversely related to sur lie aging period. Conversely, the percentage depletion of lees surface antioxidant activity during aging was mainly determined by the length of aging, regardless of wine characteristics. To examine the influence of cell wall thiol groups and adsorbed polyphenols on lees' protective effect, their presence on cell surfaces was assessed. They accounted for 25 ± 11% and 54 ± 7% of the antioxidant activity measured by DPPH, respectively, and 0.3 ± 0.1% and 39 ± 8% measured by FRAP, respectively. Only a part of the remnant antioxidant activity of lees surface measured by FRAP could be theoretically explained by the presence of cell wall mannans.

Journal of the Science of Food and Agriculture, 2002

In this study the antioxidant activity of methanolic extracts of oregano and sage samples was tes... more In this study the antioxidant activity of methanolic extracts of oregano and sage samples was tested. Samples of oregano belonged to Origanum onites and O indercedens species, whilst samples of sage belonged to Salvia officinalis and S fruticosa species. Two methods were used to evaluate the antioxidant activity of sage and oregano extracts: the crocin test and the Rancimat test. The methanolic extracts were also analysed by HPLC for the qualitative/quantitative determination of phenolic compounds. The total phenolic compound content of oregano samples showed no significant differences between the two species, but rosmarinic acid was present in higher amount in O indercedens. Carvacrol content sharply differentiated flowers from leaves. Samples of O indercedens had a higher antioxidant activity evaluated by the crocin test, whereas no differences were evidenced by the Rancimat test. For sage samples, carnosic acid and methyl carnosate showed a significant difference between the two species, with S fruticosa samples having a higher content than S officinalis samples. Samples of S fruticosa also had a higher antioxidant activity evaluated by the crocin test. The antioxidant activities of sage samples were, on average, higher than those of oregano samples. Some samples of sage had a very high antioxidant activity, with induction times more than 10-fold higher than that of lard used as the reference sample.

Die Nahrung, 2001

Herbs and their extracts with antioxidant capacity could be used directly as stabilisers of fat a... more Herbs and their extracts with antioxidant capacity could be used directly as stabilisers of fat and indirectly as feed additives, in order to improve quality and shelf-life of meat and fat-containing food. In this work a sensitive analytical method is proposed for determination of the antioxidant activity measured by photochemiluminescence (PCL) in lard stabilised with extracts of sage (Salvia officinalis L.) or oreganum (Origanum vulgare L.). A prior step of purification of fat samples is required, in order to separate and concentrate the phenolics from lipidic substances. The method was validated by determination of recovery rate and repeatability. In addition fat samples originating from pigs fed with feed additives of Salviae folium or Origani herba were analysed to investigate the supposed antioxidative effects, that could increase the shelf-life of meat products. In contrast with lard mixed with extracts of sage or oregano, back fat samples originating from pigs fed with feed ...

European Journal of Lipid Science and Technology, 2007

ABSTRACT

Chromatographia, 1994

Gas chromatographic, high performance liquid chromatographic and GC-ion trap detector mass spectr... more Gas chromatographic, high performance liquid chromatographic and GC-ion trap detector mass spectrometric analyses of the hydroperoxides formed during thermal peroxidation of cholesteryl acetate, are reported and discussed. The hydroperoxides were separated from the thermal-oxidised mixture by solid-phase extraction, fractionated and individually collected by HPLC. Each hydroperoxide was then chemically reduced with NaBH4 to a hydroxy-derivative. The GC and MS characteristics

Food Chemistry, 2010

For the first time, we report that enological yeasts or yeast cell walls can sorb (À)geosmin, an ... more For the first time, we report that enological yeasts or yeast cell walls can sorb (À)geosmin, an undesirable molecule that causes critical organoleptic defects in wine at low concentrations (around 50 ng l À1 ). The wine is described as ''earthy" or ''mouldy". The influence of various post-harvesting processes on yeast (À)geosmin sorption capacity was studied. The dried yeast biomass obtained by the different processes was analysed by FTIR spectroscopy in ATR mode: structural differences were detected between the samples depending on the strain and the treatment used. Surface proteins and mainly phospholipids from the plasma membrane appeared to induce significantly different signals which may explain the different sorption capacities. The possible involvement of phospholipids in (À)geosmin sorption by yeasts highlights the complexity of this phenomenon.

International Journal of Food Microbiology, 2009

Volatile phenols, such as 4-ethylphenol, are responsible for a "horsey" smell in wine. Thus, the ... more Volatile phenols, such as 4-ethylphenol, are responsible for a "horsey" smell in wine. Thus, the study of volatile phenol sorption in yeasts, and their subsequent elimination from wine, helps to optimize ecofriendly wine curative processes. Here, we compared the influences of spray drying, lyophilization and evaporative drying at low water activity on yeast, for improving the 4-ethylphenol sorption capacity in a synthetic model wine. The changes that occur in the physico-chemical characteristics of the yeast surface (surface hydrophobicity, electron-donor character and zeta potential) during these drying processes were determined to assess if any correlation exists between these factors and the 4-ethylphenol sorption capacities of the cells. Evaporative drying at low water activity, spray drying and lyophilization induced, respectively, 61.5%, 169% and 192% greater 4-ethylphenol sorption than biomass without drying treatment. Surface hydrophobicity of yeasts was also significantly greater, but the zeta potential of yeast cells was significantly lower after the drying processes. This is the first report investigating changes to the physicochemical variables affected during yeast drying. These cell surface modifications were correlated with the 4ethyphenol sorption value measured.

Journal of Agricultural and Food Chemistry, 2010

Despite the potential of sesquiterpene hydrocarbons in olive oil authentication, their metabolism... more Despite the potential of sesquiterpene hydrocarbons in olive oil authentication, their metabolism in Olea europaea is poorly understood, and little is known about their biochemical regulation in olives as a function of ripening. To ascertain some metabolic relationships between sesquiterpene hydrocarbons and olive ripening, the content of sesquiterpene hydrocarbons was assessed in virgin olive oils from two olive varieties grown in the same geographical area and produced at different harvesting periods. During the ripening, the accumulation of sesquiterpenes in the olive itself, and thus in the oil, differed according to their molecular structure: bicyclic sesquiterpenes, showed decreasing concentrations the later the harvest, while acyclic farnesene-like compounds progressively increased through the olive ripening process. This is first evidence that the accumulation of sesquiterpene hydrocarbons in olive, and hence in olive oil, is modulated during ripening. Therefore, the degree of ripening of olives should be taken into consideration when considering the sesquiterpenic profile of virgin olive oil for their authentication.

European Journal of Lipid Science and Technology, 2015

To identify critical points during olive mill pre-processing operations, the effect of the closed... more To identify critical points during olive mill pre-processing operations, the effect of the closed circuit washing stage on olive microbiological contamination, and the influence of the successive short-term storage on olives and virgin olive oil (VOO) quality were evaluated. Microbiological, physical, and chemical parameters were assessed in olives and oils at three mill pre-processing stages: reception, washing, and short-term storage. Olive washing in closed loop systems was shown to be a critical control point at the olive mill due to microbiological cross-contamination and fruit physical damage. Moreover, when the olives were short-term stored before oil extraction, positive VOO sensory attributes decreased by as much as one point of intensity, as justified by the changes observed in phenolic and lipoxygenase derived volatile compounds. These results confirm the high risk of fruit cross-contamination due to the poor hygiene of the water used in olives mills to wash olives, and point out the effect on VOO quality of a common practice such as short term silo storage of olives.

Food Chemistry, 2011

Two analytical procedures were applied, HS-SPME and SDE, coupled to GC–MS to analyse the volatile... more Two analytical procedures were applied, HS-SPME and SDE, coupled to GC–MS to analyse the volatile composition of white salsify. More than 80 of volatile compounds which belonged to distinct chemical families were analysed. SDE led to the identification of mainly high molecular weight sesquiterpenes, acids and esters. Given that SDE involves high temperatures, heat-sensitive compounds may undergo chemical alteration or

Food Control, 2007

Twenty eight mono- (MAHs) and polyaromatic hydrocarbons (PAHs) were simultaneously determined in ... more Twenty eight mono- (MAHs) and polyaromatic hydrocarbons (PAHs) were simultaneously determined in fifty-four virgin olive oils from three successive crops in the same geographical region. MAHs such as: toluene, C2-, C3- and C4-benzenes, and PAHs species containing 2, 3 and 4 aromatic rings were detected and quantified. MAHs were predominant in all of the samples, and had a mean concentration

Journal of Agricultural and Food Chemistry, 2009

Volatile phenols are spoilage compounds of many foods, which have also been detected in the volat... more Volatile phenols are spoilage compounds of many foods, which have also been detected in the volatile fraction of defective virgin olive oils (VOOs). However, their formation in olive fruits or VOOs, as well as the factors affecting their production, has yet to be elucidated. In the present study, the evolution of volatile phenols was monitored for the first time in VOOs obtained from olives stored during different periods under two different conditions of limited aerobiosis. Moreover, their odor activity values (OAVs) in VOO samples were calculated as a first assessment of their sensory importance, and the microbiological profile of the olives' surface was evaluated at each sampling point in order to clarify the possible causes of volatile phenols formation. Although volatile phenols seem to acquire their sensory significance at advanced stages of olives' alteration, they were significantly correlated to the time of olives' storage and in accordance with sensory evaluation, indicating that they could be considered as analytical indices of olive fruits' degradation during storage, likely reflecting the microbiological activity. KEYWORDS: Virgin olive oil; volatile phenols; solid phase microextraction; quality markers; off-flavor; olive fruit degradation; olives' storage

International Journal of Food Microbiology, 2010

Cell surface properties were determined for the first time for lees of Saccharomyces cerevisiae, ... more Cell surface properties were determined for the first time for lees of Saccharomyces cerevisiae, and they proved to be significantly dependent on the time of sparkling wine ageing on lees. Cell surface hydrophobicity decreased from approximately 44% to 11% of affinity to hexadecane. Electron acceptor capacity (calculated as % affinity to ethyl acetate − % affinity to decane) increased from approximately − 27% to 10 % and zeta potential from approximately − 4 to 6 mV. Mannoproteins are released from the external cell wall layer during the autolytic process, as confirmed by TOF-SIMS analysis of the cell wall chemical composition. This could explain the modifications of lees cell surface properties observed during ageing. Lees flocculation capacity, calculated by the Helm's method, decreased during the period of ageing from approximately 88 % to 40%. Stepwise multiple regression analysis indicated that lees surface hydrophobicity was the main determinant of lees flocculation capacity, explaining 70.3% of the variability (p b 0.01), followed by far by the absolute values of zeta potential, accounting for 9.9% of the variability (p b 0.05).

Food Chemistry, 2007

Volatile and semi-volatile compounds of French and American oak wood used in wine and spirits age... more Volatile and semi-volatile compounds of French and American oak wood used in wine and spirits ageing were extracted by an Accelerated Solvent Extractor (ASE) and analysed by gas chromatography-mass spectrometry. More than 90 compounds were isolated, characterised and quantified after being separated on two chromatographic columns with distinct polarity. The main oak wood components were quantitatively determined by using standard reference compounds. In addition, a number of compounds, mainly guaiacol and syringol derivatives, were detected and characterised. In particular, 10 compounds were tentatively identified as lignin dimers derivatives, whose presence in oak wood chips or barrels for wine and spirits ageing had not been previously described. Several of the characterised compounds enabled a distinction to be drawn between medium and high toasted wood chips, independently of their geographical origin.

Journal of Chromatography A, 2006

In the present article, a headspace solid-phase microextraction method coupled to GC/MS was devel... more In the present article, a headspace solid-phase microextraction method coupled to GC/MS was developed and applied for the simultaneous determination of mono-and sesquiterpenic hydrocarbons in virgin olive oils of different olive variety and geographical origin. Analysis of various oils resulted in the simultaneous detection of 15 monoterpenes and 30 sesquiterpenes. Some of these hydrocarbons were previously reported to be constituents of virgin olive oil terpenoid fraction, although we also detected some terpenic hydrocarbons that have not previously been documented as present in virgin olive oil. Significant differences were detected in the proportion of terpenic compounds in oils obtained from different olive varieties grown in different geographical areas. The monoterpene, and particularly the sesquiterpene composition of olive oil may be used to distinguish samples from different cultivar and geographical areas.

Journal of Chromatography A, 2008

Mass spectrometry-based proteomics has become the tool of choice for identifying and quantifying ... more Mass spectrometry-based proteomics has become the tool of choice for identifying and quantifying the proteome of an organism. Though recent years have seen a tremendous improvement in instrument performance and the computational tools used, significant challenges remain, and there are many opportunities for statisticians to make important contributions. In the most widely used "bottom-up" approach to proteomics, complex mixtures of proteins are first subjected to enzymatic cleavage, the resulting peptide products are separated based on chemical or physical properties and analyzed using a mass spectrometer. The two fundamental challenges in the analysis of bottom-up MS-based proteomics are as follows: (1) Identifying the proteins that are present in a sample, and (2) Quantifying the abundance levels of the identified proteins. Both of these challenges require knowledge of the biological and technological context that gives rise to observed data, as well as the application of sound statistical principles for estimation and inference. We present an overview of bottom-up proteomics and outline the key statistical issues that arise in protein identification and quantification.

Analytica Chimica Acta, 2008

In the present study the qualitative and quantitative determination of diterpenoids in commercial... more In the present study the qualitative and quantitative determination of diterpenoids in commercial distilled gin was carried out. This widely consumed juniper-based spirit is aromatized using Juniper (Juniperus communis) berries. Although juniper reportedly contains several diterpenic compounds, no studies have addressed the diterpenic composition of juniper-based spirits or beverages. With this objective, here we followed a multilevel factorial experimental design to optimize a direct immersion-solid phase microextraction (DI-SPME) method coupled to gas chromatography/mass spectrometry and analyzed eight commercial brands of gin. With total concentrations ranging from 10 to 190 microg L(-1), manool, manoyl oxide and trans-totarol were the most abundant diterpenoids of the 10 identified or tentatively identified at variable but not negligible concentrations in the distilled gin samples. The diterpenic composition allowed the brands to be differentiated. This indicates that these compounds contribute to the sensory characteristics of the distinct commercial brands, thus guaranteeing the authenticity and consequently the quality of the product.

Journal of Agricultural and Food Chemistry, 2009

During sparkling wine aging, a narrow interaction is established between wine and lees of second ... more During sparkling wine aging, a narrow interaction is established between wine and lees of second fermentation, which remain in contact during long periods. In order to contribute to the knowledge on this interaction, volatile compounds retained by lees were described in this study. With this aim, solid phase microextraction (SPME) conditions were optimized in order to increase the sensibility for the analysis of volatiles sorbed by lees. This allowed proving the capacity of sparkling wine lees of second fermentation to retain several volatile compounds related with wine aroma: esters, aldehydes, norisoprenoids and terpenes known for their positive flavor impact were found in lees headspace. Most of them were previously described in "Cava" sparkling wine, while some compounds, such as the tentatively identified trimethyl tetrahydronaphthalenes, were not previously identified in yeasts or wine.

Food Chemistry, 2009

The potential significance as odorants and markers of olive fruits degradation has been recently ... more The potential significance as odorants and markers of olive fruits degradation has been recently pointed out for volatile phenols in virgin olive oil (VOO) and related to the appearance of VOO sensory defects. The few studies carried out in order to elucidate the factors affecting their formation in olive fruits or VOOs, indicated that they could be considered as analytical indices of olive fruits degradation during storage, likely reflecting the microbiological activity. In the present study, the effect of the olive variety ('Arbequina', 'Arbosana' and 'Leccino') on the production of volatile phenols during twelve days of storage in closed plastic bags was evaluated. The different resistance of each variety to the microbiological attach was observed during olive fruit storage, and it was reflected by the evolution of guaiacol, 4-ethylphenol and 4-ethylguaiacol, and related to free acidity values. On the contrary, a scarce dependence on the microbial growth or varietal factors was observed for 4-vinyl derivatives, which appeared more directly related to the time of olives storage. The evolution of volatile phenols found certain correspondence in the sensory characteristics of the resulting VOOs, while the rest of VOO chemical quality indices did not show major variations during fruits storage.

International Journal of Food Microbiology, 2010

Given the importance of the interactions between wine and lees cell surface during sparkling wine... more Given the importance of the interactions between wine and lees cell surface during sparkling wine aging, and in view of recent results proving the antioxidant potential of yeast cell wall biomolecules, the antioxidant capacity of lees cell surface was investigated to establish its possible role in the antioxidative effect of lees. The surface antioxidant activity of lees from wines with different aging periods was determined on the whole cell by two widely used methods (DPPH and FRAP assays), obtaining maximum values of 24.5 μmol Trolox/g cells (fresh weight) by the DPPH assay, and 21.3 μmol Trolox/g cells (fresh weight) by the FRAP assay. Lees surface antioxidant activity was influenced by base wine characteristics and inversely related to sur lie aging period. Conversely, the percentage depletion of lees surface antioxidant activity during aging was mainly determined by the length of aging, regardless of wine characteristics. To examine the influence of cell wall thiol groups and adsorbed polyphenols on lees' protective effect, their presence on cell surfaces was assessed. They accounted for 25 ± 11% and 54 ± 7% of the antioxidant activity measured by DPPH, respectively, and 0.3 ± 0.1% and 39 ± 8% measured by FRAP, respectively. Only a part of the remnant antioxidant activity of lees surface measured by FRAP could be theoretically explained by the presence of cell wall mannans.

Journal of the Science of Food and Agriculture, 2002

In this study the antioxidant activity of methanolic extracts of oregano and sage samples was tes... more In this study the antioxidant activity of methanolic extracts of oregano and sage samples was tested. Samples of oregano belonged to Origanum onites and O indercedens species, whilst samples of sage belonged to Salvia officinalis and S fruticosa species. Two methods were used to evaluate the antioxidant activity of sage and oregano extracts: the crocin test and the Rancimat test. The methanolic extracts were also analysed by HPLC for the qualitative/quantitative determination of phenolic compounds. The total phenolic compound content of oregano samples showed no significant differences between the two species, but rosmarinic acid was present in higher amount in O indercedens. Carvacrol content sharply differentiated flowers from leaves. Samples of O indercedens had a higher antioxidant activity evaluated by the crocin test, whereas no differences were evidenced by the Rancimat test. For sage samples, carnosic acid and methyl carnosate showed a significant difference between the two species, with S fruticosa samples having a higher content than S officinalis samples. Samples of S fruticosa also had a higher antioxidant activity evaluated by the crocin test. The antioxidant activities of sage samples were, on average, higher than those of oregano samples. Some samples of sage had a very high antioxidant activity, with induction times more than 10-fold higher than that of lard used as the reference sample.

Die Nahrung, 2001

Herbs and their extracts with antioxidant capacity could be used directly as stabilisers of fat a... more Herbs and their extracts with antioxidant capacity could be used directly as stabilisers of fat and indirectly as feed additives, in order to improve quality and shelf-life of meat and fat-containing food. In this work a sensitive analytical method is proposed for determination of the antioxidant activity measured by photochemiluminescence (PCL) in lard stabilised with extracts of sage (Salvia officinalis L.) or oreganum (Origanum vulgare L.). A prior step of purification of fat samples is required, in order to separate and concentrate the phenolics from lipidic substances. The method was validated by determination of recovery rate and repeatability. In addition fat samples originating from pigs fed with feed additives of Salviae folium or Origani herba were analysed to investigate the supposed antioxidative effects, that could increase the shelf-life of meat products. In contrast with lard mixed with extracts of sage or oregano, back fat samples originating from pigs fed with feed ...

European Journal of Lipid Science and Technology, 2007

ABSTRACT

Chromatographia, 1994

Gas chromatographic, high performance liquid chromatographic and GC-ion trap detector mass spectr... more Gas chromatographic, high performance liquid chromatographic and GC-ion trap detector mass spectrometric analyses of the hydroperoxides formed during thermal peroxidation of cholesteryl acetate, are reported and discussed. The hydroperoxides were separated from the thermal-oxidised mixture by solid-phase extraction, fractionated and individually collected by HPLC. Each hydroperoxide was then chemically reduced with NaBH4 to a hydroxy-derivative. The GC and MS characteristics

Food Chemistry, 2010

For the first time, we report that enological yeasts or yeast cell walls can sorb (À)geosmin, an ... more For the first time, we report that enological yeasts or yeast cell walls can sorb (À)geosmin, an undesirable molecule that causes critical organoleptic defects in wine at low concentrations (around 50 ng l À1 ). The wine is described as ''earthy" or ''mouldy". The influence of various post-harvesting processes on yeast (À)geosmin sorption capacity was studied. The dried yeast biomass obtained by the different processes was analysed by FTIR spectroscopy in ATR mode: structural differences were detected between the samples depending on the strain and the treatment used. Surface proteins and mainly phospholipids from the plasma membrane appeared to induce significantly different signals which may explain the different sorption capacities. The possible involvement of phospholipids in (À)geosmin sorption by yeasts highlights the complexity of this phenomenon.

International Journal of Food Microbiology, 2009

Volatile phenols, such as 4-ethylphenol, are responsible for a "horsey" smell in wine. Thus, the ... more Volatile phenols, such as 4-ethylphenol, are responsible for a "horsey" smell in wine. Thus, the study of volatile phenol sorption in yeasts, and their subsequent elimination from wine, helps to optimize ecofriendly wine curative processes. Here, we compared the influences of spray drying, lyophilization and evaporative drying at low water activity on yeast, for improving the 4-ethylphenol sorption capacity in a synthetic model wine. The changes that occur in the physico-chemical characteristics of the yeast surface (surface hydrophobicity, electron-donor character and zeta potential) during these drying processes were determined to assess if any correlation exists between these factors and the 4-ethylphenol sorption capacities of the cells. Evaporative drying at low water activity, spray drying and lyophilization induced, respectively, 61.5%, 169% and 192% greater 4-ethylphenol sorption than biomass without drying treatment. Surface hydrophobicity of yeasts was also significantly greater, but the zeta potential of yeast cells was significantly lower after the drying processes. This is the first report investigating changes to the physicochemical variables affected during yeast drying. These cell surface modifications were correlated with the 4ethyphenol sorption value measured.

Journal of Agricultural and Food Chemistry, 2010

Despite the potential of sesquiterpene hydrocarbons in olive oil authentication, their metabolism... more Despite the potential of sesquiterpene hydrocarbons in olive oil authentication, their metabolism in Olea europaea is poorly understood, and little is known about their biochemical regulation in olives as a function of ripening. To ascertain some metabolic relationships between sesquiterpene hydrocarbons and olive ripening, the content of sesquiterpene hydrocarbons was assessed in virgin olive oils from two olive varieties grown in the same geographical area and produced at different harvesting periods. During the ripening, the accumulation of sesquiterpenes in the olive itself, and thus in the oil, differed according to their molecular structure: bicyclic sesquiterpenes, showed decreasing concentrations the later the harvest, while acyclic farnesene-like compounds progressively increased through the olive ripening process. This is first evidence that the accumulation of sesquiterpene hydrocarbons in olive, and hence in olive oil, is modulated during ripening. Therefore, the degree of ripening of olives should be taken into consideration when considering the sesquiterpenic profile of virgin olive oil for their authentication.

European Journal of Lipid Science and Technology, 2015

To identify critical points during olive mill pre-processing operations, the effect of the closed... more To identify critical points during olive mill pre-processing operations, the effect of the closed circuit washing stage on olive microbiological contamination, and the influence of the successive short-term storage on olives and virgin olive oil (VOO) quality were evaluated. Microbiological, physical, and chemical parameters were assessed in olives and oils at three mill pre-processing stages: reception, washing, and short-term storage. Olive washing in closed loop systems was shown to be a critical control point at the olive mill due to microbiological cross-contamination and fruit physical damage. Moreover, when the olives were short-term stored before oil extraction, positive VOO sensory attributes decreased by as much as one point of intensity, as justified by the changes observed in phenolic and lipoxygenase derived volatile compounds. These results confirm the high risk of fruit cross-contamination due to the poor hygiene of the water used in olives mills to wash olives, and point out the effect on VOO quality of a common practice such as short term silo storage of olives.

Food Chemistry, 2011

Two analytical procedures were applied, HS-SPME and SDE, coupled to GC–MS to analyse the volatile... more Two analytical procedures were applied, HS-SPME and SDE, coupled to GC–MS to analyse the volatile composition of white salsify. More than 80 of volatile compounds which belonged to distinct chemical families were analysed. SDE led to the identification of mainly high molecular weight sesquiterpenes, acids and esters. Given that SDE involves high temperatures, heat-sensitive compounds may undergo chemical alteration or

Food Control, 2007

Twenty eight mono- (MAHs) and polyaromatic hydrocarbons (PAHs) were simultaneously determined in ... more Twenty eight mono- (MAHs) and polyaromatic hydrocarbons (PAHs) were simultaneously determined in fifty-four virgin olive oils from three successive crops in the same geographical region. MAHs such as: toluene, C2-, C3- and C4-benzenes, and PAHs species containing 2, 3 and 4 aromatic rings were detected and quantified. MAHs were predominant in all of the samples, and had a mean concentration

Journal of Agricultural and Food Chemistry, 2009

Volatile phenols are spoilage compounds of many foods, which have also been detected in the volat... more Volatile phenols are spoilage compounds of many foods, which have also been detected in the volatile fraction of defective virgin olive oils (VOOs). However, their formation in olive fruits or VOOs, as well as the factors affecting their production, has yet to be elucidated. In the present study, the evolution of volatile phenols was monitored for the first time in VOOs obtained from olives stored during different periods under two different conditions of limited aerobiosis. Moreover, their odor activity values (OAVs) in VOO samples were calculated as a first assessment of their sensory importance, and the microbiological profile of the olives' surface was evaluated at each sampling point in order to clarify the possible causes of volatile phenols formation. Although volatile phenols seem to acquire their sensory significance at advanced stages of olives' alteration, they were significantly correlated to the time of olives' storage and in accordance with sensory evaluation, indicating that they could be considered as analytical indices of olive fruits' degradation during storage, likely reflecting the microbiological activity. KEYWORDS: Virgin olive oil; volatile phenols; solid phase microextraction; quality markers; off-flavor; olive fruit degradation; olives' storage

International Journal of Food Microbiology, 2010

Cell surface properties were determined for the first time for lees of Saccharomyces cerevisiae, ... more Cell surface properties were determined for the first time for lees of Saccharomyces cerevisiae, and they proved to be significantly dependent on the time of sparkling wine ageing on lees. Cell surface hydrophobicity decreased from approximately 44% to 11% of affinity to hexadecane. Electron acceptor capacity (calculated as % affinity to ethyl acetate − % affinity to decane) increased from approximately − 27% to 10 % and zeta potential from approximately − 4 to 6 mV. Mannoproteins are released from the external cell wall layer during the autolytic process, as confirmed by TOF-SIMS analysis of the cell wall chemical composition. This could explain the modifications of lees cell surface properties observed during ageing. Lees flocculation capacity, calculated by the Helm's method, decreased during the period of ageing from approximately 88 % to 40%. Stepwise multiple regression analysis indicated that lees surface hydrophobicity was the main determinant of lees flocculation capacity, explaining 70.3% of the variability (p b 0.01), followed by far by the absolute values of zeta potential, accounting for 9.9% of the variability (p b 0.05).

Food Chemistry, 2007

Volatile and semi-volatile compounds of French and American oak wood used in wine and spirits age... more Volatile and semi-volatile compounds of French and American oak wood used in wine and spirits ageing were extracted by an Accelerated Solvent Extractor (ASE) and analysed by gas chromatography-mass spectrometry. More than 90 compounds were isolated, characterised and quantified after being separated on two chromatographic columns with distinct polarity. The main oak wood components were quantitatively determined by using standard reference compounds. In addition, a number of compounds, mainly guaiacol and syringol derivatives, were detected and characterised. In particular, 10 compounds were tentatively identified as lignin dimers derivatives, whose presence in oak wood chips or barrels for wine and spirits ageing had not been previously described. Several of the characterised compounds enabled a distinction to be drawn between medium and high toasted wood chips, independently of their geographical origin.

Journal of Chromatography A, 2006

In the present article, a headspace solid-phase microextraction method coupled to GC/MS was devel... more In the present article, a headspace solid-phase microextraction method coupled to GC/MS was developed and applied for the simultaneous determination of mono-and sesquiterpenic hydrocarbons in virgin olive oils of different olive variety and geographical origin. Analysis of various oils resulted in the simultaneous detection of 15 monoterpenes and 30 sesquiterpenes. Some of these hydrocarbons were previously reported to be constituents of virgin olive oil terpenoid fraction, although we also detected some terpenic hydrocarbons that have not previously been documented as present in virgin olive oil. Significant differences were detected in the proportion of terpenic compounds in oils obtained from different olive varieties grown in different geographical areas. The monoterpene, and particularly the sesquiterpene composition of olive oil may be used to distinguish samples from different cultivar and geographical areas.

Journal of Chromatography A, 2008

Mass spectrometry-based proteomics has become the tool of choice for identifying and quantifying ... more Mass spectrometry-based proteomics has become the tool of choice for identifying and quantifying the proteome of an organism. Though recent years have seen a tremendous improvement in instrument performance and the computational tools used, significant challenges remain, and there are many opportunities for statisticians to make important contributions. In the most widely used "bottom-up" approach to proteomics, complex mixtures of proteins are first subjected to enzymatic cleavage, the resulting peptide products are separated based on chemical or physical properties and analyzed using a mass spectrometer. The two fundamental challenges in the analysis of bottom-up MS-based proteomics are as follows: (1) Identifying the proteins that are present in a sample, and (2) Quantifying the abundance levels of the identified proteins. Both of these challenges require knowledge of the biological and technological context that gives rise to observed data, as well as the application of sound statistical principles for estimation and inference. We present an overview of bottom-up proteomics and outline the key statistical issues that arise in protein identification and quantification.

Analytica Chimica Acta, 2008

In the present study the qualitative and quantitative determination of diterpenoids in commercial... more In the present study the qualitative and quantitative determination of diterpenoids in commercial distilled gin was carried out. This widely consumed juniper-based spirit is aromatized using Juniper (Juniperus communis) berries. Although juniper reportedly contains several diterpenic compounds, no studies have addressed the diterpenic composition of juniper-based spirits or beverages. With this objective, here we followed a multilevel factorial experimental design to optimize a direct immersion-solid phase microextraction (DI-SPME) method coupled to gas chromatography/mass spectrometry and analyzed eight commercial brands of gin. With total concentrations ranging from 10 to 190 microg L(-1), manool, manoyl oxide and trans-totarol were the most abundant diterpenoids of the 10 identified or tentatively identified at variable but not negligible concentrations in the distilled gin samples. The diterpenic composition allowed the brands to be differentiated. This indicates that these compounds contribute to the sensory characteristics of the distinct commercial brands, thus guaranteeing the authenticity and consequently the quality of the product.

Journal of Agricultural and Food Chemistry, 2009

During sparkling wine aging, a narrow interaction is established between wine and lees of second ... more During sparkling wine aging, a narrow interaction is established between wine and lees of second fermentation, which remain in contact during long periods. In order to contribute to the knowledge on this interaction, volatile compounds retained by lees were described in this study. With this aim, solid phase microextraction (SPME) conditions were optimized in order to increase the sensibility for the analysis of volatiles sorbed by lees. This allowed proving the capacity of sparkling wine lees of second fermentation to retain several volatile compounds related with wine aroma: esters, aldehydes, norisoprenoids and terpenes known for their positive flavor impact were found in lees headspace. Most of them were previously described in "Cava" sparkling wine, while some compounds, such as the tentatively identified trimethyl tetrahydronaphthalenes, were not previously identified in yeasts or wine.