1,721,105 research outputs found
Chemical and sensory characterization of DOCG wines from Marche region (Italy)
Full text linkThe present thesis work has been divided into two main chapters. The objective of the first
and principal project was to perform the chemical and sensorial characterization of the five DOCG
wines produced in Marche region, with the aim to valorise a product of excellence that is
worldwide exported and appreciated.
The chemical characterization has been performed by taking into account the fundamental
classes of compounds able to contribute to the organoleptic characteristics of wines, being volatile
and phenolic substances, minerals and organic acids. This has been carried out to try to identify
those molecules which could be used as markers to assess Marche region DOCG wines
authenticity.
The sensorial analysis of wine samples has been performed with the aim to describe their
organoleptic features and to find the possible correlation with the chemical fingerprint
discriminating one DOCG over the other and thus, further valorising a product of excellence of
Marche region. This was carried out by taking into consideration also the DOCGs subgroups.
Indeed, for “Offida” DOCG, “Pecorino”, “Passerina” and “Rosso” have been considered and, in
the same way, for “Vernaccia di Serrapetrona” DOCG the two typologies “sweet” and “dry” were
included.
Furthermore, in order to obtain a sampling that was more representative of the wine market
in the region, 18 wine samples (2-3 for every DOCG) were collected considering the wineries with
higher sales.
The analysis of the volatile substances was performed due to their importance in defining
wine aroma. This was carried out by using a new developed solid-phase microextraction method
coupled to gas chromatography-mass spectrometry (SPME-GC-MS) analysis. Extraction by
SPME includes two steps: a direct immersion followed by head space with the use of an
overcoated-fiber. By the analysis of the 18 wine samples, it was possible to detect and identify 50
volatile compounds and, in order to better investigate the results, they were divided into six
different groups, according to the chemical class (ethyl esters, other esters, alcohols, acids,
terpenes and others). The predominant classes of compounds were ethyl esters, followed by
alcohols, even if the composition was quite variable among DOCGs. Moreover, the analyses
underlined the presence of compounds which were associated to characteristics scents of the
samples investigated, or which could be possibly used as authenticity markers for DOCG wines
investigated. For example, the high presence of ethyl esters in “Verdicchio di Matelica” was able
to explain the yellow pulp fruity aroma perceived by the panel during the sensorial analysis. The analysis of short and medium chain free fatty acids was performed by using a new
developed and validated liquid-liquid extraction procedure followed by gas chromatography
coupled to flame ionization detection (LLE-GC-FID) analysis. This class of compounds is of huge
importance when considering the wine quality and the method permitted the quantification of
acetic, propionic, isobutyric, isovaleric, hexanoic and octanoic acids. The main differences raised
between the composition of white and red wines, the first being more enriched in hexanoic and
octanoic acid, while the latter in acetic, propionic, isobutyric and isovaleric acids. For every
analyte, the AOV (active olfactory value) was also calculated to assess the compounds that may
play an active role in the aroma of the samples investigated. Interestingly, for every analyte (with
except for propionic acid) AOV values >1 were obtained, meaning that these analytes may actually
take part to the overall aroma of DOCG wines.
Concerning the phenolic profile, it was assessed by performing high performance liquid
chromatography coupled to tandem mass-spectrometry (HPLC-MS/MS) analyses and a total of 37
compounds were detected and quantified. As expected, red wines were much more enriched in
polyphenols when compared to white DOCG wines. The different statistical approaches evidenced
the presence of some peculiarities able to discriminate wines made with same grape variety, or
wines produced in close geographical areas. As an example, “Offida Rosso” and “Cònero” which
are produced with a minimal amount of 85 % of Montepulciano grape variety showed a similar
polyphenolic profile. At the same time, “Offida Rosso” showed the highest concentration of
vanillic acid, which makes this compound a possible authenticity marker of this wine typology.
When considering minerals, among the 40 elements quantified by inductively coupled
plasma-mass spectrometry (ICP-MS) analysis, five were selected, being considered the ones not
consistently altered by oenological practises (and thus, more linked to the soil composition of
origin). These elements were Sr, B, Ba, Li and Mn, but, when performing different statistical
approaches, a clear discrimination did not raise between wines produced in different part of the
region, which can be due to the relatively small production geographical area.
Regarding organic acids, six compounds were identified by HPLC coupled with diode
array detector (HPLC-DAD) analysis with an analytical method which is currently under
optimization. In particular, tartaric, isocitric, shikimic, lactic, succinic, citric and malic acids were
identified and quantified. The statistical analyses of samples underlined a difference in the
concentrations of acids when comparing white and red DOCGs. White wines were generally
enriched in tartaric and isocitric acid, with the first being the main responsible of wine acid taste.
As expected, red wines showed higher concentrations of lactic and malic acids, but also of succinic
acid. Shikimic acid, which is considered to be able to discriminate grape varieties, showed characteristic concentrations. At the same time, every DOCG was characterized by a peculiar
organic acid profile, which should be better investigated to confirm its usefulness to assess their
authenticity.
Finally, through the sensorial analysis it was possible to point out features able to
characterize the 5 DOCGs with distinctive organoleptic profiles. Indeed, for example, “Verdicchio
di Matelica Riserva” and “Castelli di Jesi Verdicchio” were described by the typical anise aroma
and were the samples more enriched in methyl salycilate, which is a compound able to give the
particular note. Also, some differences raised between the two “Offida” white wines (“Pecorino”
and “Passerina”), which were described by different scents. Also differences between red wines
raised, being the “Cònero” and “Offida Rosso” described by diverse aspect and scents. Finally,
“Vernaccia di Serrapetrona” wines were the ones more described by tertiary aromas, such as
cinnamon scents.
In this project, both the chemical fingerprint and the sensorial analysis were able to
underline substantial differences between the five DOCG wines produced in the region and, by
further confirmations, their chemical fingerprints could be used in the future to assess their
authenticity. In order to do that, further developments should be performed, by considering both
more wineries and different vintages. Also, the sensorial analysis should be performed by
following quantitative methods. Indeed, by selecting a panel of judges and by training the panel to
describe the sensory characteristics of the DOCG wines investigated, a more reliable correlation
could be performed able to fully characterize the sensorial and chemical profile of these wines of
excellence.
The second part of the thesis regards the project that was carried out during the period
January-June 2022, in the Laboratorio de Análisis Aroma y Enología (LAAE) at the University of
Saragozza (Spain).
The study was focused on the optimization of a solid-phase extraction (SPE) procedure in
order to concentrate and isolate five polyfunctional mercaptans from wine. These compounds are
known to play essential roles in the organoleptic characteristics of wines. In particular, in this
study, the five mercaptans considered were 4-mercapton-4-methyl-2-pentanone, furfurylthiol,
benzyl mercaptan, 3-mercaptohexanol and 3-mercapto hexyl acetate, which are known to be
amongst the most abundant in wine. The SPE procedure has been optimized by taking into
consideration all the steps involved (loading of the sample, cleaning, washing and final elution)
and by also exploiting the CuCl salt to form strong Cu(I)-S complexes that were found to be
essential for the retention of mercaptans in the sorbent phase. Finally, an SPE procedure was optimized which enabled to obtain very pure extract. The conditions for the final extract analysis
are still under optimization through stir bar sorptive extraction (SBSE) coupled to a thermal
desorption system (TC-GC-GC-MS) aimed to lower the sensitivity of the method and to proceed
with the subsequent validation
Impoverimento in acidi grassi poliinsaturi OMEGA 6 di substrati lipidici vegetali.
No full text3° Convegno nazionale Acidi grassi OMEGA 3 e antiossidanti. Ancon
Metodiche innovative
No full textLa qualità di un prodotto alimentare, ottenuto con qualsiasi processo tecnologico, dipende non solo dalla materia prima utilizzata ma anche del sistema tecnologico impiegato (Figura 1). Infatti se è impossibile ottenere un prodotto di qualità da materie prime o semi lavorati scadenti è possibile invece il contrario, ovvero, ottenere un prodotto scadente da materie prime o semi lavorati di qualità.
Trascurando in questo contesto la qualità nutrizionale e la sicurezza igienico-sanitaria, la qualità di un prodotto alimentare è data dalla sommatoria di fattori concreti che costituiscono l’alimento e che possono essere definiti in base ad una scala o a dei parametri precostituiti. Attualmente il sostantivo “qualità” viene usato in senso magico evocativo e spesso viene confuso con un altro sostantivo, la ¬“genuinità”. A tal proposito si rende necessario ribadire che i due sostantivi non sono sinonimi per cui i parametri atti a definire la qualità non possono essere confusi con quelli che definiscono la genuinità o la naturalità di un prodotto alimentare.
La qualità dell'olio di oliva è attualmente delineata da quattro parametri: l'acidità, il numero di perossidi, le misure spettrofotometriche e le caratteristiche organolettiche (Figura 2) .
Mentre l'acidità, il numero di perossidi e le misure spettrofotometriche sono legati a trasformazioni chimiche subite dall'olio (Figura 3) e quindi determinabili chimicamente in maniera univoca, le caratteristiche organolettiche dipendono dalla composizione chimica del frutto "in toto" e la loro rilevazione con analisi chimiche strumentali costituisce un problema ancora oggi non risolto. Diversamente tutti gli altri parametri previsti dal Regolamento CEE n. 1513/01 si riferiscono alla genuinità e quindi alla naturalità del prodotto.
Pur non sottovalutando l'importanza pratica di questi parametri di qualità, si deve ricordare, alla luce delle più recenti acquisizioni della chimica delle sostanze grasse, che essi non sono sufficienti a caratterizzare l'olio di oliva.
Il forte sviluppo delle tecniche analitiche strumentali,¬ avvenuto negli ultimi anni, ha consentito di individuare nuovi parametri analitici mirati a tutelare sempre di più gli¬ oli di pregio, scoraggiando le eventuali frodi.
I presupposti fondamentali da tenere presenti nello sviluppo di nuovi percorsi analitici sono : efficacia del risultato, brevi tempi di analisi, minime operazioni di manipolazione del campione.
Nello stesso tempo il metodo analitico deve rispettare i seguenti canoni (Figura 4): precisione, riproducibilità, ripetibilità, scarsa manipolazione, velocità, basso costo e basso rischio ambientale [1]. Nella maggior parte dei casi queste caratteristiche non sono pienamente soddisfatte.
In questa ottica vengono proposte sviluppate metodiche analitiche che possono essere affiancate a quelle cosiddette “classiche” per la caratterizzazione dell’olio di oliva come ad esempio l’analisi dei diacilgliceroli, dell’intera frazione dell’insaponificabile, degli alcanoli, dei fosfolipidi e della calorimetria differenzial
Impoverishment in omega-6 polyunsaturated fatty acids of vegetable fats/Impoverimento in acidi grassi polinsaturi omega6 di substrati lipidici vegetali
No full textThe goal of this PhD thesis study is to obtain a vegetable substrate rich of omega-3 polyunsaaturated fatty acid and poor in omega-6 fatty acid. After encapsulation, this substrate, could become a dietary supplement for subjects affected by cystic fibrosis, coronary heart diseqase and Alzheimer's disease
Chromatographic and detection techniques for the characterization of the molecular species in polar lipids
No full textCharacterization of the unsaponifiable matter of coffee by means of GC/MS[Determinazione del profilo compositivo della frazione insaponificabile del caffè mediante GC/MS]
No full textThe lipid fraction of green and roasted coffee beans can be considered as a fingerprint in order to characterize coffee varieties. In particular, the analysis of the unsaponifiable fraction plays a key role to characterize different varieties of green coffee and different commercial blends. Moreover, during the roasting process several components disappear while others are generated; the roasting temperature and time, as well as the blend characteristics can affect the unsaponifiable profile. The aim of this work was the study of the unsaponifiable fraction of green and roasted coffee obtained using two different roasting temperatures. Eight samples of green coffee, four arabica and four robusta coffee beans and their roasted derivatives obtained at different roasting temperatures, and four different coffee blends were studied. The analysis of the unsaponifiable fraction was performed with GC/FID (Gas chromatography/Flame ionization detection) and GC/MS (Gaschromatography/Mass spectrometry). The unsaponifiable lipid fractions of green, arabica and robusta coffee was characterised by the presence of several diterpenes such as kahweol, cafestol, 16-O-methylkahweol, and 16-O-methylcafestol. gamma-Tocopherol, cholesterol, campesterol, 24-methylencholesterol, stigmasterol, beta-sitosterol and cicloartenol were also identified. The roasting process generated the dehydrated kahweol, and cafestol derived products. In arabica coffee a neoformation diterpene called diterpene E was identified
- …
