| Abstract | Sorata vinove loze ima jako puno, a njihove različite karakteristike, kojima doprinose sekundarni metaboliti, značajne su za specifične vinogradarske regije i države. Među najvažnije sekundarne metabolite spadaju polifenolni i hlapljivi organski spojevi, koji imaju značajan utjecaj na kvalitetu grožđa i vina. Germplazma vinove loze je raznovrsna i uključuje velik broj sorata, koje su klasificirane u različite geografske grupe. Razvojem genetičkih metoda, ova klasifikacija je potvrđena i sorte su podijeljene u genetičko-geografske (GEN-GEO) grupe. Prije analize hlapljivih organskih spojeva u grožđu, bilo je potrebno provesti optimiranje metode njihove mikroekstrakcije na čvrstoj fazi u izvedbi klina (SPME-Arrow). Stoga su ciljevi ovoga rada bili optimirati metodu ekstrakcije i analize hlapljivih organskih spojeva u grožđu i primijeniti je u analizi navedenih spojeva te provesti analizu sadržaja i sastava polifenola u grožđu sorata različitih GEN-GEO grupa. Nadalje, cilj je utvrditi razlike i pojedine spojeve koji doprinose razlikama među GEN-GEO grupa sorata.
U istraživanje je uključeno 50 sorata iz tri različite GEN-GEO grupe, to jest iz pet zemalja. GEN-GEO grupe su C2 (sorte iz Francuske i Italije), C7 (sorte iz Hrvatske) i C8 (sorte iz Španjolske i Portugala), čiji je sastav i sadržaj polifenolnih i hlapljivih organskih spojeva analiziran. Polifenolni spojevi analizirani su prema HPLC-metodi. U procesu optimiranja pokusi su generirani Box-Behnkenovim eksperimentalnim dizajnom (BBD). Promatrani uvjeti ekstrakcije su temperatura ekstrakcije, vrijeme inkubacije, vrijeme izlaganja i vrijeme desorpcije. Hlapljivi organski spojevi analizirani su prema optimiranoj metodi. Koristeći diskriminantnu analizu utvrđene su razlike među GEN-GEO grupama i izdvojeni pojedinačni spojevi koji najviše doprinose diskriminaciji. Utvrđeno je da su u postupku optimiranja ekstrakcije hlapljivih organskih spojeva najznačajniji faktori temperatura ekstrakcije i vrijeme izlaganja. Povećanje vrijednosti ova dva faktora pozitivno je utjecalo na učinkovitost ekstrakcije gotovo svih skupina hlapljivih spojeva. Što se tiče sekundarnih metabolita, najzastupljenije skupine polifenolnih spojeva su bili antocijani, flavan-3-oli i flavonoli, dok su aldehidi i alkoholi bili najzastupljenije skupine hlapljivih spojeva. Diskriminantna analiza jasno je razdvojila GEN-GEO grupe na temelju sastava i sadržaja sekundarnih metabolita. Pojedinačni spojevi iz obje skupine koji doprinose razlikama među grupama nađeni su u relativno niskim količinama. Može se zaključiti i kako diskriminaciji različitih GEN-GEO grupa više doprinose razlike u sadržaju većeg broja istraživanih polifenolnih i hlapljivih organskih spojeva, a manje razlike u sastavu spojeva unutar skupina sekundarnih metabolita. |
| Abstract (english) | Relevant aspect of wine geographic origin is related to grapevine varieties used in specific
wine country or region, and their secondary metabolites. Polyphenolic compounds, besides
being important contributor to wine quality, are becoming more important as compounds
having beneficial influence on human health. Volatile organic compounds have an important
role in winemaking industry due to their contribution to wine sensory characteristics. The
content and composition of secondary metabolites are influenced by many factors, among
which is grape variety. The grapevine germplasm is highly variable and classified into
geographic groups. These classifications were recently confirmed using genetic studies, and
further classified varieties into genetic-geographic (GEN-GEO) groups. Thus, the aims of the
research were to optimise the extraction method and analysis of free and bound volatile
organic compounds from grapes by applying it in the analysis of mentioned compounds and
to analyse polyphenolic profiles of grapevine varieties from different GEN-GEO groups.
Furthermore, the aim was to determine the differences and single compounds that contribute
to the differentiation of GEN-GEO groups.
Before analysing volatile organic compounds, it was necessary to optimise solid-phase
microextraction (SPME)-Arrow conditions. SPME-Arrow is a new extraction technique recently
employed in the analysis of volatiles in food matrices. Regarding grape and wine volatiles the
published work is scarce. Thus, the aim was to develop and validate SPME-Arrow extraction
technique coupled with GC/MS instrument. To optimise SPME-Arrow extraction conditions,
Box-Behnken experimental design and response surface methodology were used. Extraction
conditions that were optimised were extraction temperature, incubation time, exposure time,
and desorption time. Analysed volatile organic compounds were free forms directly from grape
skins, and bound forms released from grape skins after acid hydrolysis. Before starting the
optimization process, some preliminary experiments using one-factor-at-the-time methodology
were necessary for determination of sample weight, injection mode, and SPME-Arrow coating.
These parameters have an important influence on the extraction efficiency, and the best results
gave 100 mg sample weight, splitless injection mode, and DVB/CWR/PDMS fibre. After
performing the experiments generated by experimental design, the results showed that the
most significant factors were extraction temperature and exposure time for both free and bound
volatiles. For both factors, an increase in their values positively affected the extraction
efficiency for almost all classes of volatile compounds. For free volatile compound the optimum
extraction conditions are: extraction temperature 60°C, incubation time 20 min, exposure time
49 min, and desorption time 7 min. The optimum conditions for bound volatile compounds are:
extraction temperature 60°C, incubation time 20 min, exposure time 60 min, and desorption
time 7 min.
After optimization process, the polyphenolic and volatile organic compounds were analysed in
50 grapevine varieties from three GEN-GEO groups, that is from five countries. Groups
included in this research are C2 (varieties from Italy and France), C7 (varieties from Croatia),
and C8 (varieties from Spain and Portugal). The polyphenolic compounds were analysed by
HPLC, while volatile organic compounds were analysed using the optimised SPME-Arrow
method. Discriminant analysis was used to determine the differences between groups and to
define the contribution of individual compounds in the discrimination.
Polyphenolic compounds analysed belonged to the classes of anthocyanins, flavan-3-ols,
flavonols, phenolic acids, and stilbenes, while volatile compounds belonged to the classes of
aldehydes, ketones, acids, alcohols, monoterpenes, sesquiterpenes, esters. Among these
classes the most abundant for polyphenols were anthocyanins, flavan-3-ols, and flavonols,
while the most abundant volatiles belonged to aldehydes and alcohols. The polyphenolic and
volatile profiles differed among grapevine varieties, as well as GEN-GEO groups. The
discriminant analysis clearly separated groups based on their polyphenolic and volatile
profiles, with all classes of compounds contributing to the discrimination. Some of the
compounds contributing to the differentiation of groups were found in relatively small
quantities. It can be concluded that discrimination of different GEN-GEO groups is more
influenced by the differences in the content of numerous analysed polyphenolic and volatile
organic compounds, and less influenced by the composition of compounds within the classes
of secondary metabolites. |
