| Abstract | Sastav vina predmet je brojnih istraživanja, ponajviše zbog utjecaja fenolnih i aromatskih spojeva na senzorna svojstva vina čiju je koncentraciju moguće znatno modificirati primjenom različitih vinifikacijskih tehnologija. Međutim, uz utjecaj na kvalitativna svojstva vina, a s obzirom na suvremene trendove istraživanja vina koja se temelje na proučavanju bioaktivnih spojeva koji blagotvorno djeluju na ljudsko zdravlje cilj ovog istraživanja bio je i pridonijeti spoznaji o vrijednosti autohtone sorte ‘Teran’ koja je nedovoljno istražena u tom smislu. S obzirom da su bioaktivni spojevi često prisutni u vrlo niskim koncentracijama, pojavio se interes za pronalaskom tehnologija koje će povećati njihovu ekstrakciju, ali u isto vrijeme i pozitivno utjecati na aromatski profil vina te očuvati ili čak poboljšati ključne parametre senzorne kvalitete vina. Stoga je glavni cilj ovog istraživanja bio ispitati utjecaj različitih vinifikacijskih tehnologija na kemijski sastav, senzorna svojstva vina i koncentraciju bioaktivnih spojeva u vinima sorte ‘Teran’ (Vitis vinifera L.) kroz identifikaciju i kvantifikaciju fenolnih spojeva, hlapljivih spojeva arome, vitamina C i vitamina B skupine, minerala (makro- i mikroelemenata) te kroz određivanje antioksidacijskog potencijala i senzornih svojstava vina. Pokus je obuhvaćao sljedeće tretmane: kontrola - maceracija u trajanju od 7 dana - TM7 (S), produljena maceracija u trajanju od 10 dana - TM10 (S), produljena postfermentacijska maceracija u trajanju od 21 dan - TM21 (S) te predfermentacijski tretman zagrijavanja u trajanju od 48 sati na 45 °C nakon čega je uslijedila maceracija u ukupnom trajanju od 10 dana - TPHT (S). Istraživan je i utjecaj dozrijevanja vina svih prethodno navedenih tretmana u drvenim hrastovim bačvama u trajanju od šest mjeseci TM7 (Z), TM10 (Z), TM21 (Z), TPHT (Z). Osnovne fizikalno-kemijske analize provedene su prema standardnim metodama O.I.V.-a. Pojedinačni fenolni spojevi analizirani su tekućinskom kromatografijom visoke djelotvornosti (HPLC). Ukupni fenoli te ukupni i slobodni antocijani određeni su spektrofotometrijski. Antioksidacijska aktivnost određena je spektrofotometrijski pomoću FRAP i ORAC testova. Vitamin C i vitamini B skupine analizirani su tekućinskom kromatografijom visoke djelotvornosti. Multielementarnom metodom određivanja elemenata (ICP-OES) određena je koncentracija makro- i mikroelemenata. Hlapljivi spojevi arome izolirani su iz uzoraka vina mikroekstrakcijom na čvrstoj fazi pomoću SPME vlakna, a za određivanje je korištena metoda plinske kromatografije (GC-MS). Uzorci vina ocijenjeni su O.I.V. metodom od 100 bodova te kvantitativnom deskriptivnom senzornom analizom. Rezultati ovog istraživanja pokazali su da su predfermentacijski tretman zagrijavanja masulja - TPHT (S) i produljena postfermentacijska maceracija - TM21 (S) značajno utjecali na povećanje koncentracije hidroksibenzojevih kiselina i ukupnih fenola te vrijednosti antioksidacijskog kapaciteta. Tretman TPHT (S) utjecao je i na porast koncentracija hidroksicimetnih kiselina i mikroelemenata dok je tretman TM21 (S) u vinu ‘Teran’ povećao sadržaj flavan-3-ola, stilbena, slobodnih i ukupnih antocijana, vitamina B kompleksa i makroelemenata. Vina navedenih tretmana ocijenjena su višim ocjenama za senzornu kvalitetu vina, svrstana su u kategoriju vrhunskih vina i opisana višim intenzitetima pozitivnih senzornih svojstava. Dozrijevanje vina je značajno utjecalo na povećanje koncentracije slobodnih hlapljivih spojeva arome, dok su bioaktivni spojevi bili manje stabilni te su se koncentracije dozrijevanjem većinom smanjivale. Tretman dozrijevanja vina značajno je utjecao na senzornu kakvoću vina te su sva vina nakon dozrijevanja bila okusno punija s manje izraženom kiselosti, astringencijom i gorčinom. Dobiveni rezultati ovog istraživanja pridonijeli su definiranju utjecaja predfermentacijskoga zagrijavanja i duljine maceracije masulja te dozrijevanja vina na kemijski sastav, senzorna svojstva i koncentraciju bioaktivnih spojeva u vinima sorte ‘Teran’, a sve s ciljem identifikacije ključnih čimbenika relevantnih u proizvodnji visokokvalitetnih vina te razvoju vinifikacijskih tehnologija koje će maksimalno iskoristiti potencijal sorte. |
| Abstract (english) | The composition of wine is the subject of numerous studies, mainly due to how phenolic and aromatic compounds influence the sensory properties of wine, where the wine concentration can be significantly modified by applying different vinification technologies. However, in addition to influencing the qualitative properties of wine and considering the contemporary trends in wine research, which are based on the study of bioactive compounds that have a beneficial effect on human health, this research also intended to provide additional knowledge about the value of the ‘Teran’ autochthonous variety, which has been insufficiently researched. Different groups of bioactive compounds were detected in wine, including phenolic compounds, vitamin C, B complex vitamins and minerals. Phenolic compounds are the most abundant bioactive compounds in wine, and numerous studies provide evidence of the pharmacological, biological, and physiological benefits for human health, including blood pressure, cholesterol and lipids regulation, prevention of diabetes, obesity, atherosclerosis and cardiovascular diseases, as well as anti-inflammatory, antioxidant and antitumor effects. Macro- and microelements play an essential role in the human body, such as building strong bones and transmitting nerve impulses, and are also able to participate in the biosynthesis of different hormones, regulate normal heartbeat, effective in controlling blood pressure, and are involved in immune and brain systems. Wine also includes vitamins, among the nutrients required for the many physiological functions essential to life. Besides nutritional health benefits, a close relationship exists between high-quality wines and high phenolic content, given that phenolic compounds increase the sensory characteristics of wines in terms of color, astringency, and bitterness. Whether positively or negatively, macro- and microelements play an important role in the organoleptic characteristics of wines. Some of them are necessary for the fermentation process and can directly or indirectly impact the clarity and sensory properties of wines, including flavor, freshness, aroma, color, and taste. Certain vitamins are known to affect the formation of aroma compounds. Given that bioactive compounds are often present in very low concentrations, there has been an interest in finding technologies that will increase the extraction of such compounds but, at the same time, have a positive effect on the aromatic profile of wines and preserve or even improve the key parameters of the sensory quality of the wine. Therefore, the main goal of this research was to examine the impact of different vinification technologies on the chemical composition, sensory properties of wine and the concentration of bioactive compounds in wines of the ‘Teran’ variety (Vitis vinifera L.) through to identification and quantification of phenolic compounds, volatile aroma compounds, vitamin C and vitamins of the B group, minerals (macro and microelements) and determination of the antioxidant potential and sensory properties of wine. The experiment was performed in 2018 and 2019 with a grape variety called ‘Teran’, an autochthonous red grapevine variety grown for centuries in the north Adriatic regions of Croatia, Slovenia and Italy. Different vinification processes were carried out: control treatment with 7 days of maceration - TM7 (S), prolonged 10-day maceration - TM10 (S), prolonged post-fermentative 21-day maceration - TM21 (S), where fermentation of all the three treatments was conducted at 24 °C, and 48-hour pre-fermentative maceration heating at 45 °C followed by eight-day classical maceration - TPHT (S) (10 days of maceration in total). Accordingly, all the wine samples were aged in oak barrels for six months, TM7 (Z), TM10 (Z), TM21 (Z) and TPHT (Z). Treatments were done in three replications. The basic physicochemical parameters were analyzed according to
methods set by the International Organization of Vine and Wine. The separation of individual phenols (hydroxycinnamic and hydroxybenzoic acids, flavan-3-ols and stilbenes) was carried out by high-performance liquid chromatography (HPLC). Total phenolic content, free and total anthocyanins and determination of antioxidant capacity by FRAP and ORAC assays were performed on a spectrophotometer. The determination of macro- and microelements was conducted using an inductively coupled plasma optical emission spectrometer (ICP-OES). Vitamin C and vitamins of the B group were analyzed using HPLC. Volatile aroma compounds were isolated using headspace-solid phase microextraction (HS-SPME), and analyzed using gas chromatography/mass spectrometry (GC/MS). Sensory analysis was based on two evaluation methods: quantitative descriptive analysis (QDA) and the 100-point O.I.V./U.I.O.E. evaluation method. One-way analysis of variance (ANOVA) and Fisher’s least significant difference (LSD) test were used to compare the means (n = 3) at the level of significance of p < 0.05. The data were subjected to unsupervised statistical analysis using PCA to visualize the relationship between the Teran wines obtained from different treatments and bioactive compounds. Based on the results of the two-year research, the conclusion is that the treatment of pre-fermentation mash heating - TPHT (S) and the treatment of prolonged post-fermentation maceration - TM21 (S) in the Teran wine significantly increased the concentrations of hydroxybenzoic acids, total phenols and the values of antioxidant capacity. In addition, the treatment of pre-fermentation mash heating - TPHT (S) influenced the increase in the concentration of hydroxycinnamic acids and microelements, while the treatment of prolonged post-fermentation maceration - TM21 (S) in the Teran wine increased the content of flavan-3-ol, stilbene, free and total anthocyanin, vitamin B complex and macroelements. TPHT (S) treatment and TM21 (S) treatment reduced the concentration of almost all groups of free volatile compounds compared to the control treatment. However, despite the reduction in the concentration of free volatile compounds, the wines of the mentioned treatments were evaluated with higher scores for the sensory quality of the wine. They were classified in the category of premium wines and described with higher intensities of positive sensory properties, among which dry/dried fruit and spicy/aromatic herbs, while the fullness of the body, the presence of tannins and the aftertaste stand out among the taste properties. In the olfactory properties, the treatment TM21 (S) additionally stood out for its accentuated fruitiness and viscosity, and sweetness of taste, while the intensity of bitterness and astringency was not overemphasized despite the significantly higher concentration of phenolic compounds, especially flavan-3-ol.The application of prolonged maceration treatment for 10 days - TM10 (S), as well as the application of maceration for seven days, which was the control treatment - TM7 (S), did not significantly affect the increase in the concentration of bioactive wine compounds. However, the mentioned treatments resulted in significantly higher concentrations of almost all groups of free volatile aroma compounds compared to the remaining two treatments. Despite the increase mentioned above in the concentration of free volatile aroma compounds, the mentioned treatments were characterized by a lower intensity of almost all olfactory properties and emphasized freshness, acidity, astringency, and bitterness. Maturation of wine in oak barrels for six months had a significant impact on increasing the concentration of free volatile aroma compounds, especially from the group C-13 norisoprenoids, volatile phenols, furans and lactones. Other compounds, especially bioactive compounds such as vitamins of the B group, macroelements, and microelements, as well as most phenolic compounds, were less stable, and their concentrations mostly decreased with maturation. The wine maturation treatment significantly influenced the sensory quality of the wine, and fruity aromas characterized the wines of all treatments after maturation, while the TM21 (Z) and TPHT (Z) treatments stood out with more pronounced aromas of dried and dried fruit, jam, and liqueur. After maturation, all wines had a fuller taste with less pronounced acidity, astringency, and bitterness. The obtained results of this
research contributed to the definition of the influence of pre-fermentation heating and length of maceration and wine maturation on the chemical composition, sensory properties, and concentration of bioactive compounds in wines of the ‘Teran’ variety, all due to the identification of key factors relevant in the production of high-quality wines and the development of vinification technologies which maximize the potential of the variety. |
