Vino ´Plavac mali´ poznato je po svojoj intenzivnoj rubin crvenoj boji te naglašenoj trpkoći uslijed velikog kapaciteta nakupljanja polifenolnih spojeva u kožici i sjemenki tijekom dozrijevanja grožđa te ekstrakciji istih tijekom procesa maceracije. Plavac mali dozrijeva u IV epohi u skupini kasnih sorata. Područje uzgoja ove najzastupljenije crne sorte u Republici Hrvatskoj se značajno širi, pri čemu je važno istaknuti kako su u proteklom desetljeću podignute velike površine vinograda ´Plavca malog´ na melioriranom kršu. Fenolni spojevi, antocijani i fenolne kiseline, flavan-3-oli i stilbeni među glavnim su nosiocima kakvoće i to posebice boje i okusa crnih vina. Promatrano na razini fenoloških događanja na trsu vinove loze, dozrijevanje grožđa predstavlja složeni proces koji se očituje kao splet ireverzibilnih promjena koncentracija primarnih i sekundarnih metabolita. Akumulacija polifenolnih spojeva ovisi o agroekološkim uvjetima vegetacijske sezone, roku berbe te primijenjenoj vinogradarskoj tehnici. Stoga, vrlo često neodgovarajući rok berbe te duljine maceracije i dovodi do preniske ili previsoke stope ekstrakcije polifenolnih spojeva što u konačnici može imati i negativan utjecaj na kakvoću vina. Cilj ove disertacije bio je utvrditi optimalni rok berbe i duljine ekstrakcije polifenolnih spojeva te njihov utjecaja na polifenolni sastav, antioksidacijsku aktivnost i senzorna svojstva vina. U 2016. i 2017. godini grožđe sorte ´Plavac mali ´pobrano je u dva roka berbe te macerirano 7, 21 i 42 dana. U gotovim vinima provedena je analiza osnovnog fizikalno-kemijskog sastava, pojedinačnih i ukupnih polifenolnih spojeva, antioksidacijska aktivnost te senzorna ocjena. Dobiveni rezultati ukazali su na značajan utjecaj roka berbe na osnovne parametre kakvoće vina te duljine maceracije na profil antocijana, fenolnih kiselina te flavan-3-ola. U konačnici, rezultati senzorne analize vina dobiveni metodom 100 bodova te metodom redoslijeda u obje godine istraživanja najboljim su ocijenili vina proizvedena od grožđa pobranog u drugom roku berbe i maceriranog 21 dan.
Plavac Mali is a leading red grape variety primarily grown in the coastal region of Croatia, Central and South Dalmatia. This late-ripening variety requires a warm and extended growing season to reach optimal ripeness and fully accumulate sugars, phenolic compounds, and aroma precursors in berries. It is well known for producing full-bodied wines high in both alcohol and tannins, with intense flavors of blackberry, dark cherry, blackcurrant, plum, pepper, carob, dry figs, and often some herbal and spice notes. Phenolic compounds, including anthocyanins (responsible for color) and tannins (carriers of bitterness and astringency which contribute to the structure and aging potential of wine), are primarily located in the skins, seeds, and stems of grapes. The extraction of phenolic compounds from grapes during maceration is a crucial step in winemaking, as it influences the color, flavor, aroma, mouthfeel, and aging potential of the resulting wine. Prolonged maceration is a winemaking technique where the crushed grape solids (skins and seeds) are left in contact with the fermenting wine for an extended period beyond what is typical for the grape variety and wine style.
The sensory characteristics of Plavac Mali wines can be connected with some negative sensations such as less intense coloration, and accentuated bitterness and astringency due to inappropriate harvest dates and uniform oenological techniques of simultaneous maceration and fermentation. A review of similar research on phenolic maturation and extraction of phenolic compounds, with an emphasis on so far conducted research on Plavac Mali, project hypothesis, and aims are presented in the introduction chapter.
In this research, it is assumed that the extended harvest date and the application of the extended maceration technique will have a significant positive impact on the rate of extraction of polyphenolic compounds as well as sensory profile. Late harvest date wines and prolonged maceration after alcoholic fermentation will have a higher concentration of flavanols and better organoleptic characteristics, and overall quality will be better compared to wines produced by usual, standard production technology.
This research project aimed to characterize wines of Plavac Mali harvested at two different harvest dates and to examine the most suitable between three proposed length of maceration as 7, 21, and 42 days.
The second chapter gives an overview of the latest research about the extraction of phenolic compounds, the reactions, and interactions between different phenolic compounds in wine matrix, and the impact of vinification techniques on the polyphenol composition of wine. The chapter is organized into five subdivisions and includes an overview of 274 literature references. The results achieved by different authors, showed a beneficial impact of prolonged maceration on color extraction (wines with more intense hues, desirable for red wines), tannin structure, flavor complexity, and aging potential. While tannins are important for structure and aging potential in red wines, excessive or harsh tannins can be unpleasant. Prolonged maceration can lead to the extraction of smoother and more integrated tannins even more it can soften and refine extracted tannins. So, extended contact with grape solids can enhance the complexity of the wine's flavor profile. This can result in wines with a broader range of aromas and flavors of dark fruits, and spices. Also, red wines produced with prolonged maceration tend to have better aging potential because increased tannins and phenolic concentrations can contribute to the wine's ability to age. The negative sides of prolonged maceration could be over-extraction of phenolic compounds, loss of freshness, yield reduction, much time and labor compared to traditional maceration. The impact of prolonged maceration on wine quality depends on the grape variety, the wine style desired, and the winemaker's skill and judgment. Winemakers often experiment with different maceration times and techniques to find the optimal balance for their specific wine. It's important to note that not all red wines benefit from prolonged maceration, and shorter maceration times are appropriate for many styles, especially for wines meant to be consumed young and fruity.
Material and methods used in this research for the determination of harvest date and prolonged maceration technique impact on polyphenolic compounds extraction and sensory characteristics of Plavac Mali wines during two years are given in the third chapter. Grapes harvested at two different harvest dates from vineyards of Volarević winery located on slopes in Komarna were subjected to three different lengths of maceration, 7, 21, and 42 days. In the final wines basic physicochemical compounds, the antioxidative potential and identification and quantification of individual phenolic compounds was performed. Sensory evaluation of wines was done using ranking method for evaluation of samples according to harvest date and evaluation of samples using maceration length. Also all wines were sensory analyzed using the 100-point OIV method.
The fourth chapter consists of 11 tables presenting the individual and total polyphenolic compounds data according to the influence of two harvest dates and three different maceration length. In the fifth chapter all results were discussed throughout seven subdivisions. Basic chemical composition of Plavac mali wines were mainly influenced by harvest data leading to higher alcohol strength, pH values and lower total acidity in late, second harvest date in both investigated years. Total phenols concentration was strongly influenced by harvest date with higher values achieved by later harvest date while total anthocyanin values were higher in the wines from first harvest date with prolonged
maceration having in general negative effect. Antioxidation activity of wines was defined by ORAC, FRAP, ABTS i DPPH methods. All of them showed marked influence of prolonged maceration on antioxidation activity of Plavac mali wines from both harvest dates with FRAP method being the most consistent. Concentrations of flavan-3-ol monomeric as well as dimeric compound were significantly influenced by maceration length with the highest values achieved by 42 day maceration time, among them catehine and epicatehine as well as procyanidin B1 and B2 dimer. At the contrary concentration of B3 dimer was significantly higher in wines produced by 7 days maceration from grapes harvested by earlier date. In this research, among the anthocyanins, the most represented was malvidin-3-O-glucoside, whose concentrations were directly and significantly influenced by the length of maceration. The influence of the length of maceration was also visible in the sum of glucosidic, acylated and coumaryl forms as well as the total sum of individual anthocyanins, whose concentrations in both years were significantly the highest in wines produced by maceration for 7 days. Among the analyzed phenolic acids in both years of the research, gallic acid was the most abundant, followed by syringic acid, where both the length of maceration and the time of harvest had a significant effect on their concentrations in the ´Plavac mali´ wines. Between the hydroxycinnamic acids, caftaric acid was the most abundant in both years of the study, the concentrations of which significantly decreased under the influence of the length of maceration. Finally, by sensory evaluation using O.I.V. 100 method prolonged maceration of late harvest grape lasting 21 days was distinguished by its positive influence on the sensory properties of the wine ´Plavac mali´ regardless of the year of harvest. The ranking method also confirmed these results.
The conclusions were stated on the basis of the achieved and presented main findings. The extended harvest date and prolonged maceration for 21 days had a beneficial effect on the organoleptic properties and the overall quality of the Plavac Mali wines in both vintages.