Changes in the composition and content of polyphenol compounds during the ripening of red grape varieties

Polifenoli su sekundarni biljni metaboliti te važni organski spojevi prisutni u grožđu, moštu i vinu. Važnost polifenolnih spojeva prisutnih u grožđu uglavnom je vezana uz kakvoću vina obzirom da utječu na boju, okus, astringenciju, trpkost, gorčinu te potencijal starenja vina. Posljednjih godina, uslijed brojnih istraživanja polifenolnog sastava grožđa, prepoznata je i njihova nutritivna vrijednost koja pokazuje mnogobrojne pozitivne učinke na ljudsko zdravlje. Njihov blagotvoran učinak na organizam proizlazi iz antioksidacijskih sposobnosti, kelatnog djelovanja te inaktivacije određenih enzima zbog čega im se pripisuju antikancerogena, antimikrobna, antialergijska, neuroprotektivna, protuupalna te mnoga druga svojstva. U bobici grožđa pronađena je velika grupa polifenolnih spojeva poput fenolnih kiselina (hidroksicimetne i hidroksibenzojeve kiseline), stilbena te flavonoida (antocijanini, flavonoli i flavan-3-oli). Najveći udio polifenolnih spojeva u bobici grožđa sadržan je u sjemenkama, zatim kožici te mesu bobice. Fenolni spojevi su osobito važni u tehnologiji proizvodnje vina crnih sorata, jer uvelike utječu na boju te karakterističan okus vina. Stoga je predmet ovog istraživanja utvrditi promjene koje se javljaju u polifenolnom profilu (hidroksicimetne kiseline, anotocijani, flavonoli, flavan-3-oli) 11 crnih autohtonih sorata vinove loze tijekom dozrijevanja na vinogradarsko-vinarskom pokušalištu „Jazbina“. Uzorci sakupljeni periodično adekvatno su pohranjeni, liofilizirani te podvrgnuti ekstrakciji, a dobiveni ekstrakti analizirani su tekućinskom kromatografijom visoke djelotvornosti. Temeljem dobivenih rezultata utvrđeno je da su antocijani najzastupljeniji polifenolni spojevi u kožicama bobica istraživanih sorata, potom flavanol-glikozidi, flavanol-3-oli te naposljetku hidroksicimetne kiseline. Maseni udio antocijana i flavonol-glikozida u kožicama bobica povećava se od početka šare prema tehnološkoj zrelosti, dok se maseni udio flavan-3-ola, hidroksicimetnih kiselina te flavonol-glikozida kod pojedinih sorata smanjuje prema tehnološkoj zrelosti.Polyphenols are secondary herbal metabolites and important organic compounds present in grapes, must and wine. The importance of polyphenolic compounds presence in grapes is mainly related to the quality of the wine. Those coumpounds affect the color, taste, astringency, bitterness and potential of wine aging. Recently, due to numerous researches of the polyphenolic composition of grapes, their nutritional value as well as many positive effects on human health have been recognized. Their beneficial effect on the organism derives from antioxidant capabilities, chelating activity, and inactivation of certain enzymes that are attributed to antitumor, antimicrobial, antiallergic, neuroprotective, anti-inflammatory and many other properties. A large group of polyphenolic compounds such as phenolic acids (hydroxycetone and hydroxybenzoic acid), flavonoid stilbenes (anthocyanins, flavonols and flavan-3-ol) have been found in grape berry. The largest proportion of polyphenolic compounds in grape berries is contained in the seeds, then skin and pulp. Phenolic compounds are particularly important in red grape wine production technology, because they greatly affect the color and the characteristic taste of wine. Therefore, the subject of this study is to determine the changes that occur in the polyphenol profile (hydroxycitic acid, anotoxic, flavonol, flavan-3-ol) of 11 red autochthonous grape varieties during ripening on the experimental vineyard of "Jazbina". Samples were collected periodically and were adequately stored, lyophilized and subjected to extraction. The obtained extracts were analyzed with high performance liquid chromatography. Based on the obtained results, anthocyanins are the most common polyphenol compounds in the skin of the investigated varieties, followed by flavanol glycosides, flavanol-3-ol and hydroxymethyl acids. The mass fration of anthocyanin and flavonol glycosides in berry skin increases from the beginning of the veraison to the technological maturity, while the mass fraction of flavan-3-ol, hydroxymethyl acids and flavonol glycosides decreases by technological maturity