# The Effect of Seed Removal and Extraction Time on the Phenolic Profile of Plavac Mali Wine
## 1 Introduction  
Grape berry skin and seeds are the main sources of phenolic compounds that are extracted into the wine during the maceration process [1]. The extractability and concentration of these phenolic compounds largely depend on their location in the berry as well as the characteristics of different grape varieties and winemaking steps applied during wine production [2, 3]. Hence, their profile is also one of the major determinants of red wine organoleptic quality associated with sensory attributes such as the color, body, bitterness, astringency, mouthfeel, and aftertaste [4]. Phenotic compounds in grapes include the glycosylated and acylated forms of anthocyanins which are mainly responsible for the wine color and flavanols (which include flaxan-3-ol monomers and proanthocyanidins), also known as tannins, which are responsible for wine gustatory characteristics as well as tactile sensation of astringency [5]. Anthocyan are extracted from the skin by diffusion and their concentrations usually decrease after several days of contact when the rate of anthocyanins undergoing various condensation reactions exceeds the extraction rate [6]. As reported by [7] and proved by many published data, the highest color parameters and anthocyanin levels are obtained in wine macerated for three to six days, while during prolonged maceration time the wine colorintensity decreases. The main _Vitis viinifera_ varieties of anthocyanins are delphinidin, cyanidin, petunidin, and malvidin mono glucosides, and the acylated derivatives with acetic, P-coumaric, and caffeic acids [8]. The extraction rate of skin and seed flavanol compounds defer as most skin proanthocyanus due to their location and are solubilized and extracted in the first days of maceration. Whereas, the extraction of seed proanthocyanus requires a longer maceration time and is triggered in the presence of ethanol [2]. According to [9], flavanol monomers such as epicatechin-3-O-gallate, galactectin, and catechin; dimers such as procyanidins B1, B2, B3, and B4; and trimers such as procyanidins C1 are mostly being associated with the perception of bitterness, while the presence of tannins and certain flavonoids has been linked with stringent sensation. However, a bitter taste can be caused also by particular flavonoids and hydroxycinnamates as well as benzoic acids and their derivatives [10]. The maceration process, as one of the necessary winemaking steps in red wine production, can have a marked impact on phenolic compound extraction by varying the duration and temperature [11]. Generally, the contact of grape solids with the must is related to the length of the preferentative phase and the duration of alcoholic fermentation which usually lasts for 7 to 15 days after the crushing. In the case of extended or prolonged maceration, the contact time of the grape solids with wine can vary between 30 days to 2 months [5,11]. The main difference compared to classic maceration time is the higher tannin solubility, especially from seeds whose outer lipid cuticle is disrupted by the presence of ethanol and excessive time which enables them to fully hydrate and collapse [12,13]. Thus, from the sensory point, prolonged maceration can decrease the color and increase the bitterness and astringency, mainly correlating with monomeric flavan-3-ols and oligomeric tannins in higher concentrations [14,15]. However, a longer maceration period is not always connected to an increase in phenolic concentration possibly due to their interaction with cell wall polysaccharides whose presence is linked with continuous depetention of the berry pomace [16]. The influence of early grape seed removal was reported by [17] showing higher concentrations of total anthocyanins and minor differences in color measurement values. Seed removal in Monastrell wine production positively influenced the overall quality [18]. Among the red grape varieties being cultivated in Croatia, Plavac mali is the most planted: it covers an area of 142,662 ha [19] and has a high potential for producing exceptional wines.