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Phenolic acids and stilbenes are important groups of non-flavonoid phenolic compounds present in grapes and wine. Their content in wine may be modulated by the vinification technique applied. The present study aimed to determine the impact of the application of different grape mash maceration treatments on the composition of hydroxycinnamic (HCA) and hydroxybenzoic acids (HBA) and stilbenes in Malvazija istarska wines. The research was conducted at the Institute of Agriculture and Tourism (Poreč, Croatia) with Malvazija istarska (Vitis vinifera L.), an autochthonous Croatian white grape variety. A total of six vinification treatments were carried out: two days maceration treatment at 8 °C (CRYO), and seven (M7), 14 (M14), 21 (M21), and 42 days (M42) maceration treatments at 16 °C, compared with the control treatment without maceration (C). Identification and quantification of phenolic acids and stilbenes was performed after direct injection of the filtered wine sample, using a high performance liquid chromatograph (HPLC) equipped with a diode array detector (DAD). The obtained results were statistically processed by one-way analysis of variance (ANOVA) and Fisher's test of least significant differences (LSD). According to the obtained results, the highest concentration of total HBAs was recorded in prolonged post-fermentative maceration treatment M42, and among all HBAs gallic acid had significantly the highest concentrations. Regarding HCAs, the total content was significantly the highest in seven days maceration treatment (M7), while in longer maceration treatments (M14, M21, M42) total HCA content 58 gradually decreased as maceration progressed. When observing individual HCAs, transcaftaric acid had the highest concentrations, especially in M7 treatment wine, while caffeic and ferulic acids reached the highest concentrations in pre-fermentative two days (CRYO) treatment. Regarding total stilbene content, treatments M7, M14, and M21 obtained the highest concentrations, but did not significantly differ between each other, and when observing individual stilbenes, cis-piceid concentrations were the highest in those treatments and among all identified stilbenes. Obtained results show that HBA content benefits from the prolonged maceration, while for the most HCAs and stilbenes concentrations increase up to seven days of maceration and then decrease during prolonged maceration, possibly due to oxidation and other reactions.

To investigate the effect of different maceration techniques on the mineral composition of Malvazija istarska wines, five different maceration treatments were carried out. Maceration techniques of two days at 8 °C (CRYO), and seven (M7), 14 (M14), 21 (M21), and 42 days (M42) at 16 °C, were studied and compared to control treatment without maceration (C). Analysis of macro- and microelements was conducted by inductively coupled plasma- optical emission spectrometry (ICP-OES). According to the obtained results, the longest maceration treatments (M21 and M42) resulted with the highest concentration of almost all macroelements. A proportional increase with maceration time was observed in the concentration of all analyzed microelements, with M42 treatment wine resulting in significantly highest concentrations.

Wine is a rich source of various nutritive bioactive compounds, including macro- and microelements. A moderate wine consumption of 250-300 ml/day contributes to the requirements of the human organism for essential elements. Current studies attribute the consumption of foods rich in nutrients even as potential inhibitors of SARS-CoV-2. Moreover, supplementation of micronutrients may positively impact the recovery from COVID-19 infection. However, some metals can be potentially toxic when consumed in excess, and the maximum acceptable levels in wine have been established. The aim of this study was to determine the effects of vinification techniques on mineral composition and estimate the changes in composition during the barrel aging. The experiment was performed in vintage 2019, with grapes from Teran (Vitis vinifera L.) variety. Vinification took place in the experimental wine cellar of the Institute of Agriculture and Tourism in Poreč (Croatia). The study covered seven days of maceration as a control treatment (TM7), prolonged 10-day maceration (TM10), prolonged post-fermentative 21-day maceration (TM21), and 48-h pre-fermentative maceration heat treatment at 45 °C followed by eight-day standard maceration (TPHT). The fermentation of all treatments was conducted at 24 °C. Accordingly, all the wine samples were aged in oak barrels for six months (TM7-B, TM10-B, TM21-B, TPHT-B). The determination of eight elements was conducted by Optima DV 2000 inductively coupled plasma-optical emission spectrometer. Analysed elements were identified by ICP-OES and were quantified by the direct calibration method. Statistical data analysis was performed using one-way analysis of variance (ANOVA) and Fischer’s least significant difference (LSD) to compare the means (n = 3) at the level of significance of p ≤ 0.05. In the investigated wines, K, Ca, Mg, and Na were identified as macroelements, and Al, Cu, Fe, and Mn as microelements. Results in this study showed the significant impact of different treatments on mineral composition. More precisely, compared to control (TM7), TM10, and TM21 treatments showed significantly higher concentrations of total macroelements, while TPHT treatment showed significantly lower concentrations. The significantly highest concentration of macroelements in aged wines was found in TM21-B wines. It is important to note that wine barrel aging significantly reduced the level of all investigated macroelements except Mg, which remained stable in all treatments. The content of total microelements in young wines was significantly the highest in pre-fermentative heating treatment. The same trend continued in aged wines, with the highest concentration in TPHT-B treatment. It should be pointed that the concentration of all investigated microelements was significantly reduced during barrel aging. This result indicates that some interesting differences can be obtained among wines by applying maceration, heating, and barrel aging in the composition of macro- and microelements. In addition, since metals can form organometallic complexes with anthocyanins and tannins and cause the formation of precipitates, it was very interesting to monitor the evolution of wines during maturation and aging. Obtained results can probably be attributed to the different extraction mechanisms/kinetics from solid parts of grapes, particularly the skin, which was shown to be the most important fraction in terms of metal concentration. Regarding aging, earlier studies indicated, that metal composition is not stable, which was also confirmed in this research. However, the intensity of these changes can vary depending on grape and wine composition. This study was funded by the Croatian Science Foundation under the projects VINUM SANUM (IP 2018-5049) and DOK-2018-09.

Besides its hedonic nature, wine is a natural beverage with certain health-related properties, which is why the consumer’s interest towards wines with a higher concentration of bioactive compounds has increased over recent years. Extracted from grapes, antioxidants and vitamins are naturally present in wines but their concentrations differ according to the applied winemaking technique. The maceration process is less frequently carried out for the production of white wines in relation to red wines for several reasons, but its application may be suggested to increase wine antioxidant capacity and nutritional value. The aim of this study was to investigate the effect of applying different maceration processes on antioxidant capacity and vitamin content of wines produced from an autochthonous Croatian white grape variety, Malvazija istarska (Vitis vinifera L.). Vinification took place in vintage 2019 at the Institute of Agriculture and Tourism (Poreč, Croatia) where six vinification treatments were carried out: non-maceration control treatment (C), pre-fermentative two days cryomaceration treatment at 8 °C (CRYO), seven days maceration treatment at 16 °C (M7), and prolonged post-fermentative maceration treatments at 16 °C for 14 days (M14), 21 day (M21), and 42 days (M42). The antioxidant capacity of the wines was determined by the ferric reducing/antioxidant power, FRAP (mM Fe2+) assay and the oxygen radical absorbance capacity, ORAC (mM Trolox) assay. Chromatographic analyses were performed on a liquid chromatography system with a DAD and single quadrupole mass detector equipped with electrospray ionization interface. Identification of five vitamins (B1, B2, B3, B6 and C) was carried out by comparison to the retention times of authentic standards and their spectral properties. Statistical data analysis was performed using one-way analysis of variance (ANOVA) and Fischer’s least significant difference (LSD). According to both FRAP and ORAC assay, antioxidant capacity increased proportionally with the maceration duration, with control treatment wine having the lowest, opposed to M42 treatment wine having the highest values. Such results indicate that the antioxidant properties are mostly related to phenolic compounds which are mainly present in prolonged maceration treatments such as M42. Contrary results were noted for vitamin C content that showed a decreasing trend as maceration progressed. Vitamin C was not detected in M42 treatment wine while the highest concentration was reported in control treatment wine. When observing total B-group vitamins, a significant difference was noted between treatments. Prolonged post-fermentative maceration treatment M42 resulted with the highest concentration of total B-group vitamins in relation to other treatments. The increase in total B-group vitamin was proportional with maceration time, while CRYO and M7 treatments did not significantly differ from control treatment wine. Regarding the concentrations of each individual vitamin, vitamin B3 reached the highest values, and its concentration was significantly the highest in M42 treatment wine. A similar trend was noted in the concentration of vitamin B6. Obtained results showed that prolonged maceration significantly affects both the antioxidant capacity of the wines and their vitamin content, particularly B-group vitamins. Such information may serve producers for choosing the adequate technological practice for improving wine quality and its nutritional value. The study was funded by the Croatian Scientific Foundation under the projects VINUM SANUM (IP 2018-5049) and DOK-2020-01-1901.