engleski

Influence of maceration duration, heat treatment, and barrel aging on mineral composition in Teran wines

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.

maceration ; mineral composition ; Teran wines

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