Influence of maceration time and temperature on some bioactive compounds in Malvazija istarska white wines

Abstract

The rising trend of moderate wine consumption as a part of a healthy lifestyle promotes white wines with higher phenolic content because of their bioactive properties. Duration and temperature of the maceration process have a marked impact on the content and composition of wine phenolics. The aim of this study was to explore the effect of applying maceration processes of different durations and temperature on total phenolic content and flavan-3-ol compounds concentration of Malvazija istarska (Vitis vinifera L.) wines, an autochthonous Croatian white grape variety. Vinification took place at the Institute of Agriculture and Tourism (Poreč) where 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) were studied and compared to non-maceration control treatment (C). Total phenolic content was determined by the Folin-Ciocalteu colorimetric method using a UV/VIS spectrophotometer and the results were expressed as gallic acid equivalents (mg/L GAE). The analysis of flavan-3-ols was carried out by high performance liquid chromatography (HPLC). Identification was performed by comparing retention times and spectra with those of pure standards. Procyanidins B1, B2, B3, C1, and (+)-catechin and (-)-epicatechin were identified in all wine samples. Statistical data analysis was performed using one-way analysis of variance (ANOVA) and Fischer’s least significant difference (LSD), while Pearson’s correlation was used to observe the relationship between total phenolic content and total flavan-3-ols. According to the obtained results, total phenolic content increased in all maceration treatments when compared to C treatment wine. The increase in total phenolic content was the highest in post-fermentative maceration treatments, M14 and M42. Total flavan-3-ol content showed a similar trend, also reaching the highest values in M14 and M42 treatment wines, while the lowest concentrations were observed in both C and CRYO treatments. A high positive correlation was observed between total phenolic content and total flavan-3-ols. When observing individual flavan-3-ol compounds, (-)-epicatechin reached the highest concentrations, especially in M42 treatment. Procyanidin B3 and C1 significantly increased only when 42 days maceration was applied, while shorter maceration durations or temperature did not affect the increase in these compounds. It can be concluded that the investigated phenolics highly depended on the maceration conditions applied. Additionally, the increase levels of bioactive phenols resulting from the application of the investigated maceration practices might attract those consumers interested in moderate white wine consumption for specific health reasons. The study was funded by the Croatian Scientific Foundation under the projects IP 2018-5049 and DOK-2020-01-1901.