Chemical and Chromatic Effects of Fermentation Temperature on Three Clones of Pinot noir over Two Consecutive Vintages

Abstract

Three different Pinot noir clones (115, 777, and 828), from the Central Coast of California, were submitted to different maceration temperature regimes for 14 days, using triplicate fermentations (Cold: 10°C, Hot: 25°C, Variable: 10°C, day 0 to 7; 25°C, day 8 to 14), to determine the effect of maceration temperature on color and phenolic extraction across all three clones over two consecutive vintages (2019 and 2020). In 2019, the Hot treatment and the Hot portion of the Variable treatment were realized by exposing the fermentors to direct sunlight, whereas in 2020 this was achieved by artificial heating. Spectrophotometric analyses showed that at time of pressing, extraction of total phenolics for Cold, Variable, and Hot temperature treatments was 723 mg/L, 894 mg/L, and 1031 mg/L, respectively. Similar trends were observed for anthocyanins for Cold, Variable, and Hot treatments (208, 265, 284 mg/L, respectively), tannins (68, 81, 123 mg/L, respectively), and polymeric pigments (0.40, 0.46, 0.51 absorbance units (AU), respectively). Similarly, the average of both vintages’ Cold, Variable, and Hot treatments for monomeric anthocyanin concentration analyzed via HPLC was 210 mg/L, 269 g/L, and 267 mg/L, respectively; and that of flavonols was 26 mg/L, 28 mg/L, and 30 mg/L, respectively. Color analysis showed a negative correlation with temperature for CIELab lightness values across Cold, Variable, and Hot treatments (86.69, 84.89, 83.37, respectively), while indicating a positive correlation for red hues (16.05, 17.73, 20.50, respectively), and wine color (AU 420+520+620 nm (0.48, 0.54, 0.60, respectively). Finally, differences in heating method between the two vintages (direct sunlight for 2019 and temperature-controlled room for 2020) proved to be a major factor in phenolic extraction.