The phenolic content of red wine is responsible for the color, mouthfeel, and aging potential of the wine. While many fermentation parameters and winemaking techniques have been shown to affect phenolic extraction it is generally agreed that one of the prime factors is fermentation temperature; however, temperature is not uniform during the course of the fermentation, with thermal gradients forming between the cap and the liquid portion. To determine the effects of temperature on phenolic extraction research scale (120 L) Cabernet Sauvignon fermentations were performed in which the cap and must were either maintained at the same temperature or a constant thermal gradient was maintained between the two during the period of active fermentation. All fermentations were sampled twice daily and phenolic content was determined by reverse-phase HPLC for monomeric phenolics and UV-VIS spectroscopy for total anthocyanins and condensed tannins. These experiments showed that cap and must temperature have noticeable effects on phenolic extraction based on where the phenolics originated. For skin phenolics temperature affected primarily the rate of extraction but not the final concentration, with increasing temperatures favoring faster extraction. For seed phenolics increases in fermentation temperature increased both the rate of extraction and also the final concentration. Comparison of the extraction data for the two sets of fermentations showed that must temperature, rather than cap temperature, appears to be more important in driving extraction.

The effects of temperature and ethanol concentration on the kinetics of anthocyanin adsorption and desorption interactions with five cell wall materials (CWM) of different composition were investigated. Using temperatures of 15 °C and 30 °C and model wine with ethanol concentrations of 0% and 15% (v/v) over 120 min, the adsorption and desorption rates of five anthocyanin-glucosides were recorded in triplicate. Small-scale experiments were conducted using a benchtop incubator to mimic a single berry fermentation. Results indicate that more than 90% of the adsorption occurs within the first 60 min of the addition of anthocyanins to CWM. However, desorption appears to occur much faster, with maximum desorption being reached after 30 min. The extent of both adsorption and desorption was clearly dependent not only on temperature and ethanol concentration but also on the CWM composition.