Identification of Factors that Influence the Level of Tannins and Polymeric
This project had only one objective; to conduct an experiment on a small experimental wine lot with the goal of accounting for all of the tannin in fruit at harvest, showing how it is partitioned during fermentation and taking into account tannin that might be tightly bound to cell wall material in the pomace and gross lees. This objective was accomplished and we were able to account for nearly all of the tannin from the fruit in the various fractions resulting from fermentation including, pomace, lees, seeds from the lees and the resulting wine. The major result from this research is that compared to fruit there appears to be an increase in the amount of tannin in the pomace and lees that is not extractable with acetone. It is thought that this increase in non-extractable tannin represents tannin from the skin and seeds that becomes attached to the insoluble matrix of the berry such that after fermentation it is no longer extractable with acetone. While the mechanism for this phenomenon is unknown, it represents a significant portion of the extractable tannin in fruit at harvest. Understanding the winemaking parameters that influence this phenomenon should enable winemakers to more carefully control tannin extraction during red wine fermentations.