Addition Protocols and Their Effects on Extraction and Retention of Grape Phenolics during Red Wine Fermentation and Aging

Abstract

Extraction and retention of red wine phenolics, particularly anthocyanins and tannin, have historically been a primary concern for many red wine producers. This research compares two competing protocols designed to facilitate the extraction and retention of grape phenolics through the addition of exogenous enological tannin to evaluate their relative effectiveness. The first protocol involves adding exogenous tannin in a single full-dose at or immediately after destemming/crushing the grapes. The second protocol, commonly referred to as the “sacrificial” protocol, involves splitting the addition into two half-doses. The first half-dose, or sacrificial dose, is applied at or immediately after destemming/crushing, and the second half-dose is added a few days later. The specific mechanisms involved in the extraction dynamics are not elucidated here, however, phenolic profiling before and during fermentation as well as one full year after, using UV-Vis and AWRI tannin portal methodology, has shown a clear advantage to the use of a single-dose protocol with respect to the extraction and retention of grape phenolics. Possible explanations are proposed and discussed.