Effect of Different Enological Practices on Skin and Seed Proanthocyanidins in Three Varietal Wines

Abstract

Proanthocyanidins are important for wine quality since they participate in astringency, bitterness and color. Given the localization of proanthocyanidins in the berry (skin and seeds), different methods have been developed that help to modulate the release of these phenolic compounds. In this study, the effect of two low prefermentative temperature techniques (cold soak and must freezing with dry ice) and the use of macerating enzymes has been studied during the vinification of three different varietal wines (Monastrell, Syrah and Cabernet Sauvignon) to assess their influence on wine proanthocyanidin concentration and composition. Syrah wines showed the lowest proanthocyanidin content, together with the lowest mDP and the highest percentage of galloylation in its proanthocyanidins. Monastrell and Cabernet Sauvignon wines showed similar proanthocyanidin concentration. The application of the low temperature prefermentative maceration (cold soak) was the most effective treatment, increasing the proanthocyanidin concentration in Monastrell and Cabernet Sauvignon wines although neither of the treatments had any effect on Syrah wines. As regards the effect of the different treatments on the proanthocyanidin composition, the results seem to indicate that the observed increases were mainly due to an increase in seed proanthocyanidins, even in the case of cold soak treatments, which occur in the absence of ethanol, suggesting that ethanol is not so crucial in the extraction of seed proanthocyanidins.

Effect of Ethanol on Grape Seed Proanthocyanidin Extraction

“…Prefermentative maceration not only would extract a considerable amount of seed tannins but also, in some way, would prepare seeds for a linear extraction during fermentative maceration. These results confirm those obtained by Alvarez et al (2005) and Busse-Valverde et al (2010, 2011, who found increased seed PA content and galloylation in wines after applying low temperature prefermentative macerations.…”

“…a Different letters within the same column indicate significant differences (p < 0.05). a theoretical seed proanthocyanidin extraction of 9.2%, 7.2%, and 8.7% was obtained in wines from Monastrell, Cabernet Sauvignon, and Syrah grapes, respectively (Busse-Valverde et al 2010). Higher theoretical seed proanthocyanidin extraction was found from Merlot grapes (42%) (Cerpa-Calderón and Kennedy 2008).…”

Role of cell wall deconstructing enzymes in the proanthocyanidin–cell wall adsorption–desorption phenomena

“…In the grape, they are located in the skin and seeds and are transferred to the must/wine during the maceration step of winemaking. However, previous studies have shown that the quantities found in wines are frequently lower than expected (Adams & Scholz, 2007;Busse-Valverde, Bautista-Ortín, Gómez-Plaza, Fernández-Fernández, & Gil-Muñoz, 2012;Busse-Valverde et al, 2010), which may not only be related to the fact that PAs are not extensively extracted from the skin and seeds but also to the finding that a substantial proportion of them are adsorbed by the skin and pulp cell walls (CWs) in suspension in the must after crushing the grapes and that finally precipitates during settling (Bindon, Smith, Holt, & Kennedy, 2010).…”

“…Agrovin.com). We chose this enzyme since we have experience working with it in real wine samples and information on the effect, on real vinifications, on proanthocyanin extraction (Busse-Valverde et al, 2010), cell wall degradation (Apolinar-Valiente, Romero-Cascales, Gómez-Plaza, López-Roca, & Ros-García, 2015) and polysaccharide liberation (Apolinar-Valiente et al, 2013) is available. In this second step, the CW-PA complexes formed in the first step were recovered, thoroughly washed and once again introduced into a new model solution, in the presence of the commercial maceration enzyme.…”

Effect of cold pre-fermentative maceration on the color and composition of young red wines cv. Tannat

“…The increase of tannins contents could be atributed to the total lenght of skin contact because the pre-fermentative maceration was continued by a classical fermentation on skins. Nevertheless, Busse-Valverde et al (2010) indicated that the increases in tannin contents by cold soak treatments were mainly due to an increase in seed proanthocyanidins, which also were extracted in the absence of ethanol. Moreover, the increase in catechin contents could be due to the differential extraction of these compounds in aqueous medium at pre-fermentation (Álvarez et al 2006).…”