Changes in Tannin Composition of Syrah Grape Skins and Seeds during Fruit Ripening under Contrasting Water Conditions.

Maria Kyraleou,Nikolaos Theodorou,Stamatina Kallithraka,Stefanos Koundouras,Pierre-Louis Teissedre,Yorgos Kotseridis

doi:10.3390/molecules22091453

Maria Kyraleou, Nikolaos Theodorou + Show 4 more

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https://doi.org/10.3390/molecules22091453

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Abstract

Tannin accumulation and composition were determined in skins and seeds isolated from Vitis vinifera cv. Syrah grapes submitted to contrasting water regimes under semiarid climatic conditions. Three irrigation treatments were conducted, starting at berry set through harvest of two growing seasons, 2011 and 2012: irrigation at 100% of crop evapotranspiration ETc (FI), irrigation at 50% of ETc (DI) and non-irrigated (NI). Seed total tannins did not vary with maturity but those of skins underwent a progressive decline (especially in 2011), expressed both on a fresh weight and on a per berry basis. Skin total tannin concentration and content per berry were increased under NI and DI conditions, mainly in 2012. In contrast, seed total tannins (in 2012) and flavan-3-ol monomers and tannin oligomers (both years) were higher in the fully irrigated vines (FI). Skin polymer size increased during ripening, NI and DI skins showing higher mean degree of polymerization (mDP) compared to FI at harvest. NI was also associated with a lower percentage of galloylation (%G) in skin oligomeric fraction (in 2012) and a lower percentage of prodelphinidins in the skin polymeric fraction (both years) at harvest. The mDP and %G of seed extracts did not vary during ripening and were higher in NI but only in 2012. According to the results, management of vine water status was shown to influence tannin amount and composition of Syrah grapes grown under semiarid conditions.

Highlights

IntroductionProanthocyanidins or condensed tannins are responsible for the astringent and bitter properties of the wines and are released from both grape skins and seeds [1,2]
Among grape phenolic compounds, proanthocyanidins or condensed tannins are responsible for the astringent and bitter properties of the wines and are released from both grape skins and seeds [1,2]
Chira et al [1], polymeric compounds are increasingly reactive with proteins with increasing mean degree of polymerization (mDP), our results suggest a higher astringency potential of Syrah skins under NI conditions

Summary

Introduction

Proanthocyanidins or condensed tannins are responsible for the astringent and bitter properties of the wines and are released from both grape skins and seeds [1,2]. Grape tannins derived from skins and seeds vary in their relative amount, length, subunit composition and sensory properties. Tannin content of the skins is reported to be lower than seeds [1,4]. Seed tannins are shorter, with a lower mean degree of polymerization (mDP), while skin tannins are generally larger with a higher mDP [1,5]. Seed tannins are usually composed of C, EC and ECG [6] whereas skin

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