Sensory and nephelometric analysis of tannin fractions obtained by ultrafiltration of red wines

Alcoholic fermentation using no Saccharomyces wine is an effective means of modulating wine aroma. This study investigated the impact of coinoculating Torulaspora delbruecki with two Saccharomyces cerevisiae commercial yeast (QA23, Lallemand; Red Fruit, Sepsa-Enartis) on enological quality parameters, volatile composition and sensory analysis. The following assays were performed on Tempranillo variety: Saccharomyces QA23 (CTQA), Saccharomyces Red Fruit (CTRF), coinoculated T. delbrueckii + S.cerevisiae QA23 (CIQA) and coinoculated T. delbrueckii + S.cerevisiae (CIRF).

For several years, numerous studies aimed at limiting the use of SO2 in wines (thermal treatments, pulsed electric fields, microwaves …). Processes must be able to preserve the organoleptic qualities of wines with low energy consumption. In this context, ultraviolet radiations (UV-C), at 254 nm, are well known for their germicidal proprieties. In order to inactivate microorganisms in grape juice and wine without affecting the quality of the product, efficiency of UV-C treatment process should be optimized.

One of the key factors of the economical development of viticulture and wine industry in specific limited areas is the exploitation of ancient, local grape varieties. Therefore, in recent years the growing interest to rediscover minor varieties, previously cultivated, has promoted many studies. With this regard, the focus of this study was the Vitis vinifera L. cultivar Moscato nero d’Acqui, nowadays found only in old vineyards in the Acqui zone (North-West Italy). In particular, the aims of this work were: i) to investigate secondary metabolites profile of the grapes, and ii) to evaluate the attitude to the production of special wines.

Tyrosol (TYR) and hydroxytyrosol (HYT) are bioactive phenols present in olive oil and wine, basic elements of the Mediterranean diet. TYR is reported in the literature for its interesting antioxidant, cardioprotective and anti-inflammatory properties. In wine, its concentration can reach values as high as about 40 mg/L
[Pour Nikfardjam et al. 2007] but, more frequently, this phenol – derived from yeast metabolism of tyrosine during fermentation – is present at lower levels, generally higher in red wines compared to whites. HYT was measured for the first time by Di Tommaso et al. [1998] in Italian wines – with maximum values of 4.20 mg/L and 1.92 mg/L for red and white wines, respectively – while definitely lower concentrations have been found later in Greek samples.

Flavonols are a class of flavonoid compounds derived from plant secondary metabolism. There they play different roles like antioxidants, internal regulators and UV screenings. In red wines, flavonols have increasingly received consideration by part of scientific and winemakers according their properties began to arise known. Among these stand out wine colour stabilization and their value as bioactive compounds. In this work the complete series of the acetylated and p-coumaroylated derivatives of the 3-O-glycosides of methoxylated flavonols, namely isorhamnetin, laricitrin and syringetin, have been identified in grapes and their respective wines from Vitis vinifera cv. Tannat.