Chemical and sensorial investigation of in-mouth sensory properties of grape anthocyanins.

Anthocyanins are water-soluble pigments found in the cell vacuoles of fruits and flowers, performing several roles from insects attraction to stress protection. Their antioxidant activity contributes to human health, and consuming plant-derived products provides their higher source in the diet. Although their colour and nutritional features, their contribution to sensory properties of foods has not been widely investigated. In wine, preferences are connected with sensory attributes of colour, aroma, taste, and mouthfeel. In this study, grape anthocyanin extracts (TAE) were fractionated using centrifugal partition chromatography (CPC) and preparative HPLC in three fractions, i.e glucoside (GF), acetylated (AF) and cinnamoylated (CF) anthocyanins. Sensory properties were investigated by chemical analysis, as reactivity towards bovin serum albumin (BSA) and salivary proteins, and in tasting sessions to assess anthocyanins best estimated thresholds (BET) in wine-like solution. Anthocyanins reacted with both BSA and salivary proteins, but to different extents, because higher interaction between salivary proteins and anthocyanins were found. Cinnamoylated anthocyanins are the most reactive to salivary proteins. Tasting sessions suggested an involvement of anthocyanins as in-mouth contributors in wine, since their BETs were 255, 297, 68, and 58 mg/L for TAE, GF, AF, and CF, respectively, and the descriptors reported were astringency and bitterness.

Adaptation of two groups of Oenococcus oeni strains to red and white wines: the role of acidity and phenolic compounds.

AIMS: Oenococcus oeni is the lactic acid bacteria species which is the most adapted to wine. Recently, two groups of strains that form two genetic lineages were described in red and white Burgundy wines. The aim of this study was to analyse the phenotypes of these strains in order to determine how they have adapted specifically to either red or white wine. METHODS AND RESULTS: Four strains from each group were tested in grape must and in wines to evaluate their tolerance to pH and to phenolic compound content. White wine strains proved to be the most tolerant to low pH, both in grape must and in wine, whereas they were inhibited by the presence of grape tannins in wine. Red wine strains were more sensitive to acidity, but very resistant to phenolic compounds. CONCLUSIONS: The results suggest that pH and phenolic compounds drive strain selection at several stages of wine production. SIGNIFICANCE AND IMPACT OF THE STUDY: Although it is well known that O. oeni is well adapted to wine, this study shows that strains of some genetic lineages within this species have evolved to adapt better than others to specific types of wines.

A preliminary characterization of Aglianico (Vitis vinifera L. cv.) grape proanthocyanidins and evaluation of their reactivity towards salivary proteins.

The flavan-3-ol and proanthocyanidin composition of Aglianico seeds and skins were for the first time determined by HPLC-MS in comparison with the international grapes Merlot and Cabernet Sauvignon. Monomers [(+)-catechin C, (-)-epicatechin EC, (-)-epicatechin-3-O-gallate, ECG] and oligomers [B1, B2, B3, B4 dimers and trimer C1] were identified and quantified in grape extracts. In order to evaluate the reactivity towards salivary proteins of model wine solutions of seeds and skins monomeric/oligomeric and polymeric fractions, the Saliva Precipitation Index (SPI) was carried out. Fractions were also analyzed for their mean degree of polymerization (mDP), percentage of galloylation (%G) and of prodelphinidin (%P) by phloroglucinolysis. Aglianico was the most effective in precipitating proteins than Merlot and Cabernet Sauvignon, mainly for the high percentage of galloylation of grape fractions. The mDP and the percentage of ECG in terminal units resulted to significantly contribute to the precipitation of salivary proteins by grape proanthocyanidins.

Kinetics of browning, phenolics, and 5-hydroxymethylfurfural in commercial sparkling wines.

We analyzed the degree of browning (absorbance at 420 nm), the phenolics, and the 5-hydroxymethylfurfural (5-HMF) content in six sparkling wines series kept at three temperatures (4, 16, and 20 °C) for over 2 years. Caffeic acid, trans-coutaric acid, p-coumaric acid, and 5-HMF were the compounds with the greatest correlation with browning and time. 5-HMF was the only compound that evolved linearly at all temperatures. We propose that 5-HMF is a better time-temperature marker than the A420 parameter or phenolics, because it shows higher linearity with time at all temperatures, is more sensitive to temperature changes, and has lower variability. The kinetics of 5-HMF was studied showing a zero-order behavior. We propose mathematical models that wineries can use to predict the browning shelf life of their sparkling wines as a function of the storage time and temperature.

Characterization of seed and skin polyphenolic extracts of two red grape cultivars grown in Croatia and their sensory perception in a wine model medium.

A study of proanthocyanidin and anthocyanin composition and concentrations in seed and skin extracts of two Croatian native red grape cultivars (Plavac mali and Babic) by HPLC-UV-Fluo/MS analysis was conducted in this work. A sensory analysis of extracts astringency and bitterness intensity was also performed. In the seeds, Babic showed generally higher concentrations of proanthocyanidins, while in the skins, Plavac mali showed higher concentrations of proanthocyanidins and anthocyanins. Babic proanthocyanidin seed fractions, greater in polymer size and percentage of galloylation, were perceived to be significantly more astringent. Babic proanthocyanidin skin fractions, greater in polymer size and lower in percentage of galloylation and prodelphinidins, were perceived to be significantly bitterer, but only in polymeric fractions. A positive correlation was found between the degree of polymerization, the percentage of galloylation and astringency intensity in the seeds. A negative correlation was found between the percentage of prodelphinidins and bitterness intensity in the skins.