Quantification of red wine phenolics using ultraviolet-visible, near and mid-infrared spectroscopy combined with chemometrics

The assessment of red wine mouthfeel relies primarily on the sensory description of its tannic properties. This evaluation could be improved by gaining a better understanding of the physicochemical properties of these tannins. Hence, the objectives of the present study were threefold: (1) to gain an insight into the sensory properties of subpopulations of proanthocyanidic tannins of different molecular sizes obtained through several ultrafiltration steps, (2) to quantify the kinetics of haze formation of these proanthocyanidic tannins in a dynamic polyvinylpyrrolidone (PVP) precipitation test, (3) to determine whether a correlation exists between the sensory and the precipitation data.

Consumers typically prefer wines with floral and fruity aromas over those presenting green-pepper, vegetal or herbaceous notes. Pyrazines have been identified as causatives for herbaceous notes in wines, especially Bordeaux reds. However, pyrazines are not universally responsible for herbaceousness, and several other wine volatile compounds are known to produce distinct vegetal/herbaceous aromas in wines. Specifically, volatile aldehydes elicit sensations of herbaceousness or grassiness and have been described in wines well above their perception thresholds.

Not only vintner’s decisions in the vineyard, but also winemaker’s choices of technology approaches in the cellar play a significant role in the final wine style and quality. Whereas traditional technologies within chosen terroir are quite well explored and thus somehow predictable, there is no proper knowledge available on possible outcomes in case of implementing novel, alternative winemaking strategies. To reveal their effects on wine aroma compounds and sensory characteristics, two alternative strategies
(cryoextraction or addition of whole grape berries during last stages of fermentation) were compared to classical Vipava valley winemaking approach as normally used for an autochthonous variety Zelen. After separate vinification and bottling, all the experimental wines were subjected to semiquantitative metabolic profiling of volatile compounds (VOCs) by means of GC/MS and were then also sensorialy evaluated by pre-trained panel.

The impact of minute amounts of headspace oxygen on the post-bottling development of wine is generally considered to be very important, since oxygen, packaging and storage conditions can either damage or improve wine quality. This is reflected in the generalised use of inert bottling lines, where the headspace between the white wine and the stopper is filled with an inert gas. This experiment aimed to address some open questions about the chemistry of the interaction between wine and oxygen, crucial for decisions regarding optimal closure. While it is known that similar amounts of oxygen affect different wines to a variable extent, our knowledge of chemistry is not sufficient to construct a predictive method.

Beihong and Beimei are two wine cultivars from ‘Muscat Hamberg’ (V. vinifera L.) and wild V. amurensis Rupr., which were released in China in 2008. Here，two enology practices were reported. Firstly, the impact of different yeasts including D254, GRE, K1, D21 and BDX on dry wine quality of Beihong and Beimei was investigated. For Beihong, among wines fermented by all yeasts, residual sugar content was the lowest, total anthocyanin and resveratrol contents were the highest in the wine by D254. However, the wine by D254 had lower titrable acid than those by the other yeasts except BDX.