Metabolomics of grape polyphenols as a consequence of post-harvest drying: on-plant dehydration vs warehouse withering

Phenolic compounds are very important in crop plants and have been the subject of a large number of studies. Three main reasons can be cited for optimizing the level of phenolic compounds in crop plants: their physiological role in plants, their technological significance for food processing, and their nutritional characteristics1 Indeed, an enormous diversity of phenolic antioxidants is found in fruits and vegetables, and their presence and roles can be affected or modified by several pre- and postharvest cultural practices and/or food processing technologies (Ruiz-García et al. 2012, Goldman et al. 1999, Tudela et al. 2002). In winegrapes, the technological importance of phenolic compounds, mainly flavonoids, is well-known.

Climate change and harvest date decisions have led to the evolution of must quality over the last decades. Increases in must sugar concentrations are among the most obvious consequences, quantitatively. Saccharomyces cerevisiae is a robust and acid tolerant organism. These properties, its sugar to ethanol conversion rate and ethanol tolerance make it the ideal production organism for wine fermentations. Unfortunately, high sugar concentrations may affect S. cerevisiae and lead to growth inhibition or yeast lysis, and cause sluggish or stuck fermentations. Even sublethal conditions cause a hyperosmotic stress response in S. cerevisiae which leads to increased formation of fermentation by-products, including acetic acid, which may exceed legal limits in some wines.

Like France, Hungary has many oak forests used for making barrels since many years. But if the differences between the woods of the North, the East and the South-West forests of France are well known, this is probably not the case of Hungarian forests. However taking into account the essential differences of climates and soils, differences must be significant and the general name “Hungarian oak” must not have any real meaning. We have studied precisely (determination of concentrations of volatile and non-volatile wood compounds, anatomical criteria, measurement of antioxidant capacity) of oaks collected from northeastern Hungary and others collected from the Danube valley in the northwest of the country.

Wine is a widely consumed alcoholic beverage with a high commercial value. More specifically, the worldwide consumption of rosé wine has increased by 20% since 2002[1]. But because of its high commercial value, it can become a subject of fraud, and authenticity control is necessarily required. More than one hundred polyphenols have been recently quantified in various rosé wines [2]. They are key components defining color, taste and quality of wines. Their amount and composition depend on many different factors such as grape variety, winemaking and age of the wine. In this study, the influence of geographic origin of some rosé French wines was investigated. An original and very fast UPLC-QTOF-MS method was developed and used to predict the geographic origin authenticity of rosé wines.

Bioactive polyphenols from grapes and wines, like stilbenes and flavonols (SaF), are often determined to nutritional evaluation, but also for many other purposes. The objective of this study was to quantify SaF in red wines from “Campanha Gaúcha”, a large and young viticultural region from South Brazil. Moreover, through statistical analysis, evaluate the influence of these compounds according to varieties, production process, harvest years and micro-regions of cultivation. A total of 58 samples of red wines were analyzed by high-performance liquid chromatography coupled to diode array detector (HPLC-DAD) for determination of trans-resveratrol (R), quercetin (Q), myricetin (M), kaempferol (K), trans-e-viniferin (V) and their precursor, cinnamic acid (C).