Monitoring the process to obtain red wine enriched in resveratrol and piceatannol without quality loss
Introduction
Numerous epidemiological studies have shown that long-term, moderate consumption of wine is linked to a lower level of cardiovascular illnesses. In 1992 a study conducted by Renaud and De Lorgeril revealed that the incidence of heart infarction in France is about 40% lower than in the rest of Europe; this was termed the “French paradox”, which appeared to be related to regular consumption of red wine (Renaud & De Lorgeril, 1992). Numerous other beneficial qualities, with positive effects on health, have been attributed to wine, including anti-oxidant, anti-carcinogenic and anti-spasmodic properties, enhancement or activation of bile secretion, antibacterial and antihistaminic agents (Pignatelli et al., 2006). The findings that red wine possesses more health-promoting activity than beer or spirits have led to research attention being focused on phenolic compounds; within this group, stilbenes (in particular, trans-resveratrol) seem to show high bioactivity.
In the last few years, interest in resveratrol has increased greatly, due to its numerous health-promoting properties (according to the ISI Web of Knowledge, there have been 4768 bibliographic entries in the last 10 years). Resveratrol has been described as a compound capable of preventing or reducing a wide range of diseases, such as cancer (Jang et al., 1997), cardiovascular diseases, and ischaemic damage (Bertelli, 2007); it can also increase the resistance to stress and prolong the lifespan of diverse organisms, from yeast to vertebrates (Guerrero, García-Parrilla, Puertas, & Cantos-Villar, 2009). Studies in mice have shown that obese animals, whose diet was supplemented with resveratrol, not only lived longer, but were more active and produced fewer cases of the negative effects of a high-calorie diet (Baur et al., 2006). Regarding bioavailability, numerous studies in animals and humans have shown that resveratrol is metabolised with relative difficulty. However, a relatively low dose of resveratrol obtained regularly from red wine or other dietary sources could be therapeutic in some cases (Bertelli, Bertelli, Gozzini, & Giovannini, 1998).
Apart from resveratrol, the presence in wine of other stilbenes, such as piceid, astringin, piceatannol and viniferins, has been described. Piceatannol is rarely found in wines and its presence in wines is very interesting since it is bioactive and has a long plasma half-life. It exhibits a pronounced anti-oxidant activity and exerts immunosuppressive, anti-leukaemic, and anti-tumorigenic activities in various cell lines and animal models (Murias et al., 2005). It has also been demonstrated that viniferins present anti-inflammatory and anti-proliferative activities (Kitanaka et al., 1990). All these stilbenes show high bioactivity but they are present in concentrations even lower than that of resveratrol, and less research has been done on them.
Dietary sources of resveratrol are rather limited, grapes and their derivatives being the main source (Guerrero et al., 2009). Resveratrol is found in the seed and skin of grapes (not in the flesh) and, hence, in grape juice and wine. Its concentration in red wine is higher than in white one because in red winemaking the must, grape skin and seed are in contact during the whole fermentation process. The amount of resveratrol in wines varies widely depending on many factors: grape variety, geographic region, agronomic factors, climate, plant stress conditions and oenological practices all have an influence (Bavaresco, 2003). Regarding optimum oenological practices for increasing resveratrol content, all the processes that maximize the extraction of phenols from skin are recommended (Vrhovsek, Wendelin, & Eder, 1997). It is difficult to predict the amount of resveratrol in wines because of many factors affecting resveratrol biosynthesis.
Different strategies can be undertaken to increase the concentration of stilbenes in grape, since these compounds are phytoalexins and, therefore, can be induced via different kinds of stress. In particular, postharvest treatment of grapes by ultraviolet-C light (UVC) has been suggested as suitable stress-promoting technology to obtain stilbene-enriched wine under laboratory conditions (Cantos, Espín, & Tomás-Barberán, 2003); however, the validity of the process needs to be confirmed in a standard-scale experimental winery as a prior step to industrial-scale production. Stilbene-enriched wines potentially offer added value compared to traditional wines (Barreiro, Colombo, & Cantos, 2008).
In this study, the winemaking process has been monitored both by oenological parameters and by content in stilbene compounds, to obtain a stilbene-enriched wine of standard quality, using grapes enriched by postharvest UVC treatment. In addition, the organoleptic characteristics of the resulting wine were also investigated using a tasting panel and GC–olfactometry.
Section snippets
Reagents
trans-Resveratrol and piceatannol were purchased from Sigma–Aldrich (Madrid, Spain). The trans isomers were transformed to cis forms under UV light. Acetic acid, dichloromethane, formic acid and methanol, all of analytical grade, were supplied by Panreac (Barcelona, Spain). Ultrapure water from a Milli-Q system (Millipore Corp., Bedford, MA) was used throughout this research.
Grapevine
The local red grape variety Jaen tinto (Vitis vinifera) was grown in Jerez de la Frontera (IFAPA, Rancho de la Merced).
Stilbene content and oenological parameters in grape
Grapes were sampled weekly, to monitor ripeness from veraison until harvesting (data not shown). Grapes were harvested at the appropriate stage of ripeness, while their capacity for the induction of resveratrol was preserved (Jeandet, Bessis, & Gautheron, 1991). As described in the Materials and Methods section (Fig 1), grapes were separated into three batches (CT–CT, CT and UV). The CT–CT grapes were de-stemmed and crushed immediately, while the CT and UV grapes were stored in tanks at 20 °C to
Conclusion
Although warm climates are associated with a low content of stilbenes in grape and wine, the stilbene content in grapes notably increased with postharvest UVC treatment. Grapes of the UV batch showed increased content in piceatannol, trans-resveratrol and viniferins, respectively, to around 7.4, 9.6 and 4.7 times the content measured in the non-treated controls.trans-Resveratrol concentration decreased progressively during winemaking, especially during AF; this is a finding which requires
Acknowledgements
The authors would like to thank the INIA for financing this study via the Project RTA2008-00014, and to the CSIC for permitting the use of Patent WO/2002/085137; ES 2177465.
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