Methyl jasmonate: effect on proanthocyanidin content in Monastrell and Tempranillo grapes and wines

Proanthocyanidins or “condensed tannins” play an important role in the organoleptic properties of wines, and their levels in both grapes and wines can be achieved by several means. One such way is based on the use of elicitors, agrochemicals which were originally designed to improve resistance to plant pathogens, but whose action mechanism has also been found to increase polyphenol levels. Among these chemical elicitors, jasmonic acid and, especially, its methyl ester, methyl jasmonate (MeJ), can increase the production of secondary metabolites such as anthocyanins, flavonoids, phenolic acids, and other antioxidant molecules, enhancing the fruit quality and post-harvest life, as well as increasing their health-related properties. The objective of this study was to determine whether the application during two consecutive years of MeJ to Monastrell and Tempranillo varieties at the veraison period had any effect on the accumulation of proanthocyanidins and subsequently on their extractability into wine. The results obtained indicated that treatments increased the grape proanthocyanidin content only in one of the years but for both varieties tested, as well as their levels in the corresponding wines.This work was made possible by financial assistance from the Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria. RTA2013-00053-C03-02 and RTA2013-00053-C03-01. J. P. and T. G.-C. also wish to thank the INIA-Gobierno de La Rioja and European Social Fundfor their contracts. T. G.-C. also thanks MINECO for funding her Ramón y Cajal contract.Peer reviewe

Chemical and physical methodologies for the replacement/reduction of sulfur dioxide use during winemaking: review of their potentialities and limitations

Sulfur dioxide (SO 2 ) is probably one of the most versatile and efficient additives used in winemaking due to its antiseptic and antioxidant properties. This compound is also important for minimizing phenolic polymerization rate and color loss during wine aging. However, allergies caused by SO 2 -derived compounds, namely the sulfites, are becoming more frequent, causing symptoms such as headaches, nausea, gastric irritation, and breathing difficulties in asthma patients. Consequently, the legislated maximum concentration of SO 2 allowed in wines has been gradually reduced. For this reason, it is crucial in a competitive global winemaking market strategy, to reduce or even eliminate the use of SO 2 as a preservative and to search for new healthier and safe strategies. This work gives an overview of the main methodologies that have been proposed so far and that have potential to be used in winemaking as an alternative to SO 2 . The addition of compounds such as dimethyl dicarbonate, bacteriocins, phenolic compounds, and lysozyme, and the use of physical methods, namely pulsed electric fields, ultrasound, ultraviolet radiation, and high pressure are discussed and critically evaluated