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A study in order to differentiate Tempranillo and Tempranillo blanco grapes and wines from A.O.C. Rioja (Spain) has been carried out. The three most important groups of chemical compounds in grapes and wines were determined: nitrogen and phenolic compounds by HPLC–DAD, and volatile compounds by GC–MS. A machine learning approach was carried out to achieve the most important chemical parameters to differentiate Tempranillo and Tempranillo blanco grapes and wines based on the Kruskal–Wallis test, F-score feature selector, and support vector machine classification. Four importance levels were established for both grape and wine discrimination. The first level is composed of variables that can differentiate Tempranillo and Tempranillo blanco grapes and wines by analyzing the chemical concentrations. The second, third, and fourth level of importance is composed of a variable set that can correctly classify the samples, each one determined according to the F-score importance ranking and the SVM discriminations. Some chemical compounds demonstrated to be good predictors to wine and grape discriminations, whereas some chemicals are only a good predictor to one discrimination approach.

Nowadays, consumers are demanding high-quality and healthy wines. This change in the trend of consumption could be considered a challenge to wine industry. For this reason, new technologies are being studied to better know their possible implementation in the oenological industry. One of these promising technologies is the pulsed electric field (PEF). This is a nonthermal technology in which high-intensity but short micropulses are applied to a liquid material placed between two electrodes. The energy causes the electroporation of cells what have two direct applications in oenology. The first technique is aimed to electroporate vegetal cells to enhance the extraction of interesting must and wine compounds and the other one is focused on electroporating the microorganism cells to render them inactivate. Both applications have demonstrated to be interesting and positive for general wine quality. PEF increases the grape volatile composition and reduces the volatile acidity of wines, furthermore interesting phenolic compounds related to color and healthy molecules as resveratrol are more extracted from grape skins after PEF treatments. Additionally, PEF inactivates the natural microbiota present in wines, being especially effective for bacteria as acetic acid and lactic acid bacteria populations. In spite of these positive applications of PEF for must and wine quality, further research is still needed to solve some possible problem of the scale-up of PEF from pilot plant to oenological industrial level.

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.

Two hundred young wines from the D.O.Ca. Rioja (Spain) coming from two consecutive vintages, 100 wines from 2012 and 100 wines from 2013, were analysed and compared with respect to physicochemical composition and Brettanomyces presence. This microorganism was tested using two techniques: qPCR and an odorimetric test. In 2013, the harvest was characterized by late ripening, health problems with the grapes, and difficulties during vinification. Differences between 2012 and 2013 wines were found both for analytical parameters and as for the presence of the spoilage yeast, Brettanomyces, which was much more prevalent in the 2013 vintage. Moreover, the results showed that for some wines in which Brettanomyces was detected by qPCR at concentration higher than 102 cells/ml, no “Brett” character was found in the odorimetric test. This would indicate that the contamination of a wine by this yeast is not the only factor involved in spoilage. The strains of Brettanomyces, their physiological state, and viability, besides the specific composition of wine, could be important in the “Brett” character appearance. In this study, the wines which developed spoilage in the odorimetric test had slightly lower pH and alcoholic strength values, but higher levels of volatile acidity, reducing sugars and density in comparison with those wines than were not affected. Most of these factors are favourable for the development of Brettanomyces.

This chapter provides a brief introduction to PEF technologies and its fundamentals. It also summarizes the potential applications of PEF treatments to improve the alcoholic fermentation of must, through the different studies that have been performed in this respect. These include the application of PEF to inactivate the microbial population of grape must and its potential as an alternative method to reduce or eliminate the addition of SO2 during the alcoholic fermentative process and ageing in bottles. It comprises, as well, the potential uses of PEF to increase the rate and the yield of mass transfer processes occurring during the vinification of red and rosé wines. In addition, the benefits of PEF on aiding the pressing process of grapes for white winemaking are mentioned.

[Aim] The aim was to study the effects of two different cover crops (leguminous versus gramineous) on soil NO3−-N availability, grapevine N status, and yeast-assimilable N (YAN) and amino acid profile in the must of a cv. Tempranillo vineyard from La Rioja (Spain) over 3 years., [Methods] Three treatments were established: gramineous (barley) and leguminous (Persian clover) cover crops and conventional tillage. Soil total N and extractable NH4+-N at bloom, soil NO3−-N content from budbreak to postharvest, leaf N content at bloom, and free amino acids and ammonia in must were monitored., [Results] Each year, the barley cover crop treatment had lower soil NO3−-N than tillage, while the clover treatment showed lower soil NO3−-N than tillage in 2009 and showed higher values in 2010 and 2011. In 2011 leaf N content, yeast-assimilable N (YAN), and some amino acids in the grapes were lower in barley cover crop treatment thus affecting the amino acid profile. Meanwhile, the clover cover crop did not have these effects. Furthermore, relationships between leaf N content and various amino acids were also found., [Conclusions] With the barley cover crop treatment, soil N availability decreased from the first year of the experiment, provoking a decrease in N grapevine status and in content of YAN and various amino acids at the third year. In contrast, clover cover crop maintained N grapevine status, YAN, and amino acid profile similar to conventional tillage. Therefore, our study shows how soil N can be managed both within a year and from year to year when two different cover crops are sown and how the grapevine N nutritional status and YAN content and amino acid profile can be modified in the must.

Brettanomyces bruxellensis is a major cause of wine spoilage due to the production of ethyl phenols, and it has become a major worldwide oenological concern in recent years. The most critical factor in volatile phenol production is the presence of microorganisms responsible for biosynthesis. In this work, carried out during three consecutive harvests, grapes and the first step in grape processing (stemming–crushing) have been evaluated as the origin of wine contamination by these spoilage yeasts. Results showed that there was nil or minimal presence of Brettanomyces yeasts in grapes and on the stemmer, in levels that the method was not able to detect. This shows that the main contamination of wines by this microorganism occurs in later stages of the vinification process and/or during storage. The contamination of many wines with Brettanomyces, either via the fruit or from the winery environment, during the early stages of vinification and before the start of aging, was confirmed by analyzing 100 recently made red wines, in which this yeast was detected in a high percentage of wines (27 %). However, the level of Brettanomyces yeasts found in the samples was low, with values which would not be sufficient to cause organoleptic defects. Consequently, this study confirms that many wines are still tainted by Brettanomyces when the winemaking phase comes to an end. It was also found that wines with problems during fermentation had a higher level of Brettanomyces. This is why it is essential to ensure strict controls during fermentation processes and conservation to prevent wine becoming spoiled or tainted.