Red Wine Technology

Antonio Morata

• Publisher: Academic Press
• Year: 2018
• ISBN:
  9780128144008
• Topic: Technology & Engineering
• Subtopic: Food Science
• Index: Technology & Engineering

Red Wine Technology is a solutions-based approach on the challenges associated with red wine production. It focuses on the technology and biotechnology of red wines, and is ideal for anyone who needs a quick reference on novel ways to increase and improve overall red wine production and innovation. The book provides emerging trends in modern enology, including molecular tools for wine quality and analysis. It includes sections on new ways of maceration extraction, alternative microorganisms for alcoholic fermentation, and malolactic fermentation. Recent studies and technological advancements to improve grape maturity and production are also presented, along with tactics to control PH level.This book is an essential resource for wine producers, researchers, practitioners, technologists and students.

• Winner of the OIV Award 2019 (Category: Enology), International Organization of Vine and Wine
• Provides innovative technologies to improve maceration and color/tannin extraction, which influences color stability due to the formation of pyranoanthocyanins and polymeric pigments
• Contains deep evaluations of barrel ageing as well as new alternatives such as microoxigenation, chips, and biological ageing on lees
• Explores emerging biotechnologies for red wine fermentation including the use of non- Saccharomyces yeasts and yeast-bacteria coinoculations, which have effects in wine aroma and sensory quality, and also control spoilage microorganisms

Chapter 1

Grape Maturity and Selection

Automatic Grape Selection

Susana Río Segade, Simone Giacosa, Vincenzo Gerbi and Luca Rolle, Department of Agricultural, Forestry and Food Sciences, University of Turin, Grugliasco (TO), Italy

Abstract

Grape maturity at harvest strongly affects wine quality and, therefore, an adequate strategy of berry selection based on objective quality indicators is a key issue to produce high-quality and premium wines. In red wine technology, phenolic composition, aromatic profile, chromatic characteristics, mechanical properties, reducing sugars content, and acidity contribute most to grape quality.

In the field, preharvest berry selection makes possible the identification of vineyard sections or even homogeneous groups of vineyards with similar grape composition. Precision viticulture approaches are highly profitable to manage harvest but require the use of advanced mapping technologies, involving drones, satellites, global positioning systems, geographic information systems, or local and remote sensors. However, intra- and intercluster variability in berry quality can be only solved in the winery. In this case, postharvest strategies are used such as manual sorting tables or automatic selection based on berry density and optical measurements (near-infrared/visible spectrometry) combined with multi- and hyperspectral imaging.

Keywords

Grape maturity; quality assessment; berry sorting; precision viticulture; chemical composition; mechanical properties; chromatic characteristics; near infrared spectroscopy; spectral imaging; chemometrics

1.1 Physicochemical Characteristics of Enological Interest

Modern enology bases the premises about wine quality on the synergic “vineyard–winery” alliance that permitted to surpass the dualism that, in recent years, has often characterized an enological production that is particularly quantity oriented. The basis of wine quality is intrinsically confined in that of its raw material: the grape. In particular, grape quality at harvest derives from the compositional balance of several primary and secondary metabolites: sugars, organic acids, colorant and tannic substances, odorous compounds, and their precursors. In particular, the phenolic component in red wines is strategic for wine characteristics, since it influences the color, the gustative perceptions, and overall the longevity. Together with the aroma precursors, the phenolic substances are therefore mainly responsible for the wine “typicity.” These aspects are even more relevant for a varietal enology (i.e., winemaking of a single grape variety, which is often the expression of a determined territory), where the emphasizing of the raw material must be at the maximum level. In fact, in this case there is not the possibility of finding the right sensorial balance that can derive from the blend of grapes from different cultivars.

The importance of phenolic compounds contained in the solid parts of the berries (skins and seeds) and their essential role in the sensorial characterization of different red wines are nowadays a known aspect, and have been known in scientific literature since the 1980s (Arnold et al., 1980; Robichaud and Noble, 1990). The chromatic characteristics, astringency, and bitterness of a wine are highly influenced by the content and degree of polymerization and/or condensation of phenolic compounds (Blanco-Vega et al., 2014; Cheynier et al., 2006). Knowing the polyphenolic content and profile of the grapes allows the maceration and winemaking process to be planned, allowing winemakers to fully exploit the potentiality that the grape attains in the vineyard (Zanoni et al., 2010).

Nowadays, thanks to advanced chromatographic techniques, better performing detectors, and specific analytical protocols dedicated to grape extracts and wines (Aleixandre-Tudo et al., 2017; Valls et al., 2009), it is possible to determine and quantify the several molecules belonging to the different classes of the phenolic compounds and their derivatives, which have been classified as: anthocyanins, hydroxybenzoic acids, hydroxycinnamic acids, stilbenes, flavanol, flavonol, and others (Ribèreau-Gayon et al., 2006). In parallel with this new knowledge, numerous recent studies have researched and valued the relationships existing among the mouthfeel properties, the different polyphenolic classes/molecules, and the relative sensory perceptions threshold (Brossaud et al., 2001; Gonzalo-Diago et al., 2014; Laguna et al., 2017a). In particular, regarding grape and wine tannins, the molecular sizes and the monomeric composition of proanthocyanidins have a large influence on the sensation of astringency. More specifically, the greater degree of polymerization and the greater percentage of galloylation will cause a greater sensation of astringency (Laguna et al., 2017b; Kontoudakis et al., 2011; Vidal et al., 2003).

Despite this important new knowledge, because of the high scientific competence requested from the analysts and the cost itself of the analysis, these chromatographic methodologies are still limited by not being very applicable directly to the evaluation of the grape in preharvest, at least when there are a lot of samples to be examined. Therefore, spectrophotometric analysis of phenolic compounds in grapes and wines are still the most used in the viticultural-enology sector (Aleixandre-Tudo et al., 2017). Although characterized by a major spectra of determinable molecules, global indexes such as total anthocyanin, total polyphenol, oligomeric flavanols (flavan reactive to vanillin), or polymeric tannins (proanthocyanindin) are evaluated in commercial and winery laboratories by spectrophometric methods based on their ease of use as a routine analytical technique (Di Stefano and Cravero, 1991; Rolle et al., 2011a).

Even though the use of spectrophotometric indexes permits to best assess the content of anthocyanins and tannins present in the grape skin and seed, in many cases adequate direct correlations were not found with the corresponding analytical parameters in related produced wines.

In fact, in maceration during skin contact, only part of the phenolic compounds is extracted. Consequently, in the last two decades, winemakers have been very interested in a new concept called “Phenolic Maturity,” defined by Glories and Augustin (1993) as the concentration of phenolic compounds in grapes, and the ease with which they are released. This definition encompasses the anthocyanin concentration in the skin, their degree of extractability (cell maturity index; EA%), and the flavanol concentration in the seeds and skins and their degree of polymerization (seed maturity index; Mp%). These two indexes, determined with some modifications with respect to the original methods useful only for French varieties, are nowadays quite commonly used in the enology sector in order to select the grape ripeness thanks to high correlation with the color index (CIE L*a*b* parameters, color intensity and hue) and phenolic characteristics of wines (Cagnasso et al., 2008; Romero-Cascales et al., 2005). There have been authors, though, that proposed different methodologies, that are cheaper and less laborious, to determine a correct grape phenolic maturity (Celotti et al., 2007; Kontoudakis et al., 2010).

Grape maturity is associated with physicochemical changes in the skin and pulp cell walls. During the ripening, changes in the composition and structure of the cell wall, as well as in the structure of the tissue, may determine the mechanical resistance and the texture of the berry (Zouid et al., 2013). These structural changes can be assessed in a subjective way by simple berry tasting, an immediate means of grape evaluation. In addition to berry mechanical traits and sugars/acidity ratio estimation, the berry sensory assessment was found to be useful for the evaluation of skin and seed astringency, important parameters related also to overall grape ripeness. However, a high experience of the matter is necessary to perform meaningful sensory assessments, especially for seed phenolic ripeness evaluation, since it is a complicated task and it leads very quickly to sensory fatigue (Le Moigne et al., 2008; Olarte Mantilla et al., 2012). To exploit these changes, a very innovative instrumental approach was proposed by Río Segade et al. (2008), where phenolic ripeness of grape skin was assessed by texture analysis. A significant multiple linear regression was found between EA%, berry skin break force, and thickness. Subsequent studies have shown that the break force and the thickness of berry skin can be considered mechanical properties, adequate for the estimation of the degradability of the skin cell wall and, therefore, of the extractability of anthocyanins from skin to must/wine (Río Segade et al., 2011a; Rolle et al., 2008). More recently, the evolution of mechanical and acoustic texture parameters of grape seed during maturation was studied (Rolle et al., 2012a,b), and important relationships with extractable phenols were found (Rolle et al., 2013). Like this, the characterization of the mechanical properties of grape berries appears to be an important parameter to understand grape ripening. However, published studies have shown that the changes of several grape textural properties during ripening are strongly influenced by the growing conditions and vintage. So, the “terroir” effect on mechanical behavior must be considered in the data interpretation (Le Moigne et al., 2008; Río Segade et al., 2011b).

All of this research activity, to some extent even pioneering, permitted, on one hand, to give useful tools and methodologies to the sector operators in order to objectively define the level of grape ripeness, and, on the other hand, to increase the awareness of the red wine winemakers to find new criteria and indexes in addition to the traditional measurement of technological variables (i.e., sugars, organic acid content, pH), in the choice of the harvest date. Therefore, over the last years there has been a clear inclination of the enterprises toward increased consideration of polyphenolic maturity or aroma. Harvest dates need to be carefully considered since they can be based on objective chemical–physical data interpretation or also only subjective evaluations of optimum berry composition in view of ultimate wine quality, whose definition is exposed to individual interpretation and trends, and may also depend on commercial targets, market constraints, processing capacity, and other factors.

The synthesis and accumulatio...

Table of contents

• Cover image
• Title page
• Table of Contents
• Copyright
• List of Contributors
• Prologue
• Chapter 1. Grape Maturity and Selection: Automatic Grape Selection
• Chapter 2. Acidification and pH Control in Red Wines
• Chapter 3. Maceration and Fermentation: New Technologies to Increase Extraction
• Chapter 4. Use of Non-Saccharomyces Yeasts in Red Winemaking
• Chapter 5. Yeast Biotechnology for Red Winemaking
• Chapter 6. Malolactic Fermentation
• Chapter 7. Yeast-Bacteria Coinoculation
• Chapter 8. Molecular Tools to Analyze Microbial Populations in Red Wines
• Chapter 9. Barrel Aging; Types of Wood
• Chapter 10. Emerging Technologies for Aging Wines: Use of Chips and Micro-Oxygenation
• Chapter 11. New Trends in Aging on Lees
• Chapter 12. Evolution of Proanthocyanidins During Grape Maturation, Winemaking, and Aging Process of Red Wines
• Chapter 13. Wine Color Evolution and Stability
• Chapter 14. Polymeric Pigments in Red Wines
• Chapter 15. Spoilage Yeasts in Red Wines
• Chapter 16. Red Wine Clarification and Stabilization
• Chapter 17. Sensory Analysis of Red Wines for Winemaking Purposes
• Chapter 18. Management of Astringency in Red Wines
• Chapter 19. Aromatic Compounds in Red Varieties
• Chapter 20. The Instrumental Analysis of Aroma-Active Compounds for Explaining the Flavor of Red Wines
• Chapter 21. SO2 in Wines: Rational Use and Possible Alternatives
• Chapter 22. Red Wine Bottling and Packaging
• Chapter 23. Red Winemaking in Cool Climates
• Chapter 24. Red Winemaking in Cold Regions With Short Maturity Periods
• Author Index
• Subject Index