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Sensory Analysis of Red Wines for Winemaking Purposes
C H A P T E R
17 Sensory Analysis of Red Wines for Winemaking Purposes Pablo Ossorio1 and Pedro Ballesteros Torres2 1
Winemaker and Oenology Consultant, Bodegas Hispano-Suizas, Ctra. Nacional 322, Valencia, Spain 2 Agronomical Engineer, Master of Wine, Av Bourgmestre Herinckx 16, Brussels, Belgium
17.1 TASTING OF GRAPES The main aim of tasting grapes is to determine the best moment to harvest. Since grapes are solid and differentiated, they cannot blend, it is of particular importance to apply a sound sampling procedure.
17.1.1 Field Sampling By their nature, grapes tend to have relevant degrees of heterogeneity among them. Since they get together in the vats during winemaking, it is crucial for the decision maker to have as precise as possible a picture of the average quality, state of health, and ripeness of the plot of land. As a previous step, sampling will be more precise and useful if there is good knowledge of soils, exposures, vines diversity, and in general all key vineyard descriptors. It will also benefit installed capacities to harvest by uniform plots. A compromise between an ideal situation in which all grapes come from an uniform plot, the possibilities in the winery to separate lots, and the expected commercial value of the wine needs to be reached in each occasion. Once the plots have been classified, up to whichever level of detail is possible and convenient, a sampling protocol can be applied. It is crucial that the sampling protocol is consistent from year to year, in reference to operations as well as the sampling points. By keeping consistency, the vine grower will build the vineyard’s track record and gain the necessary experience to understand the vineyard. A minimum of 100 grapes are collected for each tasting exercise and each plot. Those grapes shall come from all parts in the bunch—shoulders, middle, and lower tip—in a predetermined and fixed proportion (to be decided upon cluster shape and tightness, principally). In general, grapes tend to ripen earlier when they are closer to the vine trunk. Grapes from the tip of the bunch take some more time to ripen.
17.1.2 Grape Tasting The objective of the sensory analysis of the grapes in the field is to assess their composition and balance, as well as their ripeness. Tasting is undertaken in four consecutive phases: visual (with the eyes), tactile (with hands and palate), flavors (palate), and smell (nose and palate).
Red Wine Technology. DOI: https://doi.org/10.1016/B978-0-12-814399-5.00017-7
253
© 2019 Elsevier Inc. All rights reserved.
254
17. SENSORY ANALYSIS OF RED WINES FOR WINEMAKING PURPOSES
The visual phase’s main objective is to assess the sanitary quality of the grape—mostly that it is not infected by fungus or harmed by pests, and that it does not show any viral or structural malformation. It is also useful to ascertain the color and its intensity. The tactile phase is exclusive to grape tasting, because of the solid nature of grapes, and provides crucial information about the grape’s maturity. A number of indicators must be observed and registered. First, when collecting the grapes, the operators can have an idea on ripening degree by assessing the resistance offered to its separation from the pedicel (more resistance less maturity, obviously). The state of lignification of the stalks and the pedicel should also be registered (colors tending toward red and brown indicate ripeness, lignified stalks are also indicative of ripeness). It is very important to keep in mind that those indications are relative. Some grape varieties’stalks tend to ripen quite easily, while others never reach full lignification, although the fruit is in full maturation. Crushing the grape with the finger is the first really tactile operation. When ripe, grapes tend to be softer and less resilient to pressure, breaking easily. Again, this is a relative measure, which makes sense only if compared to similar exercises with the same variety in a similar plot or, even better, if compared with previous vintages in the same plot. Vintage variability makes things more difficult. In warm and drought-affected seasons, for instance, grapes tend to be more flaccid, while other conditions do not change. Tasting in palate is the most relevant phase in terms of the information to be acquired. The operation should provide data on the grape’s quality potential in terms of fruit and aroma precursors, the acidity, the sweetness, the bitterness, and the tannicity. In order to taste adequately, it is first of all necessary to separate pulp, skins, and seeds since each one of those grape components contributes to the wine in a different way. The physical process of separating skin, sedes, and pulp provides useful information: the easier the separation, the riper the grape (upon ceteris paribus conditions: all other conditions equal). The pulp should be tasted first, with a carefully applied protocol, aimed to ensure that all grapes are tasted the same. Normally, it is chewed in a homogeneous way, four or five times. The taster should then note her evaluation concerning sugar concentration in the pulp, any mineral impression and the acid tasting, with discernment between malic and tartaric acid. Malic acid is a key indicator of ripeness. Depending upon varieties, wine types, and climates, malic acid should be well below 2 g/L when harvesting, so that its presence in grapes should be barely detectable for grape tasters. The pulp’s sweetness is determined by the concentration of glucose and fructose, but it is partially compensated when tasting by the acidity (mostly tartaric) in the grape. It is of crucial importance not to underestimate the sweetness of grapes because of this cross-effect, since an error in this appreciation can result in jammy overripe high-pH wines. This is of particular importance in the present times, when the still not well known effects of climate change result in gaps between commercial, phenolic, and acid maturity. The pulp tends to be riper and sweeter in the central part, while it is slightly greener closer to the skins and closer to the seeds. Skin tasting is paramount to determine the grape’s state in what concerns polyphenolic maturation. As for the pulp, the taster should chew the skins in a homogeneous way, three to four times, following exactly the same operation for each grape in the tasting lot. The most relevant characteristics to note and register are the skins tasting profile, flavor intensity, and astringency. When tannins are not ripe, grapes’ skins tend not to be intensely flavored, give a strong feeling of dryness, and show herbaceous notes. After chewing, it is most convenient to note the color of the skins, and how quickly it gets out, which tends to give a good indication of its extractability. Besides, the riper the grape, the more intense the color found in the skins once chewed, and the quicker the color extraction when chewing. The grape seeds provide a lot of information about its state of phenological maturity. Tasting the seeds is essential to define the aging profile for the wine. It is also necessary to consider, when tasting seeds, that the proportion of seeds is variable. Such a proportion is to be noted each year, since it can complicate winemaking if excessive. The seeds, which are kept apart from pulp and skins, should be bitten with the teeth. Ripe seeds tend to be crunchy, not to be very astringent, and to release nutty flavors when bitten. Green seeds are hard to crack and very drying, releasing herbaceous and green aromas when open. The grape tasting always has to be accompanied by the chemical analysis of the different components of the grape, and with all the parameters the winemaker will be the one who decides at what time the harvest should start depending on the type of wine she wants to make.
RED WINE TECHNOLOGY
17.2 TASTING IN THE PRODUCTION OF RED WINE
255
17.2 TASTING IN THE PRODUCTION OF RED WINE Once grape are harvested and brought to the cellars, for fermentation and maceration, daily tasting of each vat becomes a very important activity enabling the winemakers to assess and keep under control the transformation of the must in the wine that is intended. As for the grapes, a clear tasting protocol, to be respected scrupulously, is of vital importance. A most important operation is to make each sample representative of its vat, by homogenizing the liquid, by pumping over or any other available system. The first tasting, before fermentation starts, should confirm the results of grape tasting in terms of quality and potential. Fresh fruit aromas, and any other notes typical of the variety or the place, as well as the initial color indications, should be consistent with the results in the vineyard. Once yeasts are added, or when natural fermentation starts, tasting the must becomes a less useful evaluation, since the organoleptic characteristics are hidden by the yeast activity. When the fermentation is well under way, the must in transformation recovers and gets new aromas as a consequence of the activity of the yeasts. The cold maceration of the first days of fermentation results in color intensification and the appearance of newly formed aromatic components, but at that moment it is quite difficult to get a precise idea on developments through tasting, because sugar is very high. Besides, tannins seem to be much softer than in the final wine, because of the very low concentration of alcohol in the first stages of fermentation (tannins extracted in water taste softer than in hydroalcoholic solution). Tasting during the beginning of the fermentation should be perceived mainly in the mouth, through a slight sensation of carbon in the tip of the tongue. The tasting of the must-wine at the beginning of the fermentation is usually very appealing, since the fermentation frees primary aromas and synthesizes secondary aromas that are more volatile with the presence of carbon dioxide in the liquid, and so more intense to the nose. It is easily perceived, on a day to day basis, how sweetness reduces and acids and tannins appear more prominent. If there is insufficient ripeness in the grapes, it shows up already in these early stages, with herbaceous and/or vegetal notes that become more nuanced later on in the winemaking process. Once the tumultuous fermentation begins, tasting becomes again complicated, because there is a lot of background “noise” that can interfere in the perception of aromatic profile and structure of the wine. In particular, sulfur compounds that are formed by lack of oxygen and easily assimilable nitrogen in wines during fermentation are quite prominent. It is crucial to pay attention to flaws that may appear during fermentation. Some of them are transient (can be corrected during fermentation), others are structural, and may result detrimental to wine quality. Flaws produced by sulfides and sulfur compounds are easily identifiable because of their rotten eggs, gas, dirty water notes. These compounds are produced by a high dose of sulfur at the beginning of fermentation, a high pH in the medium, or because of high fermentation temperatures that result in a lot of biomass, or lack of assimilable nitrogen and organic residues that absorb oxygen. The application of organic and inorganic nutrients together with oxygen serves to eliminate those compounds during fermentation, so that the off-odors disappear and the aromatic character of the base wine appears again. If not properly managed, those sulfur flaws can result in mercaptanoethanol, which gives rag, gunpowder, farmyard odors. Those odors are permanent; in order to eliminate them it is necessary to treat with copper sulfate or silver chloride. At tasting during fermentation, it is also possible to detect amyl notes, often described as pharmacy or medicinal, mainly due to excess of inorganic ammonium, at high pH and high fermentation temperatures. This aroma is very persistent and will remain in the wine. Pyrazines, particularly typical in wines made with cabernet and merlot varieties, can be avoided by allowing over ripeness in the grapes. Vegetal aromas of the type of freshly cut grass, green beans, crushed leaves, etc., are also present during the fermentation of grapes from plots with lack of phenological maturity or excessive yields. The treatment with protein of animal, vegetable, or fish origin decreases the effect significantly. A more serious problem is the detection through tasting and analysis of acetic acid and ethyl acetate. They can be produced at moderate quantities during the fermentation, with neutral or positive effects, but when there are fermentation arrests those problems can become grave, and difficult to eliminate from the wine. Sour smells, solvent, nail polish note, etc. are indicative of those problems.
RED WINE TECHNOLOGY
256
17. SENSORY ANALYSIS OF RED WINES FOR WINEMAKING PURPOSES
Deciding when to rack off the fermentation vats is crucial in defining the type of wine to be produced. Depending upon oxygenation strategies during fermentation, wines to be sold young are racked after a shorter period of time than wines that will be aged in oak. The key tasting notes to consider for racking decisions are based upon the tactile profile, indicating the tannin extraction in the wine and the color intensity. Wines racked at high densities, above 1020, are normally made as young wines, built upon soft harmonious round tannins, rather than more abundant firmer tannins typical of wines for aging. Just after the finalization of the alcoholic fermentation, the red wine is very complicated to taste, because there is far too much organic matter with strong taste, together with malic acid that highlights the tannin’s astringency. However, tasting becomes crucial immediately after, if it is decided to apply microoxygenation before malolactic fermentation. The most accurate way of deciding ethanal contents before the second fermentation is sensory analysis.
17.3 TASTING DURING MALOLACTIC FERMENTATION The malolactic fermentation is the second fermentation that takes place in a red wine to ensure its stability and harmony in the mouth. Lactic bacteria carry out this fermentation, which should be tightly controlled in order to avoid possible organoleptic alterations in the wines. Red wines with malolactic effect are much more stable aromatically and microbiologically over time. If the red wine is high pH, low alcohol, and low SO2, malolactic fermentation is highly likely to trigger spontaneously in uncontrolled conditions. Upon those conditions, it is probable that the wine acquires aromas of putrefaction, which are associated with molecules such as Putrescine, or sweat aromas, stagnant water, which are indicative of Cadaverine. Both Putrecine and Cadaverine are organic molecules derived from the enzymatic decarboxylation of some amino acids. Lactic bacteria will use up all acetaldehyde produced during microoxygenation for those red wines that have been produced under this process. The wines will then develop from initial aromas of freshly cut apple and a certain bitterness in the mouth to a marked ripe fruit character, with softer tannins and less green impression. The end of the malolactic fermentation is indicated by the presence of diacetyl, which in low proportions reduces the fruit character of the wine and in higher quantity releases notes of vanilla, milk, and caramel. Some bacteria strains can transform cinnamic acids present in the grapes into vinyl phenols, which are the substrate for the synthesis of ethyl phenols, which release odors of barnyard, leather, horse sweat, in the case of ethyl phenol, and aromas of burnt gum and spices, in the case of ethyl guaiacol.
17.4 CONCLUSIONS The use of tasting at all the steps of the winemaking process and in the control of grape quality is an indispensable tool to modulate wine flavor and to correct organoleptic deviations. Moreover, it is critical to take the suitable enological decisions to reach the wine type one is intending. It needs the sensory ability but also winemaking experience to predict how the evolution of the wine will proceed in order to reach the sensory quality that consumers are expecting.
RED WINE TECHNOLOGY
17 Sensory Analysis of Red Wines for Winemaking Purposes Pablo Ossorio1 and Pedro Ballesteros Torres2 1
Winemaker and Oenology Consultant, Bodegas Hispano-Suizas, Ctra. Nacional 322, Valencia, Spain 2 Agronomical Engineer, Master of Wine, Av Bourgmestre Herinckx 16, Brussels, Belgium
17.1 TASTING OF GRAPES The main aim of tasting grapes is to determine the best moment to harvest. Since grapes are solid and differentiated, they cannot blend, it is of particular importance to apply a sound sampling procedure.
17.1.1 Field Sampling By their nature, grapes tend to have relevant degrees of heterogeneity among them. Since they get together in the vats during winemaking, it is crucial for the decision maker to have as precise as possible a picture of the average quality, state of health, and ripeness of the plot of land. As a previous step, sampling will be more precise and useful if there is good knowledge of soils, exposures, vines diversity, and in general all key vineyard descriptors. It will also benefit installed capacities to harvest by uniform plots. A compromise between an ideal situation in which all grapes come from an uniform plot, the possibilities in the winery to separate lots, and the expected commercial value of the wine needs to be reached in each occasion. Once the plots have been classified, up to whichever level of detail is possible and convenient, a sampling protocol can be applied. It is crucial that the sampling protocol is consistent from year to year, in reference to operations as well as the sampling points. By keeping consistency, the vine grower will build the vineyard’s track record and gain the necessary experience to understand the vineyard. A minimum of 100 grapes are collected for each tasting exercise and each plot. Those grapes shall come from all parts in the bunch—shoulders, middle, and lower tip—in a predetermined and fixed proportion (to be decided upon cluster shape and tightness, principally). In general, grapes tend to ripen earlier when they are closer to the vine trunk. Grapes from the tip of the bunch take some more time to ripen.
17.1.2 Grape Tasting The objective of the sensory analysis of the grapes in the field is to assess their composition and balance, as well as their ripeness. Tasting is undertaken in four consecutive phases: visual (with the eyes), tactile (with hands and palate), flavors (palate), and smell (nose and palate).
Red Wine Technology. DOI: https://doi.org/10.1016/B978-0-12-814399-5.00017-7
253
© 2019 Elsevier Inc. All rights reserved.
254
17. SENSORY ANALYSIS OF RED WINES FOR WINEMAKING PURPOSES
The visual phase’s main objective is to assess the sanitary quality of the grape—mostly that it is not infected by fungus or harmed by pests, and that it does not show any viral or structural malformation. It is also useful to ascertain the color and its intensity. The tactile phase is exclusive to grape tasting, because of the solid nature of grapes, and provides crucial information about the grape’s maturity. A number of indicators must be observed and registered. First, when collecting the grapes, the operators can have an idea on ripening degree by assessing the resistance offered to its separation from the pedicel (more resistance less maturity, obviously). The state of lignification of the stalks and the pedicel should also be registered (colors tending toward red and brown indicate ripeness, lignified stalks are also indicative of ripeness). It is very important to keep in mind that those indications are relative. Some grape varieties’stalks tend to ripen quite easily, while others never reach full lignification, although the fruit is in full maturation. Crushing the grape with the finger is the first really tactile operation. When ripe, grapes tend to be softer and less resilient to pressure, breaking easily. Again, this is a relative measure, which makes sense only if compared to similar exercises with the same variety in a similar plot or, even better, if compared with previous vintages in the same plot. Vintage variability makes things more difficult. In warm and drought-affected seasons, for instance, grapes tend to be more flaccid, while other conditions do not change. Tasting in palate is the most relevant phase in terms of the information to be acquired. The operation should provide data on the grape’s quality potential in terms of fruit and aroma precursors, the acidity, the sweetness, the bitterness, and the tannicity. In order to taste adequately, it is first of all necessary to separate pulp, skins, and seeds since each one of those grape components contributes to the wine in a different way. The physical process of separating skin, sedes, and pulp provides useful information: the easier the separation, the riper the grape (upon ceteris paribus conditions: all other conditions equal). The pulp should be tasted first, with a carefully applied protocol, aimed to ensure that all grapes are tasted the same. Normally, it is chewed in a homogeneous way, four or five times. The taster should then note her evaluation concerning sugar concentration in the pulp, any mineral impression and the acid tasting, with discernment between malic and tartaric acid. Malic acid is a key indicator of ripeness. Depending upon varieties, wine types, and climates, malic acid should be well below 2 g/L when harvesting, so that its presence in grapes should be barely detectable for grape tasters. The pulp’s sweetness is determined by the concentration of glucose and fructose, but it is partially compensated when tasting by the acidity (mostly tartaric) in the grape. It is of crucial importance not to underestimate the sweetness of grapes because of this cross-effect, since an error in this appreciation can result in jammy overripe high-pH wines. This is of particular importance in the present times, when the still not well known effects of climate change result in gaps between commercial, phenolic, and acid maturity. The pulp tends to be riper and sweeter in the central part, while it is slightly greener closer to the skins and closer to the seeds. Skin tasting is paramount to determine the grape’s state in what concerns polyphenolic maturation. As for the pulp, the taster should chew the skins in a homogeneous way, three to four times, following exactly the same operation for each grape in the tasting lot. The most relevant characteristics to note and register are the skins tasting profile, flavor intensity, and astringency. When tannins are not ripe, grapes’ skins tend not to be intensely flavored, give a strong feeling of dryness, and show herbaceous notes. After chewing, it is most convenient to note the color of the skins, and how quickly it gets out, which tends to give a good indication of its extractability. Besides, the riper the grape, the more intense the color found in the skins once chewed, and the quicker the color extraction when chewing. The grape seeds provide a lot of information about its state of phenological maturity. Tasting the seeds is essential to define the aging profile for the wine. It is also necessary to consider, when tasting seeds, that the proportion of seeds is variable. Such a proportion is to be noted each year, since it can complicate winemaking if excessive. The seeds, which are kept apart from pulp and skins, should be bitten with the teeth. Ripe seeds tend to be crunchy, not to be very astringent, and to release nutty flavors when bitten. Green seeds are hard to crack and very drying, releasing herbaceous and green aromas when open. The grape tasting always has to be accompanied by the chemical analysis of the different components of the grape, and with all the parameters the winemaker will be the one who decides at what time the harvest should start depending on the type of wine she wants to make.
RED WINE TECHNOLOGY
17.2 TASTING IN THE PRODUCTION OF RED WINE
255
17.2 TASTING IN THE PRODUCTION OF RED WINE Once grape are harvested and brought to the cellars, for fermentation and maceration, daily tasting of each vat becomes a very important activity enabling the winemakers to assess and keep under control the transformation of the must in the wine that is intended. As for the grapes, a clear tasting protocol, to be respected scrupulously, is of vital importance. A most important operation is to make each sample representative of its vat, by homogenizing the liquid, by pumping over or any other available system. The first tasting, before fermentation starts, should confirm the results of grape tasting in terms of quality and potential. Fresh fruit aromas, and any other notes typical of the variety or the place, as well as the initial color indications, should be consistent with the results in the vineyard. Once yeasts are added, or when natural fermentation starts, tasting the must becomes a less useful evaluation, since the organoleptic characteristics are hidden by the yeast activity. When the fermentation is well under way, the must in transformation recovers and gets new aromas as a consequence of the activity of the yeasts. The cold maceration of the first days of fermentation results in color intensification and the appearance of newly formed aromatic components, but at that moment it is quite difficult to get a precise idea on developments through tasting, because sugar is very high. Besides, tannins seem to be much softer than in the final wine, because of the very low concentration of alcohol in the first stages of fermentation (tannins extracted in water taste softer than in hydroalcoholic solution). Tasting during the beginning of the fermentation should be perceived mainly in the mouth, through a slight sensation of carbon in the tip of the tongue. The tasting of the must-wine at the beginning of the fermentation is usually very appealing, since the fermentation frees primary aromas and synthesizes secondary aromas that are more volatile with the presence of carbon dioxide in the liquid, and so more intense to the nose. It is easily perceived, on a day to day basis, how sweetness reduces and acids and tannins appear more prominent. If there is insufficient ripeness in the grapes, it shows up already in these early stages, with herbaceous and/or vegetal notes that become more nuanced later on in the winemaking process. Once the tumultuous fermentation begins, tasting becomes again complicated, because there is a lot of background “noise” that can interfere in the perception of aromatic profile and structure of the wine. In particular, sulfur compounds that are formed by lack of oxygen and easily assimilable nitrogen in wines during fermentation are quite prominent. It is crucial to pay attention to flaws that may appear during fermentation. Some of them are transient (can be corrected during fermentation), others are structural, and may result detrimental to wine quality. Flaws produced by sulfides and sulfur compounds are easily identifiable because of their rotten eggs, gas, dirty water notes. These compounds are produced by a high dose of sulfur at the beginning of fermentation, a high pH in the medium, or because of high fermentation temperatures that result in a lot of biomass, or lack of assimilable nitrogen and organic residues that absorb oxygen. The application of organic and inorganic nutrients together with oxygen serves to eliminate those compounds during fermentation, so that the off-odors disappear and the aromatic character of the base wine appears again. If not properly managed, those sulfur flaws can result in mercaptanoethanol, which gives rag, gunpowder, farmyard odors. Those odors are permanent; in order to eliminate them it is necessary to treat with copper sulfate or silver chloride. At tasting during fermentation, it is also possible to detect amyl notes, often described as pharmacy or medicinal, mainly due to excess of inorganic ammonium, at high pH and high fermentation temperatures. This aroma is very persistent and will remain in the wine. Pyrazines, particularly typical in wines made with cabernet and merlot varieties, can be avoided by allowing over ripeness in the grapes. Vegetal aromas of the type of freshly cut grass, green beans, crushed leaves, etc., are also present during the fermentation of grapes from plots with lack of phenological maturity or excessive yields. The treatment with protein of animal, vegetable, or fish origin decreases the effect significantly. A more serious problem is the detection through tasting and analysis of acetic acid and ethyl acetate. They can be produced at moderate quantities during the fermentation, with neutral or positive effects, but when there are fermentation arrests those problems can become grave, and difficult to eliminate from the wine. Sour smells, solvent, nail polish note, etc. are indicative of those problems.
RED WINE TECHNOLOGY
256
17. SENSORY ANALYSIS OF RED WINES FOR WINEMAKING PURPOSES
Deciding when to rack off the fermentation vats is crucial in defining the type of wine to be produced. Depending upon oxygenation strategies during fermentation, wines to be sold young are racked after a shorter period of time than wines that will be aged in oak. The key tasting notes to consider for racking decisions are based upon the tactile profile, indicating the tannin extraction in the wine and the color intensity. Wines racked at high densities, above 1020, are normally made as young wines, built upon soft harmonious round tannins, rather than more abundant firmer tannins typical of wines for aging. Just after the finalization of the alcoholic fermentation, the red wine is very complicated to taste, because there is far too much organic matter with strong taste, together with malic acid that highlights the tannin’s astringency. However, tasting becomes crucial immediately after, if it is decided to apply microoxygenation before malolactic fermentation. The most accurate way of deciding ethanal contents before the second fermentation is sensory analysis.
17.3 TASTING DURING MALOLACTIC FERMENTATION The malolactic fermentation is the second fermentation that takes place in a red wine to ensure its stability and harmony in the mouth. Lactic bacteria carry out this fermentation, which should be tightly controlled in order to avoid possible organoleptic alterations in the wines. Red wines with malolactic effect are much more stable aromatically and microbiologically over time. If the red wine is high pH, low alcohol, and low SO2, malolactic fermentation is highly likely to trigger spontaneously in uncontrolled conditions. Upon those conditions, it is probable that the wine acquires aromas of putrefaction, which are associated with molecules such as Putrescine, or sweat aromas, stagnant water, which are indicative of Cadaverine. Both Putrecine and Cadaverine are organic molecules derived from the enzymatic decarboxylation of some amino acids. Lactic bacteria will use up all acetaldehyde produced during microoxygenation for those red wines that have been produced under this process. The wines will then develop from initial aromas of freshly cut apple and a certain bitterness in the mouth to a marked ripe fruit character, with softer tannins and less green impression. The end of the malolactic fermentation is indicated by the presence of diacetyl, which in low proportions reduces the fruit character of the wine and in higher quantity releases notes of vanilla, milk, and caramel. Some bacteria strains can transform cinnamic acids present in the grapes into vinyl phenols, which are the substrate for the synthesis of ethyl phenols, which release odors of barnyard, leather, horse sweat, in the case of ethyl phenol, and aromas of burnt gum and spices, in the case of ethyl guaiacol.
17.4 CONCLUSIONS The use of tasting at all the steps of the winemaking process and in the control of grape quality is an indispensable tool to modulate wine flavor and to correct organoleptic deviations. Moreover, it is critical to take the suitable enological decisions to reach the wine type one is intending. It needs the sensory ability but also winemaking experience to predict how the evolution of the wine will proceed in order to reach the sensory quality that consumers are expecting.
RED WINE TECHNOLOGY