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The quality of grapes, as well as wine quality, flavor, stability, and sensorial characteristics depends on the content and composition of several different groups of compounds from grapes. One of these groups of compounds are sugars and consequently the alcohol content quantified in wines after alcoholic fermentation. During grape berry ripening, sucrose transported from the leaves is accumulated in the berry vacuoles as glucose and fructose. The wine alcohol content continues to be a challenge in oenology, as it is also the study of the role of chemosensory factors in alcohol intake and consumer preferences. Several technical and scientific advances have occurred in recent years, such as identification of receptors and other important molecules involved in the transduction mechanisms of flavor. In addition, consumers know that wines with high alcohol content can causes a gustatory disequilibrium affecting wine sensory perceptions leading to unbalanced wines. Hence, the object of this review is to enhance the knowledge on wine grape sugar composition, the alcohol perception on a sensorial level, as well as several technological practices that can be applied to reduce the wine alcohol content.
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Beverages 2015, 1, 292-310; doi:10.3390/beverages1040292
ISSN 2306-5710
From Sugar of Grape to Alcohol of Wine: Sensorial Impact of
Alcohol in Wine
António M. Jordão 1, Alice Vilela 2 and Fernanda Cosme 2,*
1 Agrarian Higher School, Polytechnic Institute of Viseu (CI & DETS), Estrada de Nelas,
Quinta da Alagoa, Ranhados, Viseu 3500-606, Portugal; E-Mail:
2 CQ-VR, Chemistry Research Centre, School of Life Sciences and Environment, Department of
Biology and Environment, Universidade de Trás-os-Montes e Alto Douro, Edifício de Enologia,
Apartado 1013, Vila Real 5001-801, Portugal; E-Mail:
* Author to whom correspondence should be addressed; E-Mail:;
Tel.: +351-259-350-657; Fax: +351-259-350-480.
Academic Editor: Lorenzo Stafford
Received: 30 August 2015 / Accepted: 23 October 2015 / Published: 2 November 2015
Abstract: The quality of grapes, as well as wine quality, flavor, stability, and sensorial
characteristics depends on the content and composition of several different groups of
compounds from grapes. One of these groups of compounds are sugars and consequently
the alcohol content quantified in wines after alcoholic fermentation. During grape berry
ripening, sucrose transported from the leaves is accumulated in the berry vacuoles as
glucose and fructose. The wine alcohol content continues to be a challenge in oenology, as
it is also the study of the role of chemosensory factors in alcohol intake and consumer
preferences. Several technical and scientific advances have occurred in recent years, such
as identification of receptors and other important molecules involved in the transduction
mechanisms of flavor. In addition, consumers know that wines with high alcohol content
can causes a gustatory disequilibrium affecting wine sensory perceptions leading to
unbalanced wines. Hence, the object of this review is to enhance the knowledge on wine
grape sugar composition, the alcohol perception on a sensorial level, as well as several
technological practices that can be applied to reduce the wine alcohol content.
Keywords: alcohol content; alcohol reduction technologies; grapes; sensory perception;
sugar accumulation; wine
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1. General Introduction
The sugar composition of berries has a key role in wine quality, since they determine the alcohol
content of the wines. Grape berry sugar composition and concentration change during grape ripening
and can be influenced by many factors, such as environment and viticulture management.
Alcohol is the most abundant volatile compound in wine and it can modify both the sensory
perception of aromatic attributes and the detection of volatile compounds [1]. Therefore, alcohol is
important for wine sensory sensations but also by their interaction with other wine components, such
as aromas [1] and tannins [2,3], also influencing wine viscosity and body [4] and our perceptions of
astringency, sourness, sweetness, aroma, and flavor [5].
In the last years, the alcohol content in wines has tended to increase, due to different factors. One of
them is the potential sugar increase in musts, attributed to the probable climate change [6,7]. However,
at the same time, a great number of consumers from several countries, especially from Europe, demand
more reduced alcohol beverages (9%–13% v/v) as a result of health and social concerns (i.e., traffic
penalties) [8–10]. The increasing alcohol levels in wine could be resolved using techniques to remove
or lower the wine alcohol content. However, it is important to know the limitations of these techniques
on the wine sensorial characteristics, as well as providing information related to wine quality and
consumer acceptance of these wines.
Mouthfeel and texture are the major determinants for consumer’s preference for foods, including
beverages [11–13]. Viscosity, density, and surface tension are the essential rheological properties
which affect the mouthfeel of liquid food products, such as wine. They also modify other sensory
properties like saltiness, sweetness, bitterness, flavor, and astringency [14–16]. It is important to
understand how and where the interactions are generated as they have impacts on the flavor perception
and the key sensory profile of food products. There are physical interactions between the components
in the food or beverage matrix influencing the volatiles release [17] and/or viscosity [18], and
multi-modal interactions resulting from the cognitive or psychological integration of the anatomically-
independent sensory systems [19].
Physical viscosity, density, and yield stress have also been used to give a more comprehensive
profile of the rheological properties of fluids [20]. While white wine alcohol concentration was found
to be highly correlated with the perceived intensity and physical measurements of viscosity and
density, the perceived viscosity and perceived density maxima were best described by quadratic and
cubic models, respectively [4]. Intensity maxima for viscosity and density occurred at 10% (v/v) and
12% (v/v) white wine alcohol concentration, respectively, although white wines of 7% (v/v) to
14% (v/v) alcohol concentration were not statistically differentiated for either attribute (perceived
viscosity and density) [4]. For example, alcohol is commonly utilized in composing various beverages
and flavored vodkas. For instance, in 2008, Finland Vodka Company noted a 30% increase in the sale
of flavored vodkas, which contain herb extracts and essences, plant distillates, fruits and their juices, and
volatile aromas [21]. According to the work of Pankiewicz and Jamroz [21], a link was found between
the concentrations of alcohol in pure vodka and in its blends with pear nectar and the perceived
sensory viscosity and density of the drink.
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Thus, the intention of this review is to contribute to a better knowledge on the grape sugar
composition, including the factors that influenced their accumulation during grape ripening, the alcohol
perception on sensorial level, as well as technological practical to reduce the wine alcohol content.
2. Grape Berry Composition—Sugars
Sugar accumulation in grape berries is an important phenomenon which has a great impact on the
amount of alcohol in wine. In addition, in berries, total sugar is also an important fruit quality factor in
table grapes. The predominant sugars that are present in grapes are glucose and fructose, with only
trace content of sucrose in grape berries of most cultivars. Only a few high-sucrose content cultivars
are detected in Vitis rotundifolia and hybrids between Vitis labrusca and Vitis vinifera [22–24].
Shiraishi et al. [25] identified two types of grapes based on sugar composition: hexose accumulators
for which the glucose/(fructose + sucrose) ratio was >0.8, and sucrose accumulators for which this
ratio was <0.8. According to Dai et al. [24], most Vitis vinifera cultivars have a glucose/fructose ratio
of 1 at maturity, while this ratio varies from 0.47 to 1.12 in wild species. In addition, only few a
species (Vitis champinii and Vitis doaniana) accumulate more glucose than fructose. Liu et al. [26]
analyzed sugar concentration of 98 different grape cultivars and concluded that glucose and fructose
were the predominant sugars in grape berries ranging from 45.86 to 122.89 mg/mL and from 47.64 to
131.04 mg/mL, respectively. Additionally, sucrose was present at trace amounts in most of the
cultivars studied (except for two cultivars of hybrids between Vitis labrusca and Vitis vinifera, which
contained large amounts of sucrose).
The accumulation of sugar in the form of glucose and fructose within the cellular medium,
specifically in the vacuoles, is one of the main features of the ripening process in grape berries and is a
major commercial consideration for the grape grower, winemaker, and dried grape producer. Thus,
sugar content is an indicator often used to assess ripeness and to mark the harvest. Moreover, as most
of the sugar is fermented to alcohol during the winemaking process, the measurement of sugar content,
the so-called “must weight”, allows the control of alcohol content in the wine.
3. Sugar Accumulation during Grape Ripening
A schematic representation of grape berry development, sugar uptake, and metabolism during grape
maturation is shown in Figure 1. Thus, during grape berry sugar accumulation, sucrose is produced
in leaves by photosynthetic carbon assimilation and is transported to the berry in the phloem [27].
Sucrose is loaded into the phloem by either a symplastic or apoplastic mechanism [28]. The presence
of an apoplastic step requires the involvement of membrane-located sugar transporter proteins
(“hexose transporters” in Figure 1) mediating the exit of sucrose from the phloem, and the uptake and
compartmentation of sugars across the plasma membrane and the tonoplast of flesh cells [29].
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Figure 1. Schematic representation of grape berry development, sugar uptake, and
metabolism during grape maturation. The curve indicates changes in berry size and two
possible pathways are indicated for sugar uptake and metabolism. Legend: (-----) berry
changes size. P
and V
Hexose transporters; P
and V
Sucrose transporters.
In the first phase of berry growth most of the sugar imported into the fruit is metabolized and grapes
contain relatively low levels of sugars. However, at véraison sugar accumulation begins and the
imported sucrose is converted into hexoses, which are stored in the vacuole. The grape berries
accumulate glucose and fructose in equal amounts at a relatively constant rate during ripening [30].
According to several authors [31,32], massive accumulation of glucose and fructose in the vacuoles of
mesocarp cells occurs after véraison and, twenty days after this period, the hexose content of the grape
berry is close to 1 M, with a glucose/fructose ratio of 1. Since sucrose is the major translocated sugar
in grape vine, the rapid accumulation of hexoses characterizing berry ripening must involve the
activity of invertases. Their expression is high at early stages of berry development, but it declines
greatly when hexose accumulation starts [28]. In addition, Hawker [33] found that invertase enzyme
activity in Sultana berries increased immediately after flowering and that the activity peaked 6–7
weeks later, at véraison, when the rapid accumulation of hexoses commenced. According to the same
author, another enzyme that might be involved in the breakdown of sucrose is sucrose synthase, which
also increases during véraison, but their maximal activity is low compared to the level of invertase
activity (200–300 times less). Invertases catalyze hydrolysis of sucrose provided by the phloem
conducting complex into glucose and fructose. Different invertase isoforms are localized in the cell
wall, cytoplasm, and vacuole. Hydrolysis of sucrose by cell wall invertase may promote unloading by
preventing its retrieval by the phloem, and by maintaining the sucrose concentration gradient.
4. Factors that Affect the Sugar Accumulation and Level in Grape Berries
Berry sugar accumulation is regulated by complex mechanisms. For example, the expression of
disaccharide transporter genes (DSTs) and monosaccharide transporter genes (MSTs), sugar
transporter proteins that mediate the exit of sucrose from the phloem and the uptake of sugars across
the plasma membrane and the tonoplast of flesh cells, may be affected by various parameters,
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including light, water, and ion status, wounding, fungal and bacterial attacks, and hormones [34–36].
According to several authors [24,37] sugar composition is mainly determined by genotype, and sugar
concentration is strongly affected by several factors, such as environment and cultural management.
For example, irrigation has a variable effect on sugar accumulation in the grape berries. Thus,
according to several studies [38–42], there is a variation in sugar concentration (increase, decrease or
no changes) as a result of irrigation practice. Esteban et al. [39] analyzed the impact of water
availability on the yield and must composition of Vitis vinifera L. cv. Tempranillo grapes during
three-year period and concluded that total soluble solids, and the concentration of glucose and fructose
were significantly higher in the irrigated vines than in the non-irrigated vines, mainly towards the end
of ripening. On the other hand, Intrigliolo et al. [41] consider that the effects of irrigation on must and
wine composition are largely dependent of climatic characteristics of each year, namely by the
different rainfall amount and crop levels.
For several researchers [43,44] temperature is an important environmental factor that affects the
grape sugar accumulation. For temperatures above 25 °C, net photosynthesis decreases even at
constant sun exposure [45]. In addition, for temperatures above 30 °C, several authors [46,47] have
reported a reduction of berry size and weight, and metabolic processes and sugar accumulation may
completely stop. However, although high temperatures accelerate grape maturation, according to
Coombe [47] temperature effects on final sugar accumulation are reported to be relatively small.
Higher temperatures (30 °C) may lead to higher suspended solid concentrations, but Brix levels higher
than 24–25 Brix (238.2 g/L of sugar to 249.7 g/L of sugar; 14.15% (v/v) estimated alcohol to 14.84%
(v/v) estimated alcohol) are likely not due to photosynthesis and sugar transport from leaves and wood,
but to concentration by evaporation [48,49]. In the last years, the alcohol content of wines tended to
increase, due to different factors. One of them is the sugar increase in grapes and must, attributed to the
climate change [50]. However, according to [44], the extremely high sugar concentrations reached at
harvest today, especially in warm climates, may be rather associated with the desire to optimize
technical or polyphenolic and/or aromatic maturity. Finally, moderate water deficit, UV-B radiation,
and low temperatures (below 30 °C), have a positive effect during grape ripening by the increasing of
sugar content in grape berries [51,52]. Duchêne and Schneider [53] showed that, over the last 30 years,
the estimated alcohol level of Riesling grapes in Alsace, increased 2.5% (v/v) due to warmer ripening
periods and earlier phenology. Additionally, Godden and Gishen [54] observed in Australian wines an
increase in the alcohol content from 12.3% (v/v) to 13.9% (v/v) for red wines and from 12.2% (v/v) to
13.2% (v/v) for white wines, between 1984 and 2004.
5. Psychophysiology of Alcohol Perception
Taste strongly influences food intake [55], including alcohol consumption [56,57]. Alcohol
activates olfactory, taste, and chemesthetic receptors and each modality is carried centrally by different
nerves; these inputs affect the perception evoked by alcohol. Chemesthesis is defined as the chemical
sensibility of the skin and mucous membranes. Chemesthetic sensations arise when chemical
compounds activate receptors associated with other senses that mediate pain, touch, and thermal
perception. Examples of chemesthetic sensations include the burn-like irritation from chili pepper, the
coolness of menthol in mouthwashes and topical analgesic creams, the stinging or tingling of
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carbonation in the nose and mouth, and the tear-induction of onions. The oral consumption of alcohol
by humans is accompanied by chemosensory perception of flavor, which plays an important role in its
acceptance or rejection. Three independent sensory systems, taste, olfaction, and chemosensory
irritation, are involved in the perception of flavor in food and in wine in particular (Figure 2) [58].
Figure 2. Mechanism of flavor perception in food and wine intake. Adapted from
Redondo et al. [59].
As reported by Allen et al. [60], humans perceive alcohol as a combination of sweet and bitter tastes
odors (Figure 3), and oral irritation (burning sensation). However, several researchers like Lanier et al. [58]
found that some people describe experiences of more bitterness and less sweetness when drinking
alcohol, and this directly relates to the genes they have inherited and individual differences in
bitterness and sweetness are predictors of alcohol liking and intake in young adults. In addition, the
perception of bitterness and sweetness also vary as a function of alcohol concentration [61,62].
Figure 3. Diagram showing the signal transduction pathway of bitter taste. A, taste bud;
B, taste cell; and C, neuron attached to B. Adapted from Hldavis4 [63].
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Multiple studies [64,65] have linked variation in TAS2R (taste receptor, type 2) bitter receptor
genes to alcohol intake. An important gene contributing to PTC (the ability to taste the bitterness of
phenylthiocarbamide) perception has been identified [66]. The gene (TAS2R38—taste receptor,
type 2, member 38), located on chromosome 7q36, is a member of the bitter taste receptor family.
There are two common molecular forms (proline-alanine-valine (PAV) and alanine-valine-isoleucine
(AVI)) of this receptor defined by three nucleotide polymorphisms that result in three amino acid
substitutions: Pro49Ala, Ala262Val, and Val296Ile. Duffy et al. [67] reported that TAS2R38
haplotypes are associated with alcoholic intake, with AVI homozygotes, who perceive less bitterness
from the bitter compound propylthiouracil (6-n-propylthiouracil (PROP) is a thiouracil-derived drug
used to treat hyperthyroidism, including Graves’ disease, by decreasing the amount of thyroid hormone
produced by the thyroid gland) consuming, significantly, more alcoholic drinks than heterozygotes or
PAV homozygotes. More recently, Dotson et al. [68] reported associations between TAS2R38 and
TAS2R13 polymorphisms and alcohol intake derived from the Alcohol Use Disorders Identification
Test (AUDIT) in head and neck cancer patients.
In addition, to bitter and sweet sensations, as we mentioned before, alcohol also causes irritation
commonly described as burning or stinging [58]. Burning sensations in the mouth are due, in part,
to activation of the transient receptor potential vanilloid receptor 1 (TRPV1) that is activated by
noxious heat, capsaicin [69,70], and alcohol even at relatively low concentrations (0.1% to 3% v/v) [71].
When the TRPV1 gene is knocked out in mice, knockouts have a higher preference for alcohol and
consume more than wild-type mice [72]. Collectively, these data suggest the TRPV1 receptor likely
plays a role in the perception and acceptability of alcohol.
Many factors underlie the role that alcohol flavor plays in the development of alcohol preference
and consumption patterns. Such factors include the activation of peripheral chemoreceptors by
alcohol [70]; central mechanisms that mediate the hedonic responses to alcohol flavor [73]; learned
associations of alcohol’s sensory attributes and its post digestive effects and early postnatal exposure
to alcohol flavor [74,75]; and genetically determined individual variation in chemosensation [21,61].
The study of the role of chemosensory factors in alcohol intake and preferences is of special interest
because the past decade has witnessed significant technical and scientific advances, which include
identification of receptors and other key molecules involved in the transduction mechanisms of
olfaction [76,77], chemosensory irritation [78], and taste [79–82].
6. The Effects of Ethanol on the Body and Other Sensory Characteristics of Wines
The terms “body” and “fullness” are wine attributes frequently used to describe the in-mouth
impression of both red and white table wines [83]. Wines are regularly classified as being light,
medium, or full bodied. Presumably as wines of different style appeal to different market segments,
and are consumed in different social and culinary contexts. However, despite its widespread use and
application, there appears to be a lack of common understanding within the wine trade as to what
sensory aspects contribute to wine body. Most importantly, there appears to be no agreed position on
the necessary conditions for “fullness” in wine or other alcoholic beverages. Despite the apparent lack
of agreement on what constitutes body in wine, Gawel [84] showed that experienced wine tasters, with
extensive practical training, had an equivalent understanding of “body” in white wines, and considered
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the feature important in distinguishing between the wines. It has long been speculated that alcohol
strongly contributes to palate fullness in white wine [85]. Pickering et al. [4] were the first to formally
test this premise. They found that the perceived density of a de-alcoholized wine generally increased
with increasing alcohol over a 14% (v/v) range, while its perceived viscosity was highest at 10% (v/v)
ethanol. Later work [86] using model wine solutions showed a positive monotonic effect of alcohol
content on both perceived viscosity and density over the same alcohol range, further supporting the
existence of a positive relationship between alcohol content and fullness in white wine.
The contribution of ethanol to wine sensory properties extends beyond that of possibly enhancing
fullness. Ethanol affects the headspace concentrations of many wine volatiles [87], and also contributes
to sweetness [88]. Furthermore, ethanol induced palate warmth and perceived viscosity may indirectly
affect both aroma and flavor perception. Moreover, according to the work of Joshi and Sandhu [89] the
results of sensory evaluation of different vermouths prepared with different ethanol concentrations,
sugar levels and spices extract showed significant differences for various sensory quality parameters.
The data obtained revealed that for color and appearance, 12% (v/v) and 15% (v/v) of alcohol with
2.5% (w/v) spices extract scored better, but for aroma virtually all the treatments were comparable.
However, in total acidity vermouth with 18% (v/v) ethanol scored lower than those with 12% (v/v) and
15% (v/v). In bitterness and astringency, vermouths of all the treatments were comparable. In overall
quality, apple vermouth with 15% (v/v) ethanol, 2.5% (w/v) spices extract, and 4% (v/v) sugar content
scored the highest. So, bitterness, astringency, and total acidity are influenced by the alcohol vermouth
concentration. However, for Noble [90], the higher concentrations of alcohol in wines contribute to
enhance bitterness intensity, but have no effect on perception of astringency.
7. Technological Practical to Reduce the Wine Alcohol Content and Their Sensorial Impact
Alcohol fermentation is done by yeast and some types of bacteria. These microorganisms convert
berry sugars into ethyl alcohol and carbon dioxide. Alcoholic fermentation begins after glucose enters
the yeast cell (Saccharomyces cerevisiae). The glucose is broken down into pyruvic acid, which is then
converted to carbon dioxide, ethanol, and energy for the cell. Humans have taken advantage of this
process in making wine, bread and beer.
Nowadays, the market in general, appreciated full body red wines with intense and complex flavor
profiles produced from grapes with adequate phenolic ripeness, optimal flavor balance and lower
acidity [91–95], but the juice from such grapes also contains high sugar content and consequently leads
to wines with high alcohol contents (14%–16%, v/v) [91,96]. Alcohol taste near or above this
threshold is described as bitter or as sweet and/or sour [88]. Nevertheless, in recent years there is a
consumer demand for wines with lower alcohol content (9%–13%, v/v), that apparently are healthier
since the consumer’s attitudes are changing [8,9,97]. In addition, consumers also perceive that high
alcohol levels affects wine sensory perceptions, leading to unbalanced wines. On the other hand, wines
made from grapes with high sugar levels will probably show low acidity and poor aromatic notes.
These wines can be perceived as more hot on the palate and the volatility and sensory perception of
other volatile compounds affects detection thresholds [5]. Additionally, in some countries, winemakers
have to pay taxes when alcohol content in wine is over 14.5% (v/v), increasing in this way the wine
final price [97].
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Wines with higher alcohol levels changed their wine sensory profile [98], partly by decreasing the
volatility of wine aroma compounds, since up to a certain level of alcohol a decrease in fruity aromas
was observed, being that many of these wines considered out of balance, and dominated by
alcohol-associated attributes [1]. The effect of alcohol on the sensory perception of fruitiness from a
mixture composed by nine fruity compounds at the maximum concentrations found in the wines was
evaluated by Escudero et al. [99]. According to these authors, when there is no alcohol in the mixture,
the smell is strong; however, the intensity of the smell decreases with the content of alcohol in the
mixture being at 14.5% (v/v) no longer perceived. It was also observed by other authors [2,5] that the
bitterness intensity was higher when the alcohol content increased and astringency decreased linearly
when the content of alcohol increased, too. However, Noble [90] showed also that higher
concentrations of alcohol enhance bitterness intensity in wines, but observed no effect on perception of
astringency. According to the author [90], subjects with high salivary flow rates perceived maximum
intensity sooner and reported shorter duration of both bitterness and astringency than low-flow judges.
In spite of the final quality and acceptance of wines, musts with high sugar content usually show
additional oenological problems, as difficulty to carry out alcoholic fermentation, with sluggish
fermentation, and even fermentation stops [100]. This fact gives origin to new problems, due to the
microbiological instability of wines with high levels of residual sugars. In an effort to meet the
demands of consumers for wines with lower alcohol, winemakers are searching for technological
strategies to low the wine alcohol content. There are some technical procedures to reduce the alcohol
content that could be done either by reducing the concentration of sugar present in grapes [50,101], or
by removing alcohol from wine [92].
The grape sugar reduction involves harvesting grapes at an earlier stage of ripening [94]. However,
the wine composition and quality changed due to fewer aromas flavor and color intensity, and
increased acidity.
During alcoholic fermentation, respiration of sugars by non-Saccharomyces yeasts has been
recently proposed for lowering alcohol levels in wine. Development of industrial fermentation
processes based on such an approach requires the identification of yeast strains able to grow and
respire under the relatively severe conditions found in grape must. In a work performed by
Quirós et al. [102], physiological features of some strains of Metschnikowia pulcherrima and
Kluyveromyces yeasts that constitute the main part of the microbiota of sound ripe grapes, and are
known to predominate during the initial stages of wine fermentation [103], suggest that they are
appropriate for lowering alcohol yields by respiration. Although the concentration of molecular oxygen
is particularly low during fermentation, mainly due to carbon dioxide release, several practices
employed during the first stages of winemaking such as pumping over, délestage, or
macrooxigenation, can increase oxygen concentration. These, or ad hoc oxygenation practices, would
allow for the partial respiration of grape sugars by the appropriate yeast strains. However, in a regular
fermentation, S. cerevisiae usually dominates the fermentation, being this practice somewhat difficult
and with poorer results.
For using S. cerevisiae strains in alcohol reduction, different techniques have been applied like
expression of NADH-dependent lactate dehydrogenase or a bacterial NADH oxidase in yeast [104].
Although both techniques reduced alcohol production, the wine quality has been spoiled due to
the detrimental byproducts, like lactic acid, acetaldehyde, and some oxidized compounds [104].
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Non-genetically modified (non-GM) approaches, such as evolutionary engineering, has been practiced
thanks to adaptive evolution [105]. Adaptive evolution can be applied by diversion of carbons towards
the pentose phosphate (PP) pathway leading to lower availability of carbons for ethanol production by
elimination of carbons in the form of carbon dioxide and reduced acetate production and increased
ester formation. Another approach is evolutionary engineered yeasts with sugars diverted towards
glycerol and 2,3-butanediol. According to Tilloy et al. [104] these engineered yeasts have ability to
reduce the alcohol content of wine by 0.5% to 1% (v/v).
It is also possible to reduce the sugar in musts to obtain wines with a slight alcohol reduction by the
use a several technologies, namely nanofiltration. Thus, according to García-Martín et al. [50] the
sugar reduction in must by using the nanofiltration technology resulted in a satisfactory alcohol
reduction in the resulting wine, but with a slight loss in the color and aroma.
Several membrane technologies have also been developed for alcohol removal from wine, in the
winery. They are reported to allow the reduction of the alcohol content under soft conditions in order
to try to preserve the sensory characteristic of the original wine [8,92,106]. Semi-permeable
membranes by which alcohol can be separated from wine have been available since the 1970s [92].
The benefit of membrane technologies (nanofiltration, membrane contactor, reverse osmosis, and other
membrane techniques) is the low operations cost, and the advantage to work at low to moderate
temperatures, being limited by the negative effects on wine aroma chemical reactions or degradation [107].
This procedure will be used to reduce only 1% or 2% (v/v) of the alcohol content in order to obtain
more balanced wines with complete aromatic potential and phenolic ripeness [93,108], as established
by the European regulation (EC Reg. 606/2009) [109] reduction of the actual alcoholic strength by
volume may not be more than 2% (v/v), but more recently this limit has been changed. Thus,
according to the Commission Regulation (UE) N 144/2013 [110] the alcohol content may be reduced
by a maximum of 20% (v/v), OIV-ECO 433-2012 [111]. The separating techniques that can be used to
reduce the alcohol content according to OIV (Resolution OIV-Oeno 394A-2012) [112] are: partial
vacuum evaporation, membrane techniques, and distillation. Of these, the most used in the wineries are
the spinning cone column and reverse osmosis system to produce lower alcohol wines or to adjust the
ethanol content [3,92]. Reverse osmosis, is a membrane separation process that is probably the most
successfully-employed procedure for partial dealcoholization [113]. The results showed that this
technique has the advantage of having a minimal negative influence on wine taste, by modifying only
the wine alcohol content while the other parameters remained unaffected, since it is performed at low
temperature [92]. Reverse osmosis could be a technique for improving a wine’s balance in regions
where wines can reach high alcohol content. However, this wine alcohol reduction process could also
negatively affect the wine sensorial quality, leading in the worst cases to an unacceptability of the
wine, by changing the complex equilibrium among organic compounds responsible for wine taste,
flavor and mouth feel. The observed modifications in reduced alcohol wine sensorial characteristics
could be due to the reduction in alcohol content, which plays an important role in wine taste [5], mouth
feel [2,4], and olfactory wine properties [1,99]; and in the losses of volatile and polyphenolic
compounds, during the alcohol reduction process [106,114]. Removal of alcohol from wine reduced
fruity aromas, and enhanced vegetative and sweaty aromas in white wines [93]. According to King and
Heymann [115] reducing the alcohol content of oaked white wine using spinning cone technology
results in a minimal impact on sensory composition and consumer preferences since no perceptible
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changes to the sensory profile were observed. These authors showed that panelists and consumers were
unable to detect changes among wines with a 1% (v/v) difference. This work suggests that the use of
technology to partially reduce the white wine alcohol content without reducing the wine quality is of
beneficial use to the wine industry. However, Meillon et al. [3], using the reverse osmosis treatment to
reduce the wine alcoholic degree of Merlot and Syrah wines, showed that the wine sensory perception
and their appreciation/acceptability by consumers was modified, particularly a decrease in the
perception of the wine balance was observed. According to the same authors, a significant impact on
the sensory properties of red wines with a decrease in the perception of hotness, bitterness, aromas, and
persistency in the mouth was observed, and also an increase in the perception of astringency and a
decrease in the perception of wine complexity. Generally, alcohol reduction was less well accepted for
red than for white wines, and it was also variable from one grape variety to another one. In this way,
there are several kinds of interactions between alcohol and wine components that make difficult the
generalization of alcohol reduction effect on the sensory perception of wines [3]. Lisanti et al. [116]
concluded that wine alcohol reduction using the membrane contactor technique affected the red wine
sensorial properties. The most reduced olfactory notes were those of cherry and red fruits, particularly
in wine with 5% (v/v) alcohol reduction. The alcohol reduction process also increased the intensity of
astringency, bitterness, and acidity. However, according to the same authors an alcohol reduction of
2% (v/v), has slightly affected the wine sensory profile.
8. Final Remarks
Grape sugar concentration is a parameter to predict grape and wine quality. However, in recent
years, the sugar concentration has increased in grapes, attributed to climate change; therefore, the
alcohol content of wines tended to increase. The high sugar concentrations reached at harvest today
may, rather, be associated with the desire to optimize technical or polyphenolic and/or aromatic
Though, consumption of alcohol beverages is accompanied by chemosensory perception of flavor,
which is an important factor for acceptance or rejection. Thus, the main factors for selection of the wine
alcohol-reducing technique are maintaining quality, in terms of flavor, in the final wine, and lowest cost.
The request for less alcoholic wines has led to technological innovations to low alcohol content
without changing the wine sensorial profile.
Author Contributions
António M. Jordão, Alice Vilela and Fernanda Cosme equally contributed to the paper.
Conflicts of Interest
The authors declare no conflict of interest.
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... Figure 3 shows sugars (glucose, fructose and sucrose) of the bamboo juice. The sugar composition is very crucial in wine quality since it determines the alcohol content of the wines (Jordão et al. 2015). Glucose and fructose are the main sugars in the bamboo beverage ( Figure 3). ...
... Alcohol influences various components, including sensory perceptions, making it a significant component in alcoholic beverages like wines. Additionally, it interacts with other elements of wine, such as scents and tannins, which affect the viscosity and body of the wine as well as our perceptions of astringency, sourness, sweetness, aroma, and flavour (Jordão et al. 2015). The presence of alcohol along with sugars, amino acids, and phenols defines the balance of the wine when organoleptic properties are taken into account. ...
... As a result, several nations develop innovative techniques for reducing the alcohol content of wines while retaining their quality and sensory sensations. According to Jordão et al. (2015), the demands for alcoholic beverages with lower alcohol (9-13% v/v) are driven by social and health concerns for many consumers in various nations. Based on the reported data on grape wine, i.e. the sugar content of the juice of ripe grapes varies from 150 to 250 g/L and the alcohol content of wine is 9-15% v/v (Ozturk and Anli 2014). ...
The amounts of sugars and amino acids play significant roles in defining the fermentation process and quantifying the alcohol levels in beverages, while pH affects the biological stability, colour, oxidation rate, and protein stability of alcoholic beverages. This study investigated the sugar content, amino acids, alcohol levels, and pH of bamboo beverage from Tanzania's southern highlands. During storage, the sugars significantly decreased (p < 0.05), especially when kept at room temperature from 52.96 to 0.00 (source 1), 53.35 to 0.00 (source 2) and 53.57 to 0.00 (source 3) g/L for fructose, from 47.93 to 14.78 (source 1), 47.23 to 14.91 (source 2) and 47.61 to 14.77 (source 3) g/L for glucose, and from 0.40 to 0.00 (source 1), 0.36 to 0.00 (source 2) and 0.37 to 0.00 (source 3) g/L for sucrose after six days of storage. A total of 15 amino acids were determined from the bamboo beverage with tyrosine being the most prevalent (597.68 mg/L for source 1, 599.44 mg/L for source 2 and 597.83 mg/L for source 3), followed by valine (261.13 mg/L for source 1, 261.24 mg/L for source 2 and 262.54 mg/L for source 3), threonine (76.69 mg/L for source 1, 76.91 mg/L for source 2 and 77.13 mg/L for source 3), and serine (66.37 mg/L for source 1, 67.23 mg/L for source 2 and 66.68 mg/L for source 3). After six days of storage at room temperature, there was a significant decrease in pH from 4.04 to 3.63. Alcohol content ranged from 3.11 to 9.05% v/v at the room temperature storage. These results might facilitate the optimal use of bamboo beverages, which have been neglected due to lack of scientific information such as amino acid and sugar levels.
... More recent work found that the sweetness of dry wines was not affected by the usual variations in ethanol, but it was mainly involved in wine bitterness as a consequence of sensory interactions with other compounds (Cretin et al., 2018). The removal of ethanol leads to a loss of viscosity, body and fullness, and reinforces the aggressiveness of tannins (Jordão et al., 2015;Longo et al., 2017;Schmitt and Christmann, 2022). The complete elimination of ethanol, which can represent more than 20 % of the initial wine volume depending on the technology and the ethanol concentration of the distillate (Belisario-Sanchez et al., 2009), can also indirectly contribute by concentrating non-volatile molecules, such as organic acids or polyphenols. ...
... The difference in CRT concentrations between the two matrices indicates that the contribution of ethanol to the overall balance of red wine is higher. According to the terms used by consumers to describe the test samples (Table 2), the red samples reduced in ethanol to 7.5 and 1.5 % v/v were both significantly characterised by a higher aggressivity in comparison with Chardonnay samples; this is likely due to tannins, which is in accordance with previous findings (Jordão et al., 2015;Longo et al., 2017;Schmitt and Christmann, 2022). Similar to other studies, these wines were also perceived as being more diluted, less sweet and sourer (Fischer and Noble, 1994;Martin and Pangborn, 1970;Scinska et al., 2000). ...
... However, as reflected in the terms used to describe the Chardonnay test samples at 7.8 and 1.8 % v/v (Table 2), the addition of water might have enhanced the perception of dilution and lack of taste. It might also have contributed to obtaining lower CRT values by reducing the sensory perception of non-volatile compounds, such as organic acids and tannins that can enhance aggressiveness in reduced ethanol beverages (Jordão et al., 2015;Longo et al., 2017;Schmitt and Christmann, 2022). ...
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Ethanol is one of the major components of wine, which has a substantial impact on its sensory characteristics. However, data concerning consumer response to ethanol or changes in ethanol remains limited. The aim of this study was to determine the threshold ethanol concentrations beyond which ethanol lowering becomes undesirable in Chardonnay and Syrah wines using the consumer rejection threshold (CRT) methodology. Base wines from these two cultivars were first dearomatised and fully dealcoholised using spinning cone column technology. Then, control wines with a similar ethanol content to the base wines (13.8 and 13.5 % v/v for Chardonnay and Syrah respectively) and wines with lower ethanol contents were reconstituted by mixing the final beverage, the aroma fraction, food grade ethanol and distilled water. CRT values were determined as 2.8 % v/v for Chardonnay and at 7.0 % v/v for Syrah. These particularly low and unexpected concentrations indicate that consumer sensory liking might not be necessarily driven by ethanol concentration, especially for white wines. However, the post-evaluation questionnaire showed that consumers were expecting a high minimal ethanol content for quality wines (10.9 % v/v ± 1.2 and 11.7 % v/v ± 1.5 for white and red wines respectively) and had a limited experience with low and dealcoholised wines. Overall, our data, which are still preliminary and deserve to be validated using different base wines with a larger number of consumers, show that consumers would not necessarily be refractory from a sensory standpoint to the consumption of low ethanol beverages made from wine. Our findings strongly encourage professionals from the wine industry and public authorities to raise awareness about the increase in quality of such products and their benefits for human health.
... In our case, the integration of alcohol was associated, by consensus, with the term warm. King and Heymann [86] also used the term "low hotness mouthfeel" to refer to warm, as opposed to "high hotness mouthfeel" (irritating and tingling) detected when the alcohol is causing a gustatory disequilibrium leading to unbalanced wines [89]. According to King and Heymann [86], low and high hotness mouthfeels can be referenced by respectively using 100 or 200 mL of grape spirit 50% v/v dissolved in 1 L of filtered water. ...
... The measurement of the perception of carbon dioxide is a rather difficult task, since it includes auditory, visual, nociceptive, and tactile stimuli [90]. In the case of sparkling wines, the effect of carbonation is defined as a chemesthetic sensation, including the stinging tingling of bubbles in the nose and mouth [89]. There are different methods to add CO 2 to a liquid, from natural fermentation by adding sugar to a hydroalcoholic solution and letting it ferment [91], or using semi-industrial systems of continuous injection or by injecting the gas into a closed vessel under pressure [92]. ...
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Producers of PDO (Protected Designation of Origin) wines must submit to the EU authorities’ technical specifications that include the specific sensory description of each product typology, to be subsequently checked by the competent authority in each country. Unfortunately, there is no consensual and standardized approach for the development of sensory control methods for PDO wines. The aim of this work was to develop a sensory profile for the taste and mouthfeel descriptors that allows the characterization of wines from 11 existing PDOs in Catalonia (Spain), and with the purpose of advancing the process of harmonization of the official sensory analysis of wines. This paper includes the selection process of tasters, the procedure used for the definition and grouping of descriptors, and the development of references for the selected attributes. The use of this analytical tool should allow PDO/PGI product certification and control authorities to verify compliance with their specifications (descriptive and quantitative) based on objectively evaluated results.
... In addition, basic 48 chemical analyses of grapes, such as sugar content and titratable acidity (TA) have limited 49 predictive power. It was reported that the berry sugar content tends to function as an indicator 50 of berry ripeness and wine alcohol content, with wine odour quality potentially compromised 51 from increased berry sugar content due to reductions in aromatics associated with increased 52 wine alcohol content (Jordão et al., 2015). Additionally, Luo et al. (2019) identified that the 53 accumulation of aromatic compounds (terpenes) in Shiraz grapes did not reliably align with 54 changes in sugar content, further highlighting the limitations associated with the prediction of 55 wine quality from grape sugar content. ...
Traditionally, wine producers perform early wine quality prediction on-site based on the berry morphological and sensory characteristics together with the measurement of basic chemical parameters. Incorporating analysis on grape and wine volatiles could potentially achieve accurate prediction of wine quality, but forming these models requires careful selection of grapes, controlled fermentations and standardised quality assessment. Here, we present 3 models for the prediction of quality in Shiraz wine. Modelling was done by general regression analysis with 4-fold cross-validation. Model 1 (R ² = 99.97% and 4-fold R ² = 97.61%) for prediction of wine quality from wine volatiles, Model 2 (R ² = 99.89% and 4-fold R ² = 98.42%) for early prediction of wine quality from free- and glycosidically- bound grape volatiles, and Model 3 (R ² = 91.62% and 4-fold R ² = 80.21%) for prediction of wine quality from free grape volatiles only. The accuracy of these models presents an advancement in the early prediction of wine quality and provide a valuable tool to assist grape growers and winemakers in understanding quality in the vineyard to better direct scarce resources.
... Dealcoholization of the Pinot Noir rose wine was mainly responsible for this outcome. According to some studies (Corona et al., 2019;Jordão et al., 2015;Liguori et al., 2013;Motta et al., 2017;Sam, Ma, Liang, et al., 2021), dealcoholization of wine can significantly reduce wine volatile aroma compounds, hotness, bitterness, and sweetness, while increasing color intensity, acidity, and astringency. Higher addition levels of AFEs could likely increase concentrations of the aroma compounds in RDWs to similar or higher levels than in OW, resulting in higher ratings for aroma intensity, red fruits, and fruity and floral notes in RDWs. ...
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The study examined the use of aqueous extracts of rose, peach and lily flowers (AFEs) as a new oenological tool for compensating for the loss of aroma compounds in dealcoholized rose wine (DW). Three reconstituted dealcoholized wines (RDWs) were prepared using the AFEs denoted L-RDW (for lily), P-RDW (for peach), and R-RDW (for rose) and compared with 2 controls: original rose wine (OW) and dealcoholized rose wine (DW). The chemical properties, aroma compounds, and sensory properties of the samples were investigated. The chemical properties of RDWs did not differ significantly from those of DW. Adding AFEs significantly improved the content of esters, alcohols, terpenes and C13-norisoprenoids in RDWs compared with DW. RDWs wines had better sensory properties (fruity and floral, red fruits, aroma intensity, and overall acceptability) than DW, and with almost similar sensory properties (overall acceptability) compared to OW. Rose, peach and lily AFEs can be used for the aroma enhancement of dealcoholized pinot noir rose wine.
... Besides, our data (Table 3) agree with [70,72], where glucose and fructose present higher values compared to sucrose, and the amount of fructose was slightly superior to glucose. In general, grapes treated with ZnSO4 and ZnO showed a tendency for a higher sugar content (except for ZnO 150 and ZnO 450 g ha −1 for sucrose and glucose/fructose, respectively), which is an important quality parameter for winemaking, as it affects the fermentation process and alcohol contents [73], although we must note that a high alcohol content can causes a gustatory disequilibrium affecting wine sensory perceptions, leading to unbalanced wines [74]. ...
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Nowadays, there is a growing concern about micronutrient deficits in food products, with agronomic biofortification being considered a mitigation strategy. In this context, as Zn is essential for growth and maintenance of human health, a workflow for the biofortification of grapes from the Vitis vinifera variety Fernão Pires, which contains this nutrient, was carried out considering the soil properties of the vineyard. Additionally, Zn accumulation in the tissues of the grapes and the implications for some quality parameters and on winemaking were assessed. Vines were sprayed three times with ZnO and ZnSO4 at concentrations of 150, 450, and 900 g ha −1 during the production cycle. Physiological data were obtained through chlorophyll a fluorescence data, to access the potential symptoms of toxicity. At harvest, treated grapes revealed significant increases of Zn concentration relative to the control, being more pronounced for ZnO and ZnSO4 in the skin and seeds, respectively. After winemaking, an increase was also found regarding the control (i.e., 1.59-fold with ZnSO4-450 g ha −1). The contents of the sugars and fatty acids, as well as the colorimetric analyses, were also assessed, but significant variations were not found among treatments. In general, Zn biofortification increased with ZnO and ZnSO4, without significantly affecting the physicochemical characteristics of grapes.
... The idea of using the changes in electrical conductance of metal oxides for gas detection dates from about 1962. Jordao et al. [1], Wilkinson et al. [2] and Panighel et al. [3] reported in their respective investigations that the main component in wines, in addition to water, is ethanol, in the range of 9 to 14.5%, depending on the type of wine (red, rosé or white), in contrast with the other volatile components of wine such as methanol, n-propanol, n-butanol, acetic acid, among others, which are found in most cases in very low concentrations. ...
... The membrane can be used instead of chaptalization or any other procedures to boost sugar content in wine without adding non-grape components at room temperature; it can also change and maintain the must composition. RO concentrates carbohydrates, as well as numerous other natural substances of must like malic acid, resulting in a lack of wine sensory balance [65]. Furthermore, RO requires a lot of energy and creates a lot of membrane fouling. ...
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Nanofiltration (NF) membranes are the globally recognized membrane technology, having potential use in food industries from a consistent, economical and standard operation point of view. NF has also attracted industries due to the need for lower pressure–driven membranes compared to reverse osmosis (RO) membranes. NF membranes are used in various applications for concentrating, fractionating and purifying various edible products from the dilute streams. Food processing industries are countlessly utilizing the NF membranes for beverage, dairy, vegetable oils and other food items for separation, concentration/purification, deacidification, demineralization, microbial reduction, etc. However, the increasing challenge in membrane science and technology is to develop low-cost, highly efficient, long-lasting membranes. The permeance-selectivity trade-off relationship, physical ageing and fouling are the main disputes in developing a promising membrane. This review provides a broad view of the current advancement of NF membranes in diverse fields related to the food industry. In this review article, the noteworthy growth of NF membrane in the food industries has been discussed. Various methods for the development of efficient NF membranes along with fouling control measures and research opportunities have been discussed. It is anticipated that this inclusive review may inspire a new research platform for developing next-generation NF membrane processes for diverse applications.
Global food security is at risk due to the predicted climate change, making it imperative for agronomists to provide adaptive technologies that will sustain and improve food production. Rainfed agriculture, prone to drought, covers an estimated 80% of global cropland. One of the adaptive technologies is the use of antitranspirants – products that are applied on plants to reduce transpirational water loss and increase crop performance under drought conditions. The benefits of improving antitranspirant adoption in drought mitigation are expected to be high, especially in many drought-prone low-income countries where crop production is almost wholly dependent on rainfall. The objective of this article was to review the commercial uses of antitranspirants in food and non-food crop production. The review revealed that in horticulture, antitranspirants have several commercial uses, in addition to drought mitigation, such as transplanting shock amelioration, protection of fruit against sunburn, enhancement of nutritional quality, synchronising fruit ripening, protection of fruit and nut trees against diseases. Use of antitranspirants in arable farming has been neglected for three main reasons: first, arable crops have lower market value, for example, in Melbourne (Australia) in October 2022, a tonne of grapes was worth US$ 2694.82 compared to US$ 277/tonne of wheat. Second, molecular genetics applied to crop breeding has risen as an alternative approach to drought mitigation, shifting attention from antitranspirants. Finally, the erroneous research conclusion in the 1970s that antitranspirants could not increase yield because they reduced photosynthesis discouraged commercialisation of antitranspirants in arable farming. An antitranspirant breakthrough to either lower the cost or create a multi-purpose product is needed for the production of arable crops, especially major cereals, as has been the case for non-drought amelioration uses in horticulture.
There is an increasing market share of dealcoholized wines due to rise in patronage by wine consumers. However, the aroma of such wines deteriorates the more the alcohol content is reduced. Improving the aroma with edible flowers may curb this problem. To improve the aroma of a dealcoholized Merlot red wine, extracts of peach, rose, and lily flowers (FEs) were added to develop three reconstituted dealcoholized wines (RDWS). RDWS were compared with the original wine and the dealcoholized wine (DW) based on chemical properties, aroma compounds, and sensory characteristics. FEs had no effect on the chemical parameters of RDWS. FEs improved the volatile composition of RDWS, especially ethyl octanoate, isoamyl octanoate, linalool, and geraniol. Sensory analysis showed that aroma intensity and fruity and floral notes improved in RDWS compared to DW. Among the FEs, rose was the best and can improve the aroma of dealcoholized Merlot red wine.
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Individual and total sugar and organic acid concn in the juice of 12 cultivars of muscadine grapes ( Vitis rotundifolia Michx.) were determined in each of 3 years. Fructose ranged from 3.35 to 9.28% and averaged 5.51%; glucose 3.52 to 7.70% and averaged 5.16%; sucrose 0 to 5.20% and averaged 1.89%; soluble solids 10.20 to 17.85% and averaged 13.21%; malate 0.17 to 1.16% and averaged 0.50%; tartrate 0.15 to 0.52 and averaged 0.26%; citrate ranged from a trace to 0.06% and averaged 0.04%; total titratable acidity 0.39 to 1.549% and averaged 0.839%; pH ranged from 3.50 to 2.88. ‘Roanoke’ was significantly lower in soluble solids (11.18%) than most of the other cultivars over the 3-year period. It was also exceptionally high in malic acid (0.70%) and contained significantly more malate than 7 other cultivars. ‘Roanoke’ and ‘Pamlico’ averaged the highest titratable acidities with 1.099 and 1.049%, respectively. ‘Magoon’ contained significantly more tartrate (0.41%) than all other cultivars except ‘Hunt’. When total titratable acidity values for the 12 cultivars were pooled for each season, it was apparent that yearly differences in these values were primarily due to differences in malate levels since tartrate levels were similar in each of the 3 seasons.
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The effects of moderate irrigation rates on vegetative growth, vine evapotranspiration, yield, and grape and wine composition were studied during six consecutive seasons in a mature vineyard planted with Vitis vinifera cv. Tempranillo in Requena, Spain. Vines were spur-pruned and trained to a bilateral cordon. Rain-fed vines received a yearly average rainfall of 368 mm, of which 169 mm occurred from April to harvest. Irrigated vines on average received 86 mm per year of additional water applications. Irrigation increased vegetative growth and vine evapotranspiration. As a result, yield was 31% higher in the irrigated vines. This increase in yield was primarily due to larger berry size and was correlated with vine evapotranspiration estimated by soil water balance. Irrigation did not alter the balance between the vine demand and the supply as indicated by the similar level of yield to pruning weight and leaf area to yield ratios observed in both irrigated and nonirrigated vines. On average over years irrigation had some minor negative effects on wine composition. It altered the balance between malic and tartaric acid, increasing the former and decreasing the latter. Irrigation also led to an increase in wine pH that together with a slight decrease in anthocyanin concentration reduced color intensity by 18%. However, the effects of irrigation on must and wine composition were largely different among years, probably because of the different rainfall amount and crop levels. Thus, under high crop level, irrigation tended to mitigate the negative effects of increasing yield on wine alcohol content. Copyright © 2008 by the American Society for Enology and Viticulture. All rights reserved.
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Ten trained panelists evaluated the perceived density as well as the physical and perceived viscosities of the product obtained by blending ethanol with pear nectar. There was a link between the concentrations of ethanol in pure vodka and in its blend with the nectar, and the perceived sensory viscosity and the drink density. There was a very good (R2 = 0.9442) and poor (R2 = 0.6464) correlation, respectively, between the experimentally found density and viscosity and the perceived viscosity of aqueous ethanol. These properties of aqueous ethanol and alcohol pear drinks correlated very well (R2 = 0.9430 and 0.9774) with one another. 50% ethanol with the nectar had a density similar to that of aqueous ethanol solution taken as the standard. The admixture of the pear nectar increased the sensory sensitivity of the viscosity measurements of these solutions. The correlation between the perceived and physical viscosities could be used as a guide for the sensory and qualitative control of vodkas.
As grape berries develop, they change in size and composition. Grape berries exhibit a double sigmoid pattern of growth (Coombe, 1992); the first rapid growth phase that occurs after fruit set is due to an increase in cell numbers and an expansion of existing cells. Cell division in the pericarp is largely completed in the first few weeks of development (Harris et al., 1968). In most cultivars, the first expansion phase is followed by a lag phase during which little or no growth occurs. The second growth phase, which occurs at the end of the lag phase, coincides with the onset of ripening. The French word “véraison”, which describes the change in berry skin colour as ripening commences, has been adopted as a useful term to describe the onset of ripening.
Phloem transport of assimilates provides the materials needed for the growth and development of reproductive structures, storage and developing organs, and has long been recognised as a major determinant in crop yield. Thus, the understanding of the mechanisms and regulations of sugar transport into sink tissues has an important basic and applied relevance. The Grapevine is a goodexample of a crop where sugar accumulation in the fruit has an important economic role. Massive sugar transport and compartmentation into the grape berry mesocarp cells (up to 1 M glucose and fructose) start at veraison and continues until the harvest. Sucrose transported in the phloem is cleaved intohexoses by invertases and stored in the vacuole. The Sugar content determines the sweetness of table grapes, wine alcohol content, and regulates gene expression, including, for example, several genes involved in the synthesis of secondary compounds which contribute to grape and wine quality. Many viticultural practices affect source/sink relationships, thus altering sugar concentration in the berry. Forinstance, the rootstock used, which is a potential sink, has a strong impact on source activity, by affecting the morphology and activity of the aerial part of the plant. Molecular approaches have also provided major advances in grapevine research. Monosaccharide and disaccharide transporter geneshave been recently identified and their products studied in heterologous systems. The sequencing of the grapevine genome and the development of grape microarrays have made a valuable contribution to the study of the biochemistry of grape berry development and ripening, for example, low affinity glucoseuniporters identified in the genome may also be involved in the sugar uptake. In the present chapter, the routes of sugar import and storage in the grape cells are updated and discussed and a model with the main transport steps and biochemical pathways is proposed.
Data for wines from the 2004-2014 vintages were collated from the database of analytical results of The Australian Wine Research Institute's Commercial Services Group and are reviewed in the context of historical trends in wine composition. Data for those 11 vintages were generated from 24066 commercially bottled Australian table wines (8384 white and rosé wines, and 15682 red wines), which were submitted to The Australian Wine Research Institute for analysis required to comply with the export/import requirements of destination countries. The wines include multiple vintages of a broad cross-section of Australian wines from commodity to icon status, and producers of all sizes. The wines represent a broad geographical and cultivar spread, with the proportion of wines of each cultivar strongly correlating with the planted vineyard area. The data relate to the compositional variables: alcohol, glucose plus fructose, total dry extract excluding alcohol, sugar and volatile acidity (TDE), titratable acidity at pH 8.2, pH, free sulfur dioxide (SO2), total SO2, bound SO2, and the ratio of free to total SO2. Certain previously identified year-on-year trends have continued, and in some cases appear to have accelerated in the most recent vintages, particularly with increasing glucose plus fructose concentration and pH in red wines. In other cases, previously identified trends appear to have gone into reverse, notably the rise in alcohol concentration in red wines, and for a period, rising TDE in red wines, and one new trend in red wines is apparent, namely decreasing titrable acidity. There is some indication that new trends are also apparent with white and rosé wines, namely decreasing alcohol, increasing glucose plus fructose, increasing pH and an apparent downward shift in TDE, although ANOVA indicates little statistical significance in those trends. Data related to the concentration of SO2 demonstrate upward trends in free SO2 for white and rosé, and red wines. This has occurred with a concurrent decrease in the concentration of total SO2 in red wines for the most recent vintages, leading to a consequent rise in the ratio of free to total SO2. A rise in the ratio of free to total SO2 is also seen in white and rosé wines due to increasing free SO2 concentration. Overall white and rosé wines display fewer upward or downward trends compared with that of red wines, but greater year-on-year variability in the data.