**4. Sensory impact of partial alcohol reduction**

A detailed assessment of the processes for partial alcohol reduction of wine should include a sensory evaluation as well.

First of all it is important to understand to what degree of alcohol reduction makes the wines different from the initial wine. Furthermore the changes in terms of sensory characteristics should be pointed out. A comparative study of the different physical methods helps to assess what technology is more gentle in terms of wine quality. Several sources report that a wine with an alcohol reduction by 2 vol.% is not differed from the initial wine [2, 3, 14, 39, 41, 52, 56–58].

The extensive investigations of the authors substantiate these results. A total of 39 discriminative tests with a trained panel did not show a significant difference between untreated wines and corresponding samples with 2 vol.% less alcohol. Here the grape variety, the initial alcohol content, and wine style were irrelevant and not influencing the results. These discriminative sensory tests did not show significant differences with several white and red varieties. Even trials with sparkling wines showed that 2 vol.% alcohol difference is not perceived as a significant difference in discriminative tests [59].

The treatment goes along with several collateral damages in terms of wine quality such as excessive aroma losses, oxidation, and microbiological spoilage. So it is important to mention that the alcohol reduction has to be done carefully according to the manufacturers' recommendation.

Discriminative tests comparing the initial wine with samples that have 3 vol.% and 4 vol.% less alcohol showed clearer results. The panelists could differentiate more clearly and at a significant level the treated wines from the initial wine. Nevertheless there was no clear tendency in terms of preference. That is in line with other sources [39, 40].

Several comparative tests showed that the different methods for partial alcohol reduction, mentioned before, did not differ from each other when the same wines were reduced by 2 vol.% each. Even the samples that were diluted with water to have 2 vol.% less alcohol did not differ significantly from the physical methods. That is in line with other sources [2].

When the range of alcohol reduction was 4 vol.%, e.g., from initially 14.6 vol.% to 10.6 vol.%, there was a general tendency toward methods based on distillation under vacuum (vacuum rectification and spinning cone column). Here membrane processes could not deliver the same quality.

A severe alcohol reduction by distillation has the advantage that only a partial amount is treated severely. The membrane processes, in contrast, require a relatively long treatment by multiple passes of the total amount of wine through the plant to reduce the alcohol content to the same extent. If the membrane processes are to be used to produce products that are severely reduced in alcohol content, membrane plants should be in bigger size, and short-time heating could help to shorten the treatment, so that wine quality is potentially harmed less. With all tested physical methods, an aroma recovery out of the ethanol fraction could help to improve the final result in terms of quality.

The sensory effect of alcohol is very complex in terms of wine. The partial alcohol reduction of the wine changes several sensory attributes. Due to the lower alcohol content, the wines that have 3 vol.% less than the initial wine clearly show lowered sensations in terms of body and fullness. As this attribute is clearly desired, later enological interventions could aim to buffer that loss. Depending on wine style, sweetening and addition of CO2 or tannins could help to compensate those losses.

Bitterness and the sweetness sensation is reduced when the wines have less alcohol. The perceived acidity of the wines rises by removing alcohol. The fruitiness of

**263**

**Author details**

provided the original work is properly cited.

Matthias Schmitt\* and Monika Christmann

prefer lighter wines [21, 31, 39, 41, 51, 57].

\*Address all correspondence to: matthias.schmitt@hs-gm.de

*Alcohol Reduction by Physical Methods DOI: http://dx.doi.org/10.5772/intechopen.85989*

© 2019 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium,

Institute of Enology, Hochschule Geisenheim University, Geisenheim, Germany

the wines is reduced by the alcohol reduction contrary to the theory that wines with elevated alcohol content appear less intense in terms of fruity character. The treatment by physical methods goes along with aroma losses, and that factor is stronger than the elevated volatility of the remaining aromas due to alcohol reduction. The theory of sweet spots in terms of alcohol has been accepted, so far, quite uncritical. With regard to wine, this term is mentioned in various publications that point out that even small differences in ranges of 0.1–0.2 vol.% can have severe influences on the taster's preference. This approach does not conform to other sources. Since an alcohol difference of less than 2 vol.% cannot be distinguished significantly, an experimental setup with alcohol steps of 0.1 or 0.2 vol.% is incomprehensible. The author's research showed that the panelist's preferences were widely spread at the respective tastings. So there was no significantly preferred spot when a set of seven samples with varying alcohol contents were tasted even though the initial and final alcohol content clearly made the wine different. It is important to note that the examiner's preferences spread evenly over the range of samples. That proves that the preferences in terms of alcohol content in wine are not uniform. Instead of small changes in terms of alcohol contents, it could be more interesting to clearly change wine style, thus creating wines that are favored by customers who

### *Alcohol Reduction by Physical Methods DOI: http://dx.doi.org/10.5772/intechopen.85989*

*Advances in Grape and Wine Biotechnology*

discriminative tests [59].

other sources [39, 40].

to the manufacturers' recommendation.

That is in line with other sources [2].

final result in terms of quality.

processes could not deliver the same quality.

**4. Sensory impact of partial alcohol reduction**

is not differed from the initial wine [2, 3, 14, 39, 41, 52, 56–58].

should include a sensory evaluation as well.

A detailed assessment of the processes for partial alcohol reduction of wine

First of all it is important to understand to what degree of alcohol reduction makes the wines different from the initial wine. Furthermore the changes in terms of sensory characteristics should be pointed out. A comparative study of the different physical methods helps to assess what technology is more gentle in terms of wine quality. Several sources report that a wine with an alcohol reduction by 2 vol.%

The extensive investigations of the authors substantiate these results. A total of 39 discriminative tests with a trained panel did not show a significant difference between untreated wines and corresponding samples with 2 vol.% less alcohol. Here the grape variety, the initial alcohol content, and wine style were irrelevant and not influencing the results. These discriminative sensory tests did not show significant differences with several white and red varieties. Even trials with sparkling wines showed that 2 vol.% alcohol difference is not perceived as a significant difference in

The treatment goes along with several collateral damages in terms of wine quality such as excessive aroma losses, oxidation, and microbiological spoilage. So it is important to mention that the alcohol reduction has to be done carefully according

Discriminative tests comparing the initial wine with samples that have 3 vol.% and 4 vol.% less alcohol showed clearer results. The panelists could differentiate more clearly and at a significant level the treated wines from the initial wine. Nevertheless there was no clear tendency in terms of preference. That is in line with

Several comparative tests showed that the different methods for partial alcohol reduction, mentioned before, did not differ from each other when the same wines were reduced by 2 vol.% each. Even the samples that were diluted with water to have 2 vol.% less alcohol did not differ significantly from the physical methods.

When the range of alcohol reduction was 4 vol.%, e.g., from initially 14.6 vol.% to 10.6 vol.%, there was a general tendency toward methods based on distillation under vacuum (vacuum rectification and spinning cone column). Here membrane

A severe alcohol reduction by distillation has the advantage that only a partial amount is treated severely. The membrane processes, in contrast, require a relatively long treatment by multiple passes of the total amount of wine through the plant to reduce the alcohol content to the same extent. If the membrane processes are to be used to produce products that are severely reduced in alcohol content, membrane plants should be in bigger size, and short-time heating could help to shorten the treatment, so that wine quality is potentially harmed less. With all tested physical methods, an aroma recovery out of the ethanol fraction could help to improve the

The sensory effect of alcohol is very complex in terms of wine. The partial alcohol reduction of the wine changes several sensory attributes. Due to the lower alcohol content, the wines that have 3 vol.% less than the initial wine clearly show lowered sensations in terms of body and fullness. As this attribute is clearly desired, later enological interventions could aim to buffer that loss. Depending on wine style, sweetening and addition of CO2 or tannins could help to compensate those losses. Bitterness and the sweetness sensation is reduced when the wines have less alcohol. The perceived acidity of the wines rises by removing alcohol. The fruitiness of

**262**

the wines is reduced by the alcohol reduction contrary to the theory that wines with elevated alcohol content appear less intense in terms of fruity character. The treatment by physical methods goes along with aroma losses, and that factor is stronger than the elevated volatility of the remaining aromas due to alcohol reduction.

The theory of sweet spots in terms of alcohol has been accepted, so far, quite uncritical. With regard to wine, this term is mentioned in various publications that point out that even small differences in ranges of 0.1–0.2 vol.% can have severe influences on the taster's preference. This approach does not conform to other sources. Since an alcohol difference of less than 2 vol.% cannot be distinguished significantly, an experimental setup with alcohol steps of 0.1 or 0.2 vol.% is incomprehensible. The author's research showed that the panelist's preferences were widely spread at the respective tastings. So there was no significantly preferred spot when a set of seven samples with varying alcohol contents were tasted even though the initial and final alcohol content clearly made the wine different. It is important to note that the examiner's preferences spread evenly over the range of samples. That proves that the preferences in terms of alcohol content in wine are not uniform. Instead of small changes in terms of alcohol contents, it could be more interesting to clearly change wine style, thus creating wines that are favored by customers who prefer lighter wines [21, 31, 39, 41, 51, 57].
