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Minimal Intervention Enology

Carsten Heinemeyerr, Jörg Wiedemann; 2B FermControl GmbH

Minimal Intervention Enology

The demand for a sustainable economy and resource conservation is on everyone's minds. As a result, the appeal to produce grapes and wine more sustainably and to allocate resources, is also raised in relation to winemaking. This requirement is already partly being implemented in viticulture. For example, fewer mineral fertilizers are used, and fewer plant protection agents are used by weather stations with prediction models for combating funghi. In the cultivation of so-called funghi-tolerant grape varieties (PIWlS), another possibility for saving fungicides, energy, and CO2 is seen.
In winemaking, however, a sustainable economy is only at the beginning. This is not only about the storage of energy when using machines for the production of cold, heat, pumps or filling, but also about a reduction of auxiliary materials and all other operating materials such as bottles, closures, or packaging required in winemaking. After all, the production of many auxiliaries and agents, often ignored by the public, consumes a lot of energy and resources. In addition, the disposal of some auxiliary substances after use is harmful to the environment. For minimalistic and sustainable winemaking, vineyards and cellars must therefore be considered together as a unit.


The Cellar Management Starts In The Vineyard

The approach of minimal winemaking begins in the vineyard. By using the latest knowledge and techniques in viticulture and plant protection, it is possible to produce more grapes with less effort. Only with healthy grapes can high-quality and durable wines be vinified with less use of auxiliaries. Climate change brings advantages in crop protection and grape health through often dry, hot years. On the other hand, intelligent solutions to dry stress, UV radiation and "hot vintages" are in demand. In order to implement minimalist winemaking consistently, it is necessary to plan the vineyard for sustainable grape production.
This starts with the selection of the location, adapted to the desired wine style. Soil type, water supply, grape varieties, clones, and root stocks and line exposition are the determining factors.
The aim must be to be able to produce grapes for the desired wine styles already with the consolidation of the vineyard. This saves both, unnecessary measures in viticulture and processing, as well as the need for aids and additives in winemaking. In practice, this means that new plants should allow a high degree of mechanization. This facilitates efficient measures for plant protection and soil cultivation and thereby ensures grape health. Targeted leaf wall management and soil management is equally responsible for the grape quantity and ingredients of the grapes, and thus for the expression of the different wine styles. This relates to all extract substances, acids, flavourings and phenols, as well as the necessary nutrients (YAN value) for the yeasts.
A high degree of light exposure on the vines promotes the incorporation of anthocyanins and other phenols, while lower exposure protects the primary aromatics and the better preservation of the acid. The use of full harvesters at night enables the processing of cooler grapes with a low energy requirement during further processing. A vineyard for the preparation of sparkling wine should not be planted in the best location. Locations for red wines should always be well ventilated and exposed. This means that targeted grape production enables simpler vinification with less effort in the cellar.


Solutions From The Vineyard

Climate change also has an increasing impact on cultivation and processing of the grapes. The composition of the ingredients of the grapes is increasingly changing. The average sugar content and also the phenol storage in red and white varieties are increasing. This has an influence on the processing but also the stylistics of the wines. However, consumers also ask for alcohol-reduced, fruity wines, which in turn contradicts the consequences of climate change. Today, the goal is to reduce sugar and alcohol content and to produce fruity wines without great phenolics. The characteristics of the yield clones available today, such as high yield consistency with high sugar maturity, are partly in contradiction to today's consumer requirements.
Through vine breeding measures with new, sugar-ripening rootstock varieties, as well as with yield clones, viticulture is beginning to counter the changes of climate change. Whether these developments achieve the desired goals with regard to maturity delay remains to be seen.
In the case of the PIWIS, the trend shows that almost all approved varieties are characterized by a very fast and high sugar storage. Here, especially for organic viticulture, it is important to find solutions that represent a real alternative in the long term under the changes of climate change.


Wine Style

With the increasing growing conditions due to climate change, the discussion about the optimal picking time and the desired wine style is also coming into focus. The times of winemaking with optimal sugar ripeness of the grapes and conjunction with optimal physiological ripeness at moderate alcohol levels are no longer possible in many vintages. Therefore, some producers define the time of harvest at the desired potential alcohol content of the wines. However, harvesting too early, with an eye on a potentially low alcohol level, carries risks to wine quality and shelf life.

Figure 1

A very early harvest with the focus on the sugar or low alcohol content carries the risk of even lower YAN-N values. Fermentation management becomes more difficult even at lower potential alcohol levels and relies on the addition of fermentation aids such as DAP or yeast derivatives. This also causes the tendency of such wines to premature aging and a "green" aroma of the wines. Figure 1 shows the development or storage of valuable ingredients of the grapes during ripening or veraison. Under the usual climatic conditions, the general rule for the time of harvest was: 100 days after flowering. In dry, hot years, however, the sugar maturity runs well ahead and the tartaric acid and malic acid decrease much faster. However, this does not apply to aroma maturity.


What Does Minimal Intervention In The Cellar Mean?

Today's modern cellar management offers a variety of techniques and methods for the production of various wine styles. For this purpose, the supplier industry not only offers modern machines and process technology, but also a variety of auxiliaries and additives for winemaking. However, this also leads to increased energy and resource consumption in the production of these substances and in vinification. But here, too, the industry is changing. In addition to additive oenology, in which all registers of auxiliaries and additives are pulled out, more and more winemakers are opening up to the method of so-called minimal intervention. It follows the principle of minimal influence or as little as possible and as much as necessary.
In addition, there is also a small group of winemakers who do not use any excipients. That sounds simple and tempting; but when it comes to practical implementation, nature often sets limits in terms of constancy and production reliability.

Figure 2

Figure 2 compares the advantages and disadvantages of the different approaches to winemaking. 

The public discussion of consumer organizations regarding legislation on the declaration of auxiliaries and additives for winemaking sheds new light on the use of aids. Todays wine consumers are also more enlightened and want to know what ingredients their wine contains. It is clear that in the future the declaration of the aids used will be tightened.
The minimal intervention approach anticipates this in many respects and tries to reduce the use of many oenological aids to the necessary level without losing safety in winemaking. This requires the selection of suitable excipients that can cover several applications at the same time in their function. 

Figure 3

As an example, a substitute for fresh juice and grape treatment is mentioned, which can replace a number of conventional fining agents for the removal of undesired components such as phenols, negative odours, aromas, spray residues and colour defects. It is a functional yeast cell wall preparation that can replace PVPP, casein, gelatine and silicate-containing agents in the removal of undesired components in juice and wine. But also standard applications with activated carbon can be safely replaced by such multifunctional yeast cell wall preparations.
A study from 2021 should be mentioned here.
Figure 3 shows a comparative test in which the effect of functional yeast cell walls against activated carbon was compared. The comparison showed that the organic variant has the same effect, without the sensory disadvantages of activated carbon. These yeast cell walls are also an effective substitute for products that contain microplastics, such as PVPP, PVI. The environmental impact and health hazards of microplastics have been widely reported in the media.

Figure 4

The treatment of musts and wines with increased and undesirable phenol contents is also possible with this alternative product (Figure 4).


Fermentation Management 

For the fermentation of the wines, mainly selected dried yeasts are used. In the production of dried yeasts and yeast derivatives, it is important to consider the substrates used and their impact on the ecological footprint. Here, too, there are alternative solutions that are on a par with conventional products in terms of safety and functionality.
For yeast nutrition, it is recommended to rely on a fully organic nutrient, as it offers several benefits in contrast to the use of only DAP. On the one hand, the new, fully organic yeast nutrients cover the nutritional requirements of yeasts in all phases of alcoholic fermentation. Therefore, it is not absolutely necessary to use separate nutrient products for the different phases of fermentation to supply the yeasts. This saves time and work as well as money, as the process costs are reduced.
Figure 5 shows with the blue arrows the needs of various substrates during the phases of alcoholic fermentation. The red arrows illustrate which metabolites or valuable ingredients the yeast releases into the wine during fermentation. This saves the addition of multiple separate products to increase the longevity and complexity of the wines.

Figure 5

Organic complex nutrients promote this production and the release of the valuable ingredients for the most part. In this way, these organic complex nutrients can reliably cover the demand in all phases of fermentation.  The only exception is when the initial YAN value is extremely low (< 75 ppm). Then it is recommended to raise the YAN N value with inorganic nitrogen.


Conclusions 

The minimal cellar management offers a number of alternative applications that have already proven themselves in practice in Europe and abroad for several years.
The wines from this production method are pure, high-quality and extremely durable. They meet the expectations of consumers and ambitious wine lovers alike.
In addition, the life cycle assessment plays a role in the production of excipients and additives. In addition to the use of organic raw materials, preferably from organic agriculture, the use of energy and CO2 in production and logistics should also be considered.
In addition, minimal production methods reduce costs. Even if the few individual products are slightly more expensive, the process costs demonstrably decrease and something is done for the ecological footprint.
As a conclusion, it can be stated that today's winemakers can also rely on minimal winemaking in the cellar industry without having to lose safety and quality. The best way to test the benefits of minimalist oenology is to compare it directly with additive oenology. This gives winemakers an impression of the advantages of this production method. 

 

Published on 04/18/2023
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