The full potential impact of climate change on the wine industry is yet to be comprehensively understood however research has already been undertaken to investigate what winemakers can do to mitigate some of those potential impacts and identify the role that current and new ingredient technologies can play.
In viticulture, the impact of global warming requires a reconsideration of current wine production models.
Considering the strong influence of weather and climatic factors on grapevine yields, berry quality and attributes, climate change may indeed have a significant impact. Recent-past trends already point to a pronounced extension of the growing season due to changes in mean temperatures, as well as changes in the levels and frequency of precipitation. These factors have been influencing wine typicity across some of the most renowned winemaking regions worldwide. Moreover, several climate change scenarios predict enhanced stress conditions for grapevine growth until the end of the century. Although technology offers some help, the clear evidence for significant climate change in the upcoming decades urges adaptation and mitigation measures to be taken by winemakers.
In future climate change scenarios, rising temperatures may change the timing of grape ripening and consequent harvest date and may affect grape quality and yield.
The warmer climate leads to a bigger sugar concentration in the grape/must, and then to wines with a higher ethanol level. The increasing of alcohol content of wines is reported worldwide, for example in Italy (Abruzzoi and Pugliaii), France (Côtes du Rhone,iii Alsaceiv), Californiav (Napa Valleyvi), Australia.vii
Alcohol accumulation can be a significant stress factor during fermentation. Although Saccharomyces cerevisiae is highly ethanol tolerant, relatively high alcohol concentrations inhibits cell growth and viability, making it difficult to finish the fermentations.
This represents a real challenge for winemakers, seeking to produce dry wines despite the initial high level of sugars.
Although significant efforts have been made to study ethanol stress response in past decades, mechanisms of ethanol tolerance are not well known.
It is known that yeast metabolism of Saccharomyces cerevisiae without oxygen requires several adaptations. It has also been clear that under anaerobic conditions the yeast is not able to synthesize sterols and unsaturated fatty acids and that for anaerobic growth these have to be added to the media. More recently it has been found that many more factors play a role. Several other biosynthetic reactions also require molecular oxygen, and the yeast must have alternatives for these. In addition, the composition of the cell wall and cell membrane show major differences when aerobic and anaerobic cells are compared.
The ability to ferment under conditions of high levels of alcohol differ between yeast strains. This variability is manifested by differences in the capacity to maintain the fermentation rate during the stationary phase.
Indeed, most alcoholic fermentation occurs during the stationary phase, and the ability to ferment strongly during this phase has a large effect on the total fermentation time.
The ability of the yeast cell membrane to maintain its fluidity in a high-ethanol environment has been correlated with ethanol tolerance.
Saccharomyces cerevisiae does not need oxygen to obtain energy when fermenting grape juice. However, there are some essential biosynthetic pathways that use oxygen as substrate. This is the case for the
biosynthesis of sterols and unsaturated fatty acids. During the growth phase, while the cell multiplication is active, yeast needs to build new plasma membranes continually. For that reason, yeasts must synthesize great amounts of sterols, fatty acids and phospholipids during the first stages of alcoholic fermentation.
In fact, when the ethanol concentration increases progressively, and yeasts need to adapt their plasmatic membranes to this aggressive new environment.viii Apparently, the presence of ethanol in the medium alters
drastically the fluidity of the membraneix, and when there is a lack of sterols and unsaturated fatty acids the effect is a yeast cell break and/or a difficult permeation, leading to a sluggish fermentation.
The mechanism of the alterations in membrane properties are fundamental in the mechanism of ethanol toxicity. The physical changes that the membrane structure undergoes because of alcohol presence in the
media have not been completely described. It is accepted that ethanol is intercalated in lipidic heads of the membrane, with the OH group of the ethanol associated with the phosphate group of the lipidic heads and
the hydrophobic tails aligned with the hydrophobic core of the membrane. When this interaction takes place, ethanol molecules substitute interfacial water molecules, generating lateral spaces between polar heads, and, consequently, spaces in the hydrophobic core. These gaps result in unfavourable energy, so the system tries to minimize it by creating an interdigitated phase. This modification in the membrane causes a decrease in its thickness of at least 25% and as a consequence of this thinning, alterations in membrane protein structure and function can occur, leading to cellular inactivation during the fermentation process.x
Finally, phytosterols and inactive yeast cell additions in the fermentation medium are capable of increasing sterol availability and reducing the cellular demand for lipids, which entails a decrease in the production of acetic acid.xi xii
Supplementation with sterols can also increase the production of volatile aroma compounds, such as higher alcohols. Indeed, a positive correlation between higher alcohol production and sterol content has been observed for ergosterol as well as for phytosterols.xiii
The importance of organic nutrition is crucial for other reasons too. The supplementation of nitrogen without a correct balance with lipids (unsaturated fatty acids, ergosterol) could lead to the yeast cells death during the fermentation.xix It is demonstrated that nitrogen sources can potentially have a negative impact due to their signalling effects and this need to be considered. An in-depth understanding of the specific effects of each nitrogen source under such conditions is required to improve the prediction of the risks associated with nitrogen excess in lipid-limited fermentations.
So, a correct nutrition with organic nitrogen, naturally associated with lipids as inactivated or autolysate yeast is particularly important during fermentation in stress conditions, such as in high sugar must.
Pinnacle nutrition aids supply naturally all the growing factors necessary for proper fermentation in difficult conditions:
- Pinnacle FermiSafe provides physical support elements for the inoculated yeast to better disperse into the medium thus shortening fermentation lag-phase. The inactivated yeast provides survival factors (sterols) and gradually releases amino acids during fermentation. The cellulose also creates nucleation sites which avoid the toxicity effect of CO2 accumulation in the bottom of fermenting vessels.
- Pinnacle FermiFresh is an organic (ammonium salt-free) nutrient for white and rosé wines. With its gradual release of amino acids, unsaturated fatty acids, sterols and in particular antioxidant provides as other growth factors enable complete and safe fermentation.
- Pinnacle FermiTop is a very rich source of free amino acids, vitamins, minerals, unsaturated fatty acids and sterols which are immediately available for the yeast and improve cellular multiplication, viability and vitality of the cells. It provides amino acids for synthesis of transport proteins and enzymes. Gradual release of growth factors enables complete and safe fermentation. The large availability of amino acids ensures a complete and rich enzymatic pool for the yeast cells which increase aroma synthesis.
More information:
www.Pinnaclewineingredients.com
www,pinnaclewineingredients/contact
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ii Scaglione, G.; Graziani, G.; Federico, R.; Di Vaio, C.; Nadal, M.; Formato, A.; Di Lorenzo, R.; Ritieni, A. Effect of canopy managment techniques on the nutritional quality of the Montepulciano grapewine in Puglia (southern Italy). OENO One 2012, 46, 253–261.
iii Ganichot, B. Evolution de la date des vendanges dans les Côtes du Rhône méridionales. In Actes des 6e Rencontres Rhodaniennes; Institut Rhodanien: Orange, France, 2002; pp. 38–41.
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vi Vierra, G. Pretenders at the table—Are table wines no longer food friendly? Wine Business Monthly 2004, 11, 17–21.
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viii Weber, F.J., & Bont, J.A.M., (1996) Adaptation mechanisms of microrganisms to the toxic effects of organic solvents on membranes. Biochim. Biophys. Acta, 1286, 225–245.
ix Jones, R.P., & Greenfield, P.F., (1987) Ethanol and the fluidity of the yeast plasma membrane. Yeast, 3, 223–232.
x Lairón-Peris M, Routledge SJ Linney JA, Alonso-del-Real J,a Spickett, C.M. Pitt AR, Guillamon JM,a Barrio E, Goddard AD, Querol A Analysis of lipid composition reveals mechanisms of ethanol tolerance in the model yeast 2 Saccharomyces cerevisiae.
xi Belviso, S.; Bardi, L.; Bartolini, A.B.; Marzona, M. Lipid nutrition of Saccharomyces cerevisiae in winemaking. Can. J. Microbiol. 2004, 50, 669–674.
xii Deroite, A.; Legras, J.L.; Ortiz-Julien, A.; Dequin, S. Reduction of acetic acid production during wine fermentation by Saccharomyces cerevisiae × Saccharomyces kudriavzevii hybrids using adaptive evolution under lipids limitation. In Proceedings of the ISSY 34, Bariloche, Argentina, 1–4 October 2018.
xiii Rollero, S.; Bloem, A.; Camarasa, C.; Sanchez, I.; Ortiz-Julien, A.; Sablayrolles, J.-M.; Dequin, S.; Mouret, J.-R. Combined effects of nutrients and temperature on the production of fermentative aromas by Saccharomyces cerevisiae during wine fermentation. Appl. Microbiol. Biotechnol. 2015, 99, 2291–2304.
xiv Fairbairn, S.; Ferreira, A.C.S.; Bauer, F.F. Modulation of Yeast-Derived Volatile Aromas by Oleic Acid and Sterols. S. Afr. J. Enol. Vitic. 2019, 40, 1–11.
xv Varela, C.; Torrea, D.; Schmidt, S.A.; Ancin-Azpilicueta, C.; Henschke, P.A. Effect of oxygen and lipid supplementation on the volatile composition of chemically defined medium and Chardonnay wine fermented with Saccharomyces cerevisiae. Food Chem. 2012, 135, 2863–2871
xvi Rollero, S.; Mouret, J.R.; Sanchez, I.; Camarasa, C.; Ortiz-Julien, A.; Sablayrolles, J.M.; Dequin, S. Key role of lipid management in nitrogen and aroma metabolism in an evolved wine yeast strain. Microb. Cell Fact. 2016, 15, 1–15.
xvii Guittin, C.; Maçna, F.; Sanchez, I.; Poitou, X.; Sablayrolles, J.M.; Mouret, J.R.; Farines, V. Impact of high lipid contents on the production of fermentative aromas during white wine fermentation. Appl. Microbiol. Biotechnol. 2021, 105, 6435–6449.
xviii Rollero, S.; Bloem, A.; Camarasa, C.; Sanchez, I.; Ortiz-Julien, A.; Sablayrolles, J.-M.; Dequin, S.; Mouret, J.-R. Combined effects of nutrients and temperature on the production of fermentative aromas by Saccharomyces cerevisiae during wine fermentation. Appl. Microbiol. Biotechnol.
xix Catherine Tesnière, Pierre Delobel, Martine Pradal, Bruno Blondin Impact of Nutrient Imbalance on Wine Alcoholic Fermentations: Nitrogen Excess Enhances Yeast Cell Death in Lipid-Limited Must.
xx A set of nutrient limitations trigger yeast cell death in a nitrogen-dependent manner during wine alcoholic fermentation Camille Duc, Martine Pradal, Bruno Blondin.
