following: wines are sometimes aged on their yeast • integration of mouthfeel elements by lees in conjunction with addition of interaction between structural/textural exogenous b‑1,3-glucanase enzyme. This elements,3,10 procedure is an attempt to release man- • reduction in the perception of noproteins, which winemakers believe astringency and bitterness,5,11,19,23 may enhance the suppleness of a wine, • increase wine body,3 while reducing perceived astringency. • encourage growth of microorganisms,13 Wines aged on lees with no fining con- • impact bitartrate instability,14,16,17,25 tain mannoproteins, while wines fined • impact protein stability,26 prior to ageing may have a large percent- • interact with wine aroma age of mannoproteins removed. Periodic components.15 stirring sur lie increases the mannopro- tein concentration and increases the Photo by E liz a beth Cl rk, Airlie W inery, O regon BY Bruce Zoecklein native b-1,3-glucanase activity. Generally, yeast autolysis is relatively slow (in the absence of glucanase enzyme addition) raditionally, only some white and may require months or years to wines and sparkling wines were occur, possibly impacting the mannopro- left in contact with yeast lees post- tein concentration.2 fermentation. This practice is now Table I shows some important practical used frequently in many viticultural winemaking considerations regarding regions around the world today for both lees management. red and white wines.20 Lees are composed mainly of yeasts, Table I. Lees management bacteria, tartaric acid, polysaccharides, considerations and protein-tannin complexes. Red wine • Must clarification, non-soluble solids lees have a relatively high concentration level (NTU), of protein and tannin. The composition • Primary or heavy compared to is variable depending upon several fac- secondary lees or light lees, tors including: fruit quality (incidence Red wine lees remaining after Pinot Noir • Volume of lees, and type of rot), cultivar, processing wine racked out of the fermentor. • Stirring compared to non-stirring, techniques, timing of racking, malolactic method, frequency and duration, fermentation (MLF) and timing and use Lees management considerations • Type and size of vessel, of enzymes etc. Several methods of increasing manno- • Duration of lees contact, Lees contribute to colloidal macro- protein levels in wine have been sug- • MLF, timing of MLF, molecules in wine which are derived gested,6,10 including: • Timing and type of racking (protec- from three general sources, polysac- • must turbidity, tive or aerative), charides, glucans and mannoproteins.10 • selection and use of yeast which • SO2 timing and level of addition, Mannoproteins are proteins with a high produce high levels of mannoproteins • Frequency of barrel topping, carbohydrate content including mannose during alcoholic fermentation, • Use of lysated compared to fresh lees, sugars, hence the term. • yeast which autolyze rapidly upon lees products. During ageing sur lie, a breakdown completion of alcoholic fermentation, of yeast cellular membrane components • addition of b-1,3-glucanase to wines Photo by A a ron B ennett, n a can occur, releasing intracellular con- stored on lees, stituents. These macromolecules can • addition of exogenous mannoproteins positively influence structural integra- (proprietary products), lysated (broken) tion, phenols (including tannins), body, lees. aroma, oxygen buffering and wine sta- The amount of mannoprotein released bility. Some macromolecules provide a during yeast fermentation is dependent v sense of sweetness as a result of bridg- on several factors, including yeast strain. a rro winery ing the sensations among the phenolic Large differences are noted among yeasts elements, acidity and alcohol, aiding in in the amount of mannoproteins pro- wine harmony and integration. duced during fermentation and released during autolysis. Generally, the more Mannoproteins turbid the must, the lower the manno- Mannoproteins in yeast cell walls are protein concentration in the fermented bound to glucans (glucose polymers), wine.12 and exist in wines as polysaccharides Mannoproteins released during yeast and proteins.10 They are released from fermentation are more reactive than cell walls by the action of an enzyme, those released during the yeast autolysis b-1,3-glucanase. b-1,3-glucanase is active process in modifying astringency. This during yeast growth and during ageing helps provide additional justification to in the presence of non-multiplying yeast measure the non-soluble solids of juice cells. Stirring increases the concentra- (NTUs) pre-fermentation. 9 Photo caption tion. Lees mannoproteins can impact the In Burgundy and other regions, red
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of proteolysis, whereby proteins are tity of SO2 are important stylistic con- Juice clarification and non-soluble hydrolyzed to amino acids and peptides. siderations. Early addition increases the solids These compounds result in an increase in number of components that bind to sub- 13 Extensive crushing of red grapes can the available nitrogen content of a wine. sequent additions of SO2. The addition of result in a high level of non-soluble solids Amino acids can act as aroma/flavor too much SO2 counters the wood flavors mainly in the form of phenol compounds precursors and possibly enhance wine and limits oxidation reactions. which remain in the fermenter. White complexity. They may also help support D. Delteil compared red wines barrel- juice is generally racked prior to fermen- the growth of microorganisms in wine.13 stored on light lees for nine months and tation to eliminate precipitated juice lees those racked several times to eliminate consisting mainly of grape particulate, Lees stirring and duration lees prior to barreling and stored for the tartaric acid, polysaccharides and protein Lees stirring and frequency are impor- same time period.4 tannin complexes. tant, both as practical and stylistic con- Wines stored sur lie had a much lower During yeast fermentation, the level siderations. M. Feuillat et al demonstrated perception of astringency and a greater of macromolecules continually rises, that periodic stirring of lees increases the integration of the phenolic elements. The peaking at approximately 270 mg/L.M. mannoprotein level and amount of yeast- sur lie wines also had a lower perception Guilloux‑Benatier et al found a rela- derived amino acids.9 Red and white of oak character, resulting in a higher tionship between the degree of must wines aged on their lees in barrel exhibit perception of fruit characters. clarification and the amount of yeast an increase in macromolecules. Lees components such as polysaccha- macromolecules recovered in the wine.10 Stirring is a stylistic tool that generates rides and proteins are known to react When the must was not clarified pre-fer- an oxidative process that can change the with phenolic compounds, thus reducing mentation, there was limited production sensory balance between fruit, yeast and astringency. Such reduction can cause an of yeast macromolecules.12 wood by enhancing yeast components, increase in the wine’s volume or body. However, mild must clarification, such reducing the fruit and, to a lesser degree Lees contact is particularly effective at as cooling for 12 hours, increased the the perception of wood-derived aroma/ modifying wood tannin astringency by amount of yeast-produced macromol- flavor. binding free ellagic tannins, thus lower- ecule production by an average of 76 Stirring may have the effect of enhanc- ing the proportion of active tannins. Sur mg/L, and heavier must clarification, ing secondary chemical reactions, pos- lie storage can reduce the free ellagic acid such as bentonite fining, increased the sibly as the result of oxygen pick-up. W. by as much as 60%, while increasing the production by about 164 mg/L. S. Boivin Stuckey et al demonstrated increases in percentage of ellagic tannins bound by et al found that the amount of macromol- sensory scores in Chardonnay wines 24%.18,22 ecules produced varied between 230 and stored for five months without stirring. 630 mg/L, and they contain 20 – 30% Non-stirred wines had greater fruit Addition products glucose and 70 – 80% mannose.1 intensity. 24 Proprietary products or treatment of lees with b-glucanases may aid in the Heavy and light lees Malolactic fermentation and lees increase of mannoproteins and glucans Winemakers differentiate between light MLF reduces the harshness of new oak in a wine. The mannoproteins in com- or secondary lees and heavy or pri- and aids in development of complexity. mercial addition products may be differ- mary lees. Heavy or primary lees can be Traditionally, stirring is continued until ent than those produced by yeast. Unlike defined as those that precipitate within MLF is complete. After that, lees are many commercial products, yeast- 24 hours immediately post-fermenta- more dense, which aids in clarification. derived mannoproteins generally have tion,4 and are composed of large particles This regime may be changing with the a mannose/glucose ratio of 1 to 1 and a (greater than 100 micrometers) consisting increase in co-fermentation of yeast and relatively high protein content. Thus, it of grape particulates, agglomerates of lactic acid bacteria. As Lactobacillus spp. is likely that yeast mannoproteins will tartrate crystals, yeasts, bacteria and pro- have proteolytic activity, there may be react differently in wine than some com- tein-polysaccharide-tannin complexes. an increase in the mannoprotein compo- mercial products. Light or secondary lees can be defined as nents, polysaccharides and proteins in Some winemakers age wines in the those that precipitate from the wine more their presence.20 presence of lysated (broken) lees instead than 24 hours post-fermentation.3 These of fresh lees in order to reduce the time are composed mainly of small particles Sensory impacts conserved on lees and to help avoid pos- (1 – 25 micrometers) including yeasts, During élevage what is sought is slow, sible microbial and organoleptic risks. bacteria, tartaric acid, protein-tannin managed and controlled oxygenation. O. Fernandez et al outlines the dif- complexes and some polysaccharides. Some lees contact may allow for oxygen- ferences in wines produced with such There is little value in storing red or ation, while limiting oxidation. treatments and fresh lees.6 Addition of white wines on primary lees. Such stor- In Burgundy red wines have been enzymes to wines in the presence of lees age can result in off-aroma and flavors, traditionally racked off the lees in may increase the glucose concentration and depletion of SO2. Light lees storage, March, usually when MLF is completed. providing a carbon source for micoor- however, can have a significant advan- Frequently this is an aerobic racking, ganisms such as Brettanomyces.13 tage in structural balance, complexity then back into oak on light lees, followed and stability. by an SO2 addition. Light lees are said Summary impact of yeast lees: to help “nourish” a wine. A subsequent Color and Mouthfeel — High lees con- Bâtonnage racking often occurs in early July, and is centration can reduce color, as a function During lees contact, wine composition in the absence of air. of adsorption onto the yeast cell surface changes as the yeast commence enzy- and possibly as a result of anthocyanin matic hydrolysis of their cellular con- SO2 additions destabilization from b-glucosidase activ- tents. An important feature is the process Timing of SO2 additions, and the quan- ity. Additionally, lees adsorb oxygen that practical winery & vineyard JULY 2013 2 wineMAKING can limit the anthocyanin-tannin polym- lees contact, the lower the need for Notes #162, available at: vtwines.info. erization, impacting both color stability bentonite for protein stability. It is not and resulting in an increase in dry tan- believed that lees hydrolyze grape pro- Bruce Zoecklein, professor emeritus nin perception. Commercial mannopro- teins, or that proteins are adsorbed by and former head of the Enology-Grape teins may cause a greater color loss than yeast. Rather, lees ageing produces an Chemistry Group at Virginia Tech in yeast-derived mannoproteins. additional mannoprotein, which adds Blacksburg, Va. Wine Aroma — Lees favor the synthe- stability. The production is increased sis of esters that can improve wine aro- with temperature, time and frequency Bibliography matics,21 but also produce long chained of stirring. 1. Boivin, S., M. Feuillat, H. Alexandre, alcohols and fatty acids, compounds Biological Stability — M. Guilloux‑ and C. Charpentier. 1998 “Effect of 7 must turbidity on cell wall porosity that can detrimentally impact aroma. Benatier et al have studied the liberation and macromolecule excretion of Aroma stabilization is dependent upon of amino acids and glucose during élevage Saccharomyces cerevisiae cultivated the hydrophobicity (ability to repel water of red Burgundy wine on lees.13 Their on grape juice.” Am. J. EnoI. & Vitic. molecules) of aroma compounds. studies were done with and without the 4: 325–331. The protein component of the manno- addition of exogenous b‑1,3-glucanase 2. Charpentier, C., and M. Feuillat. 1993 “Yeast autolysis.” In Wine protein fraction is important for overall preparations. Their most significant find- Microbiology and Biotechnology. aroma stabilization.15 Such interactions ing was an increase in glucose concentra- G.H. Fleet (ed.), pp. 225–242. can modify the volatility and aromatic tion, from 43 mg/L in the control wine, Harwood Academic Publishers, Chur, intensity of wines. to 570 mg/L in wine stored on its lees, to Switzerland. When wine is aged on yeast lees with 910 mg/L in wine stored on its lees with 3. Delteil, D. 2001 “Working with lees: no fining, mannoproteins are present added b‑1,3-glucanase. Thus, the growth Key elements to wine maturation.” 30th Annual Technical Issue of Aust. & and fortify the existing aroma compo- of the spoilage yeast Brettanomyces in NZ Grapegrower & Winemaker. nents. When wines are fined prior to barreled wine may be stimulated by the 4. Delteil, D. 2002. Verbal communica- élevage, mannoproteins can be removed availability of this carbon source. tion. and not be present to augment the exist- Bitartrate Stability — Mannoproteins 5. Escot, S., M. Feuillat, L. Dulau, and C. ing aroma components. produced by yeast can act as crystal Charpentier. 2001 “Release of poly- Additionally, when wines are inhibitors. The longer the lees contact saccharides by yeast and the influence of polysaccharides on colour stability cross‑flow filtered, eliminating a certain time, the greater is the likelihood of and wine astringency.” Aust. J. Grape percentage of macromolecules, the loss potassium bitartrate stability. Wine Res. 7: 153–159. of color intensity, aroma and flavor can Removal of Mycotoxins — The volume 6. Fernandez, O., O. Martinez, O. occur.8,21 of mycotoxins including Ochratoxin-A is Hermandez, Z. Guadalupe, and B. Yeast lees have been demonstrated to less as a result of the use of lees which Ayestaran. 2011 “Effect of presence reduce the perception and concentration can act as a fining agent to both adsorb of lysated lees on polysaccharides, color and main phenolic compounds of 4-ethyl phenol and 4-ethyl guaiacol and, in some cases electrostatically-bind of red wine during barrel aging.” found in red wines as a function of compounds and remove them from solu- Food Research Intern. 44: 84–91. Brett growth.13 This effect is significantly tion. 7. Ferrari, G., and M. Feuillat. 1988 impacted by autolysis state of the yeast Reductive Strength — Longevity, or “Holding white Burgundy wines on lees, pH, temperature, ethanol content the ability to age, is an important qual- their lees. 1. Nitrogenous compounds, and other constitutes adsorbed by the ity attribute. The reductive strength of fatty acids and sensory analysis of 20 wines.” Vitis, 27: 183–197. lees. a wine is a measure of the uptake of 8. Feuillat, M., D. Peyron, and J.L. Oak Bouquet — Lees modify oaky oxygen. This is influenced by the phe- Berger. 1987 “Influence de la micro- aromas, due to their ability to bind with nol composition and lees, among other filtration tangentielle des vins sur leur wood-derived compounds including things. composition physicochimique et leurs vanillin, furfural and methyl-octalac- The reaction of a young wine with caractères sensoriels.” Bull. OIV 60: 227–244. tones. oxygen can make that wine more resis- 9. Feuillat, M., and C. Charpentier. Oxidative Buffering Capacity — Both tant to later oxidation. This means that 1998 “Les mannoprotéines de levures: lees and tannins act as reducing agents. young wines can consume oxygen which Un adjuvant oenologique possible.” During élevage, lees release certain highly increases the reductive strength by Bull. OIV 71 (813-814): 929–940. reductive substances that can limit increasing resistance to later oxidation. 10. Feuillat, M. 2003 “Yeast macromol- wood-induced oxygenation. Wines have C. Smith noted that lees (and particu- ecules: Origin, composition, and a higher oxidation-reduction potential larly suspended lees) in a young wine enological interest.” Am. J. Enol. & Vitic. 54: 211–213. in barrels than in tanks. Inside a barrel, depletes the oxygen concentration.24 As 11. Gawel, R., P. Dumain, L. Francis, the potential diminishes from the wine such they can impact the degree of oxida- E.J. Waters, H. Herderick, and I.S. surface to the lees. Stirring helps to raise tive phenol polymerization thus increas- Pretorius. 2008 “Coarseness in white this potential. ing astringency and possibly reductive wines.” Aust. & NZ Wine Industry J. This is a primary reason why wines strength. Vol. 23. (3) 19–22. stored in large volume tanks are often Wine lees are an important tool for 12. Guilloux-Benatier, M., J. Guerreau, and M. Feuillat. 1995 “Influence not stored on lees. Such storage can cause winemakers influencing mouthfeel, of initial colloid content on yeast release of “reductive” or sulfur-contain- aroma, bouquet, oxidative, physical and macromolecule production and on the ing compounds. If there is a desire to microbiological stability. Additional metabolism of wine microorganisms.” store dry white wines in tanks sur lie, it research is needed to help clarify the Am. J. Enol. & Vitic. 46: 486–492. is recommended that the lees be stored influence of both yeast and bacterial lees 13. Guilloux-Benatier, M., D. Chassagne, in barrels for several months, then added on these and other wine features. PWV H. Alexandre, C.Charpentier, and M. 22 Feuillat. 2001 “Influence de I’autolyse back to the tank. des levures après fermentation sur le Protein Stability — The greater the This text was adapted from Enology
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développement de Brettanomyces/ Dekkera dans le vin.” J. Int. Sci. Vigne Vin 35 (3): 157–164. 14. Lubbers, S., B. Leger, C. Charpentier, and M. Feuillat. 1993 “Effet colloide- protecteur d’extraits de parois de levures sur la stabilité tartrique d’une solution hydro-alcoolique modèle.” J. Int. Sci. Vigne Vin 27 (1): 13–22. 15. Lubbers, S., A. Voilley, M. Feuillat, and C. Charpentier. 1994 “Influence of mannoproteins from yeast on the aroma intensity of a model wine.” Lebensm.-Wiss. Technol. 27: 108–114. 16. Moine-Ledoux, V. 1996 “Recherches sur le rôle des mannoprotéines de levure vis-à-vis de la stabilisation pro- tique et tartrique des vins.” Thèse de Doctorat, Université Bordeaux II. 17. Moine-Ledoux, V., and D. Dubourdieu. 2002 “Des mannoprotéines de levures vis-à-vis de la stabilisation tartrique des vins.” Bull. OIV 75 (857–858): 471–482. 18. Myers, T.E. and V.L. Singleton. 1978 “The non-flavonoid phenolic fraction of wine and its analysis.” Am. J. Enol. & Vitic. 30: 98–102. 19. Noble, A.C., C.R. Strauss, P.J. Williams, and B. Wilson. 1988 “Contribution of terpene glycosides to bitterness in Muscat wine.” Am. J. Enol. & Vitic. 39: 129–131. 20. Perez-Serradilla, J.A., and M.D. Luque de Castro. 2008 “Role of lees in wine production: A review.” Food Chemistry, 111: 447–456. 21. Post, W., and L. Adams. 1987 “Effects of yeast contact and storage time on volatile components of wine.” Mitt. Klostern. 37: 54–56. 22. Ribéreau-Gayon, P, Y. Glories, A. Maujean, and D. Dubourdieu. 2000 Handbook of Enology. The Chemistry of Wine Stabilization and Treatments. John Wiley and Sons. New York, NY. 23. Saucier, C. 1997 Les tannins du vin: Etude de leur stabilite colloidale. Thesis, University of Bordeaux. 24. Smith C. 2010. “What is vine bal- ance?” Wineries Unlimited presenta- tion. Richmond, VA March 2010. 25. Stuckey, W., P. Iland, P.A. Henschke and R. Gawel. 1991 “The effect of lees contact time on Chardonnay wine composition.” Proceedings of the Intern. Sym. on Nitrogen in Grapes and Wines. 26. Waters, E.J., P. Pellerin, and J.M Brillouet. 1994 “A Saccharomyces mannoprotein that protects wine from protein haze.” Carbohydr. Polym. 23: 185–191.
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