Sluggish/stuck fermentations

Edwards, G.G., K.M. Haag, and M.D. Gollins. 1998b. Identification of some lactic acid bacteria associated with sluggish/stuck fermentations. Am. J. Enol. Vitic. 49 445-448. 

Sablayrolles, J.M., Dubois, C., Manginot, C., Roustan, J.L., Barre, P. (1996). Efectiveness of combined ammoniacal nitrogen and oxygen additions for completion of sluggish and stuck fermentation. J. Fermen. Bioeng., 82, 377-3S1... 

Practical applications of alginates concern mainly secondary fermentation inside the bottle in sparkling wine production for easy clarification and removal of cells Other applications are the treatment of sluggish and stuck fermentations ... 

The causes of sluggish and stuck fermentations include fermentation at temperature extremes, nutritional deficiencies, osmoregulation, ethanol toxicity, and in low-temperature fermentations, long-term anaerobiosis. To these classically ascribed sources can be added failures in adequately preparing yeast starters as well as the presence of inhibitory compounds which may include pesticides and those produced by microorganisms. 

Munoz, E. and W.M. Ingledew. 1989. Effect of yeast hulls on stuck and sluggish wine fermentations Importance of the lipid component./. Appl. Environ. Microbiol. 55 1560-1564. 

Juice and wine pH play a mjgor role in the development of yeast and bacterial populations. Species respond differently in terms of growth rate as well as production of sensorially important metabohtes. In the case of Saccharomyces, growth and fermentation rates slow as pH decreases to near 3.0, concomitantly increasing the risk of sluggish or stuck fermentations. Kudo et al. (1998) found that the relative concentration of and H in a grape must plays an important role in successful completion of alcoholic fermentation, with a minimum of 25 1 being necessary. Whereas... 

Causes of sluggish (slow) and stuck (stopped) fermentations include nutritional deficiency, inhibitory substances, processing difficulties, as well as bacterial antagonism (Section 6.6.2). Although various factors can contribute to a sluggish or stuck fermentation, the exact cause (s) of a particular occurrence cannot always be identified. 

Excessive temperatures and sugar concentrations can provoke sluggish or stuck fermentations. Nutritional deficiencies and inhibition phenomena can also be involved. All of them have either chemical or physicochemical origins. Fermentation kinetics can be ameliorated by different methods which influence these phenomena. Early action appears to increase their effectiveness yeasts in their growth phase and in a medium containing little ethanol are more receptive to external stimuli. The winemaker should anticipate fermentation difficulties the possible operations are much less effective after they occur. 

Stuck fermentation continues to be a much discussed subject. In some cases, a modification of vine varieties has produced grapes that have high sugar concentrations. These grapes are more difficult to ferment than past varieties. In other cases, winemakers have recently realized that sluggish fermentations spread over several months are not ideal for making wine. 

The success of an alcoholic fermentation depends on maintaining the population of viable yeast at sufficient levels until all the fermentable sugars have been fully consumed (Bisson 1999 Zamora 2004). Otherwise, the winemaker is faced with the serious problem of stuck and sluggish fermentations. The causes and the ways to avoid stuck and sluggish fermentations are discussed later (Bisson and Butzke 2000). 

For this reason, the lack of enough BAN can make the yeast use sulphur amino acids (cysteine and methionine), thus releasing hydrogen sulphite and mercaptans. Thus, supplementing with ammonium salts is recommended not only to avoid stuck and sluggish fermentations but also to prevent reduction off-odours (Jiranek etal. 1995). 

The causes of stuck and sluggish fermentations have been the subject of several studies (Larue et al. 1982 Ingledew and Kunkee 1985 Alexandre and Charpen-tier 1998 Bisson 1999). Some of them have already been described in previous points. The following list summarizes the possible causes and solutions of stuck and sluggish fermentations. 

Presence of medium chain fatty acids The presence of MCFA can decrease yeast viability and even stop alcoholic fermentation. This problem is more prevalent in white winemaking because fermentation is usually carried out at low temperatures and without any aeration. Yeast hulls have been very useful for avoiding this problem. Yeast hulls adsorb MCFA from the media and provide sterols and UFA to the yeasts. Yeast hulls can be used as preventives (20 g/hl) or as curatives (40-50 g/hl) of stuck and sluggish fermentations. 

Alexandre, H., Charpentier, C. (1998) Biochemical aspects of stuck and sluggish fermentation in grape must. J. Ind. Microbiol. BiotechnoL, 20, 20-27. 

Several treatment agents of wine yeast cell walls, sodium caseinate, gelatin, bentonite were evaluated for their potential to bind with aroma compounds. The loss of sensory properties of wine, especially flavor modification, is partly caused by protein stabilization treatments with fining agents or ultrafiltration processing of wine (IS 14). Yeast cell walls are used in sluggish or stuck wine fermentation the effect on fermentation has been explained by the adsorption of toxic fatty acids present in the growth medium (15). Therefore yeast walls are also assumed to bind aroma compounds. 

Silva S., Ramon P.F., Silva R, Maria de Fatima T. and Strehaiano P. Use of encapsulated yeast for the treatment of stuck and sluggish fermentations. Journal International Des Sciences De La Vigne Et Du... 

Bisson, L. F. (1999). Stuck and sluggish fermentations. American Journal of Etiology Viticulture, 50, 107-119. 

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