Sluggish Fermentations Research Articles

Relationship Between Sluggish Fermentations and the Antagonism of Yeast by Lactic Acid Bacteria

Lactic acid bacteria isolated from commercial wines undergoing slow/stuck alcoholic fermentations and from wines without any known problems were tested for antagonistic activity against wine yeasts. Using a microbiological medium screening method, the majority of bacterial strains tested did not retard growth of <i>Saccharomyces bayanus</i> (strain Prise de Mousse) or <i>S. cerevisiae</i> (strain Epernay), with the exceptions of <i>Leuconostoc oenos</i> strain OENO and unidentified strains YH-15, YH-24, and YH-37. To determine whether or not these organisms could cause a slow/stuck fermentation of a grape juice, bacterial strains were inoculated into sterile-filtered Chardonnay grape juices at initial populations of <i>ca</i> 10⁵ cfu/mL. Two days later, either Epernay or Prise de Mousse was inoculated into the same juices at <i>ca</i> 10⁵ cfu/mL. Inoculation of <i>Lc. oenos</i> did not result in slow/stuck alcoholic fermentations. However, inhibition of the fermentations catalyzed by Epernay were observed in the presence of YH-24 or YH-37, in contrast to fermentations with Prise de Mousse. Strain YH-15 greatly inhibited the alcoholic fermentations by both yeast strains. Wines inoculated with YH-15 had significantly higher concentrations of volatile acidity (≈=0.30 g/100 mL) than control wines (≤0.037 g/100 mL) or wines inoculated with YH-24 or YH-37 (≤0.055 g/100 mL). Other compositional differences were observed.

Alcoholic fermentation under oenological conditions

The possibility of predicting sluggish fermentations under oenological conditions was investigated by studying 117 musts of different French grape varieties using an automatic device for fermentation monitoring. The objective was to detect sluggish or stuck fermentations at the halfway point of fermentation. Seventy nine percent of fermentations were correctly predicted by combining data analysis and neural networks.

Stuck wine fermentations: Effect of killer/sensitive yeast interactions

Mixed-strain fermentations were carried out with different proportions of killer/sensitive yeasts. It was observed that stuck and sluggish fermentations due to killer/sensitive strain interaction depended on: a. the killer/sensitive yeast proportion at the start of fermentation, b. the concentration of nitrogen source in the grape must, and c. the presence of bentonite during fermentation. The effect of the addition of active carbon and commercial yeast cell walls to sluggish fermentation media was also studied.

Biological Assay of Nitrogen Content of Grape Juice and Prediction of Sluggish Fermentations

A bioassay based upon final culture absorbance was developed and utilized to estimate nitrogen content of grape musts. Amino acid analyses of grape musts were run for comparison to the values obtained from the bioassay. In Chenin blanc and French Colombard musts, there was a good correlation between nitrogen content as measured by biomass yield with that determined from amino acid analysis. The nitrogen content of Grenache musts showed a positive correlation with cell yield in the bioassay, but was not as strongly correlated as in the other two varieties. The amino acids generally recognized as good yeast nitrogen sources were more highly correlated with biomass yield than were poorer nitrogen sources. Ammonium ion supplementation of nutrient-deficient Chenin blanc juices either stimulated fermentation rate or had no effect, depending upon the juice. Ammonium utilization was found to be dependent upon the pH and ethanol concentration of the medium. Fermentation of nitrogen deficient musts was found to be stimulated by a variety of growth factors in addition to nitrogen.

Yeast hulls in wine fermentations—a review

Abstract Yeast hulls (ghosts) have been shown to stimulate stuck or sluggish fermentations of grape juice. The mechanism of their action, however, has been contested. On the one hand, their action is claimed to be via adsorption of toxic levels of hexanoic, octanoic and decanoic acids; on the other, via the provision of ergosterol and unsaturated fatty acids used by yeast for membrane synthesis. This review summarises recent data on the subject and provides clarification of the mode of action.

Influence of Oxygen on Proline Utilization During the Wine Fermentation

In order to overcome sluggish or stuck fermentations, it may be necessary to utilize oxygen and yeast-utilizable nitrogen sources found in some yeast foods. Government regulations in the US preclude the use of large amounts of yeast foods — even those derived from yeast or proteins often employed as food ingredients. The present work describes the conditions under which proline, an amino acid naturally present in high concentrations in musts, can be utilized fully as a source of nitrogen. Oxygen is required for proline degradation; it is also a requirement to ensure sufficient yeast growth and to avoid sluggish fermentations.

An Assessment of Yeast Foods and Their Utility in Brewing and Enology

Yeast foods are occasionally utilized in high-gravity brewing and enology to eliminate sluggish or stuck fermentations that may occur in these industries as a result of a deficiency of a key yeast ...

Factors Influencing Sluggish Fermentations of Grape Juice

Attempts to overcome sluggish (very delayed or incomplete) vinifications were made by application of previous brewing and enological findings regarding requirements for oxygen and other nutrients. Ruby Cabernet juice, and a Chardonnay juice which was known to give an incomplete fermentation commercially, were totally end-fermented in only seven days at 14°C when large amounts of assimilable nitrogen and small amounts of headspace air were provided. Restriction of oxygen by nitrogen gas flushing of the headspace resulted in protracted, sluggish-to-stuck fermentations. Air and free amino nitrogen additions stimulated the duration of active yeast growth and final cell mass, thereby enhancing fermentation rates. Indications as to the timing of aeration and the concentration of yeast food required to prevent sluggish fermentations are provided.

Some Modern Methods.*-Their Practical Application in the Brewery.

The paper deals with water treatment, fuel and power economy, and the saving of materials and time (malt crushing and the mash filter). In the first section the value of eliminating the carbonates from the brewing water—particularly in cases of sluggish fermentation and the liberal employment of malt adjuncts, such as maize and rice—is explained and the use of the Archbutt-Deeley process advocated as affording the simplest and most economical means of de-carbonating the large volumes needed for actual brewing operations, as distinct from the smaller quantities required for boiler-feed purposes; whilst illustrations of the plant and details of working are given. The lactic acid treatment is fully discussed and the fallacy of any marked increase in extract yield from the malt being obtained by this very expensive process explained away; for, as should be well known, whatever gain may appear on the saccharometer is, in the main, due merely to the mineral matter in solution, part of which will be that natural to the water and part to that added to precipitate the former, but both of which are subsequently re-dissolved by the acids employed. As mineral matter, however, influences the saccharometer indication at about twice the rate of organic extract, brewers employing this treatment are therefore unwittingly deceiving themselves by imagining that they are getting from 1 to 2 lb. per quarter more from their malt than is actually the case, the apparent increment being almost solely due to the excessive amount of mineral matter in solution. It is further pointed out that after the carbonates have been removed by the inexpensive Archbutt-Deeley process, the full benefit of the lactic acid treatment can be secured by the addition of a sufficient quantity, to show a lactic acidity of 0.05 per cent., costing approximately 1 3/4d. per barrel.