Wine Yeast Oil

Synonyms cognac oil, white cognac oil, green ethyl oenanthate wine yeast oil... 

Lie de vin oil (green cognac oil or wine lees oil) is obtained by steam distillation of the yeast and other sediments (lees) formed in wine. It is a green to bluish-green liquid with a characteristic cognac aroma. 

The oil is obtained by steam distillation of wine yeast, or as by-product of marc brandy production, which is purified and, if necessary, rectified. 

Products obtained by other extraction methods, such as solvent extracts, including supercritical carbon dioxide extracts, concretes or pomades, and absolutes as well as resinoids, and oleoresins are not essential oils as they do not comply with the earlier mentioned de nition. Likewise, products obtained by enzymic treatment of plant material do not meet the requirements of the de nition of an essential oil. There exists, though, at least one exception that ought to be mentioned. The well-known essential oil of wine yeast, an important avor and fragrance ingredient, is derived from a microorganism and not from a plant. 

Fig. 1. An amplified outline scheme of the making of various wiaes, alternative products, by-products, and associated wastes (23). Ovals = raw materials, sources rectangles = wines hexagon = alternative products (decreasing wine yield) diamond = wastes. To avoid some complexities, eg, all the wine vinegar and all carbonic maceration are indicated as red. This is usual, but not necessarily tme. Similarly, malolactic fermentation is desired in some white wines. FW = finished wine and always involves clarification and stabilization, as in 8, 11, 12, 13, 14, 15, 33, 34, followed by 39, 41, 42. It may or may not include maturation (38) or botde age (40), as indicated for usual styles. Stillage and lees may be treated to recover potassium bitartrate as a by-product. Pomace may also yield red pigment, seed oil, seed tannin, and wine spidts as by-products. Sweet wines are the result of either arresting fermentation at an incomplete stage (by fortification, refrigeration, or other means of yeast inactivation) or addition of juice or concentrate.

Mutation. For industrial appHcations, mutations are induced by x-rays, uv irradiation or chemicals (iiitrosoguanidine, EMS, MMS, etc). Mutant selections based on amino acid or nucleotide base analogue resistance or treatment with Nystatin or 2-deoxyglucose to select auxotrophs or temperature-sensitive mutations are easily carried out. Examples of useful mutants are strains of Candida membranefaciens, which produce L-threonine Hansenu/a anomala, which produces tryptophan or strains of Candida lipolytica that produce citric acid. An auxotrophic mutant of S. cerevisiae that requires leucine for growth has been produced for use in wine fermentations (see also Wine). This yeast produces only minimal quantities of isoamyl alcohol, a fusel oil fraction derived from leucine by the Ehrlich reaction (10,11). A mutant strain of bakers yeast with cold-sensitive metaboHsm shows increased stabiUty and has been marketed in Japan for use in doughs stored in the refrigerator (12). 

Phenylethanol has a rose-like odour and makes the chemically produced compound the most used fragrance chemical in perfume and cosmetics, with a world market of about 7,000 t year [107, 108]. 2-Phenylethanol is also found in many foods as a characteristic flavour compound rounding off the overall aroma, especially in foods obtained by fermentation, such as wine, beer, cheese, tea leaves, cocoa, coffee, bread, cider and soy sauce [109]. In food applications, natural 2-phenylethanol is preferred rather than its nature-identical counterpart from chemical synthesis and it has a market volume of 0.5-11 year . This product is sold at market prices of up to US 1,000 per kiklogram and is mainly produced by yeast-based bioprocesses since its isolation from natural sources, e.g. rose oil, would be too costly [109]. 

Besides these simple fermentation alcohols, the yeast also forms higher alcohols as side products, "fusel oils," that have intense odors and play a role in wine aroma. Other components are carboxylic acids, such as tartaric and malic acids, that are important as "life-insurance" during aging of the wine. Some of the aromas perceived in wines stem from esters... 

Some yeasts and bacteria are able to produce different alcohols like ethanol and butanol as well as polyols like glycerin and 2,3-butandiol. These compounds- are used in drinks such as beer and wines, and also may be used in or as solvents, drugs, chemicals, oils, waxes, lacquers, antifreezing and antifoaming agents, precipitants, dyestuff, pomades, raw materials for chemical syntheses, motor fuels, and carbon sources for SCP production. These products are mainly synthesized from petroleum — derived materials like ethylene and acetaldehyde. However, because of the insufficient availability and high prices of the raw materials, the microbial production of alcohols has become an interesting area for many researchers. 

Characteristics The raw oil is a white coloured liquid with wine or cognac aroma. If the yeast gets in contact with copper, a green to greenish-blue product will result. 

Port wine is fermented in shallow receptacles of masonry in which the grapes are trodden and, after fermentation, pressed. Fermentation in Italy, Spain, and the south of France is carried out at 15° to 24° C., and is a top fermentation, but in Germany and with the finer French wines, a bottom fermentation is made at 5° to 12° C. At the higher temperature the fermentation takes from 3 to 8 days, and the wine produced is fiery, high in alcohol, and lacking in delicate aroma. At the lower temperature the first fermentation lasts a few weeks, but yields a wine of delicate flavour. When fermentation is complete, and the wine has become clear, all the yeast aud other suspended matters are deposited oil the bottom of the cask or vat, constituting the lees. From this the young wine is racked, i.e. decanted or siphoned off, and run into a clean cask. 

Besides charcoal, ancient enology treatises mention other products likely to eliminate unpleasant smells and off-flavors toasted barley or wheat, mustard flour, oil, milk, etc. All these have practically disappeared from use. Fresh yeast lees are permitted in treating wine and are effective in eliminating a number of olfactory defects. This has already been mentioned in connection with fixing certain thiols, such as methanethiol (Section 8.6.2). This treatment is also recommended for adsorbing chloroanisoles in moldy wines (Section 8.5.2). 

In addition to being important in yeast metabolism, fusel oils may collectively, and occasionally individually, play important sensory roles in wine. In table wines, they range from 140 to 420 mg/L (Amerine and Ough, 1980). Those most frequently detected include isoamyl (3-methyl-1-butanol), active amyl (2-methyl-l-butanol), isobutyl (2-methyl-l-pro-panol), and n-propyl alcohols. Quantitatively, isoamyl alcohol generally accounts for more than 50% of the total (Muller et al., 1993). 

Alcohols that contain more than two carbons are known as higher alcohols, or fusel oils. Isobutanol, n-propanol, isoamyl alcohol, and active amyl alcohol are produced in various proportions by various yeasts including Candida, Hansenula, Pichia, and Saccharomyces (Rankine, 1967 Edwards et al., 1990 Holloway and Subden, 1991 Webster et al., 1993 Lambrechts and Pretorius, 2000) and, potentially, play an important role in the sensory character of wine (Rankine, 1967). Sensory descriptors that are commonly used to describe higher alcohols include fusel (butanol), alcoholic (isobutyl alcohol), marzipan (active amyl alcohol and isoamyl alcohols), and floral or rose (phenethyl alcohol) (Lambrechts and Pretorius, 2000). 

The fermentation residue or pomace is processed into yeast-pressed wine or yeastbrandy, into wine oil (for brandy essence) and into tartaric acid. The left-over pomace is used as a feed or fertilizer. Pomace wine, obtained by fermenting a sugar solution containing the dispersed pressed-out pomace, is made only into a household drink and is not marketed. 

Foods lacking in thiamin are man-made—refined rice and cereal flours (from which almost all the natural store of the vitamin has been removed by the millers), refined sugar, separated animal and vegetable oils and fats, and alcoholic beverages. None of the thiamin in yeast used for fermentation is present in beers, wines, and spirits that enter normal commerce, although home-brewed beers and country wines may contain significant amounts. Indeed, there are communities in Africa and Latin America which derive the major part of their thiamin from native beers. 

Amoa-Awua WK, Sampson E, Takano-Debrah K (2007) Growth of yeast, lactic and acetic acid bacteria in pahn wine during tapping and fermentation from felled oil pabn Elaeis guineensis) in Ghana. J Appl Microbiol 102 599-606... 

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