Mead production yeast strain

Mead is a traditional alcoholic beverage obtained by fermenting mead wort that contains 8-18% (v/v) ethanol. Its production has been known since ancient times. However, mead fermentation and maturation requires an extended period, often lasting several months to years. Mead still remains a relatively empirical and manual exercise, requiring large capacity vessels and the investment of considerable capital in terms of the raw material. In addition, the fermentation rate depends on several factors, such as honey variety, yeast strain, yeast nutrition, and pH. Due to the lack of scientific investigation, mead production has suffered in comparison with other alcoholic beverages and so more research is needed to optimize the production process. 

The yeasts used in the production of mead are usually strains of Saccharo-myces cerevisiae, similar to that used in wine, beer, and champagne productions. These yeasts metabolize sugars, such as glucose and fructose, resulting in the formation of ethanol and carbon dioxide. Nevertheless, the yeast Hansenula anomala had also given good results (Qureshi and Tamhane, 1987). 

Seven S. cerevisiae strains were characterized relative to their resistance to sulfur dioxide (since it is a desirable feature in the fermentative yeast strains), ethanol (where tolerance is an indispensable property due to the high concentrations reached by the end of fermentation (Carrasco et al., 2001)), and osmotic stress (due to the high osmotic potential of mead at the commencement of fermentation). Pereira (2008) and Pereira et al. (2009) verified that significant differences did not exist between the strains. S. cerevisiae strains isolated from honey were similar to commercial and reference strains—all appearing to be suitable for mead production. 

Due to the high sugar contents involved in the mead production, fermentation tends to be slow and requires a yeast strain as well as pH, temperature, and growth conditions that are optimal. 

However, for mead production to become profitable, it is necessary to decrease production time. A major concern in mead fermentation is the notoriously long period required to reach completion. Although fermentation rate depends on the honey variety and its characteristics, through proper selection of yeast strain and fermentation conditions, such as, mixing during fermentation, yeast nutrition, and pH s control, it may be possible to dramatically increase fermentation rate. 

In relation to yeast strain selection, few studies have been conducted on this subject. It will be necessary to find/isolate yeast strains more resistant to, and with better fermentation performance under the harsh conditions of mead production, such as high osmotic values and low nitrogen content. Breeding may be an option. 

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