Mead production fermentation

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. 

Despite the excellent properties of honey, mead production faces several problems, namely, delays and pouts fermentations, lack of product uniformity, and production of yeast off-flavors. Many factors might be related with these problems, such as honey variety, temperature, medium composition (vitamin and nitrogen content), fermentative yeast, and pH. Due to all these factors, mead production has decreased over the years. To overcome this situation, more research is needed to optimize the production of this beverage. 

This chapter presents a comprehensive review of previous research on mead production. It will focus on honey characterization and mead production. The first section covers honey composition and the way this affects honey properties, as well as important parameters that are indicators of honey quality. The second section discusses mead production, including fermentative microorganisms, fermentation conditions, and required postfermentation adjustments and maturation conditions. The final section focuses on the problems that must be surpassed and what the future holds for mead production. 

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. 

II. Mead production—under this heading are discussed fermentative microorganisms, fermentation conditions, postfermentation adjustments, and maturation conditions. 

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. 

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. 

Mendes-Ferreira, A., Cosme, F., Barbosa, C., Falco, V., Ines, A., and Mendes-Faia, A. (2010). Optimization of honey-must preparation ad alcoholic fermentation by Saccharomyces cerevisiae for mead production. Int. J. Food Microbiol. 144,193-198. 

C. acetobutylicum is not too exacting in its growth requirements. Asparagine is needed to effect normal production of solvents in what otherwise would be an acid fermentation. Both biotin and p-aminoben-zoic acid are required in trace quantities, 0.001 and 0.05 /xg/ml, respectively. Iron is essential in small but variable quantities for attainment of maximal fermentation rates (Leviton 1946,1949 Meade et al. 1945). The requirement for iron varies with the composition of the medium potassium is also required (Davies 1942A.B, 1943 Davies and Ste-... 

Use of fermented whey as a food has been suggested. Jagielski (1871) combined whey and lactose with an appropriate culture and produced a whey kumiss. Later, Krul kevich mixed equal volumes of whey and buttermilk with kumiss yeasts, L. bulgaricus, and L. acidophilus. The finished product is claimed to resemble kumiss (Marth 1974). A condensed whey food composed, in part, of whey fermented by L. bulgaricus and P. shermanii has been described in a patent issued to Meade et al. (1945). Additional information on fermenting whey is given by Friend and Shahani (1979). 

During mead fermentation, several problems are generally encountered. For example, the anticipated alcohol content may not be achieved within the time desired. There may also be a lack of uniformity in the final product, due to differences in water content of the honey used. In some situations, such as worts with high sugar contents, successive addition of honey is needed to avoid premature termination of fermentation. This likelihood of stuck fermentation is increased as most mead is made empirically, without adjustments. This can lead to subsequent yeast refermentation and secondary fermentations by lactic and acetic acid bacteria. These can undesirably increase acidity and the production of volatile esters (Casellas, 2005). The presence of these compounds alters... 

At the completion of fermentation, mead undergoes a period of maturation that includes clarification and filtration. These are obligatory despite their increasing production costs. 

In an experiment, Gomes (2010) produced distinctive meads by varying when fermentation was stopped and whether brandy was added. Of these, the most appreciated by a Portuguese consumer panel was the sweetest, independent of the alcohol content. The sweetest mead was obtained after prematurely stopping fermentation early by the addition of brandy (77% alcohol). The product had an alcohol content of 18% (v / v) and a sweetness equivalent to 8° Baume. The alcohol content was then adjusted to 18%, 20%, and 22% (v/v). 

In the production of tropical meads, Ukpabi (2006) recommends the use of sturdy bottles to avoid bottle breakage, due to possible high internal pressure (from fermentation gases) if refermentation occurs, as well as the use of cork or equivalent for stoppering the bottles. 

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