Mead is a traditional honey-derived beverage containing 8 to 18% (v/v) of ethanol, which results from alcoholic fermentation by yeasts of diluted honey. This beverage has progressively gained economic importance (Sroka and Tuszynski, 2007), due to the therapeutic/ nutriceutical properties attributed to honey and by an increasing demand for gourmet products.Mead fermentation is atime-consuming process, oftentaking severalmonths to complete,depending on the type of honey, yeast strain and honey-must composition (Navrátil et al., 2001). Inmost of themead-producing countries, alcoholic fermentation is a result of the growth of indigenousmicroorganisms naturally present in honeys and always surviving on the substrates and equipment used (Ashenafi, 2006; Bahiru et al., 2001).In these cases, alcoholic fermentation is even more unpredictable and very often at the end of fermentation, mead is completely spoiled by contaminating yeasts and bacteria which makes it undrinkable. More recently, selected strains isolated from honey/honey-wine (Pereira et al., 2009; Teramoto et al., 2005) or commercial yeasts starter cultures (Sroka and Tuszynski, 2007; Ukpabi, 2006;Wintersteen et al., 2005) have been used to reduce the risks of contamination. However, despite the use of starter cultures for honey-must inoculation several problems still persist such as lack of uniformity of the final products, slow or premature fermentation arrest and the production of off-flavors by yeast (Pereira et al., 2009). These problems could be due to inappropriate yeast strains that are notsuitable for the specific composition/conditions in honey-musts, or the result of several stress conditions: high osmotic stress, lack of essential nutrients such as a deficiency in available nitrogen (Maugenet, 1964; McConnell and Schramm, 1995), low mineral concentration, low pH (Sroka and Tuszynski, 2007) and lowbuffer capacity (Maugenet, 1964). Some of these problems in mead alcoholicfermentation are similar to those still found inwinemaking such as sluggish or stuck fermentations (Ingledew and Kunkee, 1985; Kunkee, 1991; Salmon,1989) aswell as the generation of undesirable by-products such as S-off-flavors (Spiropoulos et al., 2000). Previous research suggested that the major cause of these problems inwines is the limited nitrogen content of some natural grape-juice (Giudici andKunkee, 1994; Hallinan et al., 1999; Spiropoulos et al., 2000; Spiropoulos and Bisson, 2000; Vos and Gray, 1979). There is a lack of scientific information about honey-must fermentations but it is accepted by mead makers that mead quality improvement includes the development of the proper additive formulation and optimization of fermentation conditions. The numerous research studies conducted in otherfermented beverages may be in some extent helpful to control honey-must fermentation. Nevertheless, research is still needed on the physiology and metabolism of Saccharomyces cerevisiae under the particular harsh honey-musts environment. Thus, the aimof this studywas to optimizemead alcoholic fermentation, by modulating honey-must composition, in order to reduce fermentation length and to obtain aconsistently higher quality and microbiologically stable product. The first task was to improve the preparation of honey-must before the various supplements have been tested. The amounts of nitrogen tested were based on previously published research (Mendes-Ferreira et al., 2004), which are in agreement with the previous European legislation for grape-must supplementation (300 mg/L supplied asdiammonium phosphate or ammonium sulphate) and with current legal limit of 1 g/L. Acidity has extensive and important functions in alcoholic beverages. Organic acids, such as tartaric andmalic acid have important functions for organoleptic characteristics, and stability of these types of beverages (Boulton et al., 1996). Moreover, these acids in equilibrium with their salts act as buffers,...
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