Abstract
Each year, winemakers can face sluggish or stuck fermentations during wine making, especially when a spontaneous fermentation is performed, even if strains of the classical wine yeast Saccharomyces cerevisiae are applied. Problems are inevitable when low ammonium concentrations (<160 mg L−1 grape must) or an excess of fructose compared to glucose are observed during grape must fermentation. S. cerevisiae strains cannot use all kinds of amino acids as the sole nitrogen source but usually need free ammonium (optimal concentration: 600 mg L−1 grape must). It preferably consumes glucose, leading often to an excess of fructose in the fermenting must, which contains glucose and fructose in an equal ratio at the beginning of fermentation. Yeast hybrids have been isolated from wines several times and different strains are already commercially available. The united properties of the parent strains can provide advantages under sophisticated fermentation conditions. However, the involvement of a hybrid yeast for the rectification of fermentation disorders in spontaneous fermentations has only been described recently in the literature. Recent investigations have provided convincing evidence that fermentation problems can be overcome when must fermentations are successively performed with Saccharomyces bayanus strain HL 77 and the triple hybrid S. cerevisiae × Saccharomyces kudriavzevii × S. bayanus strain HL 78. The triple hybrid strain HL 78 uses amino acids as a nitrogen source in the absence of ammonium and it also exhibits a fructophilic character with an enhanced uptake of fructose in comparison to glucose. The application of genetically modified yeast strains is not allowed for starter cultures in wine making, but the usage of yeast mixtures and hybrid strains could be a promising tool for winemakers to solve fermentation problems during spontaneous fermentation or for the creation of novel wine types with desired sensory characteristics under more challenging conditions, especially when the composition of the must components is not optimal because of, e.g., critical climatic or soil conditions.
Highlights
In publications about the history of wine making, McGovern [1,2] and Kupfer [3,4] provided convincing indications that cultures of vines and wine making were established between 6000 and8000 BC in regions between the Black Sea and the Caspian Sea and along the later Silk Road all the way to China
Recent investigations have provided convincing evidence that fermentation problems can be overcome when must fermentations are successively performed with Saccharomyces bayanus strain HL and the triple hybrid S. cerevisiae × Saccharomyces kudriavzevii × S. bayanus strain HL
The application of genetically modified yeast strains is not allowed for starter cultures in wine making, but the usage of yeast mixtures and hybrid strains could be a promising tool for winemakers to solve fermentation problems during spontaneous fermentation or for the creation of novel wine types with desired sensory characteristics under more challenging conditions, especially when the composition of the must components is not optimal because of, e.g., critical climatic or soil conditions
Summary
In publications about the history of wine making, McGovern [1,2] and Kupfer [3,4] provided convincing indications that cultures of vines and wine making were established between 6000 and. Saccharomyces cerevisiae likely played the most important role in wine fermentation from the beginning of viticulture [10], it was not before 1883 that the first pure yeast culture was obtained by Emil Christian Hansen These isolates were used for beer production, while around the year 1890, Hermann Mueller-Thurgau introduced yeast starter cultures to wine making. Molecular biology methods and next-generation sequencing approaches have been applied to examine and quantify the diversity and genetic variations as well as sources and roles of wine-related microorganisms This knowledge is helpful for the development of novel starter cultures [18,19,20,21]. These unwanted observations stimulate investigations for more improved microbiological strains and novel procedures to circumvent the observed fermentation obstacles
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