Many mannoprotein-based products and overproducing yeast are available for enological use, but few scientific studies have reported their use and effects on red wine composition. The effect of a selected mannoprotein overproducing yeast strain on Tempranillo winemaking was studied and the results were compared with those obtained by adding commercial mannoprotein-rich preparations in the prefermentative stage. Wines were prepared using traditional wine technology. Polysaccharides were extracted, fractionated by high-resolution size-exclusion chromatography, and quantified by gas chromatography with flame ionization detection after acidic methanolysis and derivatization. Polyphenols were fractionated by gel permeation chromatography, monomeric phenolics were analyzed by high-performance liquid chromatography with photodiode-ray detector, and proanthocyanidins by the vanillin assay. Color was measured by spectrophotometric methods. The use of mannoprotein overproducing yeast strains strongly increased high-molecular-weight mannoprotein content during the maceration. No differences were observed in terms of grape polysaccharides, monomeric phenolics, or color parameters, but proanthocyanidin content was significantly reduced when using the overproducing strain. Except for wine color, mannoproteins released from yeast strains produced the same effects as commercial mannoproteins. Winemakers could use both alternatives to reduce red wine astringency and increase wine smoothness and body, although commercial mannoproteins may cause loss of red wine stable color.
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