Possibilities for Depleting the Content of Undesirable Volatile Phenolic Compounds in White Wine with the Use of Low-Intervention and Economically Efficient Grape Processing Technology

The production of wine vinegar using different types of acetic acid bacteria

This work aimed to study the properties of acetic fermentation bacteria during the acetic fermentation of wine. Attention was focused on the ability of the bacteria to metabolize selected organic substances and their suitability for wine vinegar production. For the production of wine vinegar, white wine of the variety Veltliner Green was used. Three variants were established for this experiment. The first variant was fermented with Gluconobacter oxydans, the second with Acetobacter aceti, and the third variant of vinegar production was carried out by spontaneous fermentation. During the vinegar fermentation, samples were taken at regular 24-hour intervals and subsequently analyzed. The alcohol, acetic, malic, and tartaric acid contents were monitored. The results showed that all variants showed a strong acetic and malic acid increase. Bacteria Acetobacter aceti produced the most acetic acid within nine days (25 g.L-1). This bacterium also produced the most lactic acid (18 g.L-1). Tartaric acid was also produced in all three variants, but not to the same extent as the previous two organic acids. Acetobacter aceti was found to metabolize ethanol more rapidly than Gluconobacter oxydans.

Wine Faults: State of Knowledge in Reductive Aromas, Oxidation and Atypical Aging, Prevention, and Correction Methods

The review summarizes the latest scientific findings and recommendations for the prevention of three very common wine faults of non-microbial origin. The first group, presented by the reductive aromas, is caused mainly by excessive H₂S and other volatile sulfur compounds with a negative impact on wine quality. The most efficient prevention of undesirable reductive aromas in wine lies in creating optimal conditions for yeast and controlling the chemistry of sulfur compounds, and the pros and cons of correction methods are discussed. The second is browning which is associated especially with the enzymatic and non-enzymatic reaction of polyphenols and the prevention of this fault is connected with decreasing the polyphenol content in must, lowering oxygen access during handling, the use of antioxidants, and correction stands for the use of fining agents. The third fault, atypical aging, mostly occurs in the agrotechnics of the entire green land cover in the vineyard and the associated stress from lack of nutrients and moisture. Typical fox tones, naphthalene, or wet towel off-odors, especially in white wines are possible to prevent by proper moisture and grassland cover and alternating greenery combined with harmonious nutrition, while the correction is possible only partially with an application of fresh yeast. With the current knowledge, the mistakes in wines of non-microbial origin can be reliably prevented. Prevention is essential because corrective solutions for the faults are difficult and never perfect.