A new method for the detection of early contamination of red wine by Brettanomyces bruxellensis using Pseudomonas putida 4-ethylphenol methylene hydroxylase (4-EPMH)

Brettanomyces/Dekkera bruxellensis is a cause of major concern for the winemaking industry worldwide. If a slight presence of this spoilage yeast in red wine adds a Brett character, a strong contamination has irreversible and detrimental effects on the organoleptic qualities due to the production of volatile phenols such as 4-ethylphenol. Time is a key factor in the treatment of B. bruxellensis contaminations. Nowadays, the diagnostic and quantification resources available are time consuming and too expensive, making them either inadequate or inaccessible to most of the winemakers. This study was focused on a new, easy to use, inexpensive method that could allow winemakers to directly detect B. bruxellensis contamination in red wine at an early stage, hence, reducing wine spoilage. In this work, the ability of Pseudomonas putida 4-ethylphenol methylene hydroxylase was tested in order to catabolize the 4-ethylphenol and to elaborate an enzymatic assay with the purpose of detecting early contaminations by B. bruxellensis in red wine. We have developed a colorimetric enzymatic assay, based on the redox state of the 4-ethylphenol methylene hydroxylase co-factor, cytochrome C, that can detect and quantify low concentrations of 4-ethylphenol. The range of concentrations detected is well below the level detectable by the human nose. Combined to an enrichment step, this method allows the detection of B. bruxellensis at an initial concentration of less than 10 cells per ml

Extraction and evaluation of natural occurring bioactive compounds and change in antioxidant activity during red winemaking

Phenolic composition of red wines from Stanušina, a grape variety indigenous of the Republic of Macedonia, was compared with the regional Vranec and the international Cabernet Sauvignon. The extent of skin contact (i.e. maceration time) on levels of phenolic compounds and antioxidant activity of wines was evaluated. A total of 19 phenolic compounds were identified and quantified. Among these malvidin-3-glucoside and its derivatives were the major compounds, while caftaric acid was the predominant cinnamic acid derivative, followed by catechin, the main flavan-3-ol. The concentration of hydroxycinnamic acids, anthocyanins and (+)-catechin ranged from 224 to 511 mg/L, 22 to 360 mg/L and 26 20 to 375 mg/L, respectively and peaked at 3rd, 6th and 9th day of maceration, respectively. However, prolong maceration slightly decreased their concentration. Stanušina wines presented high levels of hydroxycinnamic acids and antioxidant activity

Phenolic composition of monovarietal red wines regarding volatile phenols and its precursors

The aim of this study was to characterise and compare wines from different grape varieties focusing on the volatile phenols and on the respective precursor compounds, both on the free form (p-coumaric, ferulic and caffeic acids) and as tartaric esters of hydroxycinnamic acids (caftaric, coutaric and fertaric acids). Fifty-eight commercial monovarietal red wines from eight selected grape varieties were used: Cabernet Sauvignon, Syrah, Aragonez, Castelão, Touriga Franca, Touriga Nacional, Trincadeira and Vinhão (Sousão). It was found that volatile phenol precursors exist mostly as esters of tartaric acid, with caftaric acid as the most abundant cinnamate (17–111 mg/L), followed by coutaric and fertaric acids. The predominant hydroxycinnamic acid was p-coumaric acid, the highest concentrations being found in Syrah and Touriga Franca (6–7 mg/L) and the lowest in Touriga Nacional and Trincadeira (2–3 mg/L). Touriga Nacional exhibits the highest difference between bound and free forms. Malvidin-3-O-(6-p-coumaroyl)-glucoside, a potential source of p-coumaric acid, was found in most of the wines with average values varying between 1 and 5 mg/L. Twenty-two percent of the wines analysed presented levels of volatile phenols above the perception threshold. Ethylphenols were the highest in Vinhão and Trincadeira, showing an average value well above the perception threshold. The concentrations found in Cabernet Sauvignon and Syrah wines were around ten times lower than those reported in previous works. The results show relevant differences among grape varieties but the availability of the precursors in meaningful amounts may not be the only factor explaining the formation of volatile phenols in wines.info:eu-repo/semantics/publishedVersio