A modified HPLC method to detect salicylic acid in must and wine after its application in the field to induce fungus resistance

Since the application of salicylic acid (SA) to induce systemic acquired resistance (SAR) in plants is currently discussed as an alternative for copper against downy mildew (Plasmopara viticola), a sensitive HPLC method with UV/Vis-DAD-detection was developed to determinate SA in must and wine. The rate of recovery was 92 % at a level of 0.15 mg . l-1 with a detection limit of 0.003 mg . l-1. We have analyzed several musts and wines from field experiments with SA application and have compared their SA concentrations with 23 commercially available German wines. Nearly all samples contained small amounts of SA. The mean concentration in white and red wines was 0.05 mg . l-1 (0.11 mg . l-1 max.) and 0.16 mg . l-1 (0.43 mg . l-1 max.), respectively. Application of SA downy mildew control did not increase the amounts of SA in must or wine

Molecularly imprinted polypyrrole based electrochemical sensor for selective determination of 4-ethylphenol

This work describes the development of an electrochemical sensor based on a molecularly imprinted polymer (MIP) for sensitive and selective determination of 4-ethylphenol in wine. The sensor has been built by means of the electrosynthesis of the MIP on a glassy carbon electrode surface using cyclic voltammetry. The electropolymerization has been performed in the presence of 4-ethylphenol and pyrrole as template molecule and functional monomer, respectively. The influence of the molar ratios of template molecules to functional pyrrole monomers and the time needed to remove the template have been optimized taking into account the differential pulse voltammetric response of 4-ethylphenol. Under the optimal experimental conditions the developed MIP/GCE sensor shows good capability of detection (0.2 μM, α = β = 0.05) and reproducibility (3.0%) in the concentration range from 0.2 to 34.8 μM. The influence of possible interfering species in the analytical response has been studied and the sensor has successfully been applied to the determination of 4-ethylphenol in different wine samples.Junta de Castilla y León (BU018G19

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