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.

Fast determination of lactic, succinic, malic, tartaric, shikimic, and citric acids in red Vranec wines by CZE-ESI-QTOF-MS.

A fast and simple method with CZE coupled to ESI/QTOF-MS was optimized and validated for quantitative determination of organic acids (lactic acid, succinic acid, malic acid, tartaric acid, shikimic acid, and citric acid) in red wines. The BGE was ammonium acetate and the separation of the analytes was performed in a polybrene-coated capillary in the presence of EOF. The sample preparation included dilution and filtration of the wine. The method showed satisfactory performance characteristics: good linearity for each organic acid, with correlation coefficients ranging from r2  = 0.9902 (shikimic acid) to r2  = 0.9990 (tartaric acid). The limit of quantification was between 0.0034 mM (for shikimic acid) and 0.107 mM (for citric acid), and the recovery data fell between 95.8% (malic acid) and 102.7% (lactic acid); the total run time was less than 4 min. The RSD values for the interday repeatability and intraday reproducibility were between 3.44 and 9.50%, and between 1.75 and 8.29%, respectively. Seventeen Macedonian red Vranec wines were studied demonstrating a wide variation in the organic acids' concentration, which should be most probably due to the variation of the climate conditions in the vine areas.

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

Phenolic composition of red wines from Stanusina, 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. Stanusina wines presented high levels of hydroxycinnamic acids and antioxidant activity.

Effect of Unsaturated Fatty Acids on Intra-Metabolites and Aroma Compounds of Saccharomyces cerevisiae in Wine Fermentation.

The small changes in concentration of unsaturated fatty acids (UFAs) cause a significant influence on the aromatic component of wines. In this work, the effect of UFAs mixture (including linoleic, oleic, and α-linolenic acids) addition on intra-metabolites and aromatic compounds of two Saccharomyces cerevisiae strain EC1118 and BDX were investigated in red wine fermentation, respectively. The results showed that the pre-fermentative addition of UFAs significantly modified the physiological and energetic state of cells, and affected the levels of intra-metabolites in glycolysis pathway and TCA cycle, redox balance, ATP pool, fatty acids, and amino acids metabolism, which consequently altered the chemical and volatile composition of the wines. Different with the control wine, the wines produced by UFAs addition were characterized with higher amounts of glycerol, C6-alcohols and higher alcohols, and lower levels of acetic acid, medium-chain fatty acids, and acetate esters. Interestingly, the production of ethyl esters showed opposite profiles in different strains due to the distinct expression of EEB1, indicating that the effect of UFAs on ethyl esters syntheses is strain-specificity. Our results highlighted the effectiveness of modulating UFAs content in shaping aroma characteristics, and verified that fine adjusting the content of UFAs combined with inoculating proper yeast is a promising strategy to modulate the aromatic quality of wine, which probably provides an alternative approach to meet the expectations of wine consumers for diverse aromatic qualities.

Fingerprinting of traditionally produced red wines using liquid chromatography combined with drift tube ion mobility-mass spectrometry.

The characterization of wine via MS-based metabolic fingerprinting techniques remains a challenging undertaking due to the large number of phenolic compounds that cannot be confidently annotated and identified within analytical workflows. The combination of high performance liquid chromatography with low-field drift tube ion mobility time-of-flight mass spectrometry (HPLC × IMS-TOFMS) offers potential for the confident characterization and fingerprinting of wine using a metabolomics-type workflow. In particular, the use of collision cross section values from low-field drift tube IMS using nitrogen as drift gas (DTCCSN2) in addition to retention time and a high resolution mass spectrum for putative compounds allows rugged statistical assessment and identity confirmation using CCS libraries (<0.5% error) to be performed. In the present work, an HPLC × IMS-TOFMS platform has been utilized for the fingerprinting of 42 traditionally produced red wines emanating from the Republic of Macedonia. After establishing the reliability of DTCCSN2 as an identification point for wine metabolomics in both ionization modes, fingerprinting of wines according to grape variety was undertaken and a full dataset containing retention, accurate mass and DTCCSN2 values used to derive lists of compounds found to be statistically characteristic for each variety. Putative compounds were further assessed by assignment of in-source and post-drift mass fragments aligned according to retention time, drift time, and accurate mass providing up to seven identification points for a single compound when data from both positive and negative mode measurements are combined.

Targeted analysis of bioactive phenolic compounds and antioxidant activity of Macedonian red wines.

Phenolic composition of twenty-two Macedonian red wines, including ten autochthonous monovarietal Vranec wines produced with different yeasts for fermentation, and twelve wines from international varieties (Syrah, Merlot and Cabernet Sauvignon) from different wine regions was studied. All wines presented relatively high value of total phenols and antioxidant activity. A total of 19 phenolic compounds were identified and quantified using HPLC-DAD and among them, malvidin-3-glucoside and its derivatives were the major compounds, followed by the petunidin derivatives, while caftaric acid was the predominant cinnamic acid derivative in all wines. The anthocyanin content was mainly affected by the grape variety and to a less extent by the yeast used in fermentation. In particular, the use of locally isolated yeasts affected higher amount of anthocyanins and phenolic acids compared to the wines fermented with commercial yeasts. Principal Component Analysis showed a satisfactory grouping of red wines according to the grape variety.