Impact of malolactic fermentation on the volatile composition of Turkish Kalecik karası red wines

The effects of spontaneous malolactic fermentation (MLF) and a malolactic starter culture (Oenococcus oeni) on the volatile compounds of Kalecik karas? red wines were investigated. The volatile compounds were extracted using liquid–liquid extraction and quantified by GC–MS–flame ionisation detection. Starter cultures of O. oeni had a positive effect in shortening MLF and producing lower volatile acidity. After MLF, the total volatile compounds increased in both the inoculated wines and the spontaneously fermented wine. Ethyl lactate, diethyl succinate and γ‐butyrolactone increased upon inoculation with cultures of O. oeni strains PN4 and VP41. MLF increased the diacetyl concentration in all Kalecik karas? wines. Strain dependent differences were found in the level of diacetyl, with O. oeni PN4 producing more diacetyl than O. oeni VP41. After MLF, the concentrations of acetoin, 4‐ethylguaicol and 4‐ethylphenol increased in spontaneously fermented wine compared with wines inoculated with O. oeni. Accordingly, the use O. oeni PN4 is recommended for a controlled MLF to produce better quality Kalecik karas? wines. © 2018 The Institute of Brewing & Distilling     

Influence of pH and ethanol on malolactic fermentation and volatile aroma compound composition in white wines

The present study investigated the influences of pH and ethanol on malolactic fermentation (MLF) and the volatile aroma profile of the subsequent white wines from Riesling and Chardonnay inoculated with two different Oenococcus oeni strains. In all cases MLF was induced after completion of alcoholic fermentation (AF). Partial MLF occurred under low pH 3.2 and high alcohol (118.3 g/L) conditions. In the cases with complete MLF, the time required for each strain varied from 13 to 61 days and was dependent on bacterial culture, cultivar and wine parameter. Chemical properties of each wine were determined after AF, complete and partial MLF. The wines showed significant differences in total higher alcohols, esters and acids that are important for the sensory profile and quality of wine. This work demonstrated that the wine matrix as well as the pH and alcohol concentration affects MLF and the final volatile aroma profile. Results indicate that changes in volatile aroma composition are not necessarily related to complete MLF and that partial MLF already has distinct influences on the wine aroma profile of white wines.     

Malolactic Fermentation and Secondary Metabolite Production by Oenoccocus oeni Strains in Low pH Wines

Abstract: Different wine varieties, including some with low pH, were studied to determine the ability to grow and produce secondary metabolites of a previously selected autochthonous Oenococcus oeni strain (C22L9), compared with a commercial strain. Monitoring of malolactic fermentation (MLF) was carried out by microbiological and chemical analysis of wines. The concentration of some major volatile compounds and biogenic amines in wines before and after malolactic fermentation was also determined. The results showed major differences in MLF duration both between wines and strains, although the differences between strains were slight for most of the analyzed compounds. Statistically significant differences in citric acid degradation were found in all wine varieties and it was confirmed that O. oeni C22L9 is a poor degrader of citric acid; this means that MLF can be prolonged without the risk of producing high concentrations of diacetyl and acetoin. Sensory analysis of wines after MLF showed similar characteristics in wines from both strains. This study thus shows that O. oeni C22L9 possesses even better sensory and fermentation properties than the commercial strain and can be used in wines with different characteristics, which makes it highly valuable for industrial use. Practical Application: The increasingly use of grape varieties of low pH in winemaking and the higher alcohol content of wines, as a consequence of the climatic change, make interesting the study of the behavior during MLF of O. oeni strains in order to determine their ability to grow, when growth conditions are not optimal, and to produce secondary metabolites. A comparative study was conducted using an autochthonous O. oeni strain (C22L9) and a commercial O. oeni strain and 4 wine varieties.     

Characterization and amino acid metabolism performances of indigenous Oenococcus oeni isolated from Chinese wines

Oenococcus oeni is a multiple physical stress-tolerant lactic acid bacterium that plays an important role in wine making. It is often added as a starter culture to carry out malolactic fermentation (MLF). In this study, a total of 22 out of 127 lactic acid bacteria, isolated from Chinese wines undergoing MLF, were identified as O. oeni by species-specific PCR and 16S rRNA sequencing. Single-enzyme amplified fragment length polymorphism (SE-AFLP) analysis showed that all strains could be typed under these conditions, and three main groups were determined by cluster analysis, which showed intraspecific homology higher than 69 %. Eight strains, representative of SE-AFLP clusters, were tested for malolactic activity. Significant differences were observed among strains with regard to the amount of malic acid consumed. Seventeen amino acids in different wines that were inoculated by 4 O. oeni strains, respectively, were analyzed before and after MLF. The results indicated that the amino acid metabolism of the 4 strains was significantly different between each strain.     

贺兰山东麓不同子产区赤霞珠葡萄自然发酵对葡萄酒香气的影响

为探究宁夏贺兰山东麓不同子产区自然发酵对葡萄酒香气的影响,利用顶空固相微萃取-气相色谱-质谱联用技术对青铜峡、红寺堡及银川3个子产区自然和接种发酵的赤霞珠葡萄酒中挥发性成分进行了定性定量测定,并采用显著性分析、主成分分析及聚类分析的统计学方法进行了分析。结果表明,3个子产区的挥发性化合物以酯类和醇类为主。银川产区挥发性化合物的总量在3个子产区中最高,自然酒精发酵和接种酒精发酵后挥发性化合物的含量分别为339.05和453.90 mg/L,自然苹乳发酵和接种苹乳发酵后挥发性化合物的含量分别为307.01和379.08 mg/L。青铜峡产区自然酒精发酵的葡萄酒中挥发性化合物的总量(312.8 mg/L)显著高于接种发酵(296.1 mg/L),自然苹乳发酵的葡萄酒中的挥发性化合物的总量(215.78 mg/L)显著高于接种发酵(202.10 mg/L)。对3个子产区葡萄酒中挥发性成分的聚类分析发现,对葡萄酒中挥发性化合物影响程度从高到低依次为产区、发酵阶段和发酵方式。     

Biogenic amines and ethyl carbamate in primitivo wine: survey of their concentrations in commercial products and relationship with the use of malolactic starter

This research was conducted to determine the biogenic amine (BA) and ethyl carbamate (EC) concentrations in commercial Primitivo wine samples and the influence of the use of malolactic starter culture on concentrations of these potentially hazardous compounds in this wine. One hundred sixty bottles of wine from eight producers in the Apulia region of southern Italy were purchased at retail and analyzed. The most common BAs were histamine, 2-phenylethylamine, tyramine, cadaverine, putrescine, spermine, and spermidine. Putrescine (derived from ornithine) was the most abundant BA in all commercial Primitivo wines (5.41 to 9.51 mg/liter), 2-phenylethylamine was detected in only two commercial wines (at less than 2.12 mg/liter), and histamine was found at concentrations of 1.49 to 16.34 mg/liter. The concentration of EC in commercial Primitivo wine was 6.81 to 15.62 ppb, which is not considered dangerous for human health. Malolactic fermentation (MLF) affected the concentrations of BAs and EC differently. For EC, no significant differences were detected between samples of wine produced by spontaneous fermentation and wine that was inoculated malolactic starter. Mean EC concentrations were 12 and 14 ppb in two batches tested (always 18 ppb or less), regardless of whether the malolactic starter was added. Although present at trace levels in wine before the MLF, histamine accumulated during the MLF process, regardless of whether the malolactic starter was added. However, the increase in histamine was higher in wines without the malolactic starter. The concentrations of putrescine and cadaverine increased after MLF, especially in the wine that spontaneously fermented. The use of a selected malolactic starter resulted in reductions in BA concentrations in wine produced by this guided MLF compared with wine produced by spontaneous MLF.     

Malolactic fermentation of Tempranillo wine: contribution of the lactic acid bacteria inoculation to sensory quality and chemical composition

Malolactic fermentation (MLF) of Tempranillo Rioja wines (Spain) inoculated with two lactic acid bacteria (LAB) strains were studied and compared with spontaneous MLF. Inoculation with selected Oenococcus oeni lyophila shortened MLF duration up to 19 days and lead to wines with more fresh and fruity characters, especially when implantation was 100%. We demonstrated modifications in the concentration of volatile and nitrogenous compounds and a good correlation between analytical and sensory attributes was also noted. In addition, the low initial amino acid concentration and the consumption of these compounds by the inoculated yeast strain during alcoholic fermentation resulted in wines with very low biogenic amines levels (under 3.75 mg L^?1) after MLF and 3 month storage period in all cases. The results showed the significance of choose the most suitable starter to elaborate quality wines and suggest the control of amino acid content in must and wine to prevent the formation of biogenic amines.     

The application of malolactic fermentation process to create good-quality grape wine produced in cool-climate countries: a review

The work presents the essence of the secondary fermentation occurring in the course of grape wines production—malolactic fermentation (MLF). The selection of wine yeast and bacteria preparations, scenario of malolactic bacteria inoculation as well as control system of the process conditions are proposed to create the specific character and style of grape wines produced in cool-climate countries, in which the acidity of grape must is often significantly enhanced and the concentration of aroma compounds is considerably low. The role played by appropriately run MLF is presented, along with the advantages and disadvantages of the process, benefits, and technological drawbacks resulting from the introduction of this procedure to the vinification process. Moreover, methods to initiate and run MLF as well as interactions occurring between microorganisms used in wine production, i.e., wine yeasts from the genus Saccharomyces and wine bacteria from the genus Oenococcus, are also presented and discussed.     

RNA fingerprinting analysis of Oenococcus oeni strains under wine conditions

Oenococcus oeni is a lactic acid bacterium of economic interest used in winemaking. This bacterium is the preferred species for malolactic fermentation (MLF) due its adaptability to the chemically harsh wine environment. MLF enhances the organoleptic properties and ensures deacidification of wines.     

Evaluating the Influence of Malolactic Fermentation Inoculation Practices and Ageing on Lees on Biogenic Amine Production in Wine

Biogenic amines are compounds, produced primarily by lactic acid bacteria (LAB) that negatively affect the wholesomeness of wine. Standard winemaking practices can greatly influence the levels of biogenic amines in wine. The aim of this study was to determine the relative contribution of different malolactic fermentation (MLF) practices and ageing of wines on fermentation lees to the final levels of biogenic amines. Wines were made on small scale over two harvest seasons with two red grape cultivars. Treatments included spontaneous MLF, co-inoculated MLF, MLF inoculated after alcoholic fermentation (conventional inoculation) and 4 months of ageing in the presence and absence of fermentation lees of all MLF treatments. Biogenic amine concentrations were measured by high-performance liquid chromatography at key winemaking stages and statistically analysed for the effects of MLF treatment and winemaking stage. Results indicate that the presence of indigenous LAB increased the risk of biogenic amine formation. Inoculation proved to reduce biogenic amine production over time compared to spontaneous MLF and co-inoculation even more than conventional inoculation. The presence of yeast lees during ageing generally led to higher final concentrations of biogenic amines in wines than the absence of lees. This study confirms other works that conclude that spontaneous MLF and uncontrolled ageing on yeast lees are generally unpredictable and pose a risk of biogenic amine contamination in finished wines.     

Volatile composition of Bobal red wines subjected to alcoholic/malolactic fermentation with oak chips

The effect of wood, in the form of oak chips, on the volatile composition of Bobal red wines caused by adding oak chips at different stages of the fermentation process has been studied. Aroma compounds were isolated by solid phase extraction (SPE) for subsequent analysis by gas chromatography–mass spectrometry (GC/MS). Bobal control wine was produced according to traditional winemaking processes, without oak chips. Oak chips were added to the rest of the wines at two dose levels (3 and 6 g/L) at different stages of the winemaking process: at one week during alcoholic fermentation (AF), during malolactic fermentation (MLF) and in young, red Bobal wine. Wines fermented with oak chips during AF showed higher concentrations of the ethyl esters of straight-chain fatty acids and ethyl, hexyl and isoamyl acetates than the control wine. A similar, trend was observed for higher alcohols. Higher concentrations of benzene compounds, oak lactones and furanic compounds were found in wines in contact with oak chips during MLF followed by young Bobal oak wines. These results reveal that the point of addition during the winemaking process and the dose level of oak chips used have a significant effect on the volatile composition of Bobal red wines.     

共发酵对蛇龙珠葡萄酒发酵动力学和香气成分的影响

以蛇龙珠葡萄为试材,对比酿酒酵母（Saccharomyces cerevisiae）单独发酵（CK）、酿酒酵母与酒酒球菌（Oenococcus oeni）顺序接种发酵（SEQ）和同时接种发酵（SIM）三种处理条件下的发酵过程,分析不同处理葡萄酒化学组分变化,并对其感官质量进行评价。结果表明,与仅进行酒精发酵相比,SEQ和SIM处理的葡萄酒中的苹果酸和柠檬酸均迅速降解,对葡萄酒的感官质量没有负面影响,SIM处理缩短了苹果酸-乳酸发酵（MLF）进程。SEQ和SIM发酵的葡萄酒,乳酸、乳酸乙酯、脂肪酸和萜烯类等物质的含量均显著增加（P＜0.05）。SEQ处理的葡萄酒中挥发性物质总量较高,为48.08 mg/L。共发酵能够丰富葡萄酒的风味结构,可以作为提高葡萄酒质量的发酵途径。     

乳酸菌Viniflora、Lalvin31在干红葡萄酒中的降酸比较

两种乳酸菌Viniflora,Lalvin31接种于佳丽酿干红葡萄酒中，分别进行苹果酸－乳酸（MLF）发酵，结果表明，Viniflora发酵速率和降酸幅度均低于Lalvin31，产生的挥发酸高于Lalvin31，经MLF后，酒体的柔和指数均有升高，但Viniflora的升高幅度低于Lalvin31,说明菌种Lalvin31的降酸效果优于Viniflora菌种。     

Effect of micro-oxygenation on the evolution of aromatic compounds in wines: Malolactic fermentation and ageing in wood

The effect of micro-oxygenation on the aromas of two varietal wines (Tempranillo and Cabernet Sauvignon) when alcoholic fermentation is complete was examined. Several factors, such as whether malolactic fermentation (MLF) took place in barrels or stainless steel vats and ageing time in oak barrels, were taken into account. Major aroma components were studied using GC-FID and minor compounds were studied by GC-MS analysis before and after MLF and after 4 and 8 months of maturation in oak barrels. Sensorial analysis was performed to describe and quantify the different wine notes. Micro-oxygenation affects different compounds but the effect depends to a great extent on the grape varietal used; the effect of micro-oxygenation was more marked on the aroma of Cabernet Sauvignon wine than Tempranillo wines. The concentration of extractable compounds of wood was higher in wines after MLF in barrels than in wines after MLF in steel vats; wines with steel vat MLF had fewer toast and wood notes. The compounds that showed significant differences in concentration after 8 months of maturation were present in higher concentrations in wines fermented in barrels than in stainless steel vats. Barrel-fermented wines were sweeter, with wood and toast notes, fewer alcohol notes and fewer reductive notes.     

Release of glycosidically bound flavour compounds of Chardonnay by Oenococcus oeni during malolactic fermentation

Glycosidases, produced by Oenococcus oeni strain Lalvin EQ54 during malolactic fermentation (MLF) performed in a chemically defined wine (CDW) medium, contributed to the release of volatile aglycons from their glycosylated precursors, present in a Chardonnay wine glycosidic extract. The liberation of wine volatiles during MLF was limited by the low activity of these enzymes in this strain. Six different aglycons examined were 3-hydroxydamascone, alpha-terpineol, vanillin, methyl vanillate, 4-hydroxybenzoic acid and tyrosol. Using p-nitrophenyl synthetic substrates, it was shown that O. oeni Lalvin EQ54 has β-glucosidase, and limited α-l-rhamnopyranosidase and α-l-arabinofuranosidase activities. Release of aglycons from the Chardonnay wine glycosidic extract was increased when purified α-l-rhamnopyranosidase and α-l-arabinofuranosidase were added to the CDW medium together with the malolactic bacteria culture. The results obtained confirmed that O. oeni has the necessary glycosidases for the sequential liberation of the disaccharide sugars from wine glycosides. The rate of MLF proceeded much faster in the CDW supplemented with the Chardonnay wine glycoside extract (8 days compared to 20 days), even though the bacterial growth was unaffected.     

几株乳酸菌对干红葡萄酒挥发性成分的影响

以完成酒精发酵的干红葡萄酒为原料,选用实验筛选的4株乳酸菌进行苹果酸-乳酸发酵（Malolactic fermentation,MLF）,以未进行MLF的试样为对照,采用顶空固相微萃取、气相色谱-质谱（HS-SPME-GC/MS）联用技术分析试样挥发性组分。结果显示,4个试样中共检出70种挥发性组分,其中酒样C5检出42种,N8检出46种,N9检出46种,N13检出48种。CK检出35种,MLF试样挥发性物质种类及挥发量均较对照多,表明MLF过程中有新的挥发性组分形成,对葡萄酒香气品质有修饰作用。4种乳酸菌中,筛自泡菜的C5菌株（Lactobacillus plantarum）用于MLF后酒样酯类组分最高,相对含量达56.48%,酸类最低,占1.23%,酒样挥发性组分构成优于其它菌株。      

Interaction of pH, ethanol concentration and wine matrix on induction of malolactic fermentation with commercial 'direct inoculation' starter cultures

The effect of the interaction between pH (2.9–3.5), alcohol concentration (12.5–14.5% v/v) and wine matrix (Chardonnay, Grenache blend and Cabernet Sauvignon) on malolactic fermentation (MLF) induced by two commercially available directly inoculated Oenococcus oeni starter cultures was determined. Wine matrix had greatest impact on the rate of MLF, followed by pH and alcohol; the matrix effect was significantly modified by pH and bacterial culture. The rate of L-malic acid degradation by starter culture A was 3.3–61.3% in the Grenache blend and 3.3–4.5% in the Chardonnay wine compared to the Cabernet Sauvignon wine, for the pH/alcohol ranges 2.9/14.5 to 3.5/12.5. L-malic acid degradation rate by starter culture B was lower but less affected by wine matrix. The rate of L-malic acid degradation was closely related to culture viability, with a high rate of L-malic acid degradation being associated with bacterial growth and vice versa . Treatment of two wines in which MLF had previously failed to complete with various combinations of nutrients, carbon fining and heating, restored MLF, suggesting that a growth-limiting nutrient was absent and/or a toxic substance not related to pH, alcohol or SO₂ concentration was present. This work demonstrated that the wine matrix may affect culture viability more significantly than either pH or alcohol concentration. A high rate of MLF was shown to depend on factors permitting bacterial growth, however, the two strains studied responded differently to the wine matrix, suggesting that malolactic bacteria vary in tolerance to various stresses in the wine environment.     

The influence of malolactic fermentation and Oenococcus oeni strain on glycosidic aroma precursors and related volatile compounds of red wine

Free and glycosidically bound volatile compounds of red wine were measured after malolactic fermentation (MLF) with four different commercial starter cultures of Oenococcus oeni. MLF resulted in a significant decrease in the concentration of total glycosides, expressed as phenol‐free glycosyl glucose. Gas chromatographic analyses of wine enzyme hydrolysates showed that the extent of hydrolysis of glycosides during MLF was dependent on both bacterial strain and chemical structure of the substrate. The highest decrease was observed for glycosidic precursors of primary terpene alcohols. Glycoside‐related aroma compounds such as linalool, farnesol, and β‐damascenone were increased after MLF with all the bacterial strains tested. Two of the strains were also able to release significant amounts of vinylphenols during MLF. Copyright © 2006 Society of Chemical Industry