Malic Acid Degradation Research Articles

Role of Pre-Harvest Sorbitol–Calcium Treatments in Controlling Berry Drop in Bagged Table Grapes of the “Doña María” Variety

Cv ‘Doña María’ table grape is a high-quality table grape variety included in the Protected Designation of Origin (PDO) of the European Union “The bagged grape of the Vinalopó”. The PDO stipulates that grape clusters must be protected with paper bags from inclement weather and insects, which helps enhance the final grape quality. However, ‘Doña María’ is a variety prone to high shattering in the late stages of ripening on the vine and during postharvest. Inorganic calcium treatments are one of the most commonly used tools to reduce this disorder, but the translocation of this mineral from veraison onward has been questioned. In this study, five applications were performed, from veraison to harvest, using sorbitol-chelated calcium (0.7% + 1.0%), Ca(NO3)2 (Ca) at 0.7% and sorbitol at 1%. It was observed that bagged grapes (not wetted with the solutions) only increased the concentration of total and bound calcium when treated with sorbitol–Ca. This resulted in reduced berry drop during cultivation and postharvest and improved fruit firmness. Additionally, it reduced grape metabolism indicators such as respiration rate, weight loss, malic acid degradation, prevented abscisic acid (ABA) and malondialdehyde (MDA) accumulation, and favored the accumulation of secondary metabolites such as total polyphenols, increased antioxidant activity, and sugar content. The application of sorbitol-chelated calcium is an effective and safe tool that enhances fruit quality and prevents losses due to shattering during postharvest.

Characterization of varietal effects on the acidity and pH of grape berries for selection of varieties better adapted to climate change.

Climate change is drastically modifying berry composition and wine quality across the world. Most wine regions with a history of winemaking are suffering from a loss of typicity and terroir expression because of climate change impact on berry components at harvest, including wine acidity, with total acidity decreasing and pH increasing. Such changes can have a major impact on wine stability and quality. One important option for adaptation is the selection of grapevine varieties better adapted to warmer and drier conditions. Weekly measurement of tartaric acid, malic acid, pH and titratable acidity from veraison until maturity were carried out on 51 varieties over seven years in two experimental plots. Varietal differences were shown for the rate of malic acid degradation during the ripening period, with some varieties metabolizing malic acid faster per unit of thermal time than others. Some varietal differences were also noticed regarding tartaric acid modulation, which can occur under exceptionally high temperatures. Differences in the dynamics of pH evolution in grape must over the growing season were evaluated and varieties characterized with regard to organic acids (tartaric acid and malic acid), inorganic compounds (cations) as well as pH levels and stability. This multi-trait approach allows the selection of grapevine varieties based on parameters linked to their acidity, which is of particular importance in the context of climate change.

Bunch transpiration is involved in the hastening of grape berry ripening under elevated temperature and low relative humidity conditions

The present study aimed: i) to evaluate the impact of the changes in temperature and relative humidity (RH), projected by the year 2100, on grape ripening, and ii) to assess if bunch transpiration is a key physiological process involved in the advancement in grape development under future climate conditions. Fruit-bearing cuttings of Vitis vinifera L. cv. ‘Tempranillo’ were grown, from fruit set to maturity, in glasshouses under two conditions: 24°C/14°C and 55%/70% RH (day/night) (T) vs 28°C/18°C and 43%/58% RH (T+4). To elucidate the role of bunch transpiration in grape development in a future climate scenario, the bunches of half of the plants in the T+4 glasshouse were sprayed with an antitranspirant (AT+4). T+4 increased bunch transpiration, hastened the ripening process, increasing the rate of total soluble solid (TSS) accumulation and malic acid degradation, and reduced the concentration of total anthocyanins. The application of antitranspirant partially alleviated the effects of combined high temperature and low RH on maturation times, through lower TSS accumulation rates. Berries in AT+4 had the lowest concentrations of anthocyanins and color, likely related to a reduction in light transmittance by the antitranspirant film and to higher anthocyanin degradation due to the longer exposure to elevated temperatures. The results show a negative impact of elevated temperature and low RH on grape composition. The increased bunch transpiration under these conditions played an important role in the changes observed in phenology and sugar accumulation.

Effects of Vine Water Status on Malate Metabolism and γ-Aminobutyric Acid (GABA) Pathway-Related Amino Acids in Marselan (Vitis vinifera L.) Grape Berries.

Malic acid is the predominant organic acid in grape berries, and its content is affected by abiotic factors such as temperature (fruit zone microclimate) and water (vine water status). The objectives of this study were to explore the potential mechanisms behind the effects of vine water status on the biosynthesis and degradation of berry malic acid and the potential downstream effects on berry metabolism. This study was conducted over two growing seasons in 2021 and 2022, comprising three watering regimes: no water stress (CK), light water stress (LWS), and moderate water stress (MWS). Compared to CK, a significantly higher level of malic acid was found in berries from the MWS treatment when the berry was still hard and green (E-L 33) in both years. However, water stress reduced the malic acid content at the ripe berry harvest (E-L 38) stage. The activities of NAD-malate dehydrogenase (NAD-MDH) and pyruvate kinase (PK) were enhanced by water stress. Except for the E-L 33 stage, the activity of phosphoenolpyruvate carboxylase (PEPC) was reduced by water stress. The highest phosphoenolpyruvate carboxykinase (PEPCK) activity was observed at the berry veraison (E-L 35) stage and coincided with the onset of a decrease in the malate content. Meanwhile, the expression of VvPEPCK was consistent with its enzyme activity. This study showed that water stress changed the content of some free amino acids (GABA, proline, leucine, aspartate, and glutamate), two of which (glutamate and GABA) are primary metabolites of the GABA pathway.

Reintroducing Autochthonous Minor Grapevine Varieties to Improve Wine Quality and Viticulture Sustainability in a Climate Change Scenario

One of the major challenges that global warming poses to viticulture is the maintenance of adequate acidity at maturity in white grapes for sparkling winemaking. This issue arises from three main occurrences: (i) with higher temperatures, degradation of malic acid is significantly enhanced; (ii) with a general advancement in grapevine phenology, grape maturity may occur under suboptimal climatic conditions; and (iii) harvesting grapes at “traditional” dates results in overripe fruits for sparkling destinations. In this biennial work, we compared the fruit and must composition of a local, widely grown white grape variety in the Colli Piacentini area (cv. Ortrugo, ORT) with those of a minor autochthonous variety, namely, Barbesino (BRB). Furthermore, we compared the composition, aromatic, and sensory profiles of wines obtained from ORT and BRB grapes picked on the same date and, in addition, of a second Barbesino wine from late harvest (BRB-LH). ORT and BRB had a similar sugar accumulation dynamic, whereas BRB exhibited a delayed loss of titratable acidity. In more details, BRB had lower malic acid degradation rates when malate concentration was <9 g/L. As a result, with comparable yield and total soluble solid content (TSS) (∼20°Brix), BRB had a higher berry titratable acidity and malic acid concentration at harvest than ORT. BRB wines showed the highest titratable acidity (TA), while ORT had the lowest TA and a higher pH, and as expected, BRB-LH had the highest pH and a lower TA than BRB although still higher than those of ORT wine. The aroma profiles of wines were mainly characterized by fermentative aromas, including esters, fatty acids, higher alcohols, and C6 compounds, and BRB-LH wines showed the highest concentration of higher alcohols, while the fermentative esters were higher in ORT wines. Panelists considered BRB significantly fresher and with bigger aroma intensity than ORT, confirming that the higher acidity detected in BRB musts is well preserved in final wines. Our work demonstrates that local minor varieties can be reconsidered in light of the new climate change-related issues impairing viticulture sustainability today. In particular, currently neglected cultivars could help preserve must acidity as compared to traditional varieties having early ripening, maintaining the links with terroir and local traditions at the same time.

Effects of 1-Methylcyclopropene Treatment on the Quality and Malic Acid Metabolism of ‘Xiangjiao’ Plum under Low-Temperature Storage

‘Xiangjiao’ plum (Prunus salicina Lindl.) is a stone fruit that is vulnerable to the chilling injury (CI) that is caused by low-temperature stress. The effects of 1-methylcyclopropene (1-MCP) and ethylene absorbent (EA) treatments on the fruit quality and malic acid metabolism of ‘Xiangjiao’ plum stored at 4 °C were compared in this study. Compared with the control check (CK) and EA treatment, fumigation with 1.0 mg·L−1 of 1-MCP for 24 h could more significantly maintain the sensory and physiological quality of the fruit, increase the activity of antioxidant enzymes, and prolong the storage time of plums. Furthermore, 1-MCP treatment can regulate the high expression of the tonoplast dicarboxylate transporter (tDT) and phosphoenolpyruvate carboxylase (PEPC) gene, regulate the high expression of the NAD-malate dehydrogenase (NAD-MDH) gene at the end of storage, and inhibit the expression of the NADP-malic enzyme (NADP-ME) gene. These changes resulted in increased NAD-MDH enzyme activity and decreased NADP-ME enzyme activity, which inhibited the degradation of malic acid that is caused by CI. As a result, 1-MCP can effectively maintain the storage quality of ‘Xiangjiao’ plum, reduce the loss of pleasant sour taste, and improve the edible flavor and commercial value of the fruit.

Insights into the grape must composition effect on Hanseniaspora vineae performance and metabolic aroma compounds in Chardonnay base wine for sparkling wine production

This study compares the performance of Hanseniaspora vineae (Hv) under mixed culture fermentation with Saccharomyces cerevisiae, with a conventional control (Sc) for the production of base wine. Hv exhibited fermentation kinetics comparable to controls when its nutritional requirements were satisfied. Volatile acidity in Hv from one batch was significantly lower (–0.3 g/L) compared to the controls, while in the other two batches the levels were equal. Interestingly, Hv trials showed a significant degradation of malic acid (–0.9 g/L on average) without variations of pH. Even though the matrix influenced the volatile composition, the characteristic features of H. vineae remained intact, with 24-fold higher levels of 2-phenylethyl acetate. There was no higher production of 2-aminoacetophenone, albeit tryptophan (known as a 2-aminoacetophenone precursor) is a preferred amino acid for H. vineae. Results suggest the potential of H. vineae to produce base wine with a broad spectrum of aroma compounds that increase flavor complexity, if obtained from nutrient-balanced grape musts.

Identifying the best parameters to determine genotype capability to retain adequate malic acid at harvest and in final wines

Maintaining optimal grape acidity at harvest is one of the most complicated challenges under climate change pressures, especially in early ripening cultivars. Warming trends are compressing vine phenology and fostering berry malic acid respiration. In this work, over four years, we evaluated yield components and fruit ripening in two local varieties in the Colli Piacentini, Ortrugo (ORT) and Barbesino (BRB). Our goal was to evaluate their ability to maintain satisfying acidity at harvest and understand the limits and features of the genetic control over organic acid degradation during ripening.The two varieties exhibited comparable yield and grape total soluble solids (TSS) accumulation dynamics, but BRB showed consistently higher acidity during the entire ripening process in any of the four years. BRB's higher acidity was linked to higher malic acid concentrations. ORT had earlier onset of malic acid degradation than BRB and lower maximum malic acid degradation rates. Malic acid degradation rates were lower in ORT also later in the season, until harvest. However, correlations built between malic acid degradation rates and instantaneous malic acid concentration revealed that BRB had a consistently lower malic acid loss for values of malate < 10 g/L.Our work demonstrates that there is a genetic control over the malic acid degradation rates exhibited at varying malic acid concentrations and higher acidity at harvest can be found in varieties exhibiting low malic acid degradation rates when malic acid is < 10 g/L. Post-veraison berry growth rates could interact with genotype effects. The analysis of the correlation can be used at different scales to identify cultivars retaining higher acidity at harvest.

Combined effect of sonication and equilibrium‐modified atmosphere packaging to improve storage stability of “Angelino” plums during extended storage

AbstractThis work focuses on the combined effects of ultrasound treatment (100, 200, and 300 W for 5 min) and equilibrium‐modified atmosphere packaging (EMAP) to enhance the storage stability based on pH, aw, gas compositions in headspace, color changes (L*, a*, b*), organic acids, and texture profile of fresh “Angelino” plums for 120 days at 4°C. The results were expressed that pH values were increased (3.19‐initial to 3.69/300 W–3.86/control) and Brix values were decreased (16.9‐initial to 14.70/control–15.3/100 W) during storage. At the end of the storage, except the control group, O2 in the headspace decreased from 20.9%‐initial to 16%/300 W–18.5%/200 W and CO2 was accumulated from 0.03%‐initial to 4.9/%200 W–6.5%/300 W. Hardness (from 11,677, 6124 gf), gumminess (from 4344 g to 4335–6715 g), and chewiness (from 3831 and 2326–2638 g) consistently decreased as a function of storage. The hardness of “Angelino” plums had been maintained after the sonication combined with EMAP compared with the control during storage. The 100 W and 200 W sonication could significantly delay the degradation of malic (from 8957 to 4227–4236 mg/L) and tartaric (1796 to 1703–1722 mg/L) acid in flesh plums, but not citric acid and malonic acid over the storage period. The sonication (200 W) combined with EMAP enhanced the storage stability.Practical ApplicationsThis research demonstrates that packaging fresh Angelino plums with micro‐perforated lid films and subjecting them to sonication can enhance their storage stability, allowing for longer distribution via sea freight at a considerably reduced cost compared with air freight. This can potentially expand the producer's reach in international markets. Sonication had great potentials in stabilizing cell wall and maintaining hardness in the plums during storage. Moreover, the application of sonication, especially 200‐W for enhancing storage stability without any detrimental effects on physicochemical properties and natural main organic acids (malic acid) of “Angelino” plums during the storage.

Comparison of the influence of Saccharomyces pastorianus to Saccharomyces cerevisiae and Saccharomyces bayanus inoculation ratio to oenological characteristics of Sauvignon Blanc wine

The aim of our work was to evaluate the impact of different fermentation schemes by using mixed and pure cultures of S. pastorianus and S. cerevisiae or S. bayanus. For the mixed fermentation schemes, one strain of S. pastorianus has been inoculated under different proportions (99%/1%, 97%/3%, 95%/5%, 90%/10% and 70%/30% w/w) in co-inoculation with two commercial strains of S. cerevisiae and one commercial Saccharomyces bayanus strain. The fermentation kinetics has been controlled by density measurement and classical oenological analyses were performed based on OIV analytical methods. The population dynamics was evaluated by the specific interdelta PCR reaction of the Saccharomyces species in the beginning and in the end of the fermentation process. Volatile compounds of the wine aroma, such as esters, higher alcohols and thiols were analyzed by GC/MS. Sensory assessment by trained panel was carried out for all wines. The wines fermented with S. pastorianus, either in pure or mixed cultures, were characterized by significantly lower acetic acid production and higher malic acid degradation when compared to the wines fermented with S. cerevisiae strains. The presence of S. pastorianus strain enhanced the production of the varietal thiols when compared to the samples fermented with the S. cerevisiae pure cultures. The wines produced by the S. bayanus or cerevisiae monocultures and the ones produced by the co-culture with S. pastorianus at 70%-30% ratio (S. pastorianus to S. bayanus or cerevisiae) were overall better rated from a sensory point of view.

Exogenous salicylic acid regulates organic acids metabolism in postharvest blueberry fruit.

Fruit acidity is an essential factor affecting blueberry organoleptic quality. The organic acid content in blueberry fruit mainly contributes to fruit acidity. This study aims to evaluate the effect of exogenous salicylic acid (SA), the principal metabolite of aspirin, on the organoleptic quality and organic acid metabolism in rabbiteye blueberry (Vaccinium virgatum Ait, 'Powderblue') during cold storage (4 °C). Results showed that SA-treated fruit reduced fruit decay and weight loss delayed fruit softening, and decline of total soluble solids (TSS). TA and total organic acid amounts stayed the same during the late storage period in SA-treated fruit. Four kinds of organic acid components, malic acid, quinic acid, citric acid, and succinic acid, were at higher levels in fruit treated by SA as compared to control. SA enhanced the activities of PEPC, NAD-MDH, and CS to promote the synthesis of malic acid and citric acid. Meanwhile, the activities of NADP-ME, ACL, and ACO, which participated in the degradation of malic acid and citric acid, were inhibited by SA. qPCR results also showed that the expression of VcPEPC, VcNAD-MDH, and VcCS genes were upregulated. In contrast, SA downregulated the expression of VcNADP-ME, VcACL, and VcACO genes. In conclusion, SA could regulate the key genes and enzymes that participated in organic acids metabolism to maintain the freshness of blueberry during cold storage, therefore minimizing the economic loss.

Effect of Saccharomyces cerevisiae and Saccharomyces pastorianus Co-Inoculation on Alcoholic Fermentation Behavior and Aromatic Profile of Sauvignon Blanc Wine

Enhancing the sensory profile of wines by exposing the aromas of the grape variety through the involvement of microorganisms has always been a challenge in winemaking. The aim of our work was to evaluate the impact of different fermentation schemes by using mixed and pure cultures of different Saccharomyces species to Sauvignon blanc wine chemical composition and sensory profile. The Sauvignon blanc must has been inoculated with mixed and pure cultures of S. pastorianus and S. cerevisiae strains. For the mixed fermentation schemes, one strain of S. pastorianus has been inoculated with different proportions of S. cerevisiae (S. pastorianus to S. cerevisiae: 99%–1%, 95%–5%, 90%–10%, 80%–20% and 70%–30% w/w) in co-inoculation with two commercial strains of S. cerevisiae. A total of 13 fermentations trials, three monocultures and 10 mixed cultures were performed in biological triplicate. The fermentation kinetics have been controlled by density measurement and classical oenological analyses were performed based on the International Organisation of Vine and Wine (OIV) analytical methods. The population dynamics were evaluated by the specific interdelta PCR reaction of the Saccharomyces species at the beginning and at the end of the fermentation process. The volatile compounds of the wine aroma, such as the esters, higher alcohols and thiols were analyzed by GC/MS. Sensory assessment by trained panel was carried out for all produced wines. Complete depletion of the sugars was achieved between 10 and 13 days for all the fermentation trials. The population dynamics analysis revealed that the S. cerevisiae strain was the most predominant at the end of the fermentation process in all inoculation ratios that were tested. The wines that were fermented with S. pastorianus, either in pure or mixed cultures, were characterized by significantly lower acetic acid production and higher malic acid degradation when compared to the wines that were fermented only with S. cerevisiae strains. The aroma profile of the produced wines was highly affected by both inoculation ratio and the S. cerevisiae strain that was used. The presence of S. pastorianus strain enhanced the production of the varietal thiols when compared to the samples that were fermented with the S. cerevisiae pure cultures. The mixed inoculation cultures of Saccharomyces species could lead to wines with unique character which can nicely express the varietal character of the grape variety.

The research on the composition of organic acids in young wines “Primeur” and “Virgin” with in C.V. “Ccricova” S.A.

This research concluded in getting experimental data about the composition of organic acids in wines obtained from varieties Cabernet-Sauvignon, Merlot, Pinot Noir, Rara Neagra, Feteasca Neagra, Shiraz (Syrah) produced within C.V. ”Cricova” S.A between 2015–2019 years. Also, it was argued the need to apply the malolactic fermentation simultaneously with alcoholic fermentation in order to increase the quality of young dry red wines, which allows the launch of the finished product in a restricted period of time. The degradation of malic acid in wine was achieved by malolactic fermentation bacteria, removing the excessive fresh taste of young wines ”Primeur” and ”Virgin”.

Rosmarinic Acid Delays Tomato Fruit Ripening by Regulating Ripening-Associated Traits.

Fruits are excellent sources of essential vitamins and health-boosting minerals. Recently, regulation of fruit ripening by both internal and external cues for the improvement of fruit quality and shelf life has received considerable attention. Rosmarinic acid (RA) is a kind of natural plant-derived polyphenol, widely used in the drug therapy and food industry due to its distinct physiological functions. However, the role of RA in plant growth and development, especially at the postharvest period of fruits, remains largely unknown. Here, we demonstrated that postharvest RA treatment delayed the ripening in tomato fruits. Exogenous application of RA decreased ripening-associated ethylene production and inhibited the fruit color change from green to red based on the decline in lycopene accumulation. We also found that the degradation of sucrose and malic acid during ripening was significantly suppressed in RA-treated tomato fruits. The results of metabolite profiling showed that RA application promoted the accumulation of multiple amino acids in tomato fruits, such as aspartic acid, serine, tyrosine, and proline. Meanwhile, RA application also strengthened the antioxidant system by increasing both the activity of antioxidant enzymes and the contents of reduced forms of antioxidants. These findings not only unveiled a novel function of RA in fruit ripening, but also indicated an attractive strategy to manage and improve shelf life, flavor, and sensory evolution of tomato fruits.

Oenococcus oeni Lifestyle Modulates Wine Volatilome and Malolactic Fermentation Outcome.

In this study, nine Oenococcus oeni strains were tested for their ability to adhere to polystyrene using mMRS and wine as culture media. Moreover, planktonic and biofilm-detached cells were investigated for their influence on malic acid degradation kinetics and aroma compound production. Three strains were able to adhere on polystyrene plates in a strain-dependent way. In particular, MALOBACT-T1 and ISO359 strains mainly grew as planktonic cells, while the ISO360 strain was found prevalent in sessile state. The strain-dependent adhesion ability was confirmed by confocal laser scanning microscopy. Planktonic and biofilm detached cells showed a different metabolism. In fact, biofilm-detached cells had a better malic acid degradation kinetic and influenced the aroma composition of resulting wines, acting on the final concentration of esters, higher alcohols, and organic acids. Oenococcus oeni in biofilm lifestyle seems to be a suitable tool to improve malolactic fermentation outcome, and to contribute to wine aroma. The industrial-scale application of this strategy should be implemented to develop novel wine styles.

Effects of calcium on gluconic acid accumulation in ‘Shine Muscat’ grape

Five year old “Shine Muscat” grape was used as material to spray amino acid calcium and water-soluble calcium solution on grape leaves and ears during fruit expansion and color changing stages. The effects of exogenous calcium fertilizer on the formation of fruit rust and fruit quality of “Shine Muscat” grape were studied in a randomized block design with 1000 times of amino acid calcium solution and 1500 times of water-soluble calcium solution, and the spraying water was used as the control. The results show that: compared with calcium fertilizer in fruit expanding stage, it is more beneficial to the accumulation of sugar components in pericarp to spaying calcium fertilizer in turn-color stage. The content of sugar in pulp can be increased by spraying calcium fertilizer compared with water in fruit expanding stage. Spraying calcium fertilizer in turn-color stage can promote the degradation of malic acid and citric acid in the pericarp of mature grape and inhibit the degradation of tartaric acid. Spraying calcium fertilizer in fruit expanding stage can promote the degradation of citric acid in mature grape pulp, while calcium amino acid can inhibit the degradation of oxalic acid and tartaric acid and promote the degradation of malic acid. Spraying calcium fertilizer in turn-color stage can promote the degradation of organic acids in mature grape pulp. Combined with the content of soluble sugar and titratable acid, spraying 1500 times of soluble calcium in fruit expansion period is beneficial to improve the fruit quality of “Shine Muscat” grape.

Effect of strains from different <i>Saccharomyces</i> species used in different inoculation schemes on chemical composition and sensory characteristics of Sauvignon blanc wine

Enhancing the sensory profile of wine using different microorganisms has always been a challenge in winemaking. The aim of our work was to evaluate the impact of different fermentation schemes by using mixed and pure cultures of three different Saccharomyces species at classic and cold inoculation temperatures on wine chemical composition and sensory profile. All the produced wines were analysed for the main oenological parameters (total acidity, volatile acidity, residual sugars, alcohol, and malic acid), as well as for volatile aromatic compounds, such as higher alcohols, acetate esters, ethyl esters and varietal thiols. In addition, implantation monitoring at the strain level and sensory analyses were performed in all fermentation trials. The wines fermented with S. pastorianus strains were characterised by significant lower acetic acid production and greater malic acid degradation compared to the wines fermented with S. cerevisiae strains. Interestingly, when the inoculation process for all trials was performed at a cold temperature (13 °C), the typical aromas of Sauvignon blanc were stronger than those in the classic inoculation temperature (18 °C) trials. Furthermore, the co-inoculation of S. pastorianus and S. bayanus resulted in wines exhibiting a higher intensity of citrus fruit notes than the wines fermented with the commercial S. cerevisiae strains. These results show that some strains from different Saccharomyces species other than S. cerevisiae, such as S. pastorianus and S. bayanus, could be promising starters for Sauvignon blanc wines and their performance can be modulated by the inoculation conditions.

Stilbenes Can Impair Malolactic Fermentation with Strains ofOenococcus oeniandLactobacillus plantarum

Malolactic fermentation (MLF) is an important step in winemaking to improve wine quality by deacidification, increased microbial stability, and modified wine flavor. The phenolic composition of the wine influences the growth and metabolism of the lactic acid bacteria (LAB) used for MLF. Due to increased cultivation of fungus-resistant grape cultivars, the present study aimed to analyze the influence of stilbenes on MLF because stilbenes play an important role as phytoalexins in plants to counteract fungal pathogens. The analysis showed that the grapevine-shoot extract Vineatrol and the stilbenes e-viniferin, ampelopsin A, r2-viniferin, and r-viniferin, as well as mixtures of the five stilbenes, decelerated malic acid degradation. This can be partially attributed to a reduced number of viable cells. However, the direct impact of stilbenes on the malolactic enzyme must also play a role, as shown by the finding that the viability of LAB stabilized, while at the same time, malic acid degradation was reduced. These results show that wines made from stilbene-rich grapes, such as fungus-resistant cultivars, might have a higher risk for a sluggish or incomplete MLF.

Impact of different temperature profiles on simultaneous yeast and bacteria fermentation

PurposeThe role of fermentation temperature was studied for its impact on the evolution of malolactic fermentation performed by simultaneous inoculum of yeast and bacteria in grape must. Results were discussed considering the different fermentative kinetics and the composition of obtained wines.MethodsTwo strains of bacteria belonging to the O. oeni and L. plantarum species were inoculated 24 h after the beginning of the alcoholic fermentation in 2 grape musts having different acidic and sugar profiles. Fermentations were conducted at 3 different temperature profiles (16/22 °C in 3 days, 18/24 °C in 3 days, 22/32 °C in 5 days). Evolution of microbiota was followed by flow cytometry and plate count. Chemical analysis of grape musts and wines were performed by instrumental approaches (FT-IR, enzymatic quantification of malic acid, GC-MS).ResultsL. plantarum resulted more efficient in malic acid consumption in the entire set of tests. These results are unexpected because, generally, Lactobacillus has been reported to be more sensitive to an oenological environment than O. oeni. In our experiments, O. oeni resulted inhibited by the highest fermentation temperature profile, causing incomplete malic acid degradation. Similarly, S. cerevisiae showed a higher sensitivity to environmental limiting factors in respect to what is generally known. Differences in the chemical composition of wines were observed in relation to the bacteria strain and the temperature profile. However, the statistical treatment of data identified temperature as the main variable able to influence the features of wines.ConclusionsSimultaneous inoculum of yeast and bacteria in grape must is an alternative approach in the management of malolactic fermentation which showed some interesting features. However, it is necessary to consider that the dynamics of the microbial population are different to that observed in traditional winemaking and the environmental variables act against the microorganisms in a peculiar, and in certain cases unexpected, way.

Influence Of Yeast And Lactic Acid Bacteria On The Content Of Volatile Compounds And Other Oenological Parameters Of Wines

Abstract The effect of Saccharomyces cerevisiae yeast on the content of volatile compounds, ethanol, glycerol and volatile acidity of wines as well as the importance of inoculation with non-Saccharomyces and S. cerevisiae yeast for improving the aromatic complexity and characteristic features of wines were discussed in the paper. Moreover, the consequence of sequential inoculation of S. cerevisiae and lactic acid bacteria Oenococcus oeni on the content of volatile compounds, diacetyl, acetoine, volatile acidity, degradation of malic acid, content of diethyl succinate, ethyl lactate, biogenic amines was presented. The advantage of simultaneous inoculation, which is the reduction of fermentation time, was emphasized. The work highlights the role of indigenous strains of yeast and lactic acid bacteria in increasing the regional character of wines. The importance of enzymes produced by yeast and bacteria, as well as the increased interest in the ability of non-O. oeni species, such as Lactobacillus and Pediococcus, to perform malolactic fermentation were also discussed. 1. Introduction. 2. Alcoholic and malolactic fermentation. 3. Effect of yeast and lactic acid bacteria on oenological parameters of wines. 3.1. S. cerevisiae. 3.2. Non-Saccharomyces. 3.3. Lactic acid bacteria. 4. Summary