Malolactic Fermentation Of Red Wines Research Articles

Application of white wine lees for promoting lactic acid bacteria growth and malolactic fermentation in wine

In the context of ecological transition, the use of wine by-products for industrial applications is a major challenge. Wine lees, the second wine by-product in terms of quantity, represent a source of nutrients that can be used for stimulating the growth of microorganisms. Here, white wine lees were used as a stimulating agent for the growth of wine lactic acid bacteria (LAB) and to promote wine malolactic fermentation (MLF) driven out by Oenococcus oeni. By adding freeze-dried wine lees to wines under different conditions – including different wine lees at different concentrations and different O. oeni strains at various initial populations - it was observed that wine lees can enhance the growth of LAB and reduce the duration of MLF. The chemical composition of wines was also evaluated, proving that wine lees do not compromise the quality of the wines. In addition, wine lees did not seem to promote the growth of spoilage microorganisms like as Brettanomyces bruxellensis. Altogether, this work reports the possibility of recovering the lees of white wine to obtain a product favoring the MLF of red wines. More general, we propose a recycling strategy of wine by-products to obtain new products for winemaking.

Assessment of the lysogenic status in the lactic acid bacterium O. oeni during the spontaneous malolactic fermentation of red wines

After alcoholic fermentation, most wines undergo malolactic fermentation (MLF), driven by the lactic acid bacterium Oenococcus oeni, which improves their organoleptic properties and microbiological stability. Prophages were recently shown to be notably diverse and widely disseminated in O. oeni genomes. Such in silico predictions confirmed previous cultivation-based approaches which showed frequent lysis of strains upon treatment with the inducing agent mitomycin C. Both strategies used to assess lysogeny in the species were so far applied to a number of strains collected from distinct countries, wineries, cepages and fermentation processes. Results may not therefore be representative of the lysogenic population in natural communities driving the MLF during winemaking. Here we report the prevalence of lysogeny during winemaking in three wineries in the Bordeaux area. The dominant LAB population was collected in 11 red wines upon completion of MLF. Using VNTR and prophage typing analyses, our data confirm the presence of lysogens in the population driving the spontaneous MLF in all tested wines, although lysogeny rates varied across wineries. Higher prevalence of lysogeny was associated to a reduced diversity in VNTR profiles, the dominance of a few prophage-types and presence of some bacterial genetic backgrounds that were particularly prone to lysogenization.

Compact analytical flow system for the simultaneous determination of l-lactic and l-malic in red wines

During the malolactic fermentation of red wines, l-malic acid is mainly converted to l-lactic acid. Both acids should be precisely measured during the entire process to guarantee the quality of the final wine, thus making real-time monitoring approaches of great importance in the winemaking industry. Traditional analytical methods based on laboratory procedures are currently applied and cannot be deployed on-site. In this work, we report on the design and development of a bi-parametric compact analytical flow system integrating two electrochemical biosensors that could be potentially applied in this scenario. The developed flow-system will allow for the first time the simultaneous measurement of both acids in real scenarios at the real-time and in remote way. Miniaturized thin-film platinum four-electrode chips are fabricated on silicon substrates by standard photolithographic techniques and further implemented in a polymeric fluidic structure. This includes a 15 µL flow cell together with the required fluidic channels for sample and reagent fluid management. The four-electrode chip includes counter and pseudo-reference electrodes together with two working electrodes. These are sequentially modified with electropolymerized polypyrrole membranes that entrap the specific receptors for selectively detecting both target analytes. The analytical performance of both biosensors is studied by chronoamperometry, showing a linear range from 5 × 10−6 to 1 × 10−4 M (LOD of 3.2 ± 0.3 × 10−6 M) and from 1 × 10−7 to 1 × 10−6 M (LOD of 6.7 ± 0.2 × 10−8 M) for the l-lactate and the l-malate, respectively. Both biosensors show long-term stability, retaining more than the 90% of their initial sensitivity after more than 30 days, this being a prerequisite for monitoring the whole process of the malolactic fermentation of the red wines (time between 20 and 40 days). The flow system performance is assessed with several wine samples collected during the malolactic fermentation process of three red wines, showing an excellent agreement with the results obtained with the standard method.

Influence of must yeast-assimilable nitrogen content on fruity aroma variation during malolactic fermentation in red wine

This study assessed the impact of must yeast-assimilable nitrogen (YAN) content and lactic acid bacteria (LAB) strains used for malolactic fermentation (MLF) on the formation of substituted esters, as well as the corresponding precursors (substituted acids), to investigate the modulation of fruity expression in red wines. In microvinification experiments, a Merlot must was fermented with an initial YAN content of 111 mg/L, or supplemented up to 165 and 220 mg/L. Two Oenococcus oeni LAB strains were used for MLF. Analytical methods were used to quantify substituted esters, as well as the corresponding acids, including, any enantiomeric forms. YAN supplementation of the must significantly increased concentrations of substituted esters of short- and branched-chain alkyl fatty acids produced during alcoholic fermentation (AF) (up to 67% in samples with the highest nitrogen content) and substituted esters of hydroxycarboxylic acids generated during MLF (up to 58% in samples with the highest nitrogen content). YAN supplementation in the must did not affect substituted acid formation during AF. After MLF, short- and branched-chain alkyl fatty acid levels increased in wines made from musts with the highest nitrogen content (up to 56% in samples with the highest nitrogen content), whereas concentrations of hydroxycarboxylic acids increased (up to 55%) independently of the initial YAN content, highlighting the important role of MLF. (2S)-2-hydroxy-4-methylpentanoic acid was only found in wines after malolactic fermentation, suggesting different pathways for each enantiomer and opening up new prospects for the study of bacterial metabolisms. Moreover, sensory profiles revealed a significant increase in black-berry- and jammy-fruit aromas during MLF and a strong positive correlation between these aromas and the production of substituted esters following must nitrogen supplementation and MLF. Aromatic reconstitutions revealed that variations in the concentrations of substituted esters after MLF impacted the fruity aroma of red wines.

Production of melatonin and other tryptophan derivatives by Oenococcus oeni under winery and laboratory scale

Malolactic fermentation (MLF) in Valtellina Superiore DOCG red wine was monitored in 4 cellars and the final products were analysed to determine the content of melatonin (MEL) and other tryptophan (TRP) derivatives, including tryptophan ethyl ester (TEE) and MEL isomers (MISs), and to isolate predominant O. oeni strains. MEL and TEE significantly increased in wines after MLF from two cellars out of four. Six strains were isolated during the MLF of red wines and under laboratory scale, in rich and synthetic wine cultural media, together with other four O. oeni strains able to trigger the MLF. Results showed that the presence of stressful growth factors, like ethanol and acid pH, has a pivotal role in triggering the release of TEE by oenococci. Indeed, all the strains became capable to produce also MEL and MISs, together with TEE. under harsh growth conditions, as in a synthetic wine medium. The production of these compounds was strain-dependent and a maximum amount of 0.0078 ± 0.0023 ngT/mL (UMB472) and 619.85 ± 196.16 ngT/mL (UMB436) of MEL and TEE was obtained, respectively. In particular, different MISs were detected under oenological and laboratory scale suggesting that other factors (i.e. technological and/or physico-chemical) could affect the synthesis of TRP derivatives.

Design and implementation of an ultrasonic sensor for rapid monitoring of industrial malolactic fermentation of wines

ABSTRACTUltrasound is an emerging technology that can be applied to monitor food processes. However, ultrasonic techniques are usually limited to research activities within a laboratory environment and they are not extensively used in industrial processes. The aim of this paper is to describe a novel ultrasonic sensor designed to monitor physical–chemical changes that occur in wines stored in industrial tanks. Essentially, the sensor consists of an ultrasonic transducer in contact with a buffer rod, mounted inside a stainless steel tube section. This structure allows the ultrasonic sensor to be directly installed in stainless steel tanks of an industrial plant. The operating principle of this design is based on the measurement of ultrasonic velocity of propagation. To test its proper operation, the sensor has been used to measure changes of concentration in aqueous samples and to monitor the progress of a malolactic fermentation of red wines in various commercial wineries. Results show the feasibility of using this sensor for monitoring malolactic fermentations in red wines placed in industrial tanks.

Esterase activity of lactic acid bacteria isolated from malolactic fermentation of red wines

The goal of this study was to examine the esterase activity of 243 lactic acid bacteria (LAB) strains from wines of different red grape varieties, belonging to the genera Oenococcus, Lactobacillus, Pediococcus and Enterococcus. p-Nitrophenyl octanoate was used as substrate. All strains presented esterase activity in the first screening, but only those showing higher activity were used in subsequent studies to determine the cellular location of this activity, the influence of pH, temperature and the presence of ethanol and the substrate specificity. For the thirteen selected strains, the highest activity was observed in the intracellular fraction. Responses to pH, temperature and ethanol were strain-dependent, but for all the strains, a marked decrease in activity in presence of ethanol was observed. When the influence of pH and ethanol acting together was studied at 25°C and 37°C, temperature-dependent differences were not observed for any of the strains except for Oen6. In the substrate specificity assay, the majority of strains of all genera displayed a trend to more readily hydrolyse ester substrates from C8 and longer.

Comparative metabolic profiling to investigate the contribution ofO. oeniMLF starter cultures to red wine composition

In this research work we investigated changes in volatile aroma composition associated with four commercial Oenococcus oeni malolactic fermentation (MLF) starter cultures in South African Shiraz and Pinotage red wines. A control wine in which MLF was suppressed was included. The MLF progress was monitored by use of infrared spectroscopy. Gas chromatographic analysis and capillary electrophoresis were used to evaluate the volatile aroma composition and organic acid profiles, respectively. Significant strain-specific variations were observed in the degradation of citric acid and production of lactic acid during MLF. Subsequently, compounds directly and indirectly resulting from citric acid metabolism, namely diacetyl, acetic acid, acetoin, and ethyl lactate, were also affected depending on the bacterial strain used for MLF. Bacterial metabolic activity increased concentrations of the higher alcohols, fatty acids, and total esters, with a larger increase in ethyl esters than in acetate esters. Ethyl lactate, diethyl succinate, ethyl octanoate, ethyl 2-methylpropanoate, and ethyl propionate concentrations were increased by MLF. In contrast, levels of hexyl acetate, isoamyl acetate, 2-phenylethyl acetate, and ethyl acetate were reduced or remained unchanged, depending on the strain and cultivar evaluated. Formation of ethyl butyrate, ethyl propionate, ethyl 2-methylbutryate, and ethyl isovalerate was related to specific bacterial strains used, indicating possible differences in esterase activity. A strain-specific tendency to reduce total aldehyde concentrations was found at the completion of MLF, although further investigation is needed in this regard. This study provided insight into metabolism in O. oeni starter cultures during MLF in red wine.

Electrochemical biosensors for monitoring malolactic fermentation in red wine using two strains of Oenococcus oeni

Electrochemical biosensors for monitoring malolactic fermentation in red wine using two strains of Oenococcus oeni

Electrochemical biosensors for monitoring malolactic fermentation in red wine using two strains of Oenococcus oeni

Amperometric biosensors for the determination of l-malic and l-lactic acids were optimised and used to monitor micro-malolactic fermentations (micro-MLFs) in red wine. Platinum-based probes, coupled with appropriate enzymes, were assembled in electrochemical flow-injection analysis systems. A classical lactate oxidase based sensor was used for l-lactic acid, while l-malic acid was detected via a new biosensor based on the malic enzyme immobilised in a reactor using phenazine methosulphate as mediator. After a preliminary optimisation phase, a recovery study to evaluate the effect of the matrix (red wine) on biosensor performance was carried out by the addition of different standard solutions of the two analytes to the samples. Recoveries from 93 to 100% and from 94 to 102% were observed for l-malic acid and l-lactic acid, respectively. These optimised biosensors were finally employed to monitor micro-MLFs induced by inoculation of two different strains of Oenococcus oeni into red wine. During the micro-MLFs, samples of wine were collected and assayed for l-malic, l-lactic, and citric acids by use of both biosensors and spectrophotometric techniques. In parallel the viable bacterial cell count was also evaluated. The kinetics of bacterial growth, degradation of l-malic and citric acids, and production of l-lactic acid was found to be a function of the strains inoculated.

The potential of positively-charged cellulose sponge for malolactic fermentation of wine, using Oenococcus oeni.

Malolactic fermentation (MLF) is a secondary bioconversion developed in some wines involving malic acid decarboxylation. The induction of MLF in wine by cultures of free and immobilized Oenococcus oeni cells was investigated. This work reports on the effect of surface charges in the immobilization material, a recently described fibrous sponge, as well as the pH and the composition of the media where cells are suspended. A chemical treatment provided positive charge to the sponges (DE or DEAE) and gave the highest cell loadings and subsequent resistance to removal. Preculture media to grow the malolactic bacteria before the immobilization procedure were also evaluated. We have established favorable conditions for growth (Medium of Preculture), suspension solution (Tartrate-Phosphate Buffer), suspension pH (3.5-5.5) and immobilization matrix (DE or DEAE cellulose sponge) to induce MLF in red wine. The use of a semi-continuous system permitted a high-efficiency malic acid conversion by 2 x 10(9) cfu sponge(-)(1) in at least four subsequent batch fermentations.

The effects of freezing and freeze-drying ofOenococcus oeniupon induction of malolactic fermentation in red wine

Summary The use of Oenococcus oeni starter cultures for the induction of malolactic fermentation (MLF) in wine permits control over the timing of the process and the quality of the wine. Successful inoculation of bacterial starter cultures into wine depends on the selection of suitable strains and on the preparation and conservation of those cultures. Medium for Leuconostoc oenos (MLO) is the best medium for easy and rapid growth of O. oeni cultures under laboratory controlled conditions for isolation and identification. However, this study showed that O. oeni cells inoculated in MLO failed to induce MLF in wine while cells grown in Medium of Preculture (MP) or wine, stored at −20 °C or freeze-dried retained the ability to induce MLF when inoculated in wine. Our results suggest that the use of freeze-dried cultures of O. oeni previously grown in MP is the best choice for industrial application.