Influence Of Lactic Acid Bacteria Research Articles

Influence of lactic acid fermentation on the phenolic profile, antioxidant activities, and volatile compounds of black chokeberry (Aronia melanocarpa) juice.

Lactic acid fermentation is an effective method for improving the quality of black chokeberry. This study aimed to investigate the influence of lactic acid bacteria on the phenolic profile, antioxidant activities, and volatiles of black chokeberry juice. Initially, 107 cfu/mL of Lactiplantibacillus plantarum, Lactobacillus acidophilus, and Lacticaseibacillus rhamnosus were inoculated into pasteurized black chokeberry juice and fermented for 48h at 37°C. All these strains enhanced the total phenolic and total flavonoid contents, with La. acidophilus showing the highest total phenolic (1683.64mg/L) and total flavonoid (659.27mg/L) contents. Phenolic acids, flavonoids, and anthocyanins were identified using ultrahigh-performance liquid chromatography-tandem mass spectrometry. The prevalent phenolic acid, flavonoid, and anthocyanin in the lactic-acid-fermented black chokeberry juice were cinnamic acid, rutin, and cyanidin-3-O-rutinoside, respectively. Furthermore, following fermentation, the DPPH and ABTS scavenging capacity, as well as the reducing power capacity, increased from 59.98% to 92.70%, 83.06% to 94.95%, and 1.24 to 1.82, respectively. Pearson's correlation analysis revealed that the transformation of phenolic acids, flavonoids, and anthocyanins probably contributed to enhancing antioxidant activities and color conversation in black chokeberry juice. A total of 40 volatiles were detected in the fermented black chokeberry juice by gas chromatography-ion mobility spectrometry. The off-flavor odors, such as 1-penten-3-one and propanal in the black chokeberry juice, were weakened after fermentation. The content of 2-pentanone significantly increased in all fermented juice, imparting an ethereal flavor. Hence, lactic acid fermentation can effectively enhance black chokeberry products' flavor and prebiotic value, offering valuable insights into their production. PRACTICAL APPLICATION: The application of lactic acid bacteria in black chokeberry juice not only enhances its flavor but also improves its health benefits. This study has expanded the range of black chokeberry products and offers a new perspective for the development of the black chokeberry industry.

The influence of lactic acid bacteria on the viability of the reference strain of Listeria monocytogenes 123 serotype I in plant foods

The influence of lactic acid bacteria on the viability of the reference strain of Listeria monocytogenes 123 serotype I in plant foods

Aromatic Yeasts: Interactions and Implications in Coffee Fermentation Aroma Profiles.

Nontraditional yeasts prevalent in tropical agricultural fermentations such as coffee and cocoa are known to contribute to aroma profiles, yet the functional roles and interactions between the associated microbial consortia in a farm fermentation are unclear. Here, boiled green bean extract (GBE) from green coffee beans was developed as a rich screening medium to deconstruct the microbial consortia and their interactions during the fermentation of dried green coffee beans. When cultivated in coculture with S.cerevisiae on GBE, strain-specific groupings with distinct volatile organic profiles were observed for nontraditional yeasts (e.g., Hanseniaspora spp., Pichia kudriavzevii). Further changes are evident when constructed consortia composed of nontraditional yeast, S.cerevisiae, and Lactococcus lactis var. cremoris were cultured in GBE, and a comparison with abiotically acidified GBE suggests that pH plays a major role in the influence of lactic acid bacteria (LAB) on fermentation aromas. This approach represents a tool for the development of starter culture formulations to create different flavor profiles in coffee fermentation.

Influence of different lactic acid bacteria strains and milling process on the solid-state fermented green and red lentils (Lens culinaris L.) properties including gamma-aminobutyric acid formation.

The aim of this study was to evaluate the influence of lactic acid bacteria (LAB) strains (Lactiplantibacillus plantarum No.122 and Lacticaseibacillus casei No.210) and milling process on the solid-state fermented (for 24 h, at 30°C) green and red lentils (Lens culinaris L.) properties, chiefly pH, LAB viable counts, color coordinates, free amino acid (FAA) profile, γ-aminobutyric acid (GABA) and biogenic amine (BA) concentrations, fatty acid (FA) and volatile compound (VC) profiles. Results showed that both of the tested LAB strains are suitable for the fermentation of lentils: pH of fermented lentils was <4.5 and LAB viable counts >8.0 log10 colony-forming units (CFU)/g. A very strong negative correlation was found (r = -0.973, p ≤ 0.0001) between LAB counts and pH of the samples. Also, fermentation and milling process were significant factors toward color coordinates of the lentils. In most of the cases, solid-state fermentation (SSF) increased essential FAA content in lentils; however, some of the non-essential FAA content was reduced. SSF significantly increased GABA concentration in lentils and milling process was a significant factor on GABA content of the samples (p ≤ 0.05). The main BA in lentils was spermidine, and SSF decreased their total BA content (34.8% on average in red lentils and 39.9% on average in green lentils). The main FA in lentils were linoleic and oleic. The main VC in lentils were hexanal, 1-hexanol, hexanoic acid, D-limonene and (E)-2-nonen-1-ol. Furthermore, most of the VC showed significant correlations with pH of lentil samples, LAB counts and FA content. Finally, the LAB strain used for fermentation and the milling process of lentils are significant factors for most of the analyzed parameters in lentil. Moreover, despite the higher GABA concentration found in green non-milled SSF lentils, application of combined milling and SSF is recommended because they showed the lowest BA content in addition to higher essential FAA and GABA concentrations.

Lactic Acid Bacteria as Potential Biocontrol Agents for Fusarium Head Blight Disease of Spring Barley.

Fusarium head blight (FHB) is a devastating disease encountered by spring-grown barley. Traditionally, synthetic chemicals have been used to control this disease on small grain cereals. A move toward biological control agents as part of sustainable agriculture is pertinent due to the evolutionary mechanisms employed by fungal diseases to circumvent current protection strategies. This study evaluated the effect of six lactic acid bacteria isolates on the development of FHB under in vitro and glasshouse conditions. The relative expression of Fusarium marker genes and transcription factors under Fusarium infection was examined. Dual-culture assays observed inhibition zones of up to 10 and 17% of total plate area for L. amylovorus FST 2.11 and L. brevis R2Δ, respectively. Detached leaf assays validated the antifungal activity and showed the potential of all test isolates to significantly inhibit sporulation of Fusarium culmorum and Fusarium graminearum strains. Spray inoculation of lactic acid bacteria to barley spikelets prior to Fusarium spore application significantly reduced disease severity for five candidates (P < 0.05) under glasshouse conditions. Mycotoxin analysis revealed the ability of L. amylovorus DSM20552 to significantly reduce deoxynivalenol content in spikelets (P < 0.05). A preliminary gene expression study showed the positive influence of lactic acid bacteria on the expression of important defense-related marker genes and transcription factors upon FHB. These results indicate the potential of lactic acid bacteria to be included as part of an integrated pest management strategy for the management of FHB disease. This strategy will reduce FHB severity and deoxynivalenol (DON) contamination of spring barley, leading to high acceptance in the grain market.

Influence of lactic acid bacteria on physicochemical indexes, sensory and flavor characteristics of fermented sea buckthorn juice

Sea buckthorn has been proved to be a good substrate for lactic acid bacteria (LAB), but the research on the fermentation of sea buckthorn juice (SBJ) by LAB is still rare. This study was designed to determine the performance of fermented SBJ (FSBJ) in four LAB and investigate the sensory aspects of FSBJ. The results showed that the utilization rates of reducing sugar, titratable acid, and malic acid of SBJ fermented by Lactobacillus casei (SBJLc) were the highest and that lactic acid content was the greatest. The organic acid compositions of the four kinds of FSBJs were also different. The viable counts of all FSBJs was greater than 7 log CFU/mL, and that the viable count of SBJ fermented by SBJLc was the highest. In this study, the Electronic tongue combined with Electronic nose was used for the first time to study SBJ. Results showed that compared with the control, the response value of Sourness was significantly increased, while Bitterness and Astringency were significantly decreased. There was a significant difference in four FSBJs. The results of the electronic nose showed that SBJ fermented by Lactobacillus plantarum LP56 (SBJLp) could be well identified by sensors sensitive to aromatic substances. The volatile compound contents before and after fermentation were significantly different, the highest being SBJLp. Finally, the results of sensory evaluation experiments showed that SBJLp was the most acceptable to consumers in terms of sensory evaluation.

Lactic acid bacteria starter in combination with sodium chloride controls pathogenic Escherichia coli (EPEC, ETEC, and EHEC) in kimchi

Kimchi is one of the primary sources of high sodium content in the Korean diet. Low-sodium kimchi is commercially manufactured to minimize the health effects of high salt. We investigated the influence of lactic acid bacteria (LAB) as starter culture in combination with 1% or 2.5% salt on the survival of pathogenic Escherichia coli and physicochemical properties of kimchi during fermentation at 10 °C and 25 °C. Among ten strains of LAB isolated from kimchi, Leuconostoc mesenteroides (KCTC 13374) and Lactobacillus plantarum (KCTC 33133) exhibited antimicrobial activities against pathogenic E. coli (EPEC, ETEC, and E. coli O157:H7) and strong tolerance to low pH (2 and 3) and 0.3% bile salts. Thus, L. mesenteroides and L. plantarum were used as starter cultures for kimchi that contained 1% and 2.5% salt. All pathogenic E. coli strains survived in kimchi regardless of starter cultures or salt concentration for over 15 days at 10 °C, but they died off within 4 days at 25 °C. Survival of pathogenic E. coli was better in naturally fermented kimchi (titratable acidity:0.65%) than kimchi fermented with starter cultures (titratable acidity:1.0%). At 10 °C, the average delta value of E. coli O157:H7 (16.15 d) was smaller than those of EPEC (20.76 d) and ETEC (20.20 d) in naturally fermented kimchi. Overall, survival ability of E. coli O157:H7 was lower than EPEC and ETEC, although differences were not significant. Reduced salt concentration from 2.5% to 1% in kimchi did not affect the growth of LAB and the fermentation period. Pathogenic E. coli died at a faster rate in kimchi fermented with starter cultures and 1% salt than in naturally fermented kimchi with 2.5% salt.

Dynamics of Active and Titratable Acidity in Bieno Cheese

Experimental research describes the autochthonous traditional production of bieno cheese and its importance in conditions of globalization and industrialization in food production. The purpose of this research was to present the technology of three varieties of indigenous bieno cheeses (A, B, and C) in the Mariovo region, in the Republic of North Macedonia, and to monitor the dynamics of active and titratable acidity as important parameters in the technological process. During the research, the changes of these parameters of the three variants (A, B, and C) of cheeses in different stages of maturation were monitored (in curd, cheese after dry ripening, cheese after dry salting, the 20th day of ripening, and the 45th day of ripening). The rheological properties of the cheese are greatly influenced by the active (pH) and titratable (0SH) acidity. During the ripening of cheeses under the influence of lactic acid bacteria, the biggest changes occur in lactose, which transforms lactose into lactic acid and other organic acids that play an important role in the formation of sensory and rheological characteristics of cheeses. The displayed technological parameters are of great importance for the bieno cheeses and can serve in the direction of standardization of this cheese and its protection with a designation of origin or a geographical indication based on the source technology. Keywords: Bieno cheese, technology, active and titratable acidity.

Effect of lactic acid bacteria on mackerel (Pneumatophorus japonicus) seasoning quality and flavor during fermentation

This study assessed the influence of lactic acid bacteria (LAB) on the physicochemical characteristics of low-salt fermented Mackerel (Pneumatophorus japonicus) seasonings. Key volatile compounds and their formation pathways were analyzed. The flavor of LAB-fermented mackerel seasonings was superior to that of traditional fish sauce, with sensory evaluation scores of 6.5–7.9 and 6.4, respectively. However, the reason for the improved flavor after inoculation with LAB was unclear. Latilactobacillus sakei, (LS1), which was selected from fermented aquatic products, and 2 other common LAB (Lactiplantibacillus plantarum LP1 and Weissella cibaria WC1) were used as starters to investigate the influence of LAB on the formation of flavor substances in mackerel seasonings during fermentation. Aroma extract dilution analysis was used to preliminarily identify the odor-active compounds of the mackerel seasonings. Key odor-active compound quantitation and odor activity value (OAV) calculations were performed to further detect the components impacting the overall odor profile (OAV ≥ 1). These compounds included (E)-2-nonenal, (E,E)-2,4-decadienal, (E)-2-decenal, 1-octen-3-ol, and (E,E)-2,4-nonadienal. Furthermore, the correlations between odor-active compounds and sensory characteristics were evaluated by partial least squares regression (PLSR). The results suggested that 2,4-nonadienal, furfural, (E)-2-octenal, hexanal, and (E)-2-decenal had a positive correlation with pleasant flavor attributes, and LS1 was more conducive to the formation of these compounds than LP1 and WC1.

Влияние молочнокислых бактерий на качество и хранимоспособность сливок-сырья для продуктов маслоделия

Влияние молочнокислых бактерий на качество и хранимоспособность сливок-сырья для продуктов маслоделия

Антагонистическое действие молочнокислых бактерий и их консорциума с дрожжами на патогенные микроорганизмы

Abstract-A comparative study of the influence of lactic acid bacteria and their consortium with yeast on the growth of pathogenic bacteria and fungi has been carried out. It was revealed that the proposed composition of probiotic microbial species has fungistatic activity and strongly pronounced fungicidal activity against mold micromycetes and phytopathogenic fungi, respectively. The consortium effectiveness in suppressing both bacteria and filamentous fungi exceeds that of the corresponding monocultures. Analysis of wheat seeds for the presence of fungi by germination in a humid chamber and on nutrient media showed that the association of a 3-day culture of lactic acid bacteria and yeast at a dilution of 1:100 significantly reduced the infection of plant material. The ability to suppress opportunistic and phytopathogenic microorganisms is explained by the presence in the microbial consortium culture liquid of metabolites with bactericidal and fungicidal properties: squalene, dimethyl fumarate, capric acid, lactic acid, acetic acid, caprylic acid, fumaric acid, butyric acid, decanol, butanol, pentanol and β-phenylethanol. Key words: lactic acid bacteria, consortium of microorganisms, antagonistic activity, phytopathogens, bacteria pathogenic for humans

Raw donkey milk versus raw cow's milk. A preliminary study to compare the growth of Listeria monocytogenes and Staphylococcus aureus.

Gram-positive foodborne pathogens such as Listeria monocytogenes and Staphylococcus aureus can grow in a wide variety of foods, including raw milk. The aim of the study was to compare the growth of L. monocytogenes and S. aureus inoculated in donkey and cow samples of raw milk during a storage time of 11 days at 8 °C. Moreover, the study aimed to evaluate the influence of lactic acid bacteria (LAB) content on the growth of the two microbiological populations considered. LAB content was lower in raw donkey milk than in raw cow's milk during the entire analyses; on the other hand, pH levels were higher in the donkey milk rather than in the cow's milk, although both values showed a decrease at the day 11. S. aureus showed no significant differences in the two types of milk. From day 0 to 11, L. monocytogenes increased from 3.68 ± 0.02 log CFU/mL to 6.31 ± 0.07 log CFU/mL and from 3.64 ± 0.04 log CFU/mL to 4.59 ± 1.04 log CFU/mL, in donkey milk and in cow's milk, respectively. Our results showed that donkey milk is a more favourable matrix to support the growth of L. monocytogenes than cow's milk.

Physicochemical, rheological and digestive characteristics of soy protein isolate gel induced by lactic acid bacteria

Influence of lactic acid bacteria (LAB) on gel characteristics of fermentation-induced soy protein isolate (SPI) gel, including hardness, water holding capacity (WHC), pH, solubility, turbidity, particle size, zeta potential, surface hydrophobicity, free sulfhydryl, microstructure, rheological properties and in vitro gastrointestinal digestion was evaluated. First, fermentation increased the turbidity and average particle size, which was supported by a lower degree of solubility and zeta potential absolute value. The surface hydrophobicity was reduced after lactic acid bacteria fermentation, and a similar phenomenon occurred on the free sulfhydryl groups. It was found that fermentation resulted in SPI denaturation, structural changes, and aggregates formation, which were the foundation of gel formation. Subsequently, fermentation-induced SPI gels depended on the lactic acid bacteria used for fermentation, showing the specificity of gel characteristics. Among them, Lactobacillus acidophilus (L. acidophilus), Lactobacillus plantarum (L. plantarum), Lactobacillus casei (L. casei), and mixed strains of Lactobacillus bulgaricus (L. bulgaricus), and Streptococcus thermophilus (S. thermophilus) (1:1) exhibited the high coagulation ability, which could enhance the hardness and water holding capacity of the gels. L. plantarum-G had the lowest solubility and free sulfhydryl content and the highest turbidity, particle size, and zeta potential. Scanning electron microscope (SEM) results showed that L. casei-G and L. plantarum-G exhibited a dense and uniform three-dimensional network. The rheological properties showed that the earliest gel point and the highest storage modulus (G′) and loss modulus (G″) were acquired by L. casei-G, whereas the G′ curve of L. lactis-G was still in the growth stage, and no platform was found in the growth curve. The ability of L. lactis to form gels was weaker. At the same time, the G′ and G″ of all LAB fermentation-induced gels showed strong frequency dependency. Digestion of gels was much slower than that of the soy protein isolate solution. The peptide content increased significantly during the digestion process, but, the average particle size decreased (p < 0.05). The digestion could be influenced by the microstructure of the fermentation-induced gels caused by the immobilisation of the protein in the network and the steric obstruction, including the entrance of the enzyme and release of the peptide. The current work has explored the potential of applying starters in fermented gels by performing texture, aggregation, rheological and digestive properties analysis. Our objective is to identify cultures that are suitable for developing novel functional fermentation-induced gels.

Production of Nigerian Yoghurt Using Lactic Acid Bacteria as Starter Cultures

Aim: This work was carried out to investigate the influence of Lactic Acid Bacteria (LAB) on organoleptic quality and proximate composition of yoghurt, and viability of starter cultures in yoghurt.&#x0D; Methods: The LAB starter cultures were selected based on their ability to produce diacetyl and lactic acid.&#x0D; Results: Lactobacillus caseiN1 produced the highest quantity (2.72 g/L) of diacetyl at 48 hrs of incubation while Pediococcus acidilacticiG1 had the lowest amount (0.50 g/L). The pH of produced yoghurt ranged between 4.40 and 5.58 while the corresponding lactic acid contents ranged between 0.70 and 0.96 g/L. Yoghurt produced with cow milk inoculated with L. PlantarumN24 and L. BrevisN10 had the lowest pH (4.40) at significant level of P≤0.05. Yoghurt with mixed culture of L. PlantarumN24 and L. PlantarumN17 had the highest protein content (5.13%) while spontaneous fermentation (control) produced the least (0.48%). Yoghurt produced from cow milk inoculated with L. PlantarumN24 and L. PlantarumN17 was rated best with overall acceptability (9.0) during first day of storage while the commercial yoghurt (5.8) and spontaneous fermentation (6.8) had least overall acceptability at P≤0.05.&#x0D; Conclusion: Yoghurt samples stored in refrigerator had more viable LAB counts for a period of 21 days while the samples stored at room temperature had a day count except for yoghurt produced with cow milk inoculated with L. plantarumN24 which retained its viability at the second day. The yoghurt produced with selected LAB starters are better than commercial yoghurt in terms of sensory properties, proximate composition, pH and viability.

The Influence of Lactic Acid Bacteria from Xinjiang Traditional Fermented Yogurt on Antioxidation of Geniposide in vitro

To investigate the influence of lactic acid bacteria on the antioxidant effect of geniposide in vitro, seven strains of lactic acid bacteria were isolated from natural fermented yoghurt from Xinjiang, China. Lactic acid bacteria, geniposide and their mixtures were used separately to evaluate the antioxidant effect through detecting the scavenging activity of 1,1-diphenyl-2-trinitrophenylhydrazine (DPPH), Hydroxyl free radicals and 2, 2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid)(ABTS). The results showed that, compared with the group that geniposide separately used, the strains numbered x70-1, x70-2, x70-3, x70-4 and x70-5, combined with geniposide had more remarkable antioxidant effect, while the other two strains (numbered x43-2 and x43-3)combined with geniposide showed low oxidation resistance. These results may provide a potential method to promote antioxidant effect of geniposide.

Functional properties of lactic acid bacteria in fermented fruit and vegetable juices: a systematic literature review

The development of non-dairy fermented juices based on fruits and vegetables is favoured by multiple factors, such as greater consumer awareness of health-related properties of fermented foods, a growing number of lactose intolerance cases, and an increasing popularity of food trends like veganism. Therefore, the scientific community’s interest in the design of lactic acid fermented juices and determining their functional features has increased over the past 10 years. The aim of this study was to review the latest reports concerning the influence of lactic acid bacteria on fermented fruit and vegetable juices, using the SALSA (search, appraisal, synthesis, analysis) systematic literature review framework. This approach allowed for gathering 42 most essential publications, which have undergone detailed analysis. Most studies focused on the functional properties of fruit juices (e.g. cashew apple or pomegranate juice), while vegetable (e.g. tomato or carrot juice) and mixed juices (e.g. apple–carrot juice) were studied in a lesser extent. Recent studies indicate a great commercialization potential of non-dairy fermented juices due to their adequate probiotic delivery; strong antimicrobial and antioxidant properties; high content of vitamins, total phenols, amino acids, exopolysaccharides; unique sensory characteristics as well as their anticancer, antidiabetic, and anti-inflammatory activities. All these advantages are strictly associated with the use of particular bacterial strain (mostly strains of L. plantarum) and plant matrices.

Study of the Influence of Lactic Acid Bacteria on Hydrolytic and Oxidation Processes in Stuffed Meat

Study of the Influence of Lactic Acid Bacteria on Hydrolytic and Oxidation Processes in Stuffed Meat

Influence of lactic acid bacteria, cellulase, cellulase-producing Bacillus pumilus and their combinations on alfalfa silage quality

This study assessed the effects of lactic acid bacteria (LAB), cellulase, cellulase-producing Bacillus pumilus and their combinations on the fermentation characteristics, chemical composition, bacterial community and in vitro digestibility of alfalfa silage. A completely randomized design involving a 8 (silage additives)×3 or 2 (silage days) factorial arrangement of treatments was adopted in the present study. The 8 silage additive treatments were: untreated alfalfa (control); two commercial additives (GFJ and Chikuso-1); an originally selected LAB (Lactobacillus plantarum a214) isolated from alfalfa silage; a cellulase-producing Bacillus (CB) isolated from fresh alfalfa; cellulase (C); and the combined additives (a214+C and a214+CB). Silage fermentation characteristics, chemical composition and microorganism populations were analysed after 30, 60 and 65 days (60 days followed by exposure to air for five additional days). In vitro digestibility was analysed for 30 and 60 days. Compared with the other treatments, selected LAB a214, a214 combined with either C or CB, and Chikuso-1 had the decreased (P<0.001) pH and increased (P<0.001) lactic acid concentrations during the ensiling process, and there were no differences (P>0.05) among them. Fiber degradation was not significant (P≥0.054) in any C or CB treatments. The a214 treatment showed the highest (P=0.009) in vitro digestibility of dry matter (595.0 g kg−1 DM) after ensiling and the highest abundance of Lactobacillus (69.42 and 79.81%, respectively) on days 60 and 65, compared to all of other treatments. Overall, the silage quality of alfalfa was improved with the addition of a214, which indicates its potential as an alfalfa silage inoculant.

Influence of lactic acid bacteria on stereoselective degradation of theta-cypermethrin.

The purpose of this study was to investigate the influence of four kinds of Lactic acid bacteria (LAB) on stereoselective degradation of theta-cypermethrin (CYP), including Lactobacillus plantarum, Lactobacillus casei, Lactobacillus delbrueckii, and Streptococcus thermophilus. An effective analytical method for (±)-theta-CYP in medium was developed by high-performance liquid chromatography with cellulose tris-(3,5-dimethylphenylcarbamate) chiral stationary phase. theta-Cypermethrin was spiked to LAB medium with different inoculation rates and sampled at 0, 2, 8, 24, 36, 48, 72, 120, 168, and 240hours. The results showed that LAB influenced the half-lives and enantiomer fractions of theta-CYP enantiomers, which lead a closer degradation rate between the 2 stereoisomers, and no obvious difference was found among 4 LABs. Besides, the stereoselective degradation of theta-CYP was closely related to pH. The lower the pH (pH of 3, 5, 7, and 9), the lower the enantiomer fraction (from 4.88 to 6.69). At pH of 3, 7, and 9, significant differences of half-lives between enantiomers were observed. (-)-theta-Cypermethrin decreased faster than (+)-theta-CYP under pH of 3, while opposite results were indicated under pH of 7 and 9. Moreover, the acidic condition contributed to the higher chiral configuration stability of (±)-theta-CYP. (+)-Enantiomer was influenced by pH in a greater degree than (-)-enantiomer.

Influence of lactic acid bacteria strains on ester concentrations in red wines: Specific impact on branched hydroxylated compounds

This research investigated the influence of lactic acid bacteria (LAB) strains on ester levels in Bordeaux red wines. These wines were made in five Bordeaux areas in two vintages, using three yeast strains. Malolactic fermentation (MLF) was carried out using industrial starters or indigenous strains, each in triplicate. Ester concentrations were determined by liquid-liquid-extraction- or HS-SPME-GC/MS at various stages in the winemaking process. The levels of most compounds were slightly impacted by LAB, depending on grape variety. Nevertheless, branched hydroxylated esters, such as ethyl 2-hydroxy-3-methylbutanoate and ethyl 2-hydroxy-4-methylpentanoate were the only compounds to be strongly influenced by the bacteria strain, regardless of matrix composition or the yeasts used for alcoholic fermentation. Moreover, the effect observed after MLF persisted over time, for at least 12months. These esters are apparently important markers of LAB esterase activity. To our knowledge, this was the first time they had been identified in this role.