Selection of potential probiotic lactic acid bacteria from fermented olives by in vitro tests

The present study aims to evaluate the probiotic potential of lactic acid bacteria (LAB) isolated from naturally fermented olives and select candidates to be used as probiotic starters for the improvement of the traditional fermentation process and the production of newly added value functional foods. Seventy one (71) lactic acid bacterial strains (17 Leuconostoc mesenteroides, 1 Ln. pseudomesenteroides, 13 Lactobacillus plantarum, 37 Lb. pentosus, 1 Lb. paraplantarum, and 2 Lb. paracasei subsp. paracasei) isolated from table olives were screened for their probiotic potential. Lb. rhamnosus GG and Lb. casei Shirota were used as reference strains. The in vitro tests included survival in simulated gastrointestinal tract conditions, antimicrobial activity (against Listeria monocytogenes, Salmonella Enteritidis, Escherichia coli O157:H7), Caco-2 surface adhesion, resistance to 9 antibiotics and haemolytic activity. Three (3) Lb. pentosus, 4 Lb. plantarum and 2 Lb. paracasei subsp. paracasei strains demonstrated the highest final population (>8 log cfu/ml) after 3 h of exposure at low pH. The majority of the tested strains were resistant to bile salts even after 4 h of exposure, while 5 Lb. plantarum and 7 Lb. pentosus strains exhibited partial bile salt hydrolase activity. None of the strains inhibited the growth of the pathogens tested. Variable efficiency to adhere to Caco-2 cells was observed. This was the same regarding strains' susceptibility towards different antibiotics. None of the strains exhibited β-haemolytic activity. As a whole, 4 strains of Lb. pentosus, 3 strains of Lb. plantarum and 2 strains of Lb. paracasei subsp. paracasei were found to possess desirable in vitro probiotic properties similar to or even better than the reference probiotic strains Lb. casei Shirota and Lb. rhamnosus GG. These strains are good candidates for further investigation both with in vivo studies to elucidate their potential health benefits and in olive fermentation processes to assess their technological performance as novel probiotic starters.     

Diversity of lactic acid bacteria associated with traditional fermented dairy products in Mongolia

Spontaneous milk fermentation has a long history in Mongolia, and beneficial microorganisms have been handed down from one generation to the next for use in fermented dairy products. The objective of this study was to investigate the diversity of lactic acid bacteria (LAB) communities in fermented yak, mare, goat, and cow milk products by analyzing 189 samples collected from 13 different regions in Mongolia. The LAB counts in these samples varied from 3.41 to 9.03 log cfu/mL. Fermented yak and mare milks had almost identical mean numbers of LAB, which were significantly higher than those in fermented goat milk but slightly lower than those in fermented cow milk. In total, 668 isolates were obtained from these samples using de Man, Rogosa, and Sharpe agar and M17 agar. Each isolate was considered to be presumptive LAB based on gram-positive and catalase-negative properties, and was identified at the species level by 16S rRNA gene sequencing, multiplex PCR assay, and restriction fragment length polymorphism analysis. All isolates from Mongolian dairy products were accurately identified as Enterococcus faecalis (1 strain), Enterococcus durans (3 strains), Lactobacillus brevis (3 strains), Lactobacillus buchneri (2 strains), Lactobacillus casei (16 strains), Lactobacillus delbrueckii ssp. bulgaricus (142 strains), Lactobacillus diolivorans (17 strains), Lactobacillus fermentum (42 strains), Lactobacillus helveticus (183 strains), Lactobacillus kefiri (6 strains), Lactobacillus plantarum ssp. plantarum (7 strains), Lactococcus lactis ssp. lactis (7 strains), Leuconostoc lactis (22 strains), Leuconostoc mesenteroides (21 strains), Streptococcus thermophilus (195 strains), and Weissella cibaria (1 strain). The predominant LAB were Strep. thermophilus and Lb. helveticus, which were isolated from all sampling sites. The results demonstrate that traditional fermented dairy products from different regions of Mongolia have complex compositions of LAB species. Such diversity of LAB provides useful information for further studies of probiotic strain selection and starter culture design, with regard to the industrial production of traditional fermented milk.     

The microbial diversity of water kefir

The microbial diversity of water kefir, made from a mixture of water, dried figs, a slice of lemon and sucrose was studied. The microbial consortia residing in the granules of three water kefirs of different origins were analyzed. A collection of 453 bacterial isolates was obtained on different selective/differential media. Bacterial isolates were grouped with randomly amplified polymorphic DNA (RAPD)-PCR analyses. One representative of each RAPD genotype was identified by comparative 16S rDNA gene sequencing. The predominant genus in water kefirs I and II was Lactobacillus, which accounted for 82.1% in water kefir I and 72.1% in water kefir II of the bacterial isolates. The most abundant species in water kefirs I and II were Lactobacillus hordei and Lb. nagelii followed by considerably lower numbers of Lb. casei. Other lactic acid bacteria (LAB) were identified as Leuconostoc mesenteroides and Lc. citreum in all three water kefirs. The most abundant species in water kefir III was Lc. mesenteroides (28%) and Lc. citreum (24.3%). A total of 57 LAB belonging to the species of Lb. casei, Lb. hordei, Lb. nagelii, Lb. hilgardii and Lc. mesenteroides were able to produce exopolysacchrides from sucrose. Non LABs were identified as Acetobacter fabarum and Ac. orientalis. The Acetobacter species were more prevalent in consortium III. Cluster analyses of RAPD-PCR patterns revealed an interspecies diversity among the Lactobacillus and Acetobacter strains. Aditionally, Saccharomyces cerevisiae, Lachancea fermentati, Hanseniaospora valbyensis and Zygotorulaspora florentina were isolated and identified by comparison of partial 26S rDNA sequences and FTIR spectroscopy.     

Genotypic and technological diversity of Leuconostoc mesenteroides and Lactobacillus paracasei subsp. paracasei strains for use as adjunct starter cultures in Pecorino di Filiano cheese

Seventeen Leuconostoc mesenteroides and 33 Lactobacillus paracasei subsp. paracasei from traditional Pecorino di Filiano cheese were tested for their potential use as adjunct starters, and a study of their genetic variability was carried out. Forty one per cent (41%) of Leu. mesenteroides and 46% of Lb. paracasei subsp. paracasei showed medium–high proteolytic activity, while high lipolytic activity was detected in 18% of Lb. paracasei subsp. paracasei. The aminopeptidase activity of Lb. paracasei subsp. paracasei was higher than that of Leu. mesenteroides. Strain diversity by RAPD analysis showed a high degree of heterogeneity. This study identified strains with unusual properties that could be good candidates as adjuncts in a starter to manufacture PF cheese.     

Diversity and probiotic potentials of lactic acid bacteria isolated from gilaburu,a traditional Turkish fermented European cranberrybush (Viburnum opulus L.) fruit drink

The aim of the present study was to characterize lactic acid bacteria (LAB) strains isolated from traditional fermented gilaburu fruit juice and their probiotic potential. The LAB counts of the fermented gilaburu fruit juice were in the range of 3.92–8.30 log cfu/g. Total of 332 isolates belonging to Lactobacillus and Leuconostoc species were characterized from traditional fermented gilaburu juice by genotypic methods. It was also determined that the major LAB strains belong to Lactobacillus plantarum (173 isolates), Lactobacillus casei (52 isolates) and Lactobacillus brevis (24 isolates), while Lactobacillus buchneri, Lactobacillus parabuchneri, Lactobacillus pantheris, Leuconostoc pseudomesenteroides and Lactobacillus harbinensis were the least in isolated LAB strains. In terms of the probiotic potentials, Lb. plantarum strains were able to grow at pH 2.5, but 3 of Lb. casei strains, one of each Lb. brevis and Lb. buchneri strains could not grow at the same pH. All selected LAB stains were resistant to bile salt at ≤ 0.3% concentration. While all the LAB species grew at 15 °C, two Lactobacillus hordei strains could also grow at 45 °C. The highest cell hydrophobicity degrees were for Lb. casei (G20a) and Lb. plantarum (G19e) as 87.5 and 86.0%, respectively. Listeria monocytogenes and Bacillus cereus were the most sensitive bacteria against the selected LAB strains, while Escherichia coli and Staphylococcus aureus were the most resistant. Again all the isolated LAB species were resistant to three antibiotics; kanamycin, streptomycin and vancomycin. Characterization and probiotic potentials of the LAB isolated from fermented gilaburu (Viburnum opulus) juice were studied first time, and further research needs to be done on their behaviors in similar food formulations as a probiotic.     

Lactic acid bacteria isolated from a hand-made blue cheese

Nearly 500 strains isolated from different media used to study the aerobic mesophilic and lactic acid flora of Valdeón cheese (a Spanish hand-made blue cheese) have been identified. Nearly 95% of aerobic mesophiles were lactic acid bacteria (LAB). From these, Enterococcus (40·4%) and Lactococcus (42·2%) were the dominant genera, with Lactobacillus (4·1%) and Leuconostoc (5·0%) being also found. The selectivity of the other media used was variable and this is discussed. Several species of Enterococcus were isolated from our samples (Ent. avium, Ent. faecium and Ent. durans), although one was outstanding (Ent. faecalis, 24·7% of the total of strains identified). The dominating LAB species found was Lact. lactis subsp. lactis (31·1%). Other LAB identified were Lact. raffinolactis, Lb. plantarum, Lb. casei, Leuc. mesenteroides subsp. dextranicum, Leuc. mesenteroides subsp. mesenteroides and Leuc. paramesenteroides. The evolution of the lactic-acid flora found during the manufacture and ripening of this variety of cheese showed a pattern marked by the dominance of lactococci and enterococci during the first stages and the substitution of lactococci by lactobacilli and leuconostoc from drying onwards which would be, along with enterococci, the major genera found in the cheese at the stage of consumption. From a technological point of view, the quantitative importance of certain species such as Lact. lactis and Ent. faecalis, as well as the presence of others, i.e. Lb. plantarum and Leuc. mesenteroides, suggest their possible use as starters in the industrial manufacture of this variety.     

A review on traditional Turkish fermented non-alcoholic beverages: Microbiota,fermentation process and quality characteristics

Shalgam juice, hardaliye, boza, ayran (yoghurt drink) and kefir are the most known traditional Turkish fermented non-alcoholic beverages. The first three are obtained from vegetables, fruits and cereals, and the last two ones are made of milk. Shalgam juice, hardaliye and ayran are produced by lactic acid fermentation. Their microbiota is mainly composed of lactic acid bacteria (LAB). Lactobacillus plantarum, Lactobacillus brevis and Lactobacillus paracasei subsp. paracasei in shalgam fermentation and L. paracasei subsp. paracasei and Lactobacillus casei subsp. pseudoplantarum in hardaliye fermentation are predominant. Ayran is traditionally prepared by mixing yoghurt with water and salt. Yoghurt starter cultures are used in industrial ayran production. On the other hand, both alcohol and lactic acid fermentation occur in boza and kefir. Boza is prepared by using a mixture of maize, wheat and rice or their flours and water. Generally previously produced boza or sourdough/yoghurt are used as starter culture which is rich in Lactobacillus spp. and yeasts. Kefir is prepared by inoculation of raw milk with kefir grains which consists of different species of yeasts, LAB, acetic acid bacteria in a protein and polysaccharide matrix. The microbiota of boza and kefir is affected from raw materials, the origin and the production methods.     

Survival of probiotic adjunct cultures in cheese and challenges in their enumeration using selective media

Various selective media for enumerating probiotic and cheese cultures were screened, with 6 media then used to study survival of probiotic bacteria in full-fat and low-fat Cheddar cheese. Commercial strains of Lactobacillus acidophilus, Lactobacillus casei, Lactobacillus paracasei, or Bifidobacterium lactis were added as probiotic adjuncts. The selective media, designed to promote growth of certain lactic acid bacteria (LAB) over others or to differentiate between LAB, were used to detect individual LAB types during cheese storage. Commercial strains of Lactococcus, Lactobacillus, and Bifidobacterium spp. were initially screened on the 6 selective media along with nonstarter LAB (NSLAB) isolates. The microbial flora of the cheeses was analyzed during 9 mo of storage at 6°C. Many NSLAB were able to grow on media presumed selective for Lactococcus, Bifidobacterium spp., or Lb. acidophilus, which became apparent after 90 d of cheese storage, Between 90 and 120 d of storage, bacterial counts changed on media selective for Bifidobacterium spp., suggesting growth of NSLAB. Appearance of NSLAB on Lb. casei selective media [de man, Rogosa, and Sharpe (MRS) + vancomycin] occurred sooner (30 d) in low-fat cheese than in full-fat control cheeses. Differentiation between NSLAB and Lactococcus was achieved by counting after 18 to 24 h when the NSLAB colonies were only pinpoint in size. Growth of NSLAB on the various selective media during aging means that probiotic adjunct cultures added during cheesemaking can only be enumerated with confidence on selective media for up to 3 or 4 mo. After this time, growth of NSLAB obfuscates enumeration of probiotic adjuncts. When adjunct Lb. casei or Lb. paracasei cultures are added during cheesemaking, they appear to remain at high numbers for a long time (9 mo) when counted on MRS + vancomycin medium, but a reasonable probability exists that they have been overtaken by NSLAB, which also grow readily on this medium. Enumeration using multiple selective media can provide insight into whether it is the actual adjunct culture or a NSLAB strain that is being enumerated.     

A factory-scale application of secondary adjunct cultures selected from lactic acid bacteria during Puzzone di Moena cheese ripening

The lactic acid populations of 2 seasonal Puzzone di Moena cheeses made from winter and summer raw cow's milk were characterized at different ripening times. Lactic acid bacteria (LAB) were isolated on selective media and subjected to genetic typing and identification. The species most frequently found during ripening were Lactobacillus paracasei ssp. paracasei, Lactobacillus plantarum, and Pediococcus pentosaceus. The different strains recognized by random amplification of polymorphic DNA-PCR were characterized for their acidifying and proteolytic activities to select nonstarter LAB to be used as secondary adjunct cultures (SAC). For each of the 3 above species, a strain showing weak acidification and high proteolytic capacity was selected. The 3 strains (Lb. paracasei ssp. paracasei P397, Lb. plantarum P399, and P. pentosaceus P41) constituted a mixed SAC used at 2 levels of concentration (10³ and 10⁴ cfu/mL) in experimental cheese making at dairy factory-scale. The analysis of volatile organic compounds as well as sensory analyses showed that the preferred level of SAC inoculation was 10³ cfu/mL.     

Proteolytic pattern and organic acid profiles of probiotic Cheddar cheese as influenced by probiotic strains of Lactobacillus acidophilus,Lb. paracasei,Lb. casei or Bifidobacterium sp.

Cheddar cheeses were produced with starter lactococci and Bifidobacterium longum 1941, B. lactis LAFTI^® B94, Lactobacillus casei 279, Lb. paracasei LAFTI^® L26, Lb. acidophilus 4962 or Lb. acidophilus LAFTI^® L10 to study the survival of the probiotic bacteria and the influence of these organisms on proteolytic patterns and production of organic acid during ripening period of 6 months at 4 °C. All probiotic adjuncts survived the manufacturing process of Cheddar cheese at high levels without alteration to the cheese-making process. After 6 months of ripening, cheeses maintained the level of probiotic organisms at >8.0 log₁₀ cfu g⁻¹ with minimal effect on moisture, fat, protein and salt content. Acetic acid concentration was higher in cheeses with B. longum 1941, B. lactis LAFTI^® B94, Lb. casei 279 and Lb. paracasei LAFTI^® L26. Each probiotic organism influenced the proteolytic pattern of Cheddar cheese in different ways. Lb. casei 279 and Lb. paracasei LAFTI^® L26 showed higher hydrolysis of casein. Higher concentrations of free amino acids (FAAs) were found in all probiotic cheeses. Although Bifidobacterium sp. was found to be weakly proteolytic, cheeses with the addition of those strains had highest concentration of FAAs. These data thus suggested that Lb. acidophilus 4962, Lb. casei 279, B. longum 1941, Lb. acidophilus LAFTI^® L10, Lb. paracasei LAFTI^® L26 and B. lactis LAFTI^® B94 can be applied successfully in Cheddar cheese.     

Peptide hydrolase system of lactic acid bacteria isolated from Serra da Estrela cheese

Lactobacillus paracasei subsp. paracasei ESB 230, Leuconostoc mesenteroides subsp. mesenteroides ESB 136, Lactococcus lactis subsp. lactis ESB 117 and Enterococcus faecium ESB 50, previously isolated from certified Serra da Estrela cheeses, were tested for their aminopeptidase, dipeptidyl aminopeptidase, endopeptidase, dipeptidase and carboxypeptidase activities. The crude cell-free extracts (CFE) of Lb. paracasei ESB 230 exhibited the highest aminopeptidase activity, followed by CFE of Leuc. mesenteroides ESB 136 and, at last, by CFE of L. lactis ESB 117; the aminopeptidase activity in CFE of Ent. faecium was practically non-existent. The four CFE studied also showed appreciable carboxypeptidase activities, although these were lower than their dipeptidase counterparts; in addition, their dipeptidyl aminopeptidase and endopeptidase activities were lower than their aminopeptidase activities. Dipeptides consisting of hydrophobic amino acid residues (i.e. leucine, methionine and phenylalanine) were more rapidly attacked by all CFE than those with hydrophilic amino acid residues. The peptide hydrolase system of CFE of Lb. paracasei ESB 230 was qualitatively quite similar to, but quantitatively more active than that of CFE of Leuc. mesenteroides ESB 136 (except for the endopeptidase); additionally, the CFE of L. lactis ESB 117 and of Ent. faecium ESB 50 were quite distinct from each other, and from the other two CFE tested.     

Angiotensin I converting enzyme (ACE) inhibitory activity and antihypertensive effect of fermented milk

Milk was fermented with a total of 25 lactic acid bacteria to assay in vitro inhibitory activity towards angiotensin I converting enzyme (ACE). The tested strains belonged to Lactobacillus acidophilus, Lactobacillus casei, Lacobacillus helveticus, Lactobacillus jensenii, Lactobacillus reuteri, Lactobacillus rhamnosus, Lactococcus lactis ssp. lactis, Lactococcus. raffinolactis and Leuconostoc mesenteroides ssp. cremoris. The ACE inhibitory potencies of theses strains varied and seven of them showing the highest ACE inhibitory activity were selected for further studies. The development of ACE inhibitory activity during fermentation correlated with degree of hydrolysis. Modification of fermentation conditions or pH control did not affect the ACE inhibitory activity. ACE inhibitory compounds from Lb. jensenii fermented milk were isolated by reversed phase HPLC and identified by MS-analysis and amino acid sequencing. The active compounds were peptides from β-casein. The milk fermented with Lb. jensenii caused a transient reduction of blood pressure in spontaneously hypertensive rats.     

Lactic acid bacteria population dynamics during minced beef storage under aerobic or modified atmosphere packaging conditions

A total of 266 lactic acid bacteria (LAB) have been isolated from minced beef stored at 0, 5, 10 and 15 °C aerobically and under modified atmosphere packaging consisting of 40% CO₂–30% O₂–30% N₂ in the presence MAP (+) and absence MAP (−) of oregano essential oil. Sequencing of their 16S rRNA gene along with presence of the katA gene demonstrated dominance of the LAB microbiota by Leuconostoc spp. during aerobic storage at 5, 10 and 15 °C, as well as during MAP (−) and MAP (+) storage at 10 and 15 °C; Lactobacillus sakei prevailed during aerobic storage at 0 °C, as well as at MAP (−) and MAP (+) storage at 0 and 5 °C. The sporadic presence of other species such as Leuconostoc mesenteroides, Weisella viridescens, Lactobacillus casei and Lactobacillus curvatus has also been determined. Pulsed-Field Gel Electrophoresis of high molecular weight genomic DNA revealed the dynamics of the isolated LAB strains. Prevalence of Leuconostoc spp. was attributed to one strain only. On the other hand, packaging conditions affected Lb. sakei strain spoilage dynamics.     

Variability of the species and strain phenotype composition of the non-starter lactic acid bacterial population of cheddar cheese manufactured in a commercial creamery

The non-starter lactic acid bacteria (NSLAB) present in cheddar cheese manufactured in a commercial creamery was monitored phenotypically to the strain level over a period of 12 months to examine the effects of maturity status and manufacturing practices on the composition of the population. Five Lactobacillus spp. and Leuconostoc lactis were identified among the 459 isolates selected. The predominant NSLAB, Lactobacillus paracasei and Lactobacillus brevis, were present in 59 and 31% of the cheeses examined and represented 52.7 and 25.8%, respectively, of the isolates identified. Among the NSLAB screened 71 different phenotypic profiles were identified and these included 26 biotypes of Lb. paracasei, 14 Lb. brevis, 11 Lactobacillus plantarum, 10 Lactobacillus curvatus and 7 Leuc. lactis. The average number of strains recovered from a cheese was 3.9±2.1 and ranged from 1 to 11. Although approximately 70% of the cheese samples were dominated by three or less strains the NSLAB populations were heterogeneous and the majority (61.5%) were comprised of four or more strains of one or more species. Only 30 of the biotypes were recovered from more than one population. There was no evidence for the repeated recurrence of any of the strains isolated although some of the Lb. paracasei strains were present intermittently in cheeses throughout the 12-month manufacturing period. Six Lb. brevis strains also recurred in some of the cheeses produced in a limited period during the autumn. Pronounced shifts in the species complement and strain profile occurred during maturation, while the average number of strains present in the cheese decreased with increasing maturity. Microbiological examination of the NSLAB population of cheese either produced in different vats during the same production run or manufactured in the same vat but in different production runs (vat fills) indicated that the number of strains common to paired samples from two vats or a single vat in successive production runs was only 1.7±1.4 and 1.5±1.2, respectively, and confirmed the inherent variability that exists, both within and between production runs, in the non-starter population of cheese manufactured in a commercial creamery.     

Whole cell biotransformation of major ginsenosides using Leuconostocs and Lactobacilli

Various strains of Lactobacillus and Leuconostoc species were evaluated to select the most promising strain to carry out transforming major ginsenosides into minor ginsenosides. Among the experimental lactic acid bacteria (LAB), Leuconostoc mesenteroides KFRI 690, Leuconostoc paramesenteroides KFRI 159, and Lactobacillus delbrueckii KCCM 35486 produced compound K from major ginsenosides precursors (Rb1, Rc, Rd, and F2). KFRI 690 showed the best transforming activity among them. Furthermore, these LABs could biotransform ginsenosides without disrupting the cell to release enzyme activity. The conversion ratio of Rb1 to compound K using KFRI 690 has been enhanced up to 97.8% by adding 2% sucrose into the culture medium. This is the first report on the production of compound K using whole cells of Leu. mesenteroides, Leu. paramesenteroides, and Lb. delbrueckii, which are food grade lactic acid bacteria.     

Studies on the storage stability of yayik butter

Yayik butter produced by churning of yoghurt is one of the popular traditional dairy products of Turkey. In this study, yayik butter was divided into four lots. Two lots were stored with a daylight lamp at 4 and 20°C (L4; L20) and the other two lots were stored at 4 and 20°C in dark (D4: control; D20) for 60 days. Then, the oxidative stability of yayik butter was evaluated. The end of self life was determined from sensory data. Generally acceptability was negatively correlated with peroxide value (PV), free fatty acid (FFA), thiobarbituric acid (TBA) and titratable acidity (TA). While general acceptability of control samples (D4) was between 8.26 ± 0.20 and 7.80 ± 0.10, those of L20 sample was lower than 3.00 (dislike moderately) on 60th day. As a result of decrease detected for sensory quality, the storage process was ended. L20 sample was evaluated as unacceptable on the 60th day and the evaluation result of this sample was accepted as the limiting value. The limiting values of TA, FFA and PV, TBA were determined as 0.14 ± 0.01%, 1.93 ± 0.11 mg KOH/g oil, 0.80 ± 0.007 meq O₂/g oil and 0.37 ± 0.02 mg malonaldehyde/kg butter in this yayik butter.     

Enzymatic activity of lactic acid bacteria (with antimicrobial properties) isolated from a traditional Spanish cheese

Twenty-four strains of lactic acid bacteria (LAB) isolated from a traditional Spanish cheese (Genestoso cheese) were evaluated for their enzymatic activities (acidifying and proteolytic abilities and carboxypeptidase, aminopeptidase, dipeptidase, caseinolytic and esterase activities), in order to select indigenous strains of technical interest for the manufacture of cheese. These strains were selected on the basis of their antimicrobial activity relative to five reference strains and were identified as Lactococcus lactis subsp. lactis (thirteen strains), Leuconostoc mesenteroides (two strains), Leuconostoc pseudomesenteroides (one strain), Lactobacillus paracasei (two strains), Lactobacillus plantarum (one strain) and Enterococcus faecalis (five strains).     

Analysis of volatile compounds produced by different species of lactobacilli in rye sourdough using multiple headspace extraction

Profiles of volatile organic compound (VOC) produced by nine individual lactic acid bacteria (LAB) during rye sourdough fermentation were compared by automated SPME and GC/MS‐Tof. The dough samples were inoculated with individual strains, placed inside the headspace vials and incubated during next 24 h. The production or loss of VOC‐s was followed by adsorbing volatiles onto 85‐m Car/PDMS fibre in every 4 h. Volatile profiles differed among LAB species and divided LAB into two main groups – hetero‐ and homofermentative. Hetrofermentative LAB (Lactobacillus brevis; Leuconostoc citreum; Lactobacillus vaginalis, Lactobacillus panis) showed high production of acetic acid, CO₂, ethanol, ethylacetate, producing also hexyl acetate, ethyl hexanoate and isopentyl acetate. Whereas homofermentative LAB species (Lactobacillus helveticus; Lactobacillus casei; Lactobacillus sakei; Lactobacillus curvatus) produced a considerable amount of 2,3‐butanedione. Production of l ‐leucine methyl ester was unique for Lb. sakei, Lb. casei and Lb. curvatus strains. Lb. helveticus was the only LAB that produced benzaldehyde.     

Technological characterization of lactic acid bacteria isolated from Armada cheese (a Spanish goats’ milk cheese)

Thirty-one strains of lactic acid bacteria (LAB) isolated from Armada cheese, Sobado variety, (eight strains of Lactococcus lactis subsp. lactis, four strains of Lactococcus lactis subsp. cremoris, two strains of L. lactis subsp. lactis biovar. diacetylactis, two strains of Leuconostoc mesenteroides subsp. mesenteroides, two strains of Leuconostoc mesenteroides subsp. dextranicum, five strains of Lactobacillus plantarum, six strains of Lactobacillus casei subsp. casei and two strains of Lactobacillus brevis) were screened for their acidifying capacity and enzymatic activity, that included the rapid API-ZYM system, the proteolytic activity, the amino-, di-, and carboxypeptidase activity and the caseinolytic activity. The strains of L. lactis subsp. lactis exhibited the highest acidifying and proteolytic activity. Lipase and esterase activity was practically non-existent for lactococci and lactobacilli; a certain esterase activity was observed among leuconostoc. The highest aminopeptidase activity was demonstrated by the cell-free extract (CFE) of some strains of L. plantarum, L. casei subsp. casei and L. mesenteroides subsp. dextranicum. The CFEs of L. lactis subsp. cremoris and L. lactis subsp. lactis possessed carboxypeptidase and dipeptidase activities, at levels depending on the strain. Appreciable caseinolytic activity was detected for the CFE of L. plantarum and those some lactococci.     

Textural properties of alginate–pectin beads and survivability of entrapped Lb. casei in simulated gastrointestinal conditions and in yoghurt

Lactobacillus casei was entrapped in beads made with sodium alginate (A), amidated low-methoxyl pectin (P), and blends of A–P (1:2, 1:4, 1:6 ratios) by the extrusion technique. Diameter, sphericity and textural properties of the beads and the survivability of entrapped Lb. casei in yoghurt and in simulated gastrointestinal conditions were determined. Entrapment efficiency of Lb. casei and diameter increased as the proportion of P and the total biopolymers concentration increased. Principal Component Analysis showed that the survivability of Lb. casei in yoghurt, and in simulated gastric juice, was positively correlated with the diameter and all the textural properties of the beads, while survivability after exposure to simulated gastric juice and bile salts was positively correlated with the sphericity of the beads. The beads made with A–P blends in 1:4 and 1:6 ratios provided a significant better protection to the entrapped Lb. casei under all conditions studied.