Mesophilic Starter Research Articles

A synergistic mixture of Origanum vulgare L. and Rosmarinus officinalis L. essential oils to preserve overall quality and control Escherichia coli O157:H7 in fresh cheese during storage

The effects of Origanum vulgare L. (OVEO) and Rosmarinus officinalis L. (ROEO) essential oils in combination on the counts of a mesophilic starter co-culture and Escherichia coli O157:H7 in cheese were determined during 21 days of refrigerated storage. Prevalent OVEO and ROEO terpenes, as well as the physicochemical and sensory aspects of cheese, were also determined. OVEO (0.03 μL/g) and ROEO (1.32 μL/g) did not decreased the counts of Lactococcus spp. while caused a decrease of approximately 3.0 log CFU/g in counts of E. coli O157:H7 in the earlier 12 days of storage. Terpenes of OVEO and/or ROEO decreased during storage in cheese and showed a correlation with decreases in E. coli O157:H7 counts. Eucalyptol, camphor, α-pinene and camphene were detected until 18 days of storage, and only eucalyptol, camphor and α-pinene were detected until 21 days of storage. OVEO and ROEO did not affect the physicochemical parameters and characterized the cheese by the refreshing aroma, mint-like flavor and softness. These results show the prevalent terpenes of OVEO and ROEO in fresh cheese during refrigerated storage and suggest their incorporation during manufacture as a strategy to preserve this product, with particular effects on the survival of E. coli O157: H7.

Resistance to bacteriocin Lcn972 improves oxygen tolerance of Lactococcus lactis IPLA947 without compromising its performance as a dairy starter

BackgroundLactococcus lactis is the main component of the mesophilic starters used in cheese manufacture. The success of milk fermentation relies on the viability and metabolic activity of the starter bacteria. Therefore, robust strains able to withstand the harsh conditions encountered during cheese manufacture and starter production are demanded. In this work, we have applied adaptive evolution under cell envelope stress imposed by the cell wall active bacteriocin Lcn972 to evolve strains with more robust phenotypes.ResultsConsecutive exposure of the starter strain L. lactis IPLA947 to Lcn972 yielded a stable mutant, L. lactis R5, with enhanced survival when challenged with hydrogen peroxide. L. lactis R5 exhibited faster growth rates in aerobic fermentations in broth and was able to acidify milk to a lower pH in aerated milk cultures. The improved behavior of L. lactis R5 in the presence of oxygen did not translate into a better performance in the presence of heme (i.e. respiration metabolism) or into higher survival during storage at cold temperatures or after freeze-drying compared to the wild type L. lactis IPLA947. L. lactis R5 retained the same milk acidification rate and no changes in the consumption of lactose and production of organic acids were noticed. However, the profile of volatile compounds revealed a significant increase in 3-hydroxy-2-butanone (acetoin) in curds manufactured with L. lactis R5.ConclusionsBased on our results, L. lactis R5 can be proposed as a suitable dairy starter with improved survival under oxidative stress and enhanced metabolic traits. The results support the notion that adaptive evolution under cell envelope stress might be useful to generate strain diversity within industrial L. lactis strains.

Use of mesophilic Lactic Acid Bacteria in the manufacture of Feta cheese

The use of mesophilic lactic acid bacteria (LAB) in the manufacture of Feta cheese was studied. Five selected mesophilic strains, confirmed as Lactobacillus plantarum (2 strains), Lb. paracasei subsp. paracasein Lb. brevis and Lactococcus lactis subsp. lactis, isolated from ripened Feta and Teleme cheeses, were used in 7 different combinations, alone or in combination with Lb. delbrueckii subsp. bulgaricus and Streptococcus thermophilus (the control combination) for the manufacture of Feta cheese. Each combination of strains was used to prepare four different batches of Feta cheese, keeping all the other production parameters according to the traditional technology. The cheese batches were analyzed for bacteriological, chemical and sensory characteristics. The results showed that the populations of lactobacilli and lactococci increased from the beginning of the cheese manufacture reaching a population of more than 7.0 log10cfu/g. This level was maintained during the whole ripening period (60 days) and during the subsequent 60-day storage period. Only in batches prepared with the control combination F8 {Str. thermophilus I Lb. delbrueckii subsp. bulgaricus), did the population of LAB decline to 6.0 log10cfu/g at the end of the ripening period. Also, except for the yeast population which increased, in all other bacterial groups tested (coliforms, staphylococci, total contaminating bacteria, psychrotrophic bacteria, proteolytic and lipolytic bacteria) populations gradually decreased during the ripening period. Results of the chemical analysis showed a sharp increase in acidity (the cheese pH dropped to ca. 4.5 within 3-4 d) and, whereas the values of other chemical indices (moisture content, fat content and NaCl) were stabilized between the 15* and 30* day of ripening, proteolysis (nitrogen soluble in 12% TCA) and lipolysis (ADV) progressed throughout ripening. The assessment of the overall acceptance by the sensory panel was between "very good" and "excellent" for all cheeses. This suggests that the selected mesophilic starter cultures can be used alone or in combination with the traditional culture {Lb.delbrueckii subsp. bulgaricus I Str. thermophilus) in the production of Feta cheese, as the results of this work indicate that the wild (autochthonous) strains of Lb. plantarum and Lc. lactis subsp. Lactis are well adapted to the environmental conditions that prevail in Feta cheese. Batches prepared using these mesophilic starters received the highest score in the assessment of organoleptic quality of Feta cheese. Very good results were also obtained using the combination of the mesophilic starters Lb. brevis and Lc. lactis subsp. lactis or Lb. paracasei subsp. paracasei and Lc. lactis subsp. lactis alone or in combination with Lb. delbrueckii subsp. bulgaricus and Str. thermophilus.

Metagenomic Analysis of Dairy Bacteriophages: Extraction Method and Pilot Study on Whey Samples Derived from Using Undefined and Defined Mesophilic Starter Cultures.

Despite being potentially highly useful for characterizing the biodiversity of phages, metagenomic studies are currently not available for dairy bacteriophages, partly due to the lack of a standard procedure for phage extraction. We optimized an extraction method that allows the removal of the bulk protein from whey and milk samples with losses of less than 50% of spiked phages. The protocol was applied to extract phages from whey in order to test the notion that members of Lactococcus lactis 936 (now Sk1virus), P335, c2 (now C2virus) and Leuconostoc phage groups are the most frequently encountered in the dairy environment. The relative abundance and diversity of phages in eight and four whey mixtures from dairies using undefined mesophilic mixed-strain cultures containing Lactococcus lactis subsp. lactis biovar diacetylactis and Leuconostoc species (i.e., DL starter cultures) and defined cultures, respectively, were assessed. Results obtained from transmission electron microscopy and high-throughput sequence analyses revealed the dominance of Lc. lactis 936 phages (order Caudovirales, family Siphoviridae) in dairies using undefined DL starter cultures and Lc. lactis c2 phages (order Caudovirales, family Siphoviridae) in dairies using defined cultures. The 936 and Leuconostoc phages demonstrated limited diversity. Possible coinduction of temperate P335 prophages and satellite phages in one of the whey mixtures was also observed.IMPORTANCE The method optimized in this study could provide an important basis for understanding the dynamics of the phage community (abundance, development, diversity, evolution, etc.) in dairies with different sizes, locations, and production strategies. It may also enable the discovery of previously unknown phages, which is crucial for the development of rapid molecular biology-based methods for phage burden surveillance systems. The dominance of only a few phage groups in the dairy environment signifies the depth of knowledge gained over the past decades, which served as the basis for designing current phage control strategies. The presence of a correlation between phages and the type of starter cultures being used in dairies might help to improve the selection and/or design of suitable, custom, and cost-efficient phage control strategies.

Survival of micro‐organisms and organic acid profile of probiotic Cheddar cheese from buffalo milk during accelerated ripening

The study aimed to assess the impact of ripening at elevated temperatures on the survival of probiotic micro‐organisms and production of organic acids in Cheddar cheese. Cheese was manufactured from buffalo milk using lactococci starters along with different probiotic bacteria (Lactobacillus acidophilus LA‐5, Bifidobacterium bifidum Bb‐11 and Bifidobacterium longum BB536) as adjunct cultures. The cheeses were ripened at 4–6 °C or 12–14 °C for 180 days and examined for composition, organic acids and microbial survival. The production of organic acids was accelerated at 12–14 °C when compared to normal ripening temperatures. The probiotic bacteria increased production of lactic and acetic acids, compared to cheese made with lactococci alone. The survival of the mesophilic starters was significantly (P < 0.05) reduced in all the cheese samples ripened at the higher temperature. However, the probiotic bacteria remained viable (>7.0 log10 cfu/g) throughout the 180 days of ripening, irrespective of temperature. It was concluded that Cheddar containing additional probiotic cultures can effectively be ripened at elevated temperatures without any adverse effects.

Genomic Characterization of Dairy Associated Leuconostoc Species and Diversity of Leuconostocs in Undefined Mixed Mesophilic Starter Cultures.

Undefined mesophilic mixed (DL-type) starter cultures are composed of predominantly Lactococcus lactis subspecies and 1–10% Leuconostoc spp. The composition of the Leuconostoc population in the starter culture ultimately affects the characteristics and the quality of the final product. The scientific basis for the taxonomy of dairy relevant leuconostocs can be traced back 50 years, and no documentation on the genomic diversity of leuconostocs in starter cultures exists. We present data on the Leuconostoc population in five DL-type starter cultures commonly used by the dairy industry. The analyses were performed using traditional cultivation methods, and further augmented by next-generation DNA sequencing methods. Bacterial counts for starter cultures cultivated on two different media, MRS and MPCA, revealed large differences in the relative abundance of leuconostocs. Most of the leuconostocs in two of the starter cultures were unable to grow on MRS, emphasizing the limitations of culture-based methods and the importance of careful media selection or use of culture independent methods. Pan-genomic analysis of 59 Leuconostoc genomes enabled differentiation into twelve robust lineages. The genomic analyses show that the dairy-associated leuconostocs are highly adapted to their environment, characterized by the acquisition of genotype traits, such as the ability to metabolize citrate. In particular, Leuconostoc mesenteroides subsp. cremoris display telltale signs of a degenerative evolution, likely resulting from a long period of growth in milk in association with lactococci. Great differences in the metabolic potential between Leuconostoc species and subspecies were revealed. Using targeted amplicon sequencing, the composition of the Leuconostoc population in the five commercial starter cultures was shown to be significantly different. Three of the cultures were dominated by Ln. mesenteroides subspecies cremoris. Leuconostoc pseudomesenteroides dominated in two of the cultures while Leuconostoc lactis, reported to be a major constituent in fermented dairy products, was only present in low amounts in one of the cultures. This is the first in-depth study of Leuconostoc genomics and diversity in dairy starter cultures. The results and the techniques presented may be of great value for the dairy industry.

Enhanced fertilization effect of a compost obtained from mixed herbs waste inoculated with novel strains of mesophilic bacteria

Mixed medicinal plant waste was composted with addition of novel bacterial strains belonging to the genera Streptomyces, Paenybacillus, Bacillus and Hymenobacter. The composting was followed by assessment of chemical and biological parameters including C/N ratio, loss of organic matter, phosphorous and potassium content as well as CO2 generation and dehydrogenase activity during 164 days. The selected mesophilic bacterial starters had a potential to significantly reduce the period of mixed herb waste decomposition, from about 6 months to about 2.5 months. Based on the seed germination index of four plants (Fagopirum esculentum, Thymus vulgaris, Cynara scolimus and Lavandula officinalis) the germination and radial root growth of the investigated plants was improved by the inoculated compost. The germination index of all tested species on the mature inoculated composts was in average 60% higher compared to the control compost. The research indicates that the mesophilic starter addition into the herbs waste can contribute to the speed of waste decomposition and lead to the improvement of biofertilization effect of the obtained compost.

The Effect of Probiotic Lactic Acid Bacteria on the Characteristics of Galotyri Cheese

This study evaluated the effect of probiotic bacteria on the characteristics of the traditional Greek Galotyri cheese. Four Galotyri cheeses were made with the mesophilic starter culture BT002 along with the probiotic strains Lactobacillus acidophilus NCFM, Lactobacillus acidophilus 145, Lactobacillus paracasei subsp. paracasei LbC 81 or Lactobacillus rhamnosus LC 705 and a cheese was also made without the addition of probiotics. The microbiological, physicochemical, aromatic and sensory characteristics of the products were investigating during 30 days of storage at 4oC. The results indicated that probiotics remained above the recommended level for the therapeutic minimum (106 cfu g-1) after 30days. The addition of probiotics did not change the yield, chemical composition and sensory characteristics of Galotyri cheese. A total of 32 aromatic compounds were identified, of these acetaldehyde, diacetyl and acetoin presented in higher levels in cheeses containing probiotic strains. It was concluded that high quality Galotyri cheese with improved health enhancing properties could be produced.

AVALIAÇÃO FÍSICO-QUÍMICA, MICROBIOLÓGICA E SENSORIAL DE QUEIJO MINAS FRESCAL DE LEITE DE CABRA DESENVOLVIDO POR ACIDIFICAÇÃO DIRETA E FERMENTAÇÃO LÁTICA

O objetivo deste estudo foi avaliar o efeito da acidificação direta por ácido lático e por adição de cultura starter mesofílica tipo O (Lactococcus lactis subsp. lactis e Lactococcus lactis subsp. cremoris) nas propriedades físico-químicas, microbiológicas e sensoriais de queijo Minas frescal de leite de cabra. Duas formulações de queijo Minas frescal foram elaboradas por acidificação com ácido lático e com cultura mesofílica tipo O e avaliadas quanto a qualidade microbiológica, quantificando S. aureus, psicrotróficos, bactérias láticas, coliformes termotolerantes e quanto a presença de Salmonella sp. Quanto as análises físico-químicas, foram realizadas determinação de gordura, cinzas, umidade, acidez titulável em ácido lático e pH. As modificações físico-químicas no queijo Minas frescal foram avaliadas durante o período de estocagem de 14 dias e analisada a sua aceitabilidade e intenção de compra por meio da avaliação sensorial. Os resultados revelaram que ambas as formulações do queijo Minas frescal apresentavam-se em boas condições higiênico-sanitárias e de consumo. Quanto aos parâmetros físico-químicos, os teores de gordura, cinzas e umidade dos queijos não diferiram significativamente entre si (p < 0,05). O queijo obtido por acidificação direta por ácido lático foi o que apresentou menor contagem de bactérias láticas totais e acidez, maior valor de pH e maior aceitabilidade sensorial e intenção de compra diferindo do queijo obtido por fermentação lática. Os resultados mostram que a forma de acidificação afeta as características do produto e sua aceitação pelos consumidores. A utilização do leite de cabra para produção do queijo Minas frescal apresenta potencial de aplicação na indústria de lácteos, agrega valor, tornando-o um produto alternativo aos consumidores alérgicos ao leite bovino.

Variability of biogenic amine and free amino acid concentrations in regionally produced goat milk cheeses

The free amino acid composition and biogenic amine content were analysed in pasteurised goat milk cheeses produced in different regions in Spain. These goat cheeses are made with pasteurised milk to which a mesophilic starter culture is added; they are enzymatically coagulated, uncooked, pressed cheeses. They have a firm texture with a slight but typical goat milk aroma and flavour. The total free amino acids varied markedly among the samples, ranging from 1400 to 28,000mgkg−1 DM (dry matter). Of the 20 amino acids analysed, the most abundant were leucine, proline, valine, glutamic acid, lysine, glutamine, ornithine and γ-aminobutyric acid, which accounted for over 60% of the total free amino acids. The goat milk cheeses presented low concentrations of biogenic amines, the most abundant being tyramine and/or histamine, with values ranging from 4.2 to 50.7 and from 10.2 to 60.5mgkg−1 DM, respectively. Total biogenic amine content ranged between 26.4mgkg−1 DM and 175.1mgkg−1 DM, and was always below the level that is considered dangerous for humans. Therefore, taking into consideration the concentrations of BAs, these goat milk cheeses, produced under good hygienic conditions, can be considered safe for consumers.

Effect of buffalo milk on the yield and composition of buffalo feta cheese at various processing parameters

Abstract The aim of this study was to analyze the composition of Iranian buffalo milk and study the effect of different parameters such as fat content, acidity of milk, starter culture and temperature on the composition of buffalo feta cheese. The feta cheese yields obtained from buffalo milk were higher in comparison with the yields reported for cow milk. Higher yields were obtained when the fat content of the milk was increased. Rise in the raw milk acidity increased the yield and reduced the fat, protein and lactose loses. Thermophilic and mesophilic starter cultures exhibited better activities at 38 °C and 34 °C, respectively. Pasteurization resulted in significantly (p 0.05). The results of this study revealed that buffalo milk could be regarded as a good source for the production of feta cheese due to elevated amounts of fat, protein and Ca. The results showed that optimum conditions were needed to achieve the higher yields.

Sensory quality of Camembert-type cheese: Relationship between starter cultures and ripening molds

Starter cultures and ripening molds used in the manufacture of moldy cheese aimed at obtaining characteristic flavors and textures considerably differ among dairy industries. Thus, the study of variables inherent to the process and their influence on sensory patterns in cheese can improve the standardization and control of the production process. The aim of this work was to study the influence of three different variables on the sensory quality of Camembert-type cheese: type of lactic bacteria, type of ripener molds and inoculation method. Batches of Camembert-type cheese were produced using O or DL-type mesophilic starter culture, ripened with Penicillium camemberti or Penicillium candidum and mold inoculation was made directly into the milk or by spraying. All batches were sensorially evaluated using Quantitative Descriptive Analysis (QDA) with panelists trained for various attributes. Among the combinations analyzed, those resulting in more typical Camembert-type cheese were those using O-type mesophilic starter culture and P. candidum maturation mold directly applied into the milk or sprayed and those using DL-type mesophilic starter and P. camemberti ripener mold applied by surface spraying. These results demonstrate, therefore, that the combination of different ripener molds, inoculation methods and starter cultures directly influences the sensory quality of Camembert-type cheese, modifying significantly its texture, appearance, aroma and taste.

Effect of reuterin-producing Lactobacillus reuteri coupled with glycerol on the volatile fraction, odour and aroma of semi-hard ewe milk cheese

The effect of the biopreservation system formed by Lactobacillus reuteri INIA P572, a reuterin-producing strain, and glycerol (required for reuterin production), on the volatile fraction, aroma and odour of industrial sized semi-hard ewe milk cheese (Castellano type) was investigated over a 3-month ripening period. The volatile compounds were extracted and analyzed by SPME-GC-MS and cheese odour and aroma profiles were studied by descriptive sensory analysis. Control cheese was made only with a mesophilic starter and experimental cheeses with L. reuteri were made with and without glycerol. The addition of L. reuteri INIA P572 to milk enhanced the formation of six volatile compounds. Despite the changes in the volatile compounds profile, the use of L. reuteri INIA P572 did not noticeably affect the sensory characteristics of cheese. On the other hand, the addition of L. reuteri INIA P572 coupled with 30mM glycerol enhanced the formation of twelve volatile compounds, but decreased the formation of five ones. The use of the biopreservation system did not affect overall odour and aroma quality of cheese although it resulted in a significant decrease of the odour intensity scores. In addition, this cheese received significant higher scores for “cheesy” aroma and significant lower scores for the aroma attributes “milky”, “caramel” and “yogurt-like”. The first two axes of a principal component analysis (PCA) performed for selected volatile compounds and sensory characteristics, accounting for 75% of the variability between cheeses, separated cheeses made with L. reuteri INIA P572 and glycerol from the rest of cheeses, and also differentiated control cheese from cheeses made with L. reuteri INIA P572 from day 60 onward. Our results showed that the reuterin-producing L. reuteri INIA P572 strain, when coupled with glycerol, may be a suitable biopreservation system to use in cheese without affecting odour and aroma quality.

Effects of the Essential Oil from Origanum vulgare L. on Survival of Pathogenic Bacteria and Starter Lactic Acid Bacteria in Semihard Cheese Broth and Slurry

This study assessed the inhibitory effects of the essential oil from Origanum vulgare L. (OVEO) on Staphylococcus aureus, Listeria monocytogenes, and a mesophilic starter coculture composed of lactic acid bacteria (Lactococcus lactis subsp. lactis and L. lactis subsp. cremoris) in Brazilian coalho cheese systems. The MIC of OVEO was 2.5 μl/ml against both S. aureus and L. monocytogenes and 0.6 μl/ml against the tested starter coculture. In cheese broth containing OVEO at 0.6 μl/ml, no decrease in viable cell counts (VCC) of both pathogenic bacteria was observed, whereas the initial VCC of the starter coculture decreased approximately 1.0 log CFU/ml after 24 h of exposure at 10°C. OVEO at 1.25 and 2.5 μl/ml caused reductions of up to 2.0 and 2.5 log CFU/ml in S. aureus and L. monocytogenes, respectively, after 24 h of exposure in cheese broth. At these same concentrations, OVEO caused a greater decrease of initial VCC of the starter coculture following 4 h of exposure. Higher concentrations of OVEO were required to decrease the VCC of all target bacteria in semisolid coalho cheese slurry compared with cheese broth. The VCC of Lactococcus spp. in coalho cheese slurry containing OVEO were always lower than those of pathogenic bacteria under the same conditions. These results suggest that the concentrations of OVEO used to control pathogenic bacteria in semihard cheese should be carefully evaluated because of its inhibitory effects on the growth of starter lactic acid cultures used during the production of the product.

Use of M17 and a milk-based medium enables isolation of two distinct and diverse populations of Lactococcus lactis strains from undefined mesophilic starter cultures

Dairy starter culture development and bacteriophage research depends on adequate growth media for isolation of relevant starter culture strains and their bacteriophages. We show that the use of two growth media, M17 and a milk-based medium (GMA), enables isolation of two distinct subpopulations of Lactococcus lactis ssp. from undefined mesophilic starter cultures. Phage typing revealed large diversity within each subpopulation, and interestingly, that there was very little overlap in phage sensitivity between the two sets of bacteria. Acidification activity tests performed in the presence of M17-and GMA-derived bacteriophages, both separately and in combination, demonstrated the relevance of both bacterial subpopulations in the acidification process. Use of both media enables higher diversity sampling of Lactococcus ssp., and their bacteriophages.

Comparative inhibitory effects of Thymus vulgaris L. essential oil against Staphylococcus aureus, Listeria monocytogenes and mesophilic starter co-culture in cheese-mimicking models

In the present study, we assessed the effects of Thymus vulgaris L. essential oil (TVEO) on Staphylococcus aureus and Listeria monocytogenes, pathogenic bacteria frequently associated with fresh or low-ripened cheeses (e.g., Brazilian coalho cheese), and on a starter co-culture comprising Lactococcus lactis subsp. lactis and L. lactis subsp. cremoris, which are commonly used for the production of different cheeses. To measure these effects, we determined the minimum inhibitory concentration (MIC) and assessed bacterial cell viability over time in (coalho) cheese-based broth and in a semi-solid (coalho) cheese model at 10 °C. The MIC for TVEO was 2.5 μL/mL against S. aureus and L. monocytogenes, while the MIC was 1.25 μL/mL against the starter co-culture. The TVEO (5 and 2.5 μL/mL) sharply reduced the viable counts of all assayed bacteria in cheese broth over 24 h; although, at 5 μL/mL, TVEO more severely affected the viability of the starter co-culture compared with pathogenic bacteria. The addition of 1.25 μL/g of TVEO in the semi-solid cheese model did not reduce the viable counts of all assayed bacteria. At 2.5 μL/g, TVEO slightly decreased the viable counts of S. aureus, L. monocytogenes and Lactococcus spp. in the semi-solid cheese model over 72 h. The final counts of Lactococcus spp. in a semi-solid cheese model containing 2.5 μL/mL TVEO were lower than those of pathogenic bacteria under the same conditions. These results suggest that the doses of TVEO used to control pathogenic bacteria in fermented dairy products, especially in low-ripened cheeses, should be cautiously considered for potential negative effects on the growth and survival of starter cultures.

Chemical Composition, Probiotic Survivability and Shelf Life Studies of Symbiotic Buttermilk

Cultured buttermilk is getting popular as an ingredient for bakery and for direct consumption in the U.S.. The objective of this study was to develop a symbiotic cultured buttermilk, containing inulin as a prebiotic and probiotics Lactobacillus acidophilus and Bifidobacterium spp. The cultured buttermilk was prepared using a commercial mesophilic starter CHN22 (Lactococcus lactis sbusp. cremoris, Lactococcus lactis subsp. lactis, Leuconstoc mesenteorides subsp. cermories, Lactococcus lactis subsp. lactis biovar diacetylactis) and the probiotics. The control buttermilk prepared using CHN22 and the symbiotic buttermilk were analyzed for chemical composition, probiotics survivability, mold, yeast and coliform counts. Changes in pH and titratable acid were also determined during storage at 4° C for 12 weeks. The chemical composition of the control and symbiotic buttermilk were: protein 3.29±0.05 and 3.30±0.02%; fat 3.28±0.04 and 3.26±0.06%; carbohydrate 4.55±0.05 and 5.16±0.06%; total solids 12.81±0.05 and 12.42±0.03%; ash 0.692±0.03 and 0.701±0.01%, respectively. The populations of both Lactobacillus acidophilus and Bifidobacterium spp were initially above 107 cfu/g and remained 106 cfu/g during the 12‐week and there was no mold and yeast were detected. There were significant differences in pH and titratable acid between the control and symbiotic buttermilk (p<0.05) due to addition of the probiotics.

Genome Sequences of Two Leuconostoc pseudomesenteroides Strains Isolated from Danish Dairy Starter Cultures.

The lactic acid bacterium Leuconostoc pseudomesenteroides can be found in mesophilic cheese starters, where it produces aromatic compounds from, e.g., citrate. Here, we present the draft genome sequences of two L. pseudomesenteroides strains isolated from traditional Danish cheese starters.

When and How to Evaluate the Natural Killer Cell Function

Aims: To optimize the process variables including: Lactobacillus acidophilus La-5, total starter (a mixture of mesophilic cheese starters (MCS) and thermophilic yoghurt starters (TYS), mesophilic cheese starter: thermophilic yoghurt starter (MCS: TYS) ratio and salt content in probiotic Iranian ultrafiltered soft cheese (IUSC). Methodology: In order to choose the best probiotic cheese formula with the highest Lactobacillus acidophilus La-5 count, a total of eight samples with 20 % total solids were produced using a small scale ultrafiltration system. Probiotic bacteria of Lactobacillus Original Research Article Annual Research & Review in Biology, 4(24): 4091-4103, 2014 4092 acidophilus La-5 (0.1 and 0.3 %), total starters (1 and 2 %), MCS: TYS ratio (8:2 and 7:3) and salt (NaCl) concentration (1 and 2 %) by the help of Taguchi design were inoculated into cheeses and the viable cell counts of Lactobacillus acidophilus La-5 enumerated within 45 d of shelf life at 5 oC, as well the multiple effects of process variables on probiotic count and colony morphologies of probiotic and starters evaluated. Results: The most suitable conditions for the highest Lactobacillus acidophilus La-5 stability were addition of 0.1 % w/w Lactobacillus acidophilus La-5, 1 % v/w total starter, MCS: TYS ratio of 8:2 and 1 % w/w salt content. The lowest and highest viable cell count of probiotic Lactobacillus acidophilus La-5 in IUSC ranged from 6.41 to 7.92 CFU.g, respectively. The acidified (pH 5.2) MRS agar medium used for the differentiation of the colony morphology of Lactobacillus bulgaricus and Lactobacillus acidophilus La-5, anaerobically. In all of the cheeses except for cheese 3 and 6 which the La-5 survived to 6.95 and 6.41 log orders, respectively, Lactobacillus acidophilus La-5 cell count survived to over10 CFU.g, when all the cheeses had the small amount of acetic acid taste with a creamy and soft texture. The MCS:TYS ratio of 8:2 and 0.1 % initial dosage of Lactobacillus acidophilus La-5 (P ˂ 0.05) affected the probiotic stability of Lactobacillus acidophilus La-5 in IUSC during shelf life, however the salt content (1 and 2 %) and total starter (1 and 2 %) did not significantly influence the Lactobacillus acidophilus La-5 viability. Conclusion: This study showed that Iranian ultrafiltered soft cheese has a probiotic potential to have 10 CFU.g viable cell count of Lactobacillus acidophilus La-5 strain, when process variables optimized and this progress will contribute to develop a healthier foods.

Functional implications of the microbial community structure of undefined mesophilic starter cultures.

This review describes the recent advances made in the studies of the microbial community of complex and undefined cheese starter cultures. We report on work related to the composition of the cultures at the level of genetic lineages, on the presence and activity of bacteriophages and on the population dynamics during cheese making and during starter culture propagation. Furthermore, the link between starter composition and starter functionality will be discussed. Finally, recent advances in predictive metabolic modelling of the multi-strain cultures will be discussed in the context of microbe-microbe interactions.