Traditional Dairy Research Articles

Diet Diversity in Mexican Preschool Children Living in Poverty Conditions (P11-096-19)

ObjectivesTo assess diet diversity in a national sample of children less than five years old from the lower socioeconomic tertile. MethodsData used in the present analysis comes from the National Health and Nutrition Survey ENANSUT-PROSPERA 2018 (Social inclusion program). Information from 2131 children between 1 and < 5 years old was analyzed. By using a semi-quantitative food and beverages frequency consumption questionnaire a diet diversity indicator was constructed, such indicator classified the foods in 13 groups according to their nutritional characteristics and finally divided them into two great groups: Recommended Foods Group(RFG) like fruits, vegetables, legumes, non-processed meats, dairy products and pure water and Not Recommended for regular consumption (NRFG), a group that include processed meats, fast food, fried or greasy Mexican traditional foods, snacks, sweets, desserts, sweetened cereals, dairy and non-dairy sweetened beverages. A score was calculated with the sum of the consumed food groups for each category. ResultsThe most consumed food groups were: water, dairy products, snacks, sweets and desserts and non-dairy sweetened beverages. Less than 50% (CI 95% 39.9, 54.9) of the children consumed fruits and less than 20% (CI 95% 12.4, 24.9) reported to eat vegetables daily. Consumption of recommended foods mean was 3.7 and not recommended 2.6. ConclusionsThe diversity of the diet should be considered in more general terms, since it is likely related to a better quality of the diet as a whole. Is fundamental to encourage recommended feeding habits in children, because it is in this age where lifetime behaviors are acquired. NRFG consumption must be avoided considering the current overweight prevalence in the Country. Funding SourcesFunding by PROSPERA.

Prevalence of Coxiella burnetii in Traditional and Industrial Butter and Cream Using Nested Polymerase Chain Reaction in Shahrekord, Iran

Background: A zoonotic disease of global importance known as "Q fever" is caused by Coxiella burnetii agent. The aim of the present research was to determine C. burnetii in the traditional and industrial butter and cream samples in Shahrekord, Iran. Methods: This cross-sectional descriptive study was conducted from March to September 2016. Totally, 200 traditional and industrial butter and cream samples were collected from retailers in different regions of Shahrekord and then tested for C. burnetii via nested polymerase chain reaction (PCR) assays. Results: In this survey, a total of 6 out of 200 samples (3%) were found to be positive for C. burnetii. More precisely, 4 (5.79%), 1 (5%), and 1 (2.56%) samples were related to the traditional bovine cream, traditional sheep butter, and traditional bovine butter samples, respectively. Nevertheless, no C. burnetii infections were found in the industrial butter and cream samples. Conclusions: These results proved that traditional dairy products can be considered as an important reservoir for C. burnetii infection in Iran.

Emergence of methicillin-resistant Staphylococcus aureus (MRSA) ST8 in raw milk and traditional dairy products in the Tizi Ouzou area of Algeria

Staphylococcus aureus is one of the leading causes of food-borne illness worldwide. Raw milk and dairy products are often contaminated with enterotoxigenic strains of this bacterium. Some of these strains carry antimicrobial resistance, leading to a potential risk for consumers. The aim of this study was to characterize S. aureus strains circulating in raw milk and traditional dairy products for carriage of staphylococcal enterotoxin (se) genes and antimicrobial resistance. Overall, 62 out of 270 samples (23%) were contaminated with S. aureus, and 69 S. aureus strains were identified. We studied the enterotoxin genes using 2 multiplex PCR targeting 11 se genes. Seventeen (24.6%) isolates carried one or more genes encoding for staphylococcal enterotoxins. The most commonly detected se genes were seb and sep, followed by seh, sea, and see. Using the disk diffusion method, we found that resistance to penicillin G and tetracycline was the most common. Eleven isolates of methicillin-resistant S. aureus (MRSA) carried the mecA gene. All MRSA isolates belonged to the same spa type (t024) and sequence type (ST8), and carried the seb and sep enterotoxin genes. However, none of them carried the Panton Valentine leukocidin gene (lukF/S-PV). The presence of enterotoxigenic S. aureus strains, including MRSA, in raw milk and dairy products, raises a serious public health concern, because these strains may cause food poisoning outbreaks, be disseminated to the population, or both.

Prevalence ofCoxiella burnetiiin Traditional and Industrial Butter and Cream Using Nested Polymerase Chain Reaction in Shahrekord, Iran

Background: A zoonotic disease of global importance known as "Q fever" is caused by Coxiella burnetii agent. The aim of the present research was to determine C. burnetii in the traditional and industrial butter and cream samples in Shahrekord, Iran. Methods: This cross-sectional descriptive study was conducted from March to September 2016. Totally, 200 traditional and industrial butter and cream samples were collected from retailers in different regions of Shahrekord and then tested for C. burnetii via nested polymerase chain reaction (PCR) assays. Results: In this survey, a total of 6 out of 200 samples (3%) were found to be positive for C. burnetii. More precisely, 4 (5.79%), 1 (5%), and 1 (2.56%) samples were related to the traditional bovine cream, traditional sheep butter, and traditional bovine butter samples, respectively. Nevertheless, no C. burnetii infections were found in the industrial butter and cream samples. Conclusions: These results proved that traditional dairy products can be considered as an important reservoir for C. burnetii infection in Iran.

Membrane filtration and isoelectric precipitation technological approaches for the preparation of novel, functional and sustainable protein isolate from lentils

Isoelectric precipitation and ultrafiltration were investigated for their potential to produce protein products from lentils. Higher protein concentrations were obtained when ultrafiltration was used (> 90%), whereas isoelectric precipitation resulted in higher contents of dietary fibre and some minerals (i.e., sodium and phosphorus). Differences in the functional properties between the two ingredients were found as the isoelectric precipitated ingredient showed lower protein solubilities over the investigated pH range (from 3 to 9) which can be linked to the slightly higher hydrophobicity values (2688.7) and total sulfhydryl groups (23.9 µM/g) found in this sample. In contrast, the protein ingredient obtained by ultrafiltration was superior with regard to its solubility (48.3%; pH 7), fat-binding capacity (2.24 g/g), water holding capacity (3.96 g/g), gelling properties (11%; w/w), and foam-forming capacity (69.6%). The assessment of the environmental performance showed that both LPIs exhibited promising properties and low carbon footprints in comparison to traditional dairy proteins.

Production of γ-aminobutyric acid (GABA) by lactic acid bacteria strains isolated from traditional, starter-free dairy products made of raw milk.

γ-Aminobutyric acid (GABA), an amino acid not used in protein synthesis, intervenes in several physiological functions and has both diuretic and calming effects in humans. Lactic acid bacteria (LAB) strains that produce GABA could be exploited for the manufacture of health-promoting GABA-enriched dairy products. In this study, 262 LAB strains isolated from traditional dairy products made from raw milk without starter cultures were screened for GABA production in culture media supplemented with 1% monosodium glutamate (MSG) using an enzymatic (GABase) method. About half of the strains (123) were found to be GABA producers. Of these, 24, among which were 16 Lactococcus lactis subsp. lactis and three Streptococcus thermophilus strains, produced >1 mM of GABA (range 1.01-2.81 mM) and were selected for further characterisation. GABA production was confirmed in most strains by culturing in 5 mM MSG followed by HPLC quantification. A majority of the strains were confirmed to be GABA producers by this method, although lower production levels were recorded. Using species-specific primers, the gene encoding glutamate decarboxylase (GAD) was PCR-amplified in all but one of the GABA producers analysed. Amplicons sequences were compared to one another and to those held in databases. Except for one Lactobacillus brevis strain, none of the 24 GABA producers investigated produced toxic biogenic amines, such as tyramine, histamine or cadaverine. They were therefore considered safe. Either alone, in mixtures, or in combination with industrial starter or adjunct cultures, these strains might be useful in the development of health-oriented dairy products.

Dominant Lactic Acid Bacteria in Naturally Fermented Milks from Messinese Goat’s Breed

Background: Lactic Acid Bacteria (LAB) are an important group of microorganisms responsible for the fermentation dairy products. This study was done to identify the dominant lactic acid bacteria in naturally fermented milks from Messinese goat’s breed. Methods: Eighteen individual raw milk samples collected from Messinese goat’s breed were acidified at pH 5.20 and left to spontaneously ferment at 37 °C for 4 days. All samples were analyzed for rod- and coccus-shaped LAB. Also, all presumptive LAB were isolated and differentiated according to their phenotypic properties and genetic polymorphisms and then identified by sequencing the 16S rRNA gene. Data were statistically analyzed using SAS 9.2 software. Results: Levels of coccus- and rod-shaped LAB were in the range of 1.78-7.10 log and 1.00-7.09 log colony forming unit/ml, respectively. The microbiological counts on the two different growth media were significantly (p&lt;0.05) different among the samples. Among 12 identified strains, the most numerous one was Enterococcus hirae (n=4), followed by E. faecium (n=3), while the other species (E. durans, E. faecalis, E. lactis, Lactococcus lactis, and Leuconostoc lactis) included one strain each. Conclusion: The major group identified in this study was mainly represented by members of Enterococcus genus. Although Enterococcus spp. are related to the typicality of some traditional fermented dairy products, this study highlights the need for risk assessment of pathogenic enterococci species for the consumers.

Comparison of gal-lac operons in wild-type galactose-positive and -negative Streptococcus thermophilus by genomics and transcription analysis.

Streptococcus thermophilus is one of the most important homo-fermentative thermophilic bacteria, which is widely used as a starter culture in dairy industry. Both wild-type galactose-negative (Gal-) S. thermophilus AR333 and galactose-positive (Gal+) S. thermophilus S-3 in this study were isolated from Chinese traditional dairy products. Here, to access the mechanism of the difference of galactose utilization between strains AR333 and S-3, the expression of gal-lac operons was examined using real-time qPCR in the presence of different sugars, and the gene organization of gal-lac operons was characterized using comparative genomics analysis. As compared with medium containing glucose, the expression of gal-lac operons in AR333 and S-3 was significantly activated (> 5-fold) in the presence of galactose or lactose in the medium. More importantly, the expression of gal operon in S-3 was higher than that of AR333, suggesting that the strength of gal promoter in AR333 and S-3 may be different. The genomes of AR333 and S-3 were the first time sequenced to provide insight into the difference of gal-lac operons in these two strains. Comparative genomics analysis showed that gene order and individual gene size of gal-lac operons are conserved in AR333 and S-3. The DNA sequence of gal operon responsible for galactose utilization between AR333 and S-3 is almost identical except that galK promoter of S-3 possesses single base pair mutation (G to A substitution) at -9 box galK region. Moreover, the expression of red fluorescent protein can be activated by galK promoter of S-3, but cannot by galK promoter of AR333 in galactose medium, suggesting that gal operon is silent in AR333 and active in S-3 under galactose-containing medium. Overall, our results indicated that single point mutation at -9 box in the galK promoter can significantly affect the expression of gal operon and is largely responsible for the Gal+ phenotype of S. thermophilus.

Retraction statement: Prevalence of Toxoplasma gondii and Neospora caninum in different types of raw milk and traditional dairy product samples

The above article from the Journal of Food Safety, published online on 20 November 2018 in Wiley Online Library (https://onlinelibrary.wiley.com/doi/abs/10.1111/jfs.12575), has been retracted by agreement between the journal Editor‐in‐Chief, Vivian Wu and Wiley Periodicals, Inc. The retraction has been agreed due to evidence indicating that the peer review of this paper was compromised.

Characterization of antimicrobial activity of three Lactobacillus plantarum strains isolated from Chinese traditional dairy food.

Many Lactobacillus plantarum strains can secrete some antimicrobial substances and be added to food as antimicrobial agents and preservatives. In this study, three L. plantarum strains (P1, S11, and M7) with strong antimicrobial activity against three pathogenic bacteria were isolated from Xinjiang traditional dairy products. Five common organic acids produced by fermentation of strains play a key role in inhibiting three pathogenic bacteria. At the same pH, the antimicrobial activity of the fermentation broth against Escherichia coli and Salmonella is stronger than that of the organic acid alone. Thus, three kinds of antimicrobial agents (P1‐1, M7‐1, and S11‐1) mixed with five common organic acids were produced. Moreover, the antimicrobial activity against Salmonella ASI.1174 of the antimicrobial agents was about 30% higher than that of the fermentation broth. In addition, organic acid antimicrobial agents combined in different proportions can inhibit different pathogenic bacteria. According to this result, it is a potential approach to develop novel antimicrobial agents used in food preservation by mixing different organic acids.

Probiotic Potential and Safety Evaluation of Enterococcus faecalis OB14 and OB15, Isolated From Traditional Tunisian Testouri Cheese and Rigouta, Using Physiological and Genomic Analysis.

Lactic acid bacteria (LAB) strains OB14 and OB15 were isolated from traditional Tunisian fermented dairy products, Testouri cheese and Rigouta, respectively. They were identified as Enterococcus faecalis by the MALDI TOF-MS (matrix assisted laser desorption-ionization time of flight mass spectrometry) biotyper system and molecular assays (species-specific PCR). These new isolates were evaluated for probiotic properties, compared to E. faecalis Symbioflor 1 clone DSM 16431, as reference. The bacteria were found to be tolerant to the harsh conditions of the gastrointestinal tract (acidity and bile salt). They were low to moderate biofilm producers, can adhere to Caco-2/TC7 intestinal cells and strengthen the intestinal barrier through the increase of the transepithelial electrical resistance (TER). Susceptibility to ampicillin, vancomycin, gentamicin and erythromycin has been tested using the broth microdilutions method. The results demonstrated that E. faecalis OB14 and OB15 were sensitive to the clinically important ampicillin (MIC = 1 μg/mL) and vancomycin (MIC = 2 μg/mL) antibiotics. However, Whole Genome Sequencing (WGS) showed the presence of tetracycline resistance and cytolysin genes in E. faecalis OB14, and this led to high mortality of Galleria Mellonella larvae in the virulence test. Hierarchical cluster analysis by MALDI TOF-MS biotyper showed that E. faecalis OB15 was closely related to the E. faecalis Symbioflor 1 probiotic strain than to OB14, and this has been confirmed by WGS using the average nucleotide identity (ANI) and Genome-to-Genome Hybridization similarity methods. According to these results, E. faecalis OB15 seems to be reliable for future development as probiotic, in food or feed industry.

Cost estimation and consumer acceptance studies of herbal burfi

Traditional Indian dairy product has huge liking throughout the length and breadth of our country as well as abroad in the Indian diaspora. However, increasing health consciousness among the consumers has resulted into shift in their demand to functional foods. Many reports have highlighted the scope of further enhancing traditional dairy foods market by increasing their functionality, however very limited literature is available regarding their market prospects. The present study was conducted to estimate the production cost of herbal burfi, rich in anti-oxidative activity, in comparison to control burfi and also the market potential of the same. Herbal essential oil incorporation resulted into increase in INR 6/- of the raw material cost and thus the production cost of herbal burfi was INR 6/- (2.75%) was higher than that from control burfi. Consumer survey of the developed product revealed that 22.73% of the respondents rated the product ‘excellent’ and 92.86% of 154 respondents were ready to purchase the product, when available in market even at slightly higher price.

Microbiological quality of colonial cheese sold in Porto Alegre-RS

Colonial cheese is a traditional dairy product in southern Brazil and is commonly purchased by the citizens of Porto Alegre. However, there is still a lack of technical regulation of colonial cheese, and there is little information about the microbiological quality of this product at the retail level. Thus, the objectives of this study were to (i) evaluate compliance with the legal microbiological standards of colonial cheese sampled from street fairs and the central market of the city of Porto Alegre; (ii) statistically test the hypothesis of an association between noncompliance with the standards and local purchasing (street fairs or central market); (iii) estimate the number of Listeria spp. and Listeria monocytogenes in the positive samples; and (iv) characterize the L. monocytogenes strains by serotyping and macrorestriction (PFGE). For this purpose, 205 cheese samples belonging to 17 different brands were analyzed. The microbiological analyses were conducted according to ISO standardized protocols for the detection of L. monocytogenes and Salmonella spp. or by enumeration of coagulase-positive Staphylococcus and coliforms at 45°C. Among the samples, 47.31% did not comply with at least one of the microbiological standards established by the Brazilian legislation and were thus unsuitable for human consumption. Regarding the coliforms at 45ºC and coagulase-positive Staphylococcus, 10.73% and 40.48% of the samples presented higher counts than the legal parameter, respectively. There was no association between the frequency of samples with coagulase-positive Staphylococcus counts above the legal parameter and local of purchasing; however, the commercial brand influenced the frequency of unsuitable samples. This may indicate failures of hygiene during cheese production. Salmonella spp. were not detected. Listeria monocytogenes was isolated from 2.9% of the samples. The estimated average populations of Listeria spp. and L. monocytogenes were low in the positive cheese samples at -3.3 log CFU g?1 and -2.26 log CFU g?¹, respectively. The strains of L. monocytogenes belonged to serovars 1/2a, 1/2b and 1/2c and could be grouped into five pulsotypes with no evident epidemiological relation among them. The results demonstrate the need to improve the hygiene procedures during colonial cheese production and to strengthen monitoring at the dairy plants and retail levels.

Consumption of modern and traditional Moroccan dairy products and colorectal cancer risk: a large case control study.

The main objective of this study is to describe the association between the consumption of either traditional or modern dairy products or calcium intakes and the risk of colorectal cancer (CRC) in the adult Moroccan population. A case-control study was conducted in five Moroccan hospital centers. The study was matched on sex, age (± 5years) and center. Data were collected using validated food frequency questionnaire (FFQ) taking into account different types of Moroccan dairy products. Conditional logistic regression models were used to assess the association between dairy products consumption, calcium intakes and CRC risk subtypes. In all statistical tests, the significance level was set at 0.05. Among 1453 cases and 1453 matched controls, 50.7% were women and 49.3% were men. Milk ORb 0.84, 95% CI 0.74-0.96 and yogurt ORb 0.74, 95% CI 0.64-0.86 were inversely associated with CRC risk. Similar inverse associations were observed for traditional dairy products namely Lben ORb 0.77, 95% CI 0.67-0.88, Raib ORb 0.86, 95% CI 0.76-0.96 and Jben ORb 0.77, 95% CI 0.67-0.88. The dairy calcium intake was inversely associated to CRC overall ORb 0.83, 95% CI 0.74-0.93. Our study supports previous international evidence and suggests that individuals who have a high intake of either modern or traditional dairy products are at lower risk for CRC. These findings should be further confirmed by longitudinal data and studies investigating potential pathways involved.

Characterization of Dairy Value Chains in the Case of Urban and Peri-Urban Area of Southern Tigray

The study aimed at analyzing of the existing dairy value chain in the southern zone of Tigray. Primary data were collected from multiple sources including a total of 120 dairy producers, value chain actors: 24 traders, 20 consumers and 8 service providers in Edamehoni and Alamata districts. The collected data was analyzed using application of appropriate statistical tools and simple descriptive statistics. Dairying accounted 53.33 and 23.33% of the total generated family income for urban and peri-urban dairy producers; respectively. The finding indicated that input suppliers, producers, traders, consumers and service providers are involved directly and/or indirectly along dairy value chains in the study areas. Accordingly, producing and processing, collecting, storing and marketing dairy products are the major activities which were performed by the actors. Out of all milk value chain actors about 61% retailers (café and restaurant) and 39% milk producer, were involved in the value addition of milk in both study areas. Most of the smallholder dairy producers in the study sites have been using traditional dairy production technique that results in low milk production. Creating awareness and other capacity building intervention of smallholder dairy producer for quality and quantity milk production are one of the ways to assist dairy producers in building on their resources to create more income by managing their dairy farm skillfully and get a good price in the market. Hence, all concerned organizations (chain enablers) should focus on the provision of appropriate training for both dairy producer farmers and extension agents on how to manage improved breed dairy cattle and incorporate new technologies profitably into farm level production strategies.

Genomic and phenotypic analyses of exopolysaccharide biosynthesis in Streptococcus thermophilus S-3

Streptococcus thermophilus, one of the most important industrial lactic acid bacteria, is widely used as a starter culture in the dairy industry. Streptococcus thermophilus S-3 isolated from Chinese traditional dairy products has shown great potential for the production of larger amounts of exopolysaccharides (EPS), which significantly affect the organoleptic properties of fermented milk products. To understand the relationship between the genotype and phenotype of S. thermophilus S-3 in terms of EPS biosynthesis, its genome of strain S-3 was sequenced and the genes related to carbohydrate utilization, nucleotide sugars synthesis, and EPS biosynthesis were investigated. The genomic analysis revealed that S. thermophilus S-3 can use sucrose, mannose, glucose, galactose, and lactose. Phenotypic analysis showed that S-3 prefers fermenting lactose to fermenting glucose or galactose. The genetic analysis of nucleotide sugars and EPS biosynthesis revealed that S-3 can synthesize uridine diphosphate (UDP)-glucose, deoxythymidine diphosphate-glucose, deoxythymidine diphosphate-rhamnose, UDP-galactose, UDP-N-acetylgalactosamine, and UDP-N-acetylglucosamine. A high yield of EPS from S-3 cultivated with lactose rather than glucose as the carbon source was correlated with high transcriptional levels of the genes associated with metabolism of these nucleotide sugars and EPS biosynthesis. Our results provide a better understanding of EPS biosynthesis in S. thermophilus and can facilitate enhanced EPS production by lactic acid bacteria fermentation via genetic and metabolic engineering approaches.

Biodiversity of lactic acid bacteria isolated from fermented milk products in Xinjiang, China

ABSTRACTFermented dairy products have been produced and consumed for thousands of years in Xinjiang, China. In this study, traditional culture-dependent methods and 16S rRNA gene analyses were performed to analyze the composition of lactic acid bacteria (LAB) from 86 samples of traditional fermented dairy products collected from four regions of Xinjiang. Quantitative polymerase chain reaction (qPCR) was used to quantify Bifidobacterium and Lactobacillus species. The LAB isolates (N = 705) were identified as belonging to seven genera and 26 species or subspecies. The predominant species of all isolates were Lactobacillus (Lb.) delbrueckii subsp. bulgaricus, Lb. fermentum, and Lb. helveticus. The LAB counts of these samples ranged from 5.35 to 10.06 Log CFU/mL. The bacterial counts of seven lactobacilli species and Bifidobacterium ranged from 0.98 ± 0.14 Log CFU/mL (for Lb. sakei from fermented mare milk) to 9.91 ± 0.17 Log CFU/mL (for Lb. helveticus from fermented mare milk). While the microbiota was significantly different between yak and cow milk, there was no significant difference between the Tex and Zhaosu counties. In conclusion, LAB communities in traditional fermented dairy products are complex and differ among local regions within Xinjiang.

Potential use of probiotic Enterococcus faecium and Enterococcus durans strains in Izmir Tulum cheese as adjunct culture.

In this research, Enterococcus species with probiotic properties were isolated from raw milk and some traditional dairy products and these species were identified by using biochemical, phenotypical and genotypic methods and their potential use in Izmir Tulum cheese production as adjunct culture were investigated. Among the isolated and identified Enterococcus species, three Enterococcus faecium and one Enterococcus durans strains with no vancomycin resistance, no decarboxylation activity, high antimicrobial activity and resistance to acidity were selected, and a mix culture was produced. This culture was mixed with commercial cheese culture containing Lactococcus lactis subsp. lactis and Lactococcus lactis subsp. cremoris in different proportions and used in Izmir Tulum cheese production. Cheese samples were left to ripening for 180days, and their physical, chemical, microbiological and sensory properties were evaluated with comparison to prior studies. Evaluations showed that using adjunct culture in Izmir Tulum cheese production has no negative effect on physical, chemical and microbiological properties and higher proportions of probiotic Enterococci in the culture have a positive effect on the sensory properties, especially on flavor.

Investigating the bacterial microbiota of traditional fermented dairy products using propidium monoazide with single-molecule real-time sequencing

Traditional fermented dairy foods have been the major components of the Mongolian diet for millennia. In this study, we used propidium monoazide (PMA; binds to DNA of nonviable cells so that only viable cells are enumerated) and single-molecule real-time sequencing (SMRT) technology to investigate the total and viable bacterial compositions of 19 traditional fermented dairy foods, including koumiss from Inner Mongolia (KIM), koumiss from Mongolia (KM), and fermented cow milk from Mongolia (CM); sample groups treated with PMA were designated PKIM, PKM, and PCM. Full-length 16S rRNA sequencing identified 195 bacterial species in 121 genera and 13 phyla in PMA-treated and untreated samples. The PMA-treated and untreated samples differed significantly in their bacterial community composition and α-diversity values. The predominant species in KM, KIM, and CM were Lactobacillus helveticus, Streptococcus parauberis, and Lactobacillus delbrueckii, whereas the predominant species in PKM, PKIM, and PCM were Enterobacter xiangfangensis, Lactobacillus helveticus, and E. xiangfangensis, respectively. Weighted and unweighted principal coordinate analyses showed a clear clustering pattern with good separation and only minor overlapping. In addition, a pure culture method was performed to obtain lactic acid bacteria resources in dairy samples according to the results of SMRT sequencing. A total of 102 LAB strains were identified and Lb. helveticus (68.63%) was the most abundant, in agreement with SMRT sequencing results. Our results revealed that the bacterial communities of traditional dairy foods are complex and vary by type of fermented dairy product. The PMA treatment induced significant changes in bacterial community structure.

Exopolysaccharide-producing lactic acid bacteria isolated from traditional Algerian dairy products and their application for skim-milk fermentations

Exopolysaccharide (EPS)-producing lactic acid bacteria are used in the dairy industry to obtain products with appropriate sensorial properties. Specific EPS act as stabilizers, thickeners, and/or fat-replacers, and are considered as natural biopolymers. The autochthonous microbiota of foods provides a rich reservoir of biodiversity to find biopolymers for novel applications. In this study, a collection of LAB isolated from homemade Algerian dairy products was screened for a rational selection of EPS-producing strains. Six isolates, identified as Lactobacillus plantarum, presented a stable mucoid/ropy phenotype after several sub-cultivations and they were used to ferment skimmed milk. Those fermented with strains LBIO1 and LBIO28 had higher viscosity, a smooth/creamy texture and presented lower syneresis. The kinetics of growth and EPS-production, followed for 48 h, showed that both strains had similar behaviour, the molar mass (about 2 × 106 Da) and radius of gyration (about 80 nm) of the polymers being also similar. However, LBIO28 was able to increase the apparent viscosity of the fermented milk to a higher extent than LBIO1, which could be related with the earlier accumulation of EPS in the first strain in relation to the gelation point. Thus, these two ropy EPS-producing strains are suitable for different applications in dairy fermentations.