Search Results (40)

While industrial-scale dairy fermentations often employ pasteurized milk as the substrate, many farmhouse and traditional production practices apply raw milk derived from a variety of mammals. Certain artisanal production systems rely on the autochthonous microbiota of the milk, fermentation vessels, equipment and/or environment to initiate milk coagulation. While the technological properties of lactic acid bacteria associated with dairy fermentations are well described, their interactions with other organisms during fermentation and cheese ripening are poorly investigated. This study presents an overview of the microbial ecology of raw and pasteurized milk used in the production of Irish farmhouse cheeses using metagenomic and culture-based approaches. Metagenomic analysis of four raw milk-derived cheeses established the dominant presence of either lactococci or Streptococcus spp. and with a secondary population of various lactobacilli. Interestingly, the Brie sample was also demonstrated to possess significant proportion of Hafnia spp. This was corroborated in culture-based analysis where Hafnia isolates were also identified. Furthermore, we report on the motility phenotype, lactose utilization ability and metabolic products of isolates of Hafnia paralvei and Hafnia alvei, and determine that these strains could grow in a non-antagonistic manner on plates with strains of Lactococcus lactis and Streptococcus thermophilus. As artisanal and farmhouse production systems are often associated with protected or regionally significant products, it is essential to develop a clear understanding of the microbial communities within and the complex relationships between the community members. Full article

Enterococci from raw goat milk were taxonomically allotted in the species Enterococcus faecalis using sequencing (16S rRNA and BLASTn analysis) with a percentage identity up to 99.91%. The virulence factor gene gelE was found in the strains EE/K3, EE/G3, and EE/G6. The agg gene was detected in the strain EE/G6, and the esp gene was detected in the strains EE/K5 and EE/G7. Each strain possessed at least one virulence factor gene. In the strain EE/G6, the gelE and esp genes were found. The strains EE/G6 and EE/G3 showed resistance to tetracycline and vancomycin. EE/G7 was resistant to vancomycin and gentamicin. All strains possessed low-grade biofilm-forming ability (0.1 < A570 ≤ 1.0). They possessed genes for biofilm formation (bopD, srt, and/or ace). They also produced esterase (20–40 nmo/L), esterase lipase, and α-chymotrypsin (10–40 nmoL). The values of acid phosphatase reached 20–40 nmoL. The strains EE/G3, EE/G6, and EE/G7 were observed to possess the most pathogenicity. However, all strains were susceptible to postbiotic active substances produced by two autochthonous lactococci, MK2/8 and MK1/3 (inhibitory activity up to 400 AU/mL). These postbiotic substances provide a new potential alternative to reducing contaminants in milk. Full article

The production of fermented sausages from poultry meat using traditional technologies and natural maturation conditions is a major challenge. The aim of this study was to identify indigenous microbiota with antilisterial activity from an innovative, additive-free, traditionally fermented chicken sausage. Isolates (n = 88) of lactic acid bacteria (LAB) were collected during maturation and subjected to MALDI-TOF mass spectrometry identification. The capacity to combat Listeria was screened against five strains using the agar well diffusion method in 63 selected LAB isolates. MALDI-TOF mass spectrometry identified four different LAB genera, namely Enterococcus, Lactococcus, Leuconostoc and Lactobacillus, the proportions of which differed significantly during the production phases (p < 0.001). Enterococcus faecalis was the most prevalent LAB species in the initial sausage dough. The presence of lactococci (Lactococcus lactis) and enterococci was detected during the 14- and 30-day ripening period and was gradually displaced by leuconostocs and lactobacilli. Lactobacilli appeared to be abundant during the central and late maturation phases, and consisted of only two species—Latilactobacillus sakei and Latilactobacillus curvatus. In total, 38 LAB isolates (60%) showed antilisterial activity toward at least one Listeria indicator strain. The proportions of antilisterial LAB differed significantly during sausage maturation. Inhibitory activity against all indicator Listeria was detected in the neutralized cell-free supernatants of five strains of Enterococcus faecalis, two L. sakei strains and one Leuconostoc mesenteroides strain. The antilisterial activity observed in the indigenous LAB revealed the possible role of L. sakei as a bioprotective culture, as well as the role of Ln. mesenteroides and E. faecalis as bacteriocin producers, for practical applications. Full article

Raw goat milk-derived Lactococcus lactis MK1/3 (CCM 9209) was studied to show its potential for use in the dairy industry. Finding an innovative strain indicates having a new safe, original additive for functional food. The strain has been shown to be safe using a model experiment with Balb/c mice, when no mortality was noted. Its counts were increased continually during 120 days, with the highest value on day 90 (4.38 ± 1.24 colony-forming unit per gram (CFU/g, log 10). In vivo (in the experimental mice), anti-staphylococcal effect was noted with difference 1.82 log cycles. The safety of the strain MK1/3 has been also indicated by the fact that it did not produce damaging enzymes, it has been susceptible to antibiotics, and it has shown low-grade biofilm-forming ability (0.126 ± 0.35). This strain has tolerated bile, and low pH sufficiently. It produced a postbiotic active substance with inhibitory activity against cheese and milk contaminants (Enterococci), reaching antimicrobial activity up to 3200 AU/mL. The count of the strain MK1/3 was higher in yogurts from ewe goat milk (4.66 ± 0.30 CFU/g, log 10), in comparison with its count in yogurts from ewe milk (4.10 ± 0.10 CFU/g, log 10), with no influencing yogurt pH. Its use in 100% starter culture to process fresh cheese based on goat milk was revealed in the standard cheese quality with sufficient amount of lactic acid microbiota. To support the benefit of the strain MK1/3, additional human trials have been reinforced. Full article

Sweet potatoes play an important role in the global food supply, as they are rich in bioactive components and have numerous health benefits. Their minimally processed, ready-to-eat form is increasingly popular among consumers; however, discoloration and microbiological problems threaten the safety of these products. The aim of this study is to investigate the shelf life of cleaned, cut, ready-to-eat, vacuum-packed, and refrigerated Bonita (white) and Covington (orange) varieties of sweet potatoes after soaking in apple and chokeberry pomace extracts and treatment with citric and ascorbic acids. A series of microbiological and analytical tests was conducted during the storage period. The microbiological tests included the enumeration of cells of mesophilic aerobic and facultative anaerobic microbes, as well as lactobacilli, lactococci, Enterobacteriaceae, yeasts, and moulds. The analytical tests encompassed the determination of the total phenolic content, antioxidant capacity, water-soluble solid content, and pH value. The prevalent microbial groups detected in the examined sweet potato varieties were lactic acid bacteria, which were present in both fresh samples and following storage. This study established that low-temperature refrigeration (5 °C), vacuum packaging, and organic acid treatment can effectively control lactic acid bacteria, which are pivotal to spoilage. The combination of preservation steps is of particular significance for ready-to-cook sweet potatoes, as this approach effectively extends the shelf life of these products. Full article

Bacteriophages (or phages) remain the leading cause of failure in dairy fermentations. Thereby, phage-resistant Lactococcus lactis and Lactococcus cremoris dairy starters are in continuous demand. In this work, our goal was to identify phage defense mechanisms against ceduoviruses encoded by two wild isolates of dairy origin named L. lactis IPLA517 and IPLA1064. These strains were previously subjected to experimental evolution to select derivatives that are resistant to the bacteriocin Lcn972. It was observed that the Lcn972^R derivatives became sensitive to phage infection; however, the underlying mechanism was not defined. The long-read sequencing technologies applied in this work reveal that all of the Lcn972^R derivatives shared the loss of a 41 kb endogenous plasmid (p41) that harbors a putative exopolysaccharide (EPS) gene cluster with significant homology to one described in Lactococcus garvieae. Using a CRISPR-Cas9-based approach, p41 was selectively cured from L. lactis IPLA1064. Phage infection assays with three ceduoviruses demonstrated that curing p41 restored phage sensitivity at levels comparable to the Lcn972^R-IPLA1064 derivatives. Phage adsorption to Δp41 cells was also increased, consistent with the hypothesis of EPS production hindering access to the phage receptor protein Pip. Our results reinforce the role of EPSs in protecting Lactococcus against phage infection, a phenomenon that is rarely reported for ceduoviruses. Moreover, the results also exemplify the likely horizontal gene transfer that can occur between L. lactis and L. garvieae in a dairy environment. Full article

The demand of consumers for a healthier and functional diet necessitates amongst others, extending the shelf life of the natural probiotic kefir, reducing simultaneously packaging, transportation, and storage costs. Among the different drying methods, spray drying is widely used and industrially favorable to produce powdered products. The aim of the present work was to study the effect of the final fermentation pH and the pre-drying storage temperature (4 °C for 7 days) on the physicochemical properties, moisture content, pH, color, adsorption isotherms, and the microbiological characteristics of spray dried kefir. Kefir grains were used for the fermentation and the production of the samples. Viabilities of lactococci, lactobacilli, and yeasts were determined during a storage period of 45 days. Both final fermentation pH and low-temperature storage significantly affected the properties of the kefir powders and their respective reconstituted samples. According to the findings of the study, the desirable microbial populations of the reconstituted kefir powders are possible to accomplish by using an increased final fermentation pH at 5.2 and/or by applying low-temperature storage of the fermented milk, together with the kefir grains, at 4 °C for 7 days prior to drying. The yeast population was affected the least by the studied factors, and the use of kefir grains as starter culture favored the viability of lactococci and lactobacilli after spray drying and during storage up to 45 days. Full article

The biological and nutritional value of kefir makes it imperative to widen its customer reach by extending its shelf life, enabling its storage and transport at ambient temperatures, and reducing its packaging cost requirements. A well-documented and widely used food processing method that can achieve the above-mentioned outcomes is spray drying through the formulation of kefir powder, with quality attributes that will closely resemble that of the original product. In the present work, a variety of drying carriers (trehalose, fructo-oligosaccharides, maltodextrin, gum arabic, and whey proteins) were studied with regard to their effect on the properties of powdered and reconstituted kefir samples. Particularly, the physicochemical characteristics (moisture content, pH, acidity, color), powder properties (bulk density, tapped density, water solubility index, insoluble matter), adsorption isotherms, particle size distribution, microbiological properties, and structural characteristics of the samples were evaluated. Gum arabic and maltodextrin produced kefir powder samples with the lowest moisture content. Spray drying affected a reduced acidity and, as a consequence, an increased pH in the reconstituted samples, especially without any carrier addition and with trehalose and fructo-oligosaccharides irrespective of their concentration. Desirable color attributes were achieved on the kefir powder samples with trehalose, fructo-oligosaccharides, and maltodextrin regardless of their concentration in the product. Fructo-oligosaccharides, added at 3%, gave the highest values of bulk density, while whey proteins, due to their nature, exhibited the lowest. All carriers tested improved the water solubility index when compared to the control sample. The sample with 10% whey proteins exhibited the lowest moisture adsorption compared to the control at the highest relative humidity environments employed for the test. In the absence of agglomeration, powder granule size and structural morphology were not affected by the carriers. The survival of lactococci in the powdered kefir samples, in comparison to the control product, was higher in the case where 4% trehalose or 5 to 10% whey proteins were added. On the contrary, yeast populations decreased significantly during drying and they were not affected by the presence of the different carriers. As shown by the findings of the present study, trehalose proved to be the most effective carrier, among the others used, for producing high-quality kefir powder products. However, further work is required with regard to the keeping quality of the product during long-term storage. Full article

Raw goat and ewe’s milk samples were used for the isolation of seven lactic acid bacteria new strains. After testing hemolytic activity and resistance to antibiotics, specific functional properties were evaluated; Lactococcus lactis subsp. lactis FBM_1321 and Lacticaseibacillus paracasei FBM_1327 strains resulted in the highest cholesterol assimilation percentages ranging from 28.78 to 30.56%. In addition, strong adhesion capacity to differentiated Caco-2 cells (1.77–21.04%) was mapped, and the lactobacilli strains exhibited strong antagonistic activity against foodborne pathogens compared to lactococci. The strains were able to grow at low pH and high NaCl concentrations, conditions that prevail in food systems (cell counts ranged from 1.77 to 8.48 log CFU/mL after exposure to pH 3 and from 5.66 to 9.52 log CFU/mL after exposure to NaCl concentrations up to 8%). As a next step, freeze-dried immobilized Lc. paracasei FBM_1327 cells on oat flakes were used for the preparation of functional yoghurt and ayran products. Cell loads of the functional strain remained high and stable in both products (7.69 log CFU/g in yoghurt and 8.56 log CFU/g in ayran after 30 days of storage at 4 °C) throughout their shelf life. No significant changes in the volatile profile were noticed, and the new products were accepted by the panel during the sensory evaluation. Full article

Films and coatings based on biopolymers have been extensively studied in recent years since they have less impact on the environment, can be obtained from renewable sources, have good coating and film-forming capacity, are biodegradable and can have interesting nutritional properties. In the present study, sheep’s cheese whey powder (SCWP) was used to produce edible cheese coatings. Six types of cheese samples were produced: without coating (CON); treated with natamycin (NAT); with SCWP coating without antimicrobials (WCO); with SCWP coating with a commercial bioprotective culture (WFQ); with SCWP coating with kombucha tea (WKO); and with SCWP coating with oregano essential oil (WEO). At the end of the ripening period, all the cheeses were classified as full-fat and semihard, according to the Portuguese standard. The higher hardness and adhesiveness values of samples CON, WFQ and WKO were in line with the lower moisture in defatted cheese observed in these samples, indicating that future work should address the improvement of water vapor barrier properties of the whey-based coating. The samples treated with natamycin and with oregano essential oil presented significantly lower values for hardness. Differences were also observed on titratable acidity and a_w, both between samples and because of ripening time. The color parameters of cheese samples also presented differences, chiefly in the rind, but the highest differences observed resulted from ripening time rather than between samples. In all cases, the counts of lactobacilli and lactococci surpassed log 7 CFU/g by the end of ripening. Regarding yeast and mold counts, the samples CON and WCO presented the highest values by the end of the ripening period (>log 4 CFU/g), while sample NAT presented the lowest value (ca. log 3 CFU/g). Samples WFQ, WKO and WEO presented values which were ca. 0.5 log cycles lower than samples CON and WCO. Hence, the use of SCWP alongside bioprotective culture, kombucha tea or oregano essential oil had a positive impact in the reduction of mold counts on cheese surfaces. Future work should also evaluate the joint use of different antimicrobials. Full article

Organic dairy products, including fermented milk, are gaining popularity among consumers. Traditionally, for kefir production, kefir grains are used; however, in the modern industry, freeze-dried cultures are commonly employed. This study aimed to analyze the quality of kefirs produced from organic cow milk with two fermentation times (12 and 24 h) with the use of kefir grains or freeze-dried culture. During a 3-week storage period, physicochemical properties, color, syneresis index, texture, sensory, and microbiological quality were evaluated. The results proved that organic cow milk was suitable for kefir production both with the use of kefir grains and freeze-dried culture. Using freeze-dried culture and a 24 h fermentation period resulted in kefir with the lowest syneresis tendency (3.65–9.62%), along with the best textural properties (the highest cohesiveness and viscosity index), and desired sensory characteristics. Kefir grains had a better acidification ability, and the resulting products had a higher count of yeasts, lactobacilli, and lactococci compared with kefirs obtained with freeze-dried culture. However, both the type of starter culture and the fermentation time influenced the product’s quality. The longer fermentation time of 24 h was more appropriate for the kefir production. Kefir grains, as a traditional form of kefir culture, may be preferred in organic kefir production. Full article

In this study, butter and the corresponding buttermilk samples were produced with cream fermented by aromatic (A) or probiotic (P) cultures with or without complementary bioprotective culture (BC). The samples were characterised for their composition and colour parameters. Texture and rheological properties were evaluated at 10 and 20 °C. Microbiological (lactobacilli, lactococci, and yeast and mould counts) and sensory (aroma, taste, texture, and global evaluation) analyses were also performed. All butter sample characteristics were in accordance with the Portuguese standard. Regarding colour, the sample obtained with cream fermented by probiotics plus bioprotective culture (PBC) presented higher L* and b* values, indicating a slightly higher yellow chroma. However, colour differences (ΔEab*) in the butter samples were, in most cases, not detectable by a common observer. Butter samples P and PBC presented a significantly higher viscous modulus and consequently higher dynamic viscosity values (ca. log 6.5 Pa.s at 10 °C and log 5 Pa.s at 20 °C). Butter samples presented a pseudoplastic behaviour, and rheological parameters showed a high dependence on temperature. The counts of lactobacilli and lactococci in the butter samples were of the order of log 7–8 CFU/g, while yeast and mould counts were lower than log 2 CFU/g until the 30th day of storage, after which they showed a sharp increase to ca. log 5 CFU/g between the 30th and the 60th days of storage. Regarding sensory attributes of butter, sample P received the highest overall liking, followed by samples ABC and PBC. Sample A was the least appreciated. Buttermilk samples presented significant differences regarding their composition, viscosity, and colour parameters. In all cases, lactobacilli and lactococci counts exceeded log 7 CFU/mL after 30 days of storage, but yeast and mould counts were of the order of log 5–6 CFU/mL at the 15th day of storage. Samples P and PBC presented yeast and mould counts ca. 1–2 log cycles lower than samples A and ABC, indicating the potential of probiotic and bioprotective cultures to extend the shelf life of the product. Regarding the sensory attributes of buttermilk, samples P and PBC received the highest overall liking, followed by sample ABC. Sample A received the lowest scores, as had occurred with the butter samples. However, in all cases, the scores obtained by the buttermilk samples were lower compared to the ones of the corresponding butter. It can be concluded that both probiotic butter and buttermilk present high levels of lactobacilli and lactococci and can maintain their probiotic potential throughout the storage period. Full article

In this study, Caciocavallo, a typical cheese produced in Sicily Island (Italy), was obtained from the milk of dairy cows fed with and without enriched olive cake (ECO and CTR, respectively) in order to evaluate nutritional, microbiological, volatile, and sensory differences in cheeses. ECO cheese showed greater (p < 0.05) MUFA and PUFA and polyphenols content and lower SFA content than CTR cheese. Microbiological analyses revealed the absence of Salmonella, Listeria monocytogenes, Escherichia coli, and E. coli O157, and no significant differences in the viable counts of the remaining microbial groups analyzed, between samples. Thermophilic lactococci were more prevalent in ECO cheese. The implementation of a culture-independent method, such as PCR-DGGE analyses, revealed the presence of a more diverse microbial population in both cheeses. Regarding the volatile compounds profile, long-chain free fatty acids were more abundant in the ECO cheese, resulting in a healthier free fatty acid profile. This study also showed that, especially for their appearance and taste, consumers mostly appreciated the ECO cheese. The results show that using enriched olive cake could enhance the sustainability and the quality of Ragusano cheese, improving not only the health of its consumers but also positively influencing tastes and acceptability. Full article

Currently, starter cultures for fermenting plant-based beverages are not widely available commercially, but producers can use starter cultures for dairy products. Therefore, the aim of this study was to determine the physicochemical, rheological, antioxidant and sensory properties of oat beverages with/without pectin fermented by four different dairy starter cultures. The use of a mono-starter with Lactobacillus bulgaricus or Sreptococcus thermophilus allows for the efficient use of glucose, and more lactic acid is accumulated. The beverage with L. bulgaricus is characterised by high adhesion, syneresis and low cohesiveness, and it has high antioxidant activity and a low sensory profile. Using starter with L. bulgaricus, S. thermophilus and some Lactococcus for fermentation yields a product with high sensory capacity, forming a high-viscosity beverage matrix with low syneresis, high water retention, chewy texture and stickiness. It has been observed that the absence of lactococci and the presence of Lactobacillus casei, L. Rhamnosus and L. paracasei in the starter yields a product with high antioxidant activity, especially in the presence of pectin. The use of pectin significantly improves the viscosity and textural properties of oat yoghurt, enhancing the drink’s flavour and giving it body. For many reasons, the use of different commercial starters in the dairy industry results in different viscosities of oat fermented beverages, forming a matrix with different textural, sensory and antioxidant properties. Full article

The species Lactococcus lactis is a bacterium extensively used in the dairy industry. This bacterium is Generally Recognized as Safe and was added to the European Food Safety Authority’s Qualified Presumption of Safety list. The major functions of this species in dairy fermentation are the production of lactic acid from lactose, citric acid fermentation, and the hydrolysis of casein. But, the representatives of this species that produce bacteriocin substances can also exert an inhibitory effect against spoilage bacteria. The aims of this study were to test three lactococcal strains isolated from raw goat milk for their postbiotic activity and to test their stability in goat milk yogurts after their application in encapsulated form for their further application. To achieve these aims, validated methods were used. Three Lactococcus lactis strains (identified by Blastn 16S rRNA analysis) produced bacteriocin substances/postbiotics. These concentrated postbiotics inhibited the growth of enterococci and staphylococci (by up to 97.8%), reaching an inhibitory activity of up to 800 AU/mL. The encapsulated (freeze-dried) lactococci survived in the goat milk yogurts with sufficient stability. Strain MK2/8 fortified the yogurts in the highest amount (8.1 ± 0.0 cfu/g log 10). It did not influence the pH of the yogurt. Full article