Cheese Core Research Articles

Short communication: Comparing the microbiota diversity from the core, middle part and rind of six Spanish commercial goat cheeses

The cheese core has a lower oxygen saturation and salinity and a higher acidity than the rind, but there is controversy about the incidence of such factors on the magnitude of microbial diversity. The goal of the current work was to investigate the existence of differences in α-diversity between the core, middle part, and rind of six Spanish commercial cheeses through a sequencing approach. To this end, we have collected rind, middle part, and core samples from fresh (H and M), soft semi-ripened (C and P), hard semi-ripened (B) and semi-hard aged (G) goat cheeses. After purifying deoxyribonucleic acid from these 18 samples, the V3-V4 ultravariable region of the 16S rRNA gene was sequenced. The analysis of microbial composition revealed that lactic acid bacteria from the genera Lactococcus, Lactobacillus, Streptococcus, and Leuconostoc are predominant in all six goat cheeses. Furthermore, we identified several psychrophilic taxa often associated with the post-pasteurization contamination of refrigerated milk. Comparison of three α-diversity estimators (Chao1, Shannon and Faith's phylogenetic diversity indices) of microbiota in the core, middle part, and rind of all six goat cheeses did not reveal substantial differences, being only significant (at the nominal level) the comparison of rind vs middle part for the Shannon index (P-value = 0.031). Moreover, the construction of a dendrogram based on Aitchison distances revealed that cheese samples cluster according to their manufacturing characteristics, with a clear distinction between fresh vs semi-ripened or aged cheeses. We conclude that the magnitude of microbial α-diversity in the cheese core is similar to that in the rind despite their different physicochemical attributes. This result could be because physicochemical differences between cheese compartments are often attenuated during cheese ripening.

The microbial and metabolite composition of Gouda cheese made from pasteurized milk is determined by the processing chain

Gouda cheeses of different production batches and ripening times often differ in metabolite composition, which may be due to the starter culture mixture applied or the growth of non-starter lactic acid bacteria (NSLAB) upon maturation. Therefore, a single Gouda cheese production batch was systematically investigated from the thermized milk to the mature cheeses, ripened for up to 100 weeks, to identify the main bacterial species and metabolites and their dynamics during the whole production and ripening. As this seemed to be starter culture strain- and NSLAB-dependent, it requested a detailed, longitudinal, and quantitative investigation. Hereto, microbial colony enumeration, high-throughput full-length 16S rRNA gene sequencing, and a metabolomic approach were combined. Culture-dependently, Lactococcus lactis was the most abundant species from its addition as part of the starter culture up to the first two months of cheese ripening. Afterward, the NSLAB Lacticaseibacillus paracasei became the main species during ripening. The milk was a possible inoculation source for the latter species, despite pasteurization. Culture-independently, the starter LAB Lactococcus cremoris and Lc. lactis were the most abundant species in the cheese core throughout the whole fermentation and ripening phases up to 100 weeks. The cheese rind from 40 until 100 weeks of ripening was characterized by a high relative abundance of the NSLAB Tetragenococcus halophilus and Loigolactobacillus rennini, which both came from the brine. These species were linked with the production of the biogenic amines cadaverine and putrescine. The most abundant volatile organic compound was acetoin, an indicator of citrate and lactose fermentation during the production day, whereas the concentrations of free amino acids were an indicator of the ripening time.

Exploring alternative salting methods to reduce sodium content in blue-veined cheeses

Reducing sodium content in food is a major public health challenge, especially for cheeses. Different salt reduction methods in surface dry-salted blue cheese and their effect on biochemical, physicochemical, microbiological, rheological and sensory characteristics of cheese were investigated. The cheeses were salted with coarse or fine salt using various methods. All methods decreased sodium content in cheese core (−11% to −67%) and induced higher water activity. Sprinkling (−45% NaCl content) and calcium lactate substitution (−10% NaCl content) were technically feasible. The sanitary quality and cheese microbiota were not impacted except for a reduction of yeasts and moulds. Higher indices of richness and diversity were found on salt-reduced cheeses with Streptococcus, Lactococcus and Leuconostoc mesenteroides dominating. Texture and appearance of the cheeses were also affected. The research identified the limits of salt reduction in blue-veined cheeses; sprinkling and partial substitution with calcium lactate should be further studied.

Quantitative PCR reveals the frequency and distribution of 3 indigenous yeast species across a range of specialty cheeses.

Indigenous microorganisms are important components of the complex ecosystem of many dairy foods including cheeses, and they are potential contributors to the development of a specific cheese's sensory properties. Among these indigenous microorganisms are the yeasts Cyberlindnera jadinii, Pichia kudriavzevii, and Kazachstania servazzii, which were previously detected using traditional microbiological methods in both raw milk and some artisanal specialty cheeses produced in the province of Québec, Canada. However, their levels across different cheese varieties are unknown. A highly specific and sensitive real-time quantitative PCR assay was developed to quantitate these yeast species in a variety of specialty cheeses (bloomy-rind, washed-rind, and natural-rind cheeses from raw, thermized, and pasteurized milks). The specificity of the quantitative PCR assay was validated, and it showed no cross-amplification with 11 other fungal microorganisms usually found in bloomy-rind and washed-rind cheeses. Cyberlindnera jadinii and P. kudriavzevii were found in the majority of the cheeses analyzed (25 of 29 and 24 of 29 cheeses, respectively) in concentrations up to 104 to 108 gene copies/g in the cheese cores, which are considered oxygen-poor environments, and 101 to 104 gene copies/cm2 in the rind. However, their high abundance was not observed in the same samples. Whereas C. jadinii was present and dominant in all core and rind samples, P. kudriavzevii was mostly present in cheese cores. In contrast, K. servazzii was present in the rinds of only 2 cheeses, in concentrations ranging from 101 to 103 gene copies/cm2, and in 1 cheese core at 105 gene copies/g. Thus, in the ecosystems of specialty cheeses, indigenous yeasts are highly frequent but variable, with certain species selectively present in specific varieties. These results shed light on some indigenous yeasts that establish during the ripening of specialty cheeses.

Comparison of different visual methods to follow the effect of milk heat treatment and MTGase on appearance of semi-hard buffalo cheese

• Pasteurization caused lighter yellow color by buffalo cheese independent of MTGase. • MTGase treatment led to more whitish color both for raw and buffalo cheese. • Hyperspectral imaging can be used to predict color parameters of buffalo cheese. • SEM revealed that MTGase causes more evenly distributed regular cheese holes. • Sensory analysis of yellow color was monitored both in cheese core and rind.

Biogenic Amine Content in Retailed Cheese Varieties Produced with Commercial Bacterial or Mold Cultures

Biogenic amines (BAs) are considered a potential microbiological toxicological hazard in aged cheese. Risk mitigation strategies include good hygiene practice measures, thermal treatment of milk and the use of competitive dairy cultures. The aim of this study was to evaluate the amount of BAs—tryptamine, β-phenylethylamine, putrescine, cadaverine, histamine, tyramine, spermidine and spermine—in the core and rind of cheeses ripened by bacteria (n = 61) and by mold cultures (n = 8). The microbial communities were counted, and the dominant lactic acid bacteria (LAB) were identified, corresponding to the BA concentrations. The total BA content was highest in the core of semi-hard cheeses (353.98 mg/kg), followed by mold cheeses (248.99 mg/kg) and lowest in hard cheeses (157.38 mg/kg). The highest amount of BAs was present in the rind of cheeses with mold (240.52 mg/kg), followed by semi-hard (174.99 mg/kg) and hard cheeses (107.21 mg/kg). Tyramine was the most abundant BA, represented by 75.4% in mold cheeses, 41.3% in hard cheese and 35% of total BAs in semi-hard cheeses. Histamine was present above the defined European maximum level (ML) of 100 mg/kg in only two semi-hard and three hard cheeses. High amount of BAs (above 600 mg/kg) in cheeses, mainly tyramine, were associated with the presence of Enterococcus durans, while negligible BA concentrations were found in cheeses ripened with Lacticaseibacillus rhamnosus, Lactococcus lactis or Lacticaseibacillus paracasei cultures. This study has shown that retailed cheese varieties produced with commercial bacterial or mold cultures have acceptable levels of biogenic amines with respect to consumers.

Chemometric evaluation of the metabolites and volatile profiles of mite-ripened cheeses

Cheese ripening in the presence of mites is a common practice in some European countries. In Brazil, this practice is incipient and it is still unknown whether the mite diversity and mite-mediated processes in the production of Brazilian cheeses are important for product differentiation. Here, we conducted chemometric evaluations of the volatile organic compounds (VOCs) and metabolites in two types of Brazilian cheeses (Minas and Colonial) ripened in the presence and absence of mites, using gas chromatography–mass spectrometry and nuclear magnetic resonance spectroscopy. The presence of mites during cheese ripening influenced the development of fruity VOCs on the surface (rind) of both the cheeses. However, a few influences of mite were observed in the core of cheeses. The mite presence induced the production of metabolites and VOCs that conferred sensory identity to the cheeses.

Predicting growth of Listeria monocytogenes at dynamic conditions during manufacturing, ripening and storage of cheeses – Evaluation and application of models

Mathematical models were evaluated to predict growth of L. monocytogenes in mould/smear-ripened cheeses with measured dynamic changes in product characteristics and storage conditions. To generate data for model evaluation three challenge tests were performed with mould-ripened cheeses produced by using milk inoculated with L. monocytogenes. Growth of L. monocytogenes and lactic acid bacteria (LAB) in the rind and in the core of cheeses were quantified together with changes in product characteristics over time (temperature, pH, NaCl/aw, lactic- and acetic acid concentrations). The performance of nine available L. monocytogenes growth models was evaluated using growth responses from the present study and from literature together with the determined or reported dynamic product characteristics and storage conditions (46 kinetics). The acceptable simulation zone (ASZ) method was used to assess model performance. A reduced version of the Martinez-Rios et al. (2019) model (https://doi.org/10.3389/fmicb.2019.01510) and the model of Østergaard et al. (2014) (https://doi.org/10.1016/j.ijfoodmicro.2014.07.012) had acceptable performance with a ASZ-score of 71-70% for L. monocytogenes growth in mould/smear-ripened cheeses. Models from Coroller et al. (2012) (https://doi.org/10.1016/j.ijfoodmicro.2011.09.023) had close to acceptable performance with ASZ-scores of 67–69%. The validated models (Martinez-Rios et al., 2019; Østergaard et al., 2014) can be used to facilitate the evaluation of time to critical L. monocytogenes growth for mould/smear-ripened cheeses including modification of recipes with for example reduced salt/sodium or to support exposure assessment studies for these cheeses.

Microbial communities of a variety of cheeses and comparison between core and rind region of cheeses

Understanding the microbial community of cheese is important in the dairy industry, as the microbiota contributes to the safety, quality, and physicochemical and sensory properties of cheese. In this study, the microbial compositions of different cheeses (Cheddar, provolone, and Swiss cheese) and cheese locations (core, rind, and mixed) collected from the Arbuthnot Dairy Center at Oregon State University were analyzed using 16S rRNA gene amplicon sequencing with the Illumina MiSeq platform (Illumina, San Diego, CA). A total of 225 operational taxonomic units were identified from the 4,675,187 sequencing reads generated. Streptococcus was observed to be the most abundant organism in provolone (72 to 85%) and Swiss (60 to 67%), whereas Lactococcus spp. were found to dominate Cheddar cheese (27 to 76%). Species richness varied significantly by cheese. According to alpha diversity analysis, porter-soaked Cheddar cheese exhibited the highest microbial richness, whereas smoked provolone cheese showed the lowest. Rind regions of each cheese changed color through smoking and soaking for the beverage process. In addition, the microbial diversity of the rind region was higher than the core region because smoking and soaking processes directly contacted the rind region of each cheese. The microbial communities of the samples clustered by cheese, indicated that, within a given type of cheese, microbial compositions were very similar. Moreover, 34 operational taxonomic units were identified as biomarkers for different types of cheese through the linear discriminant analysis effect size method. Last, both carbohydrate and AA metabolites comprised more than 40% of the total functional annotated genes from 9 varieties of cheese samples. This study provides insight into the microbial composition of different types of cheese, as well as various locations within a cheese, which is applicable to its safety and sensory quality.

Microbial shifts in Minas artisanal cheeses from the Serra do Salitre region of Minas Gerais, Brazil throughout ripening time

The Minas artisanal cheese is a traditional product in its way of producing. Produced in the Minas Gerais state, Brazil, this cheese is made using raw cow's milk with the addition of an endogenous starter culture called “pingo”, responsible for inoculating specific microorganisms that could enhance flavor and sensorial aspects. There are seven regions able to produce and commercialize this product - Araxá, Campo das Vertentes, Canastra Cerrado, Serra do Salitre, Serro and Triângulo Mineiro. This study aimed to assess the bacterial community of raw milk, endogenous starter culture and to uncover possible shifts in the bacterial community of the rind and core of cheeses at sixty days of ripening located in the Serra do Salitre region by Illumina MiSeq 16S rRNA gene amplicon sequencing. Raw milk and starter culture are responsible for inoculating specific bacteria into the cheese, with Planococcaceae and Streptococcaceae being prevalent throughout ripening time. The Planococcaceae family seems to develop strong interactions with the Leuconostocaceae family on the surface of these cheeses, and is associated with environmental aspects of the region, probably leading to a microbial signature of these products. Additionally, abiotic factors such as geographical location, moisture and acidity are major drivers in the microbial shift.

Cheese yeasts.

Numerous traditionally aged cheeses are surface ripened and develop a biofilm, known as the cheese rind, on their surfaces. The rind of such cheeses comprises a complex community of bacterial and fungal species that are jointly responsible for the typical characteristics of the various cheese varieties. Surface ripening starts directly after brining with the rapid colonization of the cheese surface by yeasts. The initially dominant yeasts are acid and salt-tolerant and are capable of metabolizing the lactate produced by the starter lactic acid bacteria and of producing NH3 from amino acids. Both processes cause the pH of the cheese surface to rise dramatically. This so-called deacidification process enables the establishment of a salt-tolerant, Gram-positive bacterial community that is less acid-tolerant. Over the past decade, knowledge of yeast diversity in cheeses has increased considerably. The yeast species with the highest prevalence on surface-ripened cheeses are Debaryomyces hansenii and Geotrichum candidum, but up to 30 species can be found. In the cheese core, only lactose-fermenting yeasts, such as Kluyveromyces marxianus, are expected to grow. Yeasts are recognized as having an indispensable impact on the development of cheese flavour and texture because of their deacidifying, proteolytic, and/or lipolytic activity. Yeasts are used not only in the production of surface-ripened cheeses but also as adjunct cultures in the vat milk in order to modify ripening behaviour and flavour of the cheese. However, yeasts may also be responsible for spoilage of cheese, causing early blowing, off-flavour, brown discolouration, and other visible alterations of cheese.

Milk fat composition modifies the texture and appearance of Cantal-type cheeses but not their flavor

Although the effects of cow diet on cheese sensory properties have been well documented, the putative interactions between the biochemical and microbial milk components and their respective roles in the development of the sensory properties of cheeses have yet to be explored in depth. The aim of this study was to evaluate the specific contribution of milk fat composition to the formation of cheese sensory properties. Two creams with different fat compositions were obtained from cows fed either pasture or maize silage. Cheeses were manufactured from the same skim milk (identical chemical and microbial composition) with either the pasture- or maize silage-origin pasteurized cream added. The gross composition and microbial composition of milks did not vary with cream origin. In milks and cheeses, the fatty acid (FA) profiles were modified by the origin of the cream. The concentrations of C18:0 and unsaturated FA such as cis-9 C18:1, trans-11 C18:1, C18:3n-3, total conjugated linoleic acids, and mono- and polyunsaturated FA were higher in milks and cheeses with the pasture-origin cream than in those with the maize-origin cream. In contrast, the maize milks and cheeses had higher concentrations of short- and medium-chain saturated FA, C16:0, and C18:2n-6. The level of lipolysis was 11% in the cheese rind and only 0.30% in the cheese core. The rind of pasture cheeses had a higher concentration of free C18:0 and C18:3n-3 and a lower concentration of free C14:0 and free C16:0 than the rind of maize cheeses. The levels of major microbial groups were similar in pasture and maize cheeses at different stages of ripening. The pasture cheeses had a more elastic and creamier texture, a yellower color, and a thinner rind than the maize cheeses, but the odor and aroma of cheeses were not affected by the origin of the cream, despite a few modifications in the balance of volatile compounds from FA catabolism. Based on these results, we conclude that milk fat composition modulated by cow diet had a direct role in the texture of the cheese but no effect on flavor. The high degree of lipolysis in cheese rind, along with the higher concentration of long-chain unsaturated free FA in pasture cheeses may be responsible for antimicrobial activity, which could explain differences in the appearance of cheese rind.

Calcium lactate as an attractive compound to partly replace salt in blue-veined cheese

In addition to their high sodium content, cheeses are thought to induce an acid load to the body, which is associated with deleterious effects on consumers' health. Our objective was to explore the use of alkalinizing salts in partial substitution of NaCl to reduce both the sodium content and the acid-forming potential of cheese, without altering its sensory properties. Blue-veined cheeses were produced under industrial conditions, using brine salting followed by dry salting with a 4:1 (wt/wt) mixture of calcium lactate:NaCl or calcium citrate:NaCl. Sodium chloride was used in 2 granulometries: coarse (control treatment) and fine, to obtain homogeneous mixtures with the organic salts. Cheeses were then ripened for 56 d. No major appearance defects were observed during ripening. Calcium lactate substitution decreased the Na content of the cheese core by 33%, and calcium citrate substitution increased the citrate content of the cheese core by 410%, respectively, compared with fine NaCl. This study highlighted the substantial role of salt granulometry in sodium content, with the use of the coarse salt reducing the sodium content by 21% compared with fine salt. Sensory profiles showed nonsignificant differences in bitter and salty perceptions of salt-substituted cheeses with calcium lactate and calcium citrate compared with control cheeses. The use of calcium lactate should be considered to reduce the sodium content and improve the nutritional quality of cheeses while maintaining the sensory quality of the products. Alkalinizing organic salts could replace the acidifying salts KCl or CaCl2, which are currently used in salt replacement and are not recommended for consumers with renal disease. The method described here should be considered by cheese-making producers to improve the nutritional quality of cheese. Additional nutritional optimization strategies are suggested.

Fungal diversity of “Tomme d'Orchies” cheese during the ripening process as revealed by a metagenomic study

Tomme d'Orchies is an artisanal pressed and uncooked cheese produced and marketed in the north of France. This study aimed at showing the fungal microbiota evolution of this cheese using a metagenetic based Illumina technology targeting the ITS2 domain of 5.8S fungal rDNAs. To this end, samples were taken from the rind and the core of different cheeses, after 0, 1, 3, 7, 14 and 21days of ripening. The data underpinned the prevalence of Yarrowia lipolytica and Galactomyces geotrichum for both microbiotas. Unusual species including Clavispora lusitaniae, Kazachstania unispora and Cladosporium cladosporioides were also detected, but their origins remain to be ascertained. The metagenomic revealed also the presence of Kluyveromyces and Debaryomyces species.

Relationships among house, rind and core microbiotas during manufacture of traditional Italian cheeses at the same dairy plant

This study was aimed at establishing the relationships between house, rind and core microbiotas of cheese varieties manufactured at the same industrial dairy plant. Caciotta and Caciocavallo Pugliese cheeses were chosen as model systems. Mesophilic lactobacilli, cocci and, especially, thermophilic cocci were the most abundant cultivable bacteria found on equipment, which were located in the production area. According to cell counts, catabolic profiles of microbial communities deriving from equipment, and cheese core and rind differed. As shown by 16S rRNA targeted metagenomics, Streptococcus thermophilus dominated the communities from knife surface, brine tank, curds and core cheeses as well as it was the main colonizing bacterium from drain table, rinds and ripening room of Caciocavallo Pugliese cheeses. Compared to S. thermophilus, the other starters used (Lactococcus lactis, Lactobacillus delbrueckii subsp. lactis and Lactobacillus helveticus) showed low relative abundance in cheeses and/or colonization capability. A set of other genera/species, which varied depending on the equipment surfaces and cheese making, contributed to the formation of a rather heterogeneous house microbiota. Representatives from such communities had (e.g., Lactobacillus casei, Lactobacillus plantarum group) or not (e.g., Actinobacteria) the capacity to colonize cheeses, which depended on the variety (Caciocavallo Pugliese or Caciotta cheese) and layer (rind or core). Other genera/species were mainly associated to the rind and ripening room of Caciotta (Staphylococcus species and Brochothrix spp.) or Caciocavallo Pugliese (Chromohalobacter and Sphingomonas) cheeses.

Temporal and spatial differences in microbial composition during the manufacture of a continental-type cheese.

We sought to determine if the time, within a production day, that a cheese is manufactured has an influence on the microbial community present within that cheese. To facilitate this, 16S rRNA amplicon sequencing was used to elucidate the microbial community dynamics of brine-salted continental-type cheese in cheeses produced early and late in the production day. Differences in the microbial composition of the core and rind of the cheese were also investigated. Throughout ripening, it was apparent that cheeses produced late in the day had a more diverse microbial population than their early equivalents. Spatial variation between the cheese core and rind was also noted in that cheese rinds were initially found to have a more diverse microbial population but thereafter the opposite was the case. Interestingly, the genera Thermus, Pseudoalteromonas, and Bifidobacterium, not routinely associated with a continental-type cheese produced from pasteurized milk, were detected. The significance, if any, of the presence of these genera will require further attention. Ultimately, the use of high-throughput sequencing has facilitated a novel and detailed analysis of the temporal and spatial distribution of microbes in this complex cheese system and established that the period during a production cycle at which a cheese is manufactured can influence its microbial composition.

Microbial Population Dynamics in Presence of Lactococcal Bacteriophage During Ripening of Traditional Raw Milk Romanian Cheese

Abstract A massive Lactococcus lactis ssp.lactis c2 and e72 phage contamination of raw milk burduf cheese was revealed in all analyzed samples. Contamination with c2 phage specific for Lactococcus lactis ssp.lactis C2 is lower than the contamination induced by e72 phage. The contamination level with E.coli and coliforms in the core of burduf cheese was initially high, while the initial Staphylococcus spp. contamination was not high enough to pose a threat through toxin production. During the ripening period of the analyzed cheese, there was a high statistical significant decrease in E. coli, coliforms and staphylococci counts. This decrease was highly unexpected according to the scientific literature that indicates low lactococcal counts and low microbiological quality in bacteriophage contamination cases. The presence of wild bacteriophages, known to reduce the number of lactic acid bacteria, preventing the inhibition effect of the latter on contaminating bacteria growth, was proven not to induce a poor hygiene level of the raw milk burduf cheese, even if the initial contamination was considered to be high. This study is an example of natural, persistent and statistical significant lactococcal resistance to contaminating bacteriophages. The results are also scientifically significant due to the atypical time resistance of the microbiological balance between the contaminating bacteriophages and cheese bacterial microflora with positive consequences over cheese quality.

One-year investigation of Clostridium spp. occurrence in raw milk and curd of Grana Padano cheese by the automated ribosomal intergenic spacer analysis

Abstract Late blowing is a defect of semi-hard and hard cheeses induced by butyric clostridia that, through the formation of endospores, contaminate raw milk via silage, fresh forage and animal bedding. Generally it becomes evident during ripening, when the physical and chemical conditions of the cheese core support spores outgrowth. This causes the production of undesirable off-odors and an anomalous organization of the loaf, that seriously prejudices cheeses, with significant economic losses for the dairy industry. This study describes the development of an original application of the automated ribosomal intergenic spacer analysis (ARISA) that, relying on a multi-species-specific primer set, allows to simultaneously displaying distinctive fingerprints, diagnostic for Clostridium tyrobutyricum, generally considered the main responsible of late blowing, and for the other species so far associated with the defect: Clostridium butyricum, Clostridium sporogenes, Clostridium beijerinckii, Clostridium tertium and Clostridium perfringens, also providing relative abundance estimations. This approach has been applied to the seasonal analysis of tank raw milk and curd used for Grana Padano PDO cheese production in dairies located in different areas of the Northern Padan plain. C. beijerinckii and C. tertium, occurring both in 100% milks and curds, together with C. perfringens, retrieved in 98.7% milks and 100% curds, resulted the most abundant species in all the seasons. On the other hand, C. sporogenes always resulted the less abundant species, occurring in 77.2% of milks and 86.1% of curds. Highly significant seasonal effects were detected for C. tyrobutyricum and C. beijerinckii that displayed the most marked and opposite trends. The occurrence of a spatial pattern of variation for curd was also observed, thus envisaging relevant effects presumably linked to differential breeder practices (feeding and hygiene). This ARISA approach presents important perspectives in terms of applicability along the entire dairy production chain for diagnostic purposes and for providing an estimate of the microbiological quality of milk.

Isolation and Identification of the Microbiota of Danish Farmhouse and Industrially Produced Surface-Ripened Cheeses

For studying the microbiota of four Danish surface-ripened cheeses produced at three farmhouses and one industrial dairy, both a culture-dependent and culture-independent approach were used. After dereplication of the initial set of 433 isolates by (GTG)5-PCR fingerprinting, 217 bacterial and 25 yeast isolates were identified by sequencing of the 16S rRNA gene or the D1/D2 domain of the 26S rRNA gene, respectively. At the end of ripening, the cheese core microbiota of the farmhouse cheeses consisted of the mesophilic lactic acid bacteria (LAB) starter cultures Lactococcus lactis subsp. lactis and Leuconostoc mesenteorides as well as non-starter LAB including different Lactobacillus spp. The cheese from the industrial dairy was almost exclusively dominated by Lb. paracasei. The surface bacterial microbiota of all four cheeses were dominated by Corynebacterium spp. and/or Brachybacterium spp. Brevibacterium spp. was found to be subdominant compared to other bacteria on the farmhouse cheeses, and no Brevibacterium spp. was found on the cheese from the industrial dairy, even though B. linens was used as surface-ripening culture. Moreover, Gram-negative bacteria identified as Alcalignes faecalis and Proteus vulgaris were found on one of the farmhouse cheeses. The surface yeast microbiota consisted primarily of one dominating species for each cheese. For the farmhouse cheeses, the dominant yeast species were Yarrowia lipolytica, Geotrichum spp. and Debaryomyces hansenii, respectively, and for the cheese from the industrial dairy, D. hansenii was the dominant yeast species. Additionally, denaturing gradient gel electrophoresis (DGGE) analysis revealed that Streptococcus thermophilus was present in the farmhouse raw milk cheese analysed in this study. Furthermore, DGGE bands corresponding to Vagococcus carniphilus, Psychrobacter spp. and Lb. curvatus on the cheese surfaces indicated that these bacterial species may play a role in cheese ripening.

Could cheese be the missing piece in the French paradox puzzle?

The low rates of cardiovascular mortality which have existed in France for decades despite high saturated fat consumption constitute an epidemiological phenomenon called the “French paradox”. This phenomenon was originally attributed to consumption of red wine and its major constituent resveratrol. However, recent studies have revealed the limitations of this link outside France. These observations indicate that consumption of red wine alone cannot explain the paradox and perhaps some other constituents of the typical French diet could be responsible for reduced cardiovascular mortality. We hypothesize that cheese consumption, especially of molded varieties, may contribute to the occurrence of the “French paradox”. This assumption is well supported by newly discovered facts revealing the positive effect of cheese ingestion on lipoprotein turnover and plasma lipid profile, haemorheological parameters and inflammatory status. Recent advances in cheese proteomics have allowed the identification and isolation of novel peptides capable of inhibiting the angiotensin-converting enzyme which controls systemic blood pressure. A complex time-dependent enzymatic transformation of the cheese core controlled by probiota, temperature and humidity during the ripening process has been shown to result in the formation of substances reducing major pro-inflammatory markers and cytokines (C-reactive protein, interleukin 6, tumor necrosis factor alpha). Molded cheeses, including Roquefort, may be even more favorable to cardiovascular health due to the presence of secondary metabolites produced by Penicillium roqueforti and other fungi. Among them are andrastins A–D and roquefortine, whose ability to inhibit cholesterol biosynthesis and bacterial growth may be a key mechanism in the prevention of cardiovascular disease.