Cheese Ripening Research Articles

Near-infrared hyperspectral image analysis for monitoring the cheese-ripening process

Ripening is the most crucial process step in cheese manufacturing and constitutes multiple biochemical alterations that describe the final cheese quality and its perceived sensory attributes. The assessment of the cheese-ripening process is challenging and requires the effective analysis of a multitude of biochemical changes occurring during the process. This study monitored the biochemical and sensory attribute changes of paraffin wax-covered long-ripening hard cheeses (n = 79) during ripening by collecting samples at different stages of ripening. Near-infrared hyperspectral (NIR-HS) imaging, together with free amino acid, chemical composition, and sensory attributes, was studied to monitor the biochemical changes during the ripening process. Orthogonal projection-based multivariate calibration methods were used to characterize ripening-related and orthogonal components as well as the distribution map of chemical components. The results approve the NIR-HS imaging as a rapid tool for monitoring cheese maturity during ripening. Moreover, the pixelwise evaluation of images shows the homogeneity of cheese maturation at different stages of ripening. Among the chemical compositions, fat content and moisture are the most important variables correlating to NIR-HS images during the ripening process.

Fatty acids, lipid quality parameters, and amino acid profiles of unripened and ripened cheeses produced from different milk sources

Fatty acids and amino acids are recognized to have a significant impact on the bioactivity, aroma, and flavor of ripened cheese. In this study, fatty acid profiles, lipid quality parameters, and amino acid composition of ripened and unripened cheeses produced from different milk sources were investigated. Fatty acids and amino acids were identified by using the gas chromatography-flame ionization detector and high-performance liquid chromatography, respectively. Lipid quality indicators, including atherogenicity index, thrombogenicity index, desired hypocholesterolemic fatty acids, undesired hypercholesterolemic fatty acids, hypocholesterolemic and hypercholesterolemic fatty acids ratio, and the nutritive value index of cheese samples were calculated. The results revealed that the major fatty acids detected were myristic, palmitic, stearic, and oleic. Cheese made from goat and sheep milk, such as Kashkaval, Chevrette Frico, and goat cheese with honey exhibited higher contents of capric acid representing 8.47 %, 9.56 %, and 10.07 %, respectively. In addition, fresh Roumy cheese showed higher contents of oleic (37.15 %) and linoleic (9.18 %) acids than other cheese types. The atherogenicity index of cheese fat varied between 1.13 and 3.97 for the different samples. Furthermore, cheese samples showed similar nutritive value indices. Each cheese type had its distinctive amino acid profile, which was attributed to the enzymatic activity. Milk source and ripening were the main reason for the variations in fatty acid and amino acid contents. The findings of this study could provide interesting knowledge to the dairy industry sector and could be used as a database in the field of food composition and analysis.

The effect of fresh or frozen black truffle Tuber aestivum on ripening and sensory quality of semi hard cheese

The use of truffles in food is primarily based on their pleasant smell to the consumer, to achieve this effect, artificial flavours are usually added. Considering that truffles have not only a hedonistic effect on consumers, this work aims to investigate the characteristics of semi hard cheese, using fresh or for three months frozen truffles without adding artificial flavours, as well as their influence on proteolytic changes during ripening and the sensory quality. Six experimental Gouda type cheeses were prepared: control without truffles; with fresh truffles sterilized in autoclave; with fresh truffles flambéed on burner; with frozen truffles sterilized in autoclave; with frozen truffles flambéed on burner; with addition of artificial flavoring agents. The chemical composition and proteolytic changes of the cheese, microbiological status and sensory evaluation during the three months of ripening were studied. The chemical composition did not differ significantly, but truffles significantly affect the biochemical processes of cheeses ripening. Addition of flambéed fresh or frozen truffles in cheeses, accelerate ripening processes, where the ripening index (25.03%–25.16%) was significantly higher in these cheeses than in the others (14.25%–15.81%). A 1 log unit higher number of lactic acid bacteria was also found in these cheeses and their sensory quality were excellent with ratings 98.08% and 95.41% of the maximum possible quality. It was shown that addition of flambéed fresh or frozen truffles, can be used, resulting in a completely natural cheese with pleasant odor, without the addition of artificial flavours.

Modelling and Predicting the Growth of Escherichia coli and Staphylococcus aureus in Co-Culture with Geotrichum candidum and Lactic Acid Bacteria in Milk

The growth of two pairs of co-cultures (Escherichia coli/Geotrichum candidum and Staphylococcus aureus/Geotrichum candidum) with a starter culture of lactic acid bacteria was studied in milk at temperatures ranging from 15 °C to 21 °C, related to the ripening of artisanal cheese. For an inoculum of approximately 106 CFU/mL, LAB not only induced an early stationary phase of E. coli (two isolates BR and PS2) and S. aureus (isolates 2064 and 14733) but also affected their death phase. In co-cultures with LAB and G. candidum, the numbers of E. coli and S. aureus increased in 2 logs and 1 log, respectively, reaching maximum population densities (MPDs) of less than 5 and 4 logs, respectively. After that, the populations of both bacteria represented with two isolates decreased in more than 2 logs and 3 logs within 2 days compared to their MPDs, respectively. G. candidum was found to be the subject of interactions with LAB within a given temperature range only partially. To develop a tertiary model for the growth curves of the populations, a one-step approach was used, combining the Huang-Gimenez and Dalgaard primary model with secondary square-root models for growth rate and lag time. Furthermore, the reparametrized Gompertz-inspired function with the Bigelow secondary model was used to describe the death phase of the E. coli and S. aureus isolates. The prediction ability of the growth of the H-GD tertiary model for co-cultures was cross-validated within the isolates and datasets in milk and milk medium with 1% NaCl. The study can be used as knowledge support for the hygiene guidelines of short-ripened raw milk cheeses, as was our case in Slovakia.

Proteolytic processes in cheese analogues ripening

The research relevance is predefined by the theoretic basics of their production processes not being sufficiently studied, including the proteolysis despite the wide production of cheese analogues incorporating vegetable substances. The research aims to determine the effect of the content of cheese analogues, namely milk fat substitutes, soy protein isolates, and lactobacilli species Lactococcus lactis ssp. lactis and L. lactis ssp. cremoris, L. lactis ssp lactis bv. diacetilactis as well as Leuconostoc mesenteroides by the physical, chemical, and sensorial traits, and by amino acids content of cheese analogues. Determination of the physical and chemical parameters was fulfilled according to the standards: active acidity (рН) – DSTU 8550:2015; solids content (by weight) – DSTU 8552:2015 and ISO 5534:2004; non-casein nitrogen content (by weight) – ISO 17997-1:2004; total protein (by weight) – ISO 8968-1:2014 and ISO 8968-5:2001; casein content (by weight) – ISO 17997-1:2004. The fractional composition of proteins was determined using the Polyacrylamide Gel Electrophoresis. While in the cheese dough after analysing the differences in the spectrum of free amino acids between the variants were insignificant, in ripe cheese analogues the accumulation was significantly less than in the control cheeses, only one ripe cheese analogue showed the total amount of free amino acids and was almost equal to the control. During ripening, the content of these compounds increased in cheese analogues from 2.2 times to 3.3 times, in the control the content of free amino acids increased by 2.5 times, and individual free amino acids accumulated from 3-7 to 30-40 times. Active proteolytic processes led to the appearance of all ripe products of such essential amino acids as methionine and isoleucine, there was also an increase in the level of glycine. The practical significance of the study is determined by substantiating rationale proteolytic processes in the manufacture of cheese analogues to ensure consumer quality close to the quality of cheeses made of milk

Effect of Ripening and In Vitro Digestion on Bioactive Peptides Profile in Ras Cheese and Their Biological Activities.

The effect of ripening and in vitro digestion on the biological activities, peptide profiles and release of bioactive peptides in Ras cheese has been investigated. Ras cheese ripening largely influenced the extent of protein hydrolysis. The advancement in ripening resulted in an increase in total peptides (from 0.97 to 2.46 mmol leucine/g in samples at 30 and 180 days of ripening, respectively) and bioactive peptides concentration, especially angiotensin-converting enzyme (ACE)-inhibitory, dipeptidyl-peptidase-IV-(DPP-IV)-inhibitory and antioxidant peptides. In vitro gastro-intestinal digestion further promoted protein hydrolysis and the release of bioactive peptides. Digested Ras cheese at 90 and 180 days of ripening displayed the highest bioactive peptides intensity. The variations in bioactive peptides amount during ripening and in vitro digestion were correlated with the changes in ACE-inhibitory, DPP-IV-inhibitory and antioxidant activities. The highest amounts of VPP and IPP were detected in digested Ras cheese at 90 days of ripening (17.44 and 36.50 mg/kg of cheese, respectively), whereas the highest concentrations of APFPE were found in undigested and digested 180-day ripened Ras cheese (82.09 and 52.01 mg/kg of cheese, respectively). The present investigation underlined potential differences in the biological effect after the ingestion of Ras cheese at different ripening times.

Microbial Succession in the Cheese Ripening Process-Competition of the Starter Cultures and the Microbiota of the Cheese Plant Environment.

A large variety of cheeses can be produced using different manufacturing processes and various starter or adjunct cultures. In this study, we have described the succession of the microbial population during the commercial production and subsequent ripening of smear-ripened cheese using 16S rRNA gene sequencing. The composition of the microbiota during the first 6 days of production was constant and consisted mainly of LAB (lactic acid bacteria) originating from the starter culture. From day 7, the proportion of LAB decreased as other bacteria from the production environment appeared. From the 14th day of production, the relative proportion of LAB decreased further, and at the end of ripening, bacteria from the environment wholly dominated. These adventitious microbiota included Psychrobacter, Pseudoalteromonas haloplanktis/hodoensis, Vibrio toranzoniae, and Vibrio litoralis (Proteobacteria phylum), as well as Vagococcus and Marinilactibacillus (Firmicutes phylum), Psychrilyobacter (Fusobacteria phylum), and Malaciobacter marinus (Campylobacterota phylum), all of which appeared to be characteristic taxa associated with the cheese rind. Subsequent analysis showed that the production and ripening of smear-ripened cheese could be divided into three stages, and that the microbiota compositions of samples from the first week of production, the second week of production, and supermarket shelf life all differed.

ANALYTICAL REVIEW OF BIOTECHNOLOGICAL PROBLEM OF UKRAINIAN HARD CHEESES

An analytical review of the biotechnological process of production of various hard and semi-hard cheeses in the EU and Ukraine, as well as domestic recipes of fermented cheeses for production at craft cheese factories and at home, was conducted. An analysis of the conditions of the key stages of production, including fermentation, coagulation and ripening, was carried out. The composition and type of lactic acid bacteria in sourdough for fermented cheeses, as well as enzymes for fermentolysis and coagulation of milk casein, were studied. As a result of a complex study, a total of 73 types of hard and semi-hard cheeses were analyzed: 35 recipes of the New England Cheesemaking Supply Company by Jim Wallace; 30 production processes of hard and semi-hard cheeses from the EU; 8 technical conditions of hard cheeses of Ukrainian producers. It is shown that the prospects for optimizing the development of new types of hard and semi-hard cheeses in Ukraine are mainly related to the regulation of the time and temperature of fermentation, cooking and ripening of cheeses, as well as the expansion of the biodiversity of the primary and secondary microbiome of starter cultures to improve the taste and aroma of the ready-to-use product. Purpose: to analyze the fermentation process and recipes for the production of hard cheeses in Ukraine with the main world samples, to compare the composition and type of lactic acid bacteria in industrial and craft starters, as well as the types of enzymes for fermentolysis and casein coagulation of milk, in order to optimize production to improve the taste and aroma of ready-to-use product. Materials and methods. Methodical analysis and abstract-logical method for summarizing the evaluation criteria of the biotechnological process of various hard and semi-hard domestic cheeses with world samples according to recommendations, requirements and standards with the development of patents, technical conditions of their production in the EU and Ukraine; DSTU 6003 (Solid cheeses); New England Cheesemaking Supply Company cheese recipes by Jim Wallace. The obtained data were processed by methods of statistical analysis, systematization, comparison and generalization of information. Results. In this study, the documentation was examined and the data of standards, regulations, requirements and recommendations regarding the biotechnology of hard and semi-hard cheeses were analyzed, an analysis of the market of hard cheeses and the peculiarities of the fermentation process of their production was carried out with the determination of critical points and key stages of production using industrial deposited fermentation producers and protein enzymes coagulation and biodiversity of lactic acid bacteria in sourdoughs for fermented cheeses at world productions, with an assessment of the prospects for developing new and improving the biotechnology of Ukrainian benign and safe hard cheeses for healthy nutrition.

Blue Cheeses: Microbiology and Its Role in the Sensory Characteristics

Blue cheeses are those whose matrix is veined with a blue, blue-grey, or blue-green colour due to the development of Penicillium roqueforti. There are more than 45 varieties of blue cheese produced worldwide, with some distinct features, although the manufacture process is similar. In addition to P. roqueforti, complex microbial populations interact and succeed throughout the manufacturing and ripening at the cheese’s surface (the rind) and interior (matrix). The microbiota of blue cheeses is made up of a vast array of both prokaryotic and eukaryotic microorganisms. Acidification of the curd relies on the action of lactococci and other lactic acid bacteria (LAB) species. The ripened cheeses’ final quality and shelf-life properties largely depend on the enzymatic systems of the components of the microbiota, particularly on those of LAB, P. roqueforti, and yeast species. Proteolysis is the most complex and important primary biochemical process involved in blue-veined cheeses during ripening, with P. roqueforti being considered the main proteolytic agent. Lipolysis is also strong, originating, among other compounds, ketones, which are the main aroma compounds in blue-veined cheeses. In addition, several bioactive compounds are produced during ripening. The biochemical activities, mainly of microbial origin, are responsible for the sensory characteristics of these very appreciated cheese varieties worldwide.

Influence of different genetic polymorphisms of αS1- and κ-casein on Havarti-type cheese: Effects on cheese-making efficiency and cheese quality

The effect of the composite genotypes of αS1-κ-casein (BBAA, BBBB, BCAA) on renneting properties and yield during cheese-making of a Havarti-type cheese was investigated. Milk with αS1-κ-CN BCAA showed a shorter renneting time, while milk with αS1-κ-CN BBAA obtained the highest cheese yield. 24 h after starter addition, different protein profiles were found between the cheeses with different αS1-κ-CN genotypes. After 5 months of ripening, cheese with αS1-κ-CN BBBB contained more free amino acids than αS1-κ-CN BCAA. Cheese with αS1-κ-CN BCAA expressed a higher intensity of sweetness and lower intensity of hardness than the αS1-κ-CN BBBB and BBAA cheeses. Cheeses with αS1-κ-CN BBAA had a higher intensity of sunlight flavour than cheeses with the two other αS1-κ-CN genotypes and were assessed to be less juicy than αS1-κ-CN BBBB cheeses. The composite genotypes of αS1-κ-casein affect milk coagulation, cheese yield and cheese maturation and are highly relevant for the dairy industry.

Reduction of Beta Cyclodextrin by Curd Washing in Low-Cholesterol Manchego Cheese.

Beta-cyclodextrin (β-CD) is a cyclic oligosaccharide consisting of seven glucose units. β-CD is increasingly used in food research to reduce cholesterol due to its affinity for non-polar molecules such as cholesterol and as a natural additive. The purpose of this study was to evaluate the effect of curd washing in ewe's milk cheese on the reduction in cholesterol by β-CD from pasteurized ewe's milk Manchego cheese and the characteristics of its main components: milk, lipids, and flavor. An approximately 98.45% cholesterol reduction was observed in washed experimental cheeses that were treated by using β-CD. The remaining residual β-CD from the effect of curd washing was 0.15% in mature cheese, of the initial 1% β-CD treatment of the milk. The chemical properties (fat, moisture, and protein) did not change as a result of the curd washing with or without β-CD. The curd washing with or without β-CD on the levels of the various lipid fraction (fatty acids, triglycerides, and phospholipids) were comparable in treated and untreated cheeses. The effects of curd washing and the β-CD treatment did not significantly affect flavor components or short chain free fatty acids. The β-CD molecules were edible and nontoxic; as a result, they could be used safely in cholesterol removal processing in cheese manufacturing, improving the reduction in residual β-CD by curd washing by 85%. Therefore, the present study suggests that curd washing combined with β-CD is an effective process for cholesterol removal in Manchego cheese, preserving its desirable properties.

The impact of milk storage temperatures on cheese quality and microbial communities at dairy processing plant scale

Cheese production is an applied biotechnology whose proper outcome relies strictly on the complex interactive dynamics which unfold within defined microbial groups. These may start being active from the collection of milk and continue up to its final stages of maturation. One of the critical parameters playing a major role is the milk refrigeration temperature before pasteurization as it can affect the proportion of psychrotrophic taxa abundance in the total milk bacterial population. While a standard temperature of 4 °C is the common choice, due to its general growth control effect, it does have a potential drawback. This is due to the fact that some cold-tolerant genera present a proteolytic activity with uncompleted proliferation, which could negatively affect curd clotting and regular cheese maturation. Moreover, accidental thermal variations of milk before cheese-making, in a plus or minus direction, can occur both at farm collection sites and during transfer to dairy plant. This present research, directly commissioned by a major fresh cheese-producing company, includes an in-factory trial. In this trial, a gradient of temperatures from 4 °C to 13 °C, which were subsequently reversed, was purposely adopted to: (a) verify sensory alterations in the resulting product at different maturation stages, and, (b) analyze, in parallel, using DNA extraction and 16S-metabarcoding sequencing from the same samples, the presence, abundance and corresponding taxonomical identity of all the bacteria featured in communities found in milk and cheese samples. Overall, 1,714 different variants were detected and sorted into 394 identified taxa. Significant bacterial community shifts in cheese were observed in response to milk refrigeration temperature and subsequently associated with samples having altered scores in sensory panel tests. In particular, proteolytic psychrotrophes were outcompeted by Enterobacteriales and by other taxa at the peak temperature of 13 °C, but aggressively increased in the descent phases, upon the cooling down of milk to values of 7 °C. Relevant clues have been collected for better anticipation of thermal abuse effects or parameter variations allowing for improved handling of technical processing conditions by the cheese manufacturing industry.

Physicochemical, Microbiological and Sensory Characteristics of White Brined Cheese Ripened and Preserved in Large-Capacity Stainless Steel Tanks.

The objective of the present study was to investigate the effect of ripening and preservation containers on the physico-chemical, microbiological, and textural characteristics, and volatile profile of white cheese. White cheeses were manufactured on an industrial scale using large-capacity stainless steel tanks (SST) of 500 kg, and the respective control samples in tin containers (TC) of 17 kg. No significant differences (p > 0.05) in fat in dry matter and total protein content were observed at 60 days of ripening between the TC and SST cheeses. After 60 days, of ripening, the moisture of the cheeses in SST and TC did not show significant statistical differences (p > 0.05). No significant differences (p > 0.05) were observed between the TC and SST cheeses in the mineral concentration (Ca, Mg, K, and Na) and textural characteristics. Similar results of pH and bacterial counts, as well as absence of yeasts and molds, were observed during ripening and preservation time in both groups of cheeses. Furthermore, proteolysis was not affected statistically significantly (p > 0.05). A moderately increased rate of ripening for the cheeses in TC was observed up to 90 days but, at 180 days, proteolysis was similar in both groups of cheeses. Regarding the SFA, MUFA, and PUFA content, no significant differences (p > 0.05) were observed between the TC and SST cheeses. A total of 94 volatile compounds were identified in the volatile fraction of both the SST and TC cheeses. Organic acids and alcohols were the most abundant classes of volatile compounds that were identified. The flavor and texture scores in the TC and SST cheeses were similar (p > 0.05). Overall, the TC and SST cheeses did not show any significant statistical difference in any of the analyzed parameters.

Construction of a dynamic model to predict the growth of Staphylococcus aureus and the formation of enterotoxins during Kazak cheese maturation.

Staphylococcus aureus is a common pathogen found in cheese whose Staphylococcal enterotoxins (SE) are the main pathogenic factors that cause food poisoning. The objective of this study was to construct two models to evaluate the safety of Kazak cheese products in terms of composition, changes in S. aureus inoculation amount, Aw, fermentation temperature during processing, and growth of S. aureus in the fermentation stage. A total of 66 experiments comprised of five levels of inoculation amount (2.7-4 log CFU/g), five levels of Aw (0.878-0.961), and six levels of fermentation temperature (32-44°C) were performed to confirm the growth of S. aureus and the presence of SE limit conditions. Two artificial neural networks (ANN) successfully described the relationship between the assayed conditions and the growth kinetic parameters (maximum growth rates and lag times) of the strain. The good fitting accuracy (R2 values were 0.918 and 0.976, respectively) showed that the ANN was appropriate. Experimental results showed fermentation temperature had the greatest influence on the maximum growth rate and lag time, followed by the Aw and inoculation amount. Furthermore, a probability model was built to predict the production of SE by logistic regression and neural network under the assayed conditions, which proved to be concordant in 80.8-83.8% of the cases with the observed probabilities. The maximum total number of colonies predicted by the growth model in all combinations detected with SE exceeded 5 log CFU/g. Within the range of variables, the minimum Aw for predicting SE production was 0.938, and the minimum inoculation amount for predicting SE production was 3.22 log CFU/g. Additionally, as competition between S. aureus and lactic acid bacteria (LAB) occurs in the fermentation stage, higher fermentation temperatures are conducive to the growth of LAB, which can reduce the risk of S. aureus producing SE. This study can help manufacturers to make decisions on the most appropriate production parameters for Kazak cheese products and to prevent S. aureus growth and SE production.

The impact of Brevibacterium aurantiacum virulent phages on the production of smear surface-ripened cheeses

Phages are ubiquitous and are particularly abundant in environments where their bacterial hosts thrive, such as those in the cheese industry. Although it is well documented that phages infect lactic acid bacteria, their impact has been notably overlooked on cheese ripening strains, such as Brevibacterium aurantiacum. Here, we aimed to study the impact of B. aurantiacum phages on the production of smear-ripened cheeses. We used model cheeses in industrial settings to monitor the development of the color of the cheese rind as well as of its microbial composition in presence or absence of virulent B. aurantiacum phages. Our results showed that the presence of B. aurantiacum phages significantly slowed down the development of the orange rind color in the model cheeses. In the final days of cheese ripening, phages were also detected in the control curds. By analyzing a hypervariable region of B. aurantiacum phage genomes, we detected phages with tandem repeat patterns that were different from those used in the phage-inoculated cheeses. Our results highlight the risks of using a phage-sensitive strain in smear-ripened cheese production. This is the first study to report on the impact of B. aurantiacum phages on smear-ripened cheeses.

Comparison of taste characteristics between koji mold–ripened cheese and Camembert cheese using an electronic tongue system

Koji mold, classified in the genus Aspergillus, is used to produce traditional Japanese fermented foods such as miso, soy sauce, and sake. In recent years, the application of koji mold to cheese ripening has attracted attention, and cheese surface-ripened with koji mold (koji cheese) has been studied. In this study, to evaluate the taste characteristics of koji cheese, an electronic tongue system was employed to measure the taste values of cheese samples ripened using 5 strains of koji mold in comparison with commercial Camembert cheese. All koji cheese samples exhibited lower sourness and greater bitterness, astringency, saltiness, and umami richness than the Camembert cheese samples. The intensity of each taste characteristic differed depending on the koji mold strain. These results indicate that koji cheese has a different taste value than conventional mold-ripened cheese. Furthermore, the results also indicate that various taste characteristics can be achieved by selecting different koji molds.

The Problem of Bitter Peptides Formed in the Process of Cheese Ripening

Bitter peptides are formed by the breakdown of proteins and high-molecular peptides during proteolysis. Their formation in cheeses is related to the proteolytic activity of rennet in balance with the peptidase activity of microbial enzymes of lactic acid bacteria. The bitter taste then arises when there is a disproportion between the formation and degradation of bitter peptides by increasing their concentration above the perception threshold. The extent to which bitter peptides affect the overall taste of cheese depends on the balance between their formation and breakdown to non-bitter lower peptides and amino acids. Only a perfectly balanced proteolysis process enables the creation of quality matured cheese with a characteristic taste and aroma. Therefore, a complete clarification of the mechanism is desirable, and thus also the possibility of control and regulation of this process.

Inhibition of Listeria monocytogenes by Broth Cultures of Surface Microbiota of Wooden Boards Used in Cheese Ripening

Listeria monocytogenes is a significant concern in cheese production. It has been assumed by some that wood surfaces pose a greater risk for pathogen contamination during cheese production. The goal of this study was to evaluate the effect of the microbiota obtained from wooden boards used in cheese ripening on the growth of Listeria monocytogenes. Bacterial communities from the surface of wooden boards obtained from cheese-ripening facilities were inoculated into tryptic soy broth (TSB) and incubated at 11 °C for 48 h. These communities (108 CFU/mL stationary phase cells) were co-incubated with 104–105 CFU/mL L. monocytogenes 2203 at 11 °C for up to eight days. At various times, samples were removed, diluted in sterile saline and plated on modified Oxford agar. Bacterial communities from each of the five boards from three different facilities significantly inhibited growth of L. monocytogenes in vitro, compared to growth of L. monocytogenes 2203 alone. Using 16S rRNA analysis, we identified sequences belonging to the genera Carnobacterium, Leuconostoc and Staphylococcus as the most abundant in the communities grown in TSB. Leuconostoc mesenteroides and Staphylococcus equorum isolated from the most inhibitory community significantly inhibited growth of L. monocytogenes in TSB at 11 °C, compared to growth of L. monocytogenes 2203 alone. These findings suggest that some members of the complex microbial communities on wooden boards in cheese aging facilities might inhibit the growth of L. monocytogenes.

Novel yeasts with potential probiotic characteristics isolated from the endogenous ferment of artisanal Minas cheese.

Artisanal Minas cheese (QMA) is traditionally elaborate using raw milk and endogenous ferment (pingo - whey or rala - grated ripened cheese). In the present study, 91 yeast strains were isolated and identified from pingo and rala. Eight yeast species were identified by the MALDI-TOF mass spectrometry and confirmed by sequencing of the ITS region. The yeasts' protease and lipase activities were evaluated in addition to probiotic properties such as tolerance to low pH and bile salts, hydrophobicity, autoaggregation, co-aggregation with pathogens, and antimicrobial susceptibility. The rala ferment showed a greater variety of species. Yarrowia lipolytica was the dominant specie (52.7% of isolates), followed by the Kluyveromyces lactis and Kodamaea ohmeri (9.9 and 6.6%, respectively). From the total yeasts evaluated, 74 strains showed positive enzymatic activity: 52 strains showed lipolytic (51 Y. lipolytica and one Trichosporon japonicum) and 44 proteolytic activities (18 Y. lipolytica, 13 K. ohmeri, 11 K. lactis, and 2 Wickerhamiella sp.). All evaluated isolates demonstrated tolerance to pH 2.0, and 69 isolates supported the presence of bile salts. From them, 12 isolates showed the capacity of autoaggregation (> 30%) and hydrophobicity (> 90.0%) and were then selected for co-aggregation and antibiotic resistance assays. All selected isolates showed co-aggregation with Salmonella Enteritidis, Escherichia coli, and Listeria monocytogenes greater than 30%. None of the yeast showed sensibility to the evaluated antibiotics and antagonistic activity against the evaluated pathogens. The results demonstrated that pingo and rala have different yeast composition with different enzymatic activity, which may affect the characteristics of the cheese. Furthermore, some yeast strains: Y. lipolytica (9 strains isolated from rala) and K. ohmeri (3 strains isolated from pingo) demonstrated attractive probiotic potential.

Metagenomic, microbiological, chemical and sensory profiling of Caciocavallo Podolico Lucano cheese

In this study, Caciocavallo Podolico Lucano (CPL) cheese was deeply characterized for its bacterial community, chemical composition and sensory aspects. The entire cheese making process (from milk collection to ripened cheese) was performed by strictly applying the traditional protocol for CPL production in four dairy factories (A–D) representative of the production area. The vat made of wood represents the main transformation tool for CPL cheese production and the biofilms hosted onto the internal surfaces of all vats analyzed in this study were dominated by lactic acid bacteria. Total mesophilic microorganisms present in bulk milk (4.7–5.0 log CFU/ml) increased consistently after contact with the wooden vat surfaces (5.4–6.4 log CFU/ml). The application of Illumina sequencing technology identified barely 18 taxonomic groups among processed samples; streptococci and lactobacilli constituted the major groups of the wooden vat biofilms [94.74–99.70 % of relative abundance (RA)], while lactobacilli dominated almost entirely (94.19–100 % of total RA) the bacterial community of ripened cheeses. Except coagulase positive staphylococci, undesirable bacteria were undetectable. Among chemical parameters, significant variations were registered for unsaturated, monounsaturated, polyunsaturated fatty acids and antioxidant properties (significantly lower for CPL cheeses produced in factory B). The cheeses from factories A, C and D were characterized by a higher lactic acid and persistence smell attributes than factory B. This work indicated that the strict application of CPL cheese making protocol harmonized the main microbiological, physicochemical and sensory parameters of the final cheeses produced in the four factories investigated.