Microbiological characteristics of canastra cheese during manufacturing and ripening

Physicochemical Profile of Canastra Cheese Inoculated with Starter Cultures of Kluyveromyces lactis and Torulaspora delbrueckii

Canastra cheese, an artisanal cheese produced in Serra da Canastra-Brazil, has great cultural importance. Furthermore, this cheese has nutritional and sensory attributes that make it of great economic importance. Its microbiota is composed of different bacteria and yeasts. Some yeasts already isolated by our research group have been characterized as potential probiotics. Probiotic microorganisms have garnered scientific interest, as improvements in the physical, chemical and sensory characteristics of food products have been reported when these microorganisms are used. In this context, the objective of this work was to evaluate Kluyveromyces lactis and Torulaspora delbrueckii, which were previously isolated from Canastra cheese, as autochthonous starter cultures. Canastra cheese was produced under three different conditions: (1) cheese with "Pingo" (natural starter), (2) cheese with "Pingo" + yeast mixed culture, and (3) cheese with only mixed yeast culture. The results showed that the mixed yeast inoculum significantly influenced the lactic acid bacteria population. Yeast populations remained at around 106 CFU/g after 45 days of maturation. Furthermore, cheeses containing the yeast mixed with inoculum had an initial lactose content reduced by 92.80% compared to cheese produced with "Pingo" (87.70%). The antioxidant activity, evaluated using the ABTS method, showed that cheeses containing the mixed yeast culture had higher percentages of antioxidant activity at 45 days of maturation. The texture profile of the cheeses changed over time. In general, the cheese containing the yeast mixed culture and "Pingo" and the cheese containing "Pingo" had the lowest hardness at 30 days of maturation (5245 and 5404 N, respectively). Among the volatile compounds, 3-methylbutyl octanoate, phenethyl butyrate, phenethyl propionate, isobutyl butanoate and pentyl propionate were found only in cheeses produced with yeast mixed culture. The obtained results demonstrated that the use of autochthones probiotic cultures could improve the cheese characteristics without negatively impacting the traditional physicochemical attributes of Canasta cheese.

Microbial trace based on PCR-DGGE to evaluate the ripening stage of minas artisanal cheeses from the Canastra microregion produced by different dairies

The Minas artisanal cheese from the Serra da Canastra (MAC-CM) microregion is a traditional product due to its production and ripening process. Artisanal chesses manufactured with raw cow's milk and endogenous dairy starters ("also known as pingo") have distinctive flavors and other sensory characteristics because of the unknown microbiota. The aim of this study was to evaluate the microbiota during 30 days of ripening, the physicochemical changes, and their relation in MACs produced in two different microregions located in the Serra da Canastra microregion through culture-dependent and culture-independent methods. The MACs were collected in the cities of Bambuí (MAC-CMB) and Tapiraí (MAC-CMT) in the Canastra microregion (n = 21). Cheeses uniqueness was demonstrated with the multivariate analysis that joined the microbiota and physicochemical characteristics, mainly to the proteolysis process, in which the MAC-CMT showed deeper proteolysis (DI -T0:14.18; T30: 13.95), while the MAC-CMB reached only a primary level (EI -T0:24.23; T30: 31.10). Abiotic factors were responsible for the differences in microbial diversity between the cheese farms. Different microbial groups: the prokaryotes, like Corynebacterium variabile, Lactococcus lactis, and Staphylococcus saprophyticus; and the eukaryotes, like Kluyveromyces lactis and Diutina catenulata dominated ripening over time. The microbial community and proteolysis were responsible for the predominance of volatile groups, with alcohols predominating in MAC-CMB and free fatty acids/acids and esters in MAC-CMT.

Unveiling Safety Concerns in Brazilian Artisanal Cheeses: A Call for Enhanced Ripening Protocols and Microbiological Assessments

Brazilian artisanal cheeses have recently gained significant commercial prominence and consumer favor, primarily due to their distinctive sensory attributes and cultural and historical appeal. Many of these cheeses are made with raw milk and undergo a relatively short ripening period, sometimes ranging from 4 to 8 days, though it is usually shorter than the period stated by law. Moreover, there is insufficient evidence regarding the efficacy of a short ripening period in reducing certain zoonotic foodborne pathogens, such as Brucella spp., Coxiella burnetiid, and Mycobacterium bovis (as part of the Mycobacterium tuberculosis complex). Additionally, a literature analysis revealed that the usual ripening conditions of Brazilian artisanal cheeses made with raw milk may be inefficient in reducing the levels of some hazardous bacterial, including Brucella spp., Listeria monocytogenes, coagulase-positive Staphylococcus, Salmonella, and Coxiella burnetti, to the acceptable limits established by law, thus failing to ensure product safety for all cheese types. Moreover, the assessment of the microbiological safety for this type of cheese should be broader and should also consider zoonotic pathogens commonly found in bovine herds. Finally, a standardized protocol for evaluating the effectiveness of cheese ripening must be established by considering its peculiarities.

New Genetic Determinants for qPCR Identification and the Enumeration of Selected Lactic Acid Bacteria in Raw-Milk Cheese

Lactic acid bacteria (LAB) play an important role in the ripening of cheeses and contribute to the development of the desired profile of aroma and flavor compounds. Therefore, it is very important to monitor the dynamics of bacterial proliferation in order to obtain an accurate and reliable number of their cells at each stage of cheese ripening. This work aimed to identify and conduct a quantitative assessment of the selected species of autochthonous lactic acid bacteria from raw cow's milk cheese by the development of primers and probe pairs based on the uniqueness of the genetic determinants with which the target microorganisms can be identified. For that purpose, we applied real-time quantitative PCR (qPCR) protocols to quantify Lactobacillus delbrueckii subsp. bulgaricus, Streptococcus thermophilus, and Lactococcus lactis subsp. cremoris cells in cheese directly after production and over three-month and six-month ripening periods. While L. lactis subsp. cremoris shows good acidification ability and the ability to produce antimicrobial compounds, L. delbrueckii subsp. bulgaricus has good proteolytic ability and produces exo-polysaccharides, and S. thermophilus takes part in the formation of the diacetyl flavor compound by metabolizing citrate to develop aroma, they all play an important role in the cheese ripening. The proposed qPCR protocols are very sensitive and reliable methods for a precise enumeration of L. delbrueckii subsp. bulgaricus, S. thermophilus, and L. lactis subsp. cremoris in cheese samples.

Profile of lactic acid bacteria (MALDI-TOF-MS) and physico-chemical and microbiological characteristics of the raw milk and fresh artisanal cheese from Serra Geral, Minas Gerais, Brazil

Artisanal cheese from Serra Geral, Minas Gerais, Brazil, stands out for its cultural asset and socio-economic relevance. However, standards of identity and quality and the peculiar terroir associated with the edaphoclimatic conditions have not been established. Therefore, the production flow diagram and the physico-chemical and microbiological quality of the raw milk, pingo (natural starter culture), production benches, water and fresh cheese were investigated for the first time. In addition, lactic acid bacteria (LAB) from cheese and its production environment were identified by MALDI-TOF. For that, 12 cheese making facilities were selected. The raw milk and pingo showed adequate physico-chemical characteristics for cheesemaking; however, high microbial counts were found. In the water, total and thermotolerant coliforms were also identified. The fresh cheeses were classified as 'high moisture and fat' and 'soft mass'. Most physico-chemical parameters were satisfactory; however, there were high counts of total coliforms, Staphylococcus spp. and coagulase-positive staphylococci. There were high counts of LAB in the raw milk, pingo, bench surface and fresh cheese. A total of 84 microbial biotypes from MRS agar were isolated. Lactococcus lactis was the predominant LAB, followed by Lactococcus garvieae. Leuconostoc mesenteroides (benches), Leuconostoc pseudomesenteroides (fresh cheese), and Enterococcus faecium (pingo) were identified sporadically. These results indicate the risks to public health associated with the consumption of the fresh cheese, and measures to improve its safety are needed.

Tracking microbial quality, safety and environmental contamination sources in artisanal goat cheesemaking factories

A harmonised microbiological survey was performed in two artisanal factories of raw goat milk cheeses (A and B) located in the Andalusian region (Spain). A total of 165 different control points or samples (raw materials, final products, food-contact surfaces [FCS], and air) were examined as microbial and pathogen sources of contamination of artisanal goat raw milk cheeses. For raw milk samples analysed from both producers, the concentrations of aerobic-mesophilic bacteria (AMB), total coliforms, coagulase-positive Staphylococcus spp. (CPS), lactic-acid bacteria (LAB) and moulds and yeasts ranged between 3.48 and 8.59, 2.45-5.48, 3.42-4.81, 4.99-8.59 and 3.35-6.85 log cfu/mL respectively. For the same microbial groups, the analysis of raw milk cheeses revealed concentrations ranging from 7.82 to 8.88, 2.00-6.82, 2.00-5.28, 8.11-9.57 and 2.00-5.76 log cfu/g, respectively. Although the raw material analysed from producer A presented higher microbial loads and between-batch variability, it was B the producer with the most loaded final products. Regarding the microbial air quality, the fermentation area, storage room, milk reception and packaging room were the most AMB loaded places, while the ripening chamber was the area with higher fungal loads in bioareosol from both producers. Conveyor belts, cutting machine, storage boxes and brine tank were highlighted as the most contaminated FCS evaluated. Staphylococcus aureus was the only pathogen detected within the set of 51 isolates from samples as revealed by MALDI-TOF and molecular PCR, with a prevalence of 12.5% for samples from the producer B. The public health risk attributed to the consumption of artisanal goat cheese should not be neglected, and may consider the whole cheesemaking processing chain, from microbiological quality of raw milk to the ready-to-eat final product, especially concerning the presence of S. aureus.

Evaluation of Enterotoxins and Antimicrobial Resistance in Microorganisms Isolated from Raw Sheep Milk and Cheese: Ensuring the Microbiological Safety of These Products in Southern Brazil

This study emphasizes the importance of monitoring the microbiological quality of animal products, such as raw sheep's milk and cheese, to ensure food safety. In Brazil, there is currently no legislation governing the quality of sheep's milk and its derivatives. Therefore, this study aimed to evaluate: (i) the hygienic-sanitary quality of raw sheep's milk and cheese produced in southern Brazil; (ii) the presence of enterotoxins and Staphylococcus spp. in these products; and (iii) the susceptibility of the isolated Staphylococcus spp. to antimicrobial drugs and the presence of resistance genes. A total of 35 samples of sheep's milk and cheese were examined. The microbiological quality and presence of enterotoxins were accessed using Petrifilm and VIDAS SET2 methods, respectively. Antimicrobial susceptibility tests were conducted using VITEK 2 equipment and the disc diffusion method. The presence of resistance genes tet(L), sul1, sul2, ermB, tetM, AAC(6)', tetW, and strA were evaluated through PCR. In total, 39 Staphylococcus spp. were obtained. The resistance genes tetM, ermB, strA, tetL, sul1, AAC(6)', and sul2 were detected in 82%, 59%, 36%, 28%, 23%, 3%, and 3% of isolates, respectively. The findings revealed that both raw sheep's milk and cheese contained Staphylococcus spp. that exhibited resistance to antimicrobial drugs and harbored resistance genes. These results underscore the immediate need for specific legislation in Brazil to regulate the production and sale of these products.

High Level of Interaction between Phages and Bacteria in an Artisanal Raw Milk Cheese Microbial Community

Microbial starter cultures are used in the production of many cheeses around the world, such as Parmigiano-Reggiano, in Italy, Époisses, in France, and Canastra, in Brazil, providing many of the unique features of these cheeses. Bacteriophages (phages) are ubiquitous and well known to modulate the structure of bacterial communities, and recent data indicate that cheeses contain a high abundance of naturally occurring phages. Here, we analyze the viral and bacterial metagenomes of Canastra cheese: a traditional artisanal Brazilian cheese produced using an endogenous starter culture and raw milk. Over 1,200 viral operational taxonomic units were recovered using both isolated viral-like particles and complete metagenomic DNA. Common viral families identified included Siphoviridae and Myoviridae, with 40% of putative phage genomes unidentified at the family level of classification. We observed very high phage diversity, which varied greatly across different cheese producers, with 28% of phage genomes detected in only one producer. Several metagenome-assembled genomes were recovered for lactic acid-producing bacteria, as well as nonstarter bacterial species, and we identified several phage-bacterium interactions, at the strain level of resolution, varying across distinct cheese producers. We postulate that at least one bacterial strain detected could be endogenous and unique to the Canastra cheese-producing region in Brazil and that its growth seems to be modulated by autochthonous phages present in this artisanal production system. This phage-host relationship is likely to influence the fermentation dynamics and ultimately the sensorial profile of these cheeses, with implications for other similar cheese production systems around the world. IMPORTANCE Our work demonstrated a dynamic yet stable microbial ecosystem during cheese production using an endogenous starter culture. This was observed across several distinct producers and was marked by genomic evidence of continued phage-bacterium interactions, such as the presence of bacterial defense mechanisms. Furthermore, we provide evidence of unique microbial signatures for each individual cheese producer studied in the region, a fact that may have profound consequences on product traceability. This was the first effort to describe and understand the bacteriophage composition and ecological dynamics within the Brazilian Canastra cheese production system. The study of this prototypical backslopping production system provides a solid background for further mechanistic studies of the production of many cheeses around the world.

Key aroma compounds of Canastra cheese: HS-SPME optimization assisted by olfactometry and chemometrics

An analytical method was developed to determine volatile compounds (VC) that contribute to the aroma of cheese from Serra da Canastra (Brazil) and evaluate them in three ripening stages (fresh, short-ripened, and ripened) via headspace solid-phase microextraction (HS-SPME) combined with gas chromatography (GC). Proximate and fatty acid compositions were determined to observe whether there would be changes during ripening. Multivariate designs were applied to optimize the extraction parameters of volatile compounds and assisted by GC olfactometry (GC-O) and chemometrics. The adopted strategy revealed that the best extraction condition requires 10 min of equilibration, 75.2 min of fiber exposure at 40 °C, and 1 g of sample. The data obtained evidenced the alteration of the abundance of volatile compounds, fatty acids, and proximate composition of Canastra cheese during ripening. The fatty acid profile of the samples was mainly composed of palmitic, oleic, and stearic acids. This dairy product is rich in volatile compounds and formed primarily by alcohols (n = 14), acids (n = 13), and esters (n = 11). Olfactometry indicated that the VCs that most affected the aroma of ripened Canastra cheese were acetic acid, isobutyric acid, butanoic acid, and ethyl hexanoate. The method developed effectively discriminated against Canastra cheeses at their different ripening stages.

Artisanal Brazilian Cheeses-History, Marketing, Technological and Microbiological Aspects

This review focused on the historical, marketing, technological, and microbiological characteristics of artisanal Brazilian cheese. Brazilian cheese production was introduced and developed from the influence of immigrants considering the combination of climate, races of the animals, quality and specificity of milk, technological cheese-making processes and environmental microbiology, among other factors. It resulted in cheese products with specific physicochemical, microbiological, and sensory quality, which represent the heritage and identities of the different Brazilian regions. The production of artisanal cheese increased in many Brazilian regions, mainly in the southeast, especially due to the traditional production and innovative development of new varieties of cheese. The microbiological quality and safety of raw-milk artisanal cheese continues to be a concern and many studies have been focusing on this matter. Special attention needs to be given to the cheeses produced by raw milk, since numerous reports raised concerns related to their microbiological safety. This fact requires attention and the implementation of strict hygiene practices on the production and commercialization, besides appropriate governmental regulations and control. However, more studies on the relationship between technological processes and microbiological properties, which results in a superior culinary quality and safety of artisanal Brazilian cheeses, are needed.

Brazilian Artisanal Cheeses: Diversity, Microbiological Safety, and Challenges for the Sector

Artisanal cheeses made with raw milk are highly appreciated products in Brazil. Most of these cheeses are produced in small facilities across different production regions in the country, some of which have been granted a protected designation of origin and are award winners. The most prominent state that manufactures these products is Minas Gerais (MG), but production is also gaining strength in other Brazilian states. The major challenge faced by artisanal cheese production is related to microbial risks associated with foodborne pathogens when the quality of the raw milk is unsatisfactory. Regulations created for the dairy industry are constantly been revised and adapted, considering the small-scale production of Brazilian artisanal cheeses, in order to guarantee safety at all steps of cheese production and commercialization. This text presents a summary of the huge diversity of artisanal cheeses produced in the country, grouped by geographical regions, and reviews the current challenges faced by producers and government considering the safety of these cheeses.

Microbiological quality and safety of Brazilian artisanal cheeses

The establishment of norms that regulates the production and trade of Brazilian Artisanal Cheeses (BAC) has been stimulating many small farmers for this activity. The predominance of lactic acid bacteria (LAB) is a typical characteristic of BAC, which confers desirable attributes to artisanal cheeses. However, these products can be contaminated by other microbial groups, including those that indicate hygienic failures during production and may cause spoilage, or even microorganisms that pose risks to consumers' health. A systematic review of the literature published from January 1996 to November 2020 was carried out to identify scientific data about production characteristics and microbiological aspects of BAC, with a major focus on quality and safety status of these traditional products. Studies that fulfilled the inclusion criteria indicated that artisanal chesses produced in Brazil still do not satisfactorily meet the microbiological criteria established by the national laws, mainly due to the high counts of coagulase-positive Staphylococcus and coliforms. Despite low prevalence, pathogens such as Salmonella and Listeria monocytogenes were isolated in some BAC. This review contributed to better understanding microbiological aspects of BAC, the data compiled by the authors highlight the need to improve hygiene practices along the production chain of these traditional cheeses.