Microbiological aspects of the biofilm on wooden utensils used to make a Brazilian artisanal cheese

The wooden shelf surface and cheese rind mutually exchange microbiota during the traditional ripening process

The rind acts as a protective barrier for internally-bacterial ripened cheeses. Unlike surface-inoculated smear cheeses, centripetal maturation is not assumed to occur in these cheeses. This research was aimed to evaluate the microbial diversity of the wooden shelves used for the ripening of Protected Denomination of Origin (PDO) Pecorino di Filiano and Protected Geographical Indication (PGI) Canestrato di Moliterno cheeses. The microorganisms associated with the rind of these cheeses were also investigated. Both wooden shelf surfaces and cheese rinds were sampled by brushing method to collect their biofilms. Wooden shelves showed levels of total mesophilic microorganisms (TMM) between 5.6 and 7.2 log CFU/cm2, while cheese rinds between 6.1 and 7.8 log CFU/cm2. The major dairy pathogens (Salmonella spp., Listeria monocytogenes, Escherichia coli, and Staphylococcus aureus) were never detected, while mesophilic and thermophilic bacteria dominated the surfaces of all wooden shelves and cheese rinds. LAB community was represented by Enterococcus spp., Leuconostoc spp., and Marinilactibacillus spp. Among yeasts, Debaryomyces spp., Candida spp., were identified, while Aspergillus spp., and Penicillium spp., dominated the community of filamentous fungi. MiSeq Illumina analysis identified 15 phyla, 13 classes, 28 orders, 54 families, and 56 genera among bacteria. Staphylococcus spp. was identified from all wooden surfaces, with a maximum abundance of 71 %. Brevibacterium, Corynebacterium and halophilic bacteria were detected in almost all samples. Regarding fungi, wooden shelves mainly hosted Aspergillus, Penicillium and Debaryomyces hansenii, while cheese rinds especially Penicillium and D. hansenii. Alpha diversity confirmed a strict correlation between the microbiota of wooden shelves and that of cheese rinds for the majority of factories. This study confirmed that the wooden shelves used for cheese ripening are microbiologically active and represent safe systems. Furthermore, the results of this work clarified the transfer flow between wooden shelves and PDO Pecorino di Filiano and PGI Canestrato di Moliterno cheese surfaces: smear-active microorganisms are mainly transferred from wooden shelves to cheese rind, which potentially contribute to the development of the final organoleptic characteristics; meanwhile, cheeses transfer LAB that are potentially involved in defining the safety aspects of the shelves.

A Multivariate Approach to Study the Bacterial Diversity Associated to the Wooden Shelves Used for Aging Traditional Sicilian Cheeses

The present study was carried to correlate the microbial diversity of the biofilms developed on the wooden boards used for aging traditional Sicilian cheeses with cheese typology. To this end, the microbial diversity of the shelves in contact with the cheeses PDO Pecorino Siciliano, PDO Piacentinu Ennese, and TAP Caciocavallo Palermitano, during ripening, was evaluated by a multivariate statistical approach. The shelf biofilms of this study were previously analyzed for their microbial composition, but no correlation between biodiversity and cheese type was investigated. Canonical discriminant analysis confirmed a cheese typology effect on the microbial loads of the wooden shelves investigated. Regarding the plate count data, the centroids of different cheeses were statistically distant from one another. This analysis also showed a good graphic separation of data regarding bacterial order operational taxonomy units (OTUs). Thus, the microbiological differences imputed to the cheese typologies were not affected by the environmental conditions of the facilities. Furthermore, wooden shelf lactic acid bacteria (LAB) were investigated for their ability to inhibit the main dairy pathogens. Although inhibitors were mainly enterococci, P. pentosaceus WS287 and W. paramesenteroides WS581 showed the highest inhibition activity, indicating their possible application to control the undesired bacteria in situ.

In-Depth Investigation of the Safety of Wooden Shelves Used for Traditional Cheese Ripening

The main goal of this research was to characterize the bacterial diversity of the wooden boards used for aging traditional Sicilian cheeses and to evaluate whether pathogenic bacteria are associated with these surfaces. Eighteen cheese dairy factories producing three traditional cheese typologies (PDO Pecorino Siciliano, PDO Piacentinu Ennese, and Caciocavallo Palermitano) were selected within the region of Sicily. The wooden shelf surfaces were sampled by a destructive method to detach wood splinters as well as by a nondestructive brushing to collect microbial cells. Scanning electron microscopy showed the presence of almost continuous bacterial formations on the majority of the shelves analyzed. Yeasts and fungal hyphae were also visualized, indicating the complexity of the plank communities. The amplicon library of the 16S rRNA gene V3-V4 region was paired-end sequenced using the Illumina MiSeq system, allowing the identification of 14 phyla, 32 classes, 52 orders, 93 families, and 137 genera. Staphylococcus equorum was identified from all wooden surfaces, with a maximum abundance of 64.75%. Among cheese-surface-ripening bacteria, Brevibacterium and Corynebacterium were detected in almost all samples. Several halophilic (Halomonas, Tetragenococcus halophilus, Chromohalobacter, Salimicrobium, Marinococcus, Salegentibacter, Haererehalobacter, Marinobacter, and Idiomarinaceae) and moderately halophilic (Salinicoccus, Psychrobacter, and Salinisphaera) bacteria were frequently identified. Lactic acid bacteria (LAB) were present at low percentages in the genera Leuconostoc, Lactococcus, Lactobacillus, Pediococcus, and Streptococcus. The levels of viable microorganisms on the wooden shelves ranged between 2.4 and 7.8 log CFU/cm2. In some cases, LAB were counted at very high levels (8.2 log CFU/cm2). Members of the Enterobacteriaceae family were detected in a viable state for only six samples. Coagulase-positive staphylococci, Salmonella spp., and Listeria monocytogenes were not detected. Seventy-five strains belonged to the genera Leuconostoc, Lactococcus, Pediococcus, Enterococcus, Lactobacillus, and Weissella. IMPORTANCE This study provides evidence for the lack of pathogenic bacteria on the wooden shelves used to ripen internal bacterially ripened semihard and hard cheeses produced in Sicily. These three cheeses are not inoculated on their surfaces, and surface ripening is not considered to occur or, at least, does not occur at the same extent as surface-inoculated smear cheeses. Several bacterial groups identified from the wooden shelves are typically associated with smear cheeses, strongly suggesting that PDO Pecorino Siciliano, PDO Piacentinu Ennese, and Caciocavallo Palermitano cheese rind contributes to their final organoleptic profiles.

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.

Influence of detergents and sodium hypochlorite on Yarrowia lipolytica biofilms in utensils used in industrial production of colonial cheese

The formation of microbial biofilms in materials used in the industrial production of dairy may lead to deterioration of these foods. Yarrowia lipolytica biofilms are widely found in dairy products and can modify the final characteristics of these products. Thus, this study investigated the effectiveness of hygienization by detergents and sodium hypochlorite on the formation of Y. lipolytica biofilms in different utensils usually employed during industrial cheese production, like polypropylene, hoses, and nylon/polyethylene. The utensils were sanitized using solutions of mild and alkaline detergents, and sodium hypochlorite, according to the cheese industry Standard Operation Procedure. Results showed that in all coupons there was biofilm formation with Y. lipolytica isolates. The contact angle measurements were favored to promote the adhesion of the biofilm in the evaluated surfaces. Even after treatment with sanitizers, a significant survival rate of planktonic cells was observed in all coupons tested. These results indicate that Y. lipolytica biofilms show a significant ability to adhere to polypropylene, presenting an important impact on the quality of colonial cheese.

Amplicon sequencing reveals the bacterial diversity in milk, dairy premises and Serra da Canastra artisanal cheeses produced by three different farms

In this work, the amplicon sequencing of the 16 S rRNA gene was employed to investigate the bacterial diversity in ingredients, processing environment, and ripened cheeses collected from three farms producing Serra da Canastra artisanal cheese. The data obtained indicated a remarkable variability in the bacteria consortia of the milk, whey, and environmental samples collected in farms 1, 2, and 3, despite their location in the same city. On the other hand, the starter culture and final product (ripened cheese) presented more constant and similar microbiota no matter the farm. The findings suggest that Streptococcus and Lactococcus have competitive advantages throughout Serra da Canastra cheese-making/ripening, which is crucial for their high relative abundance in the final products. An exploratory assessment based on sequencing data available in the literature showed that the Serra da Canastra cheeses sequences clustered with specific cheese varieties that are also made from raw milk but ripened for very different periods. The findings of this study highlight that despite the variability of milk and whey microbiota among the three farms, the starter culture ("pingo") has strong relevance in shaping the microbiota of the final product.

Brazilian Artisanal Cheeses: An Overview of their Characteristics, Main Types and Regulatory Aspects

A large variety of cheeses exist in Brazil, reflecting historical and cultural aspects. Brazilian artisanal cheeses present differences in the processing, ripening time (when applied), type of milk used, texture, size, shape, color, moisture content, flavor, the use or not of starter cultures, among others. This review describes the main artisanal cheeses produced in Brazil, focusing on general and particular characteristics associated with their making process and geographical identity. Overall, the high variability of the physicochemical data and deficiency of information on sensorial properties of Brazilian artisanal cheeses were noticed. On the other hand, culture-dependent methods were mostly used to expand the knowledge into the microbiology of these cheeses, whereas their microbial diversity has been recently discovered through the use of 16S rRNA gene sequencing-based methods. The certification of a geographical indication for Brazilian artisanal cheeses may encompass an essential milestone for adding value to these products. Regardless of their significance in the diet, culture, and economy of producing regions, taken together, the reviewed literature discloses the need of insightful studies to generate scientific data to support the expansion of the market, while ensuring the protection of historic aspects related to the production of Brazilian artisanal cheeses.

Performance of two alternative methods for Listeria detection throughout Serro Minas cheese ripening

The ability of pathogens to survive cheese ripening is a food-security concern. Therefore, this study aimed to evaluate the performance of two alternative methods of analysis of Listeria during the ripening of artisanal Minas cheese. These methods were tested and compared with the conventional method: Lateral Flow System™, in cheeses produced on laboratory scale using raw milk collected from different farms and inoculated with Listeria innocua; and VIDAS^®-LMO, in cheese samples collected from different manufacturers in Serro, Minas Gerais, Brazil. These samples were also characterized in terms of lactic acid bacteria, coliforms and physical–chemical analysis. In the inoculated samples, L. innocua was detected by Lateral Flow System™ method with 33% false-negative and 68% accuracy results. L. innocua was only detected in the inoculated samples by the conventional method at 60-days of cheese ripening. L. monocytogenes was not detected by the conventional and the VIDAS^®-LMO methods in cheese samples collected from different manufacturers, which impairs evaluating the performance of this alternative method. We concluded that the conventional method provided a better recovery of L. innocua throughout cheese ripening, being able to detect L. innocua at 60-day, aging period which is required by the current legislation.

Perfil microbiológico del queso de aro consumido en la Cañada Oaxaqueña

Resumen Se determinó la composición de la microbiota del queso de Aro que se comercializa en el municipio de Teotitlán de Flores Magón, Oaxaca, México. Se cuantificó el contenido de: mesófilos aerobios, psicrófilos, coliformes totales, Escherichia coli, Staphylococcus aureus, Salmonella, Enterococcus, Streptococcus, bacterias ácido lácticas, mohos y levaduras. Los resultados muestran que el queso de Aro contiene microorganismos alterantes, patógenos y de importancia industrial. Ninguna muestra analizada cumple con la NOM-243-SSA1-2010. Por lo tanto, este queso pueden ser un vehículo de transmisión de enfermedades alimentarias, por su elevado contenido de: E. coli, Staphylococcus aureus y Salmonella. La vida de anaquel del queso puede verse afectada provocando pérdidas económicas a los productores. Por otro lado, se pueden obtener microorganismos de importancia industrial (Lactobacillus y Streptococcus). Es necesario implementar sistemas se aseguramiento de la calidad que garanticen la producción de quesos inocuos.

Determining the minimum ripening time of artisanal Minas cheese, a traditional Brazilian cheese

Physical, physicochemical, and microbiological changes were monitored in 256 samples of artisanal Minas cheese from eight producers from Serro region (Minas Gerais, Brazil) for 64 days of ripening to determine the minimum ripening time for the cheese to reach the safe microbiological limits established by Brazilian legislation. The cheeses were produced between dry season (April-September) and rainy season (October-March); 128 cheeses were ripened at room temperature (25 ± 4 °C), and 128 were ripened under refrigeration (8 ± 1 °C), as a control. No Listeria monocytogenes was found, but one cheese under refrigeration had Salmonella at first 15 days of ripening. However, after 22 days, the pathogen was not detected. Seventeen days was the minimum ripening time at room temperature to reduce at safe limits of total coliforms > 1000 cfu.g (-1) ), Escherichia coli and Staphylococcus aureus (> 100 cfu.g (-1) ) in both periods of manufacture. Otherwise under refrigeration, as expected, the minimum ripening time was longer, 33 days in the dry season and 63 days in the rainy season. To sum up, we suggest that the ripening of artisanal Minas cheese be done at room temperature, since this condition shortens the time needed to reach the microbiological quality that falls within the safety parameters required by Brazilian law, and at the same time maintain the appearance and flavor characteristics of this traditional cheese.