Estrela Cheese Research Articles

Microbiological Characterization of Protected Designation of Origin Serra da Estrela Cheese.

Serra da Estrela is the oldest and most recognizable traditional protected designation of origin (PDO) cheese from Portugal. It has been extensively studied over the years, but the latest microbial characterization is 20 years old. Hence, this work aimed to perform an updated characterization of Serra da Estrela PDO cheeses and raw materials. Our analysis showed that lactic acid bacteria content on Serra da Estrela cheeses exceeded 8.8 log CFUsg-1, in all analyzed samples, with lactococci, lactobacilli and Leuconostoc spp. predominating over enterococci strains. Moreover, lactococci and lactobacilli abundance increased across the production season, while enterococci dropped considerably in late manufactures. Lastly, Leuconostoc spp. content remained unchanged in all analyzed periods. A correspondence analysis showed that L. paracasei, L. lactis, E. durans, E. faecium and L. mesenteroides are transversal in Serra da Estrela cheese manufacturing and were closely associated with milk, curd and cheese matrices. Additionally, L. casei, L. plantarum and L. curvatus were specifically associated with cheese matrices, possibly active during ripening and contributing for the development of these cheeses' organoleptic characteristics.

Evolution of Qualitative and Quantitative Lipid Profiles of High-Pressure-Processed Serra da Estrela Cheese throughout Storage

High-pressure processing (HPP) can be used as a nonthermal pasteurization technique to overcome microbial safety issues of the raw ewes’ milk Serra da Estrela cheese without negatively influencing its quality, in particular, the lipid composition partly responsible for Serra da Estrela cheese’s sensorial and textural attributes. The aim of this work was to assess HPP’s effect (600 MPa/6 min and 450 MPa/6 and 9 min) on the qualitative and quantitative lipid profiles of Serra da Estrela cheese during 15 months of refrigerated storage. Total triglycerides content (65–66 g TG/100 g) was similarly determined for HPP-treated (450 MPa/6 min) and control cheeses. Similar total contents of saturated, monounsaturated, and polyunsaturated fatty acids were reported for all cheeses during storage. A high total conjugated linoleic acid content (1.29–1.65 g FA/100 g fat) was quantified in all cheeses during storage; all cheeses revealed similar atherogenic and thrombogenic indices (~2.3 and ~2.6, respectively). HPP can be used to process Serra da Estrela cheese at conditions that assure microbial safety without influencing cheese lipid profiles.

Comparing Different Packaging Conditions on Quality Stability of High-Pressure Treated Serra da Estrela Cheeses during Cold Storage.

Serra da Estrela cheese with a Protected Designation of Origin (PDO) is a traditional cheese that is wrapped in paper without vacuum. High-pressure processing (HPP), which requires vacuum packaging of the cheese, has been used for its cold pasteurization to overcome safety issues. In this study, two packaging systems were studied: non-vacuum greaseproof paper wrapping package and vacuum packaging in plastic film. Lactococci, lactobacilli, enterococci, and total mesophiles reached ca. 8 log cfu g-1 and 4-6 log cfu g-1 in control (unpasteurized) and HPP-treated cheeses, respectively, with no significant differences between packaging systems. Spoilage microorganisms' viable cell numbers were reduced to <3 log cfu g-1 (quantification limit) in HPP-treated cheeses, independently of the packaging system. Yeasts and molds reached >5 log cfu g-1 in non-vacuum paper-wrapped cheeses. A vacuum-packaging system enabled better control of cheese proteolysis, which was revealed to be closer to that of the original control cheese values at the end of the 10-month storage period. In addition, cheese stored under vacuum film packaging became harder than non-vacuum paper-wrapped cheeses at each time point. Overall, conventional non-vacuum paper wrapping is adequate for short storage periods (<3 months), but for long periods vacuum packaging in plastic film is preferable.

Queijo Serra da Estrela PDO Cheese: Investigation into Its Morpho-Textural Traits, Microbiota, and Volatilome.

Queijo Serra da Estrela is a PDO Portuguese cheese produced through coagulation of raw ewe’s milk using cardoon (Cynara cardunculus L.) flowers. The present research was aimed at depicting an up-to-date and comprehensive overview of the microbiota of Queijo Serra da Estrela cheese. To this end, viable counting and metataxonomic analysis were carried out on cheeses sampled from four Portuguese artisan producers. Physico-chemical and morpho-textural analyses were also performed, together with the analysis of volatile organic compounds (VOCs). Finally, non-starter lactic acid bacteria (NSLAB) isolated from the cheeses were characterized for their enzymatic activities using a semi-quantitative method. According to the metataxonomic analysis, Lactococcus lactis and Lactococcus piscium were the species occurring at the highest relative abundance. The isolates collected from the cheeses were assigned to Enterococcus durans, Enterococcus faecalis, Enterococcus faecium, Enterococcus lactis, Levilactobacillus brevis, Latilactobacillus graminis, Leuconostoc mesenteroides, and the Lacticaseibacillus casei group. The enzymatic characterization of these cultures highlighted esterase, aminopeptidase, acid phosphatase, beta-galactosidase, alpha-glucosidase, and beta-glucosidase among the major enzymatic activities. Fungal populations were dominated by Debaryomyces hansenii and Kurtzmaniella zeylanoides; however, species rarely found in cheese (e.g., Candida boidinii, Vishniacozyma victoriae, and Starmerella) were also detected. The volatile compounds characterizing the analyzed cheeses were carboxylic acids and esters, followed by carbonyl compounds and alcohols.

Characterization of dairy sheep farms in the Serra da Estrela PDO region

Abstract Sheep farming plays a key role in the sustainability of the most depressed rural regions of Portugal, particularly in the Serra da Estrela region, and is recognized as an important source of income for many local farmers. Thus, the management of local sheep breeds in the region has over generations given rise to its most emblematic product: Serra da Estrela cheese, with Protected Designation of Origin (PDO). This study aims to briefly describe the sheep farms producing certified milk in the Serra da Estrela region. To this end, a survey form was drawn up and applied to 75 farms, randomly selected, from the defined geographical area of Serra da Estrela, from June to August 2020. The results show that the producers, mostly male, have an average age close to 51 years. On average, the herd size is equal to or greater than 100 animals and the daily milk production per animal varies between 0.47 and 1.0 L. The price of milk paid to the producer is, on average, at 1.25 Euros/L. Both the average herd size and the lactation length are higher than those described by others. The average daily milk production in most of these farms is in accordance with the standard average value related by other authors.

Resilience in Retrospective: The Trajectory of Agro-Pastoral Systems in the Centro Region of Portugal

Agro-pastoral systems in southern European regions have been subjected to various disturbances in the past few decades. Still, a certain amount of resilience allowed to withstand its sharp decline. The Serra da Estrela cheese production, the most representative agro-pastoral system of the Portuguese Centro Region, is a demonstrative case study. The main objective of this research is to understand the trajectory of this system up to present, its adaptation to internal and external changes and evolution trends. We used the concepts of resilience and socio–ecological system as framework in a qualitative study. Participatory methods were applied using the perspectives of local actors, in order to identify and analyze the key factors. The main drivers are socio-demographic (ageing, depopulation, social perception of the profession), economic (free market, industrialization), political (lack of adequate of national and European policies) and environmental (climate change, forest fires). Our results are in line with other European cases. To cope with these trends, the system is irreversibly transforming, moving into a new trajectory characterized by different systemic architecture. In face of the ongoing changes, the interactions between the social and the ecological subsystems are blurring, whereas local communities and traditions are being excluded.

Production of Serra da Estrela cheese from ultrafiltered sheep’s milk

The objective of this study is to elaborate Serra da Estrela cheese with sheep's milk concentrate by ultrafiltration and characterize it in relation to protein, yield, proteolysis, amino acid profile, and acceptability. The cheese elaborated with concentrate milk (F2) presented an increase of 17% yield, and protein content was 2 times higher than cheese without concentrate milk (F1). On the 30thday of storage F2 presented an increase of the amino acids and also of proteolysis extension and depth index in relation to the 1st day. Also presented better sensorial characteristic in relation to F1. Were observed positive correlations (&gt;0.85) between acceptability in relation to protein, depth index, extensionand extension index, valine, methionine, serine, phenylalanine aspartic acid, valine andproline. Cheese elaborated with concentrate milk and coagulated with thistle flower is one alternative to increase cheese yield with differential sensorial characteristics.

Influence of Cardoon Flower (Cynara cardunculus L.) and Flock Lactation Stage in PDO Serra da Estrela Cheese.

Serra da Estrela (SE) cheese is one of the most appreciated Portuguese cheeses, being produced only from raw ewe’s milk, cardoon flower and salt. Cardoon takes part in two important processes in cheese production—coagulation and proteolysis—contributing to its unique features. Furthermore, milk chemical characteristics change during the milking season, being another factor that account for the high variability of cheese attributes. Therefore, the purpose of this work is to study the influence of cardoon flower (commercial, 6 M and 3 M) and flock lactation stage (November 2018, February and April 2019) in the final characteristics of SE cheese. The parameters analysed were moisture, protein, fat and salt contents, texture and colour. Results showed that flock lactation stage has the highest influence in all the studied characteristics, corresponding the early stages of lactation to the most protein-rich and low-fat cheeses. Cardoon flower affects mainly fat and rind colour. This study allows us to conclude that seasonal changes in ewe’s milk have a considerable impact in cheese attributes, and that although cardoon type had a more restrained effect, when used with expertise it may help adjust cheese sensory characteristics in order to obtain a final product that matches consumer acceptability requirements.

Serra da Estrela cheese: A review

Serra da Estrela cheese with Protected designation of origin certification is manufactured using only raw ewes’ milk, salt, and a crude plant rennet, from the dried flowers of Cynara cardunculus L., resulting in a cheese with peculiar sensorial features (without the addition of starters or additives) that has existed over many centuries. More than 40 scientific reports concerning this cheese have been published since 1992. The composition and microbial profile have revealed certain variations among the literature. During the ripening of Serra da Estrela cheese, biochemical changes occur, which are reflected in its particular flavor and texture characteristics. An intense proteolytic activity takes place along ripening and storage, and volatiles are associated with typical flavor like “butter-cream texture.” Innovation concerning Serra da Estrela cheese has been performed within milk quality, manufacture process, and in ripened cheese. Practical applications The scientific research on Serra da Estrela cheese has been ongoing for decades, focusing the all production and ripening stages, and continues to be active. The present review summarizes the information about this cheese manufacture, composition, microbial profile, biochemical changes and sensorial attributes, and texture that can the base for comparison to other studies. Innovation in several steps of Serra da Estrela cheese have been recently reported, from milk with screening the milk origin; in cardoon: with knowledge the genotype, ecotype to improve quality and standardization; in manufacture: with inclusion of decoctions and/or dried extracts to made a functional food; and in cheese by increase cheese microbiota safety through high pressure processing.

Evaluation of texture of cheese by-products incorporated bread

Abstract This work aimed to develop new breads incorporating whey residue, “sorelho”, obtained from ewe’s milk after the production of Serra da Estrela Cheese. For this, we baked three types of bread: wheat bread (control sample), bread incorporating sorelho, and another version containing additional nutritional elements. The texture was evaluated with a texturometer, using compression and perforation tests. Results showed that sorelho can be successfully incorporated in bread. The best product was the bread with sorelho plus improved nutrition, which presented good textural characteristics during a period of 24 hours. This trend was observed for all properties evaluated: hardness, chewiness, resilience, cohesiveness, springiness (compression test) and external firmness, inner firmness, stickiness, adhesiveness (perforation test). Finally, factor analysis showed: FACTOR 1 – compression textural properties; FACTOR 2 – perforation firmness properties and FACTOR 3 – perforation adhering properties, which in total explained approximately 81% of total variance.

Serra da Estrela cheese's free amino acids profiles by UPLC-DAD-MS/MS and their application for cheese origin assessment.

Serra da Estrela cheese is a high-value Portuguese Protected Designation of Origin cheese, produced with raw ewe milk. Thus, information regarding its composition is of utmost relevance for both consumers and certified producers. In this work, the chromatographic profiles of free amino acids in cheeses (45 days of maturation, 6 producers located in 5 municipalities and produced from November 2017 to March 2018) were established by UPLC-DAD-MS/MS. The proposed method allowed detecting 19 free amino acids and cystine with overall limits of detection and quantification lower than 44 μmol/L (1.4 mg/100 g cheese, wet matter) and than 134 μmol/L (4.2 mg/100 g cheese, wet matter), respectively. In all cheeses, 17 free amino acids were quantified including 8 essential amino acids (histidine, leucine-isoleucine, lysine, methionine, phenylalanine, threonine, tryptophan and valine) and 9 non-essential amino acids (arginine, asparagine, aspartic acid, cysteine, glutamic acid, glutamine, proline, serine and tyrosine). The amounts of the free amino acids, essential free amino acids, branched chain free amino acids (leucine, isoleucine and valine) plus the free amino acids ratios (mg/g protein) were further used to identify the producer of Serra da Estrela cheeses. Linear discriminant analysis coupled with the simulated annealing variable selection algorithm was used allowing the correct classification of 96% and 90 ± 8% of the samples, for leave-one-out and repeated K-fold cross-validation procedures, respectively. The satisfactory predictive performance pointed out the possibility of using cheeses' amino acids profiles as origin biomarkers for authenticity control, warranting the correctness identification of the cheese producer/brand, which is quite relevant for ensuring the consumer confidence and satisfaction when purchasing this high-value dairy food.

Fatty acids profile of Serra da Estrela PDO cheeses and respective atherogenic and thrombogenic indices

Purpose This study aims to determine the physicochemical and fatty acids composition of Serra da Estrela cheese (SEC), as well as health-related lipid indices, like the atherogenic and thrombogenic indices, and to evaluate the influence of producer, geographical origin and production date. Design/methodology/approach All 24 SEC produced between November 2017 and March 2018 were collected at selected certified producers and analyzed by NIR spectrophotometer and by GC. Data were statistically evaluated by chemometric tools. Findings In all evaluated SEC, 23 fatty acids were quantified. Cheese origin influenced nutritional and health-related lipid indices). The cheeses were characterized by a relative high abundance of saturated fatty acids (67-76%), followed by a medium content of monounsaturated fatty acids (17-25%) and by low level of polyunsaturated fatty acids (5-7%). A putative positive association between cheese consumption and healthy lipid indices could be reached. Practical implications The contents of some medium and long chain fatty acids as well as of nutritional and health indices were influenced by cheese producer, geographical origin and production date pointing out the need for standardizing production procedures. Social implications The SEC plays a key role in the local economy, being an endogenous product with unique sensory characteristics and nutritional potential, for which the knowledge of the lipids profile and health indices is of utmost relevance. Originality/value SEC is an iconic Portuguese cheese with Protected Designation of Origin. Based on the results, like health-related lipid indices, evaluated for the first time, a positive association between cheese consumption and healthy lipid indices could be envisaged.

Evaluation of texture in Serra da Estrela cheese manufactured in different dairies

Abstract Serra da Estrela cheese is a traditional product from artisanal manufacture using raw ewe’s milk coagulated with dried, wild thistle flower. The present study aimed to investigate the variation of textural properties in Serra da Estrela cheeses manufactured in different dairies through time, namely from April to June, following the end of the cheese making season. Three types of tests were conducted: compression, puncture and spreadability. These were carried out on samples coming from six different dairies situated in the PDO (Protected Designation of Origin) region of this type of cheese. The results obtained showed some non-negligible differences for some textural properties between the top and bottom sides of the cheeses evaluated, as well as between cheeses from different dairies. Nevertheless, the properties of springiness, resilience, cohesiveness and adhesiveness (all from the compression test), were not significantly different in the samples analysed. In what concerns the variations along the milking season, it was possible to conclude that three of the considered dairies produced cheeses with a more constant textural profile in the period comprised between April and June. Furthermore, statistical analysis revealed that the correlations between the textural properties were strong for some interactions between properties form the same test and/or from similar nature.

Improvement of Certified Artisan Cheese Production through Systemic Analysis—Serra da Estrela PDO

This research was aimed at improving the overall efficiency of the PDO (Protected Designation of Origin) Serra da Estrela cheese production process, a traditional food product with cultural significance. Mapping of the manufacturing and distribution processes was developed from systemic analysis using ethnographic techniques. Critical points were identified, leading to design work. Ergonomic risks in cheese making were detected during the process of chips cutting, fostering the emergence of musculoskeletal disorders of the wrist. A tool that better fitted the job was developed. The systemic analysis provided a relational link across the boundaries of distinct domains approached through the research, including microorganism contamination, ergonomics, energy efficiency, legislation and regulation policies, transportation challenges and economic viability. Based on an analysis that connected various disciplines, maintaining a holistic perspective, a development plan to tackle critical points identified in the system was created. The results ripple across the triple bottom line of sustainability, demonstrating how systemic analysis and design are at the service of improving sustainability. By unveiling and acting on critical points that pushed the system away from zero waste, the environment is conserved; the preservation of cultural heritage has social significance; and the efficiency gains obtained in production attend financial goals.

Meta-design of the Logotype of the Protected Designation of Origin Serra da Estrela Cheese

Meta-design of the Logotype of the Protected Designation of Origin Serra da Estrela Cheese

Effect of different thistle flower ecotypes as milk-clotting in Serra da Estrela cheese

Purpose Thistle flower (Cynara cardunculus) aqueous extracts, as rich source of milk-clotting peptidases, have been widely used for cheeses marketed under the Registry of the Protected Designation of Origin, as it is the case of Serra da Estrela cheese, manufactured from raw ewes’ milk and without addition of any commercial starter culture. This paper aims at studying the influence of six different ecotypes of thistle flowers in cheese properties during the ripening and of final products. Design/methodology/approach Cheeses were produced with different thistle flower extracts and then the clotting time, weight and colour of cheeses, as well as texture properties and sensorial characteristics, were evaluated. Findings The clotting time varied from 47 to 66 min, and the weight loss along ripening varied between 32 and 40 per cent. There was some influence of thistle flower ecotype on the colour during ripening and in the final product. The results of texture analysis revealed significant differences between the thistle ecotypes: crust firmness varying from 2.4 to 5.6 N; inner firmness from 0.82 to 1.82 N; stickiness from −0.5 to −1.60 N; adhesiveness from −3.0 to −11.3 N.s; and Ecotype C was particularly distinguishable. Sensorial evaluation revealed differences among the cheeses, with Ecotype C receiving the highest score for global appreciation. Originality/value The usage of different extracts of thistle flower to produce Serra da Estrela cheese with different properties is a novelty, and it allows the possibility of manipulating this parameter in the future so as to produce cheeses with specific characteristics, addressed to different consumer targets.

RAPD and SCAR markers as potential tools for detection of milk origin in dairy products: Adulterant sheep breeds in Serra da Estrela cheese production

Serra da Estrela Protected Designation of Origin (PDO) cheese is the most famous Portuguese cheese and has a high commercial value. However, the adulteration of production with cheaper/lower-quality milks from non-autochthones ovine breeds compromises the quality of the final product and undervalues the original PDO cheese. A Randomly Amplified Polymorphic DNA (RAPD) method was developed for efficient detection of adulterant breeds in milk mixtures used for fraudulent production of this cheese. Furthermore, Sequence Characterized Amplified Region (SCAR) markers were designed envisioning the detection of milk adulteration in processed dairy foods. The RAPD-SCAR technique is here described, for the first time, to be potentially useful for detection of milk origin in dairy products. In this sense, our findings will play an important role on the valorization of Serra da Estrela cheese, as well as on other high-quality dairy products prone to adulteration, contributing to the further development of the dairy industry.

Analysis of factors influencing the physical, chemical and sensorial properties of Serra da Estrela cheeses

The objective of this study was to evaluate the chemical, color, textural, and sensorial characteristics of Serra da Estrela cheese and also to identity the factors affecting these properties, namely thistle ecotype, place of production, dairy and maturation. The results demonstrated that the cheeses lost weight mostly during the first stage of maturation, which was negatively correlated with moisture content, being this also observed for fat and protein contents. During maturation the cheeses became darker and with a yellowish coloration. A strong correlation was found between ash and chlorides contents, being the last directly related to the added salt in the manufacturing process. The flesh firmness showed a strong positive correlation with the rind harness and the firmness of inner paste. Stickiness was strongly related with all the other textural properties being indicative of the creamy nature of the paste. Adhesiveness was positively correlated with moisture content and negatively correlated with maturation time. The trained panelists liked the cheeses, giving high overall assessment scores, but these were not significantly correlated with the physicochemical properties. The salt differences between cheeses were not evident for the panelists, which was corroborated by the absence of correlation between the perception of saltiness and the analyzed chlorides contents. The Factorial Analysis of the chemical and physical properties evidenced that they could be explained by two factors, one associated to the texture and the color and the other associated with the chemical properties. Finally, there was a clear influence of the thistle ecotype, place of production and dairy factors in the analyzed properties.

Basil as functional and preserving ingredient in “Serra da Estrela” cheese

Antitumor, antimicrobial and antioxidant activities of basil were studied, along with its characterization in phenolic compounds, organic acids and soluble sugars. The results placed basil as a valuable candidate for functionalization and conservation of food products, maintaining their nutritional properties, while increasing their shelf life and potential health effects. The basil leaves were then incorporated in “Serra da Estrela Cheese”, either in its dehydrated form or as a decoction. The cheeses were then subject to a nutritional evaluation, being characterized for their fatty acids, minerals and CIE color parameters. To assess the combined effects of plant incorporation and storage time, a 2-way ANOVA was used to process the results, further analysed through a linear discriminant analysis. Overall, basil leaves provided antioxidant activity to the cheeses, reduced the moisture, and preserved the unsaturated fatty acids and proteins. Comparing both incorporation types, the decoctions had a higher functionalizing and conservative effect.

Effect of high‐pressure treatments on microbial loads and physicochemical characteristics during refrigerated storage of raw milk Serra da Estrela cheese samples

SummaryThis work studied the effect of high pressure processing (HPP) at 400, 500 and 600 MPa during 10, 5 and 3 min, respectively, on samples ewe cheese manufactured from raw milk, during storage (100 days) at 5 °C. Total aerobic mesophilic and lactic acid bacteria were slightly affected, decreasing by about 1.0 and 0.82 log CFU g−1, respectively, immediately after HPP treatment at 600 MPa for 3 min, while Enterobacteriaceae, yeasts and moulds, and Listeria innocua were reduced to below the quantification limits. Lactic acid bacteria decreased further during storage, showing increasing inactivation as the pressure level increased. Physicochemical parameters (water activity, moisture content, pH and titratable acidity) were generally not affected by HPP, while lipid oxidation increased throughout storage, with HPP samples showing lower values (50–66%) at 100 days of storage. The results indicated that HPP has potential to improve cheese microbial safety and shelf‐life, with a lower lipid oxidation level than nonpressurised cheese.