Nutritional and microbiological composition of Serra Estrela cheese: a paradigm to overcome

Background: Milk and dairy products are an excellent source of well-balanced nutrients with multiple uses as a snack, dessert or food ingredient. Serra Estrela cheese, a traditional variety manufactured in the centre region of Portugal, is part of the mankind ́s ancient cultural heritage, made from raw sheep milk it is assumed as an iconic gourmet cheese, when compared with other Portuguese cheeses. This work intended to monitor the manufacturing process along the period of production, to evaluate the factors that are decisive for the reproducibility of Serra Estrela cheese in geographical and temporal terms, as well as to achieve the knowledge of the Serra Estrela cheese lipid nutritional characteristics. Methods: Twenty-four Serra Estrela cheese samples originating from representative cheese producers of the region were analysed for their nutritional characteristics, such as moisture, fat, protein and salt, using the FT-NIR (fourier-transform near infrared spectroscopy) technique as an expeditious method. A gas chromatography with flame ionization detection (GC-FID) was used to perform the lipid fraction study. Microbiological analyses were performed for Escherichia coli and coagulase-positive Staphylococcus. Statistical analysis was performed using Statistical Package for Social Sciences (SPSS version 23.0). The level of significance was accessed by Tukey’s test considering p-value < 0.05 to be significant. Results: In the cheeses studied, the moisture varied from 46 % to 52 %, the butyric content from 19 to 30 %, the protein content between 19 and 24 % and the salt from 0.9 to 1.8 %. The determinations of Escherichia coli and coagulase-positive Staphylococcus in some Serra Estrela cheeses exceeded the maximum allowed values per law in Portugal. Regarding to the fatty acids profile, there was no obvious tendency observed, but was found a significative amount of short and medium chain saturated fatty acids, as well as polyunsaturated fatty acids. Conclusion: Considering that year 2017 was considered an exceptional year, both in terms of the severe drought and the fires that devastated the region, with repercussions on health and animal production, it is reasonable that some cheeses exceeded the maximum permissible levels of microorganisms. Although there are significantly differences between the total fat and protein content of Serra Estrela cheeses from different producers, relatively to polyunsaturated, ω-3 and ω-6 fatty acids fractions, all cheese producers are very homogeneous. This work was extremely important for an initial evaluation of the Portuguese Serra Estrela cheese production in 17/18 and for the design of future experimental work.

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