Raw Sheep Research Articles

Dominant Yeast Community in Raw Sheep's Milk and Potential Transfers of Yeast Species in Relation to Farming Practices.

Simple SummaryAchieving high-quality milk is a major objective of the dairy sector in Spain, and is particularly important for the agricultural economy of the country. The dairy farm environment can affect the microbial communities in milk, and for this reason the yeast community present in this environment could have an important role in the quality of the milk and in dairy products. The focus of this study was Castilla-La Mancha, Spain. The results showed that milk contamination from the yeast species present in the dairy farm environment is reasonable, and certain farming practices favour the presence of desirable microbiota in milk.Yeasts are always present in any type of cheese, as well as in the factories where it is produced. However, the role of the yeast community in the cheese making process, as well as the routes of contamination used by yeast species to contaminate milk from the dairy farm environment, are not well known. The objectives of this study were to broaden the knowledge of the dominant yeast community in Manchega sheep’s milk and to assess the contamination routes of the yeast species depending on the farm practices. Milk, teat surface (collected from ten ewes per farm), feed, and air (collected in milking parlours and livestock housing) samples were collected from 12 typical farms in Castilla-La Mancha, Spain with differences in farming practices, and the yeast species were identified using DNA sequencing methods. To evaluate whether certain farming practices have an effect on the distribution of species of yeast in the milk samples, a mixed model was used. The results showed that most of the dominant yeast species (mainly belonging to the genus Candida) found in milk were also found in the other samples, indicating a microbial transfer from the farm environment to the milk. Furthermore, the statistical model showed that factors influencing yeast counts in milk were the presence of yeasts in the milking parlour, the use of silage, and the frequency of acid treatment for cleaning the milking machines. In conclusion, milk contamination from the yeast species present in the dairy farm environment is related to certain farming practices such as the use of silage and the daily use of acid in the cleaning of the milking machines, which favours the presence of desirable microbiota in milk.

Identification of technological/metabolic/environmental profiles of cheeses with high GABA contents

γ-aminobutyric acid (GABA) is reported to reduce blood pressure and stress when provided as a nutritional supplement. GABA, however, appears naturally in cheese in varying amounts. The present work recorded its concentration in 100 samples of 37 European cheese varieties. Subsequent multivariate analysis identified two technological/metabolic/environmental (TME) profiles associated with a high GABA-content: 1) mature, artisanal, blue cheeses made in the Picos de Europa National Park area from raw cow's milk (or a mixture including it) under the influence of a montane oceanic climate - the TME profile of the Cabrales Protected Designation of Origin (PDO), Gamonedo PDO and Picon Bejes-Tresviso PDO varieties; and 2) aged hard cheeses made from raw sheep's milk under the influence of a temperate continental climate, with Manchego PDO and Zamorano PDO cheeses the hallmark varieties. These findings may help the cheese manufacture industry design functional GABA-enriched cheeses.

Biogenic amines content in Fiore Sardo cheese in relation to free amino acids and physicochemical characteristics.

Fiore Sardo is a Protected Designation of Origin (PDO) cheese produced in Sardinia (Italy) from raw sheep’s milk, presenting risk factors due to an accumulation of Biogenic Amines (BA). A total of 37 Fiore Sardo cheese samples produced in 19 dairy farms were collected from local retail stores to evaluate BA content and its relationship with free amino acids (FAA) and composition. The following were determined for each sample: pH, water activity, composition (moisture, dry matter, NaCl, protein and fat content). FAA and BA, after extraction, were determined by HPLC-FL. The total BA content in Fiore Sardo PDO cheese samples was 127±87 mg 100 g-1, ranging between 6 and 366 mg 100 g-1. Tyramine showed the highest concentration (82±51 mg 100 g-1), followed by putrescine (21±26 mg 100 g-1). Moreover, cadaverine, histamine, β-phenylethylamine and tryptamine were detected at concentrations lower than 10 mg 100 g-1. Overall 54% of the samples analysed exceeded the threshold of 90 mg 100 g-1 for total BA content, posing a potential risk for consumers. BA, total FAA (2233±764 mg 100 g-1) and pH were positively correlated (P≤0.01) between themselves, whereas BA content was not correlated with aw, humidity and percentage of NaCl. The hierarchical cluster analysis results, considering 37 samples and 6 variables, detected four different groups. Samples with BA ≥200 mg 100 g-1 were distributed in two groups characterized by a higher proteolysis indicator levels (FAA, pH) but significantly different for aw, humidity and NaCl concentration. The results showed that high levels of BA were detectable in some samples of Fiore Sardo PDO cheese, suggesting that effective technological conditions at production should be adopted.

MALDI-TOF MS profiling of non-starter lactic acid bacteria from artisanal cheeses of the Greek island of Naxos

Matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry (MS), a culture based alternative for microbial diversity studies, is an attractive tool to dereplicate large numbers of isolates to a smaller set of representatives for downstream characterization. In the present study, MALDI-TOF MS, combined with a database of reference spectra compiled in previous studies, was applied to identify 88 non-starter lactic acid bacteria (NSLAB) isolated from 18 samples of four different artisanal cheeses produced in the Island of Naxos, Greece, from raw sheep and goat milk without the addition of starters. Eighty-four isolates (95.5%) could be identified directly via MALDI-TOF MS. Lactobacillus brevis and Lactobacillus plantarum were the dominant species, followed by Lactococcus lactis, Leuconostoc mesenteroides Lactobacillus paracasei, Lactobacillus rhamnosus, Pediococcus pentosaceus and Enterococcus faecium. The remaining four isolates represented species present in the database; however, within-species diversity was insufficiently covered. Additionally, pheS sequencing was applied to confirm identification.

Bioactive characteristics of a semi-hard non-starter culture cheese made from raw or pasteurized sheep's milk.

In this study, the effect of pasteurization and use of starter cultures on physicochemical, microbiological and functional properties of a traditional Iranian semi-hard cheese (Lighvan cheese) was evaluated during stages of ripening (1, 60, 120days). Profiles of polar metabolites were analyzed by gas-chromatography mass-spectrometry (GC-MS). Considerable free amino acids such as gamma-aminobutyric acid (GABA) were found in samples that have higher microbial communities i.e. raw sheep's milk without use of starter cultures and pasteurized sheep's milk cheese with co-culture. However, GABA was not found in pasteurized sheep's milk cheese without starter culture during ripening. Conclusively, the application of the starter culture could reduce the ripening time of sheep's milk cheese and could be an appropriate approach to increase the functionality of the sheep's milk cheese.

Absence of Viable Toxoplasma gondii in Artisanal Raw-Milk Ewe Cheese Derived from Naturally Infected Animals.

The presence of viable Toxoplasma gondii was investigated in artisanal cheeses made from milk of naturally infected ewes. Ewe milk was analyzed beforehand for the presence and vitality of T. gondii by loop-mediated isothermal amplification (LAMP) and reverse-transcriptase PCR (RT-PCR), respectively. Cheeses were prepared from raw milk following a traditional cheesemaking process. The cheese obtained from T. gondii-positive milk was analyzed by LAMP to detect Toxoplasma DNA-positive samples. RT-PCR was then carried out to assess the viability of the parasites in T. gondii-positive milk samples and fresh cheese, after 5 and 15 days of ripening. Physical-chemical parameters of cheeses were also investigated. All cheese samples derived from T. gondii-positive milk were positive according to LAMP, at both 5 and 15 days of ripening, while none of the samples were positive according to RT-PCR. Thus, while the presence of the parasite was demonstrated by the detection of specific DNA, the absence of detectable T. gondii RNA supports the hypothesis that changes in the chemical and physical characteristics occurring during the cheesemaking process and ripening period, could be sufficient to inactivate viable T. gondii in milk, minimizing the risk of human infection through consumption of raw sheep milk cheese.

The effect of herbs added to the summer diet sheep on the lipid fraction profile of raw milk for cheese making and rennet cheese produced from it

A study was conducted on samples of raw sheep milk and bundz rennet cheese produced from it. The milk was obtained from ewes of the Koluda prolific dairy breed, from June to August. The sheep were housed indoors and fed alfalfa green forage, hay, and a mixture of concentrate feeds. Three feeding groups were established: group I ‒ control, fed without the addition of herbs to the concentrate feed, and groups II and III, in which a herb mixture was added to the concentrate feed in the amount of 10 and 20 g/sheep/day, respectively. Six experimental batches of bundz rennet cheese were made from the milk, and the effect of the addition of herbs to the diet on the lipid profile of the milk and cheese was analysed. The results indicate that the experimental factor had no statistically confirmed effect on the lipid profile of the raw milk used to make cheese. However, the milk fat from sheep fed a diet with herbs at 20 g/sheep/day showed a tendency towards reduced content of SFA (by 3.6%) and increased content of UFA (by 6.8%) and DFA (by 7.2%) relative to the control group. The experimental factor had essentially no statistically confirmed effect on the fatty acid profile of the cheese, apart from an 11.3% increase in the content of n-6 PUFA (P≤0.05) in the fat of bundz produced from the milk of sheep fed a diet with herbs at 20 g/sheep/day with respect to the control group. The cheese fat also showed a tendency towards lower content of SFA (by 3.4%) and OFA (by 4.8%) and higher content of UFA (by 7.4%), MUFA (by 7.1%), PUFA (by 9.4%), n-3 PUFA (by 11.5%) and DFA (by 7.6%) compared to the control group. The experimental factor had no statistically confirmed effect on cholesterol content in the raw milk or the bundz cheese produced from it.

The effect of herbs added to the winter diet sheep on the lipid fraction profile of raw milk for cheese making and rennet cheese produced from it

A study was conducted on samples of raw sheep milk and rennet cheese produced from it. The milk was obtained from ewes of the coloured variety of Polish Merino, from February to April. The sheep were housed indoors and fed preserved roughage and a mixture of concentrate feeds. Three feeding groups were established: group I ‒ control, fed without the addition of herbs to the concentrate feed, and groups II and III, in which a herb mixture was added to the concentrate feed in the amount of 10 and 20 g/sheep/day, respectively. Six experimental batches of bundz rennet cheese were made from the milk, and the effect of the addition of herbs to the diet on the lipid profile of the milk and cheese was analysed. The results indicated that the addition of herbs to the winter diet of sheep in the amount of 10 and 20 g/sheep/day significantly increased the content of the acid C4:0 in the raw milk used for cheese making, by 11.5% and 20.0%, respectively (P≤0.01), relative to the control group. C4:0 content in the raw milk was also increased in group III by 7.6% compared to group II (P≤0.05). The herbs had no statistically confirmed effect on other parameters of the health-promoting quality of the milk fat and the rennet cheese. In the cheese fat from group I produced from sheep milk obtained in the period from 69 to 137 days of lactation, there was an increase in the content of SFA and a decrease in UFA during the course of the experiment. The addition of herbs to the concentrate feed of the sheep improved the fatty acid profile of the fat of bundz cheese made from milk obtained from the 97th day of lactation. The experimental factor also reduced the cholesterol content in the raw milk in group II by 26.8% and in group III by 21.2% (P≤0.01) compared to group I. It did not affect the content of this lipid in rennet cheese.

Structural characteristics of triacylglycerols contribute to the distinct in vitro gastric digestibility of sheep and cow milk fat prior to and after homogenisation.

The regiodistribution of fatty acids (FAs) in triacylglycerols (TAGs) is highly correlated to the digestion and absorption of dietary fats. During in vitro gastric digestion, medium-long-medium/short chain triacylglycerols (MLM) showed the fastest digestibility among 105 TAG molecular species, for both raw and homogenised milk, resulting from the higher activity of gastric lipase towards medium-chain fatty acids (MCFAs) than towards long-chain fatty acids (LCFAs). After 60min of in vitro gastric digestion, the percentage of digestion of each MLM was 16.6-31.2% and 12.3-18.6% respectively in raw sheep and cow milk, and it reached 33.4-45.5% and 23.0-38.9% respectively, after homogenisation. Sheep milk TAGs were digested faster than cow milk TAGs in raw milk (16.1% and 12.4%, respectively) as well as after homogenisation (24.1% and 20.3%, respectively). This is due to the higher percentages of MCFAs esterified on the sn-1/3 positions of sheep milk TAGs (48.3-67.3% and 11.9-51.5% respectively for sheep and cow milk prior to and after homogenisation). Homogenisation favoured TAG lipolysis due to the increased fat globule surface area; however, it did not affect lipase regiospecificity towards TAG molecular species.

Massive sequencing of artisan cheeses from raw sheep’s milk

Lactic acid bacteria (LAB) are used in the food industry to confer aromatic characteristics and their antibacterial capacity. In this study the native flora of LAB that participates in the traditional fermentation of semi-hard cheeses made with raw sheep's milk from the region of Andalusia, Spain was analyzed. Three samples of four different commercial cheeses were taken. Massive sequencing was carried out to identify the lactic and accompanying flora. Predominant lactic flora was Lactococcus lactis, Streptococcus thermophilus, Lactobacillus paracasei and Lactococcus raffinolactis, and to a lesser extent other species of the genera Lactobacillus, Streptococcus, Pediococcus and Leuconestoc. The accompanying flora was composed of species of the genera Mycoplasma, Pseudomonas, Acinetobacter, Chryseobacterium, Mannheimia, Trueperella, Enterococcus, Vibrio, Serratia, Macrococcus, Staphylococcus, Massilia, Flavobacterium, Yersinia, Gallaecimonas, Hafnia, Leclercia, Obesumbacterium, Morganella and Kluyvera. These results show that modern molecular techniques are very good tools to identify natural LABs of artisanal dairy products. The characterization of the native flora of the artisanal cheese allows us to evaluate the microbiological diversity of the natural population of LAB and the symbiosis with another type of flora.

Estimation of Aflatoxin M1 Levels in Some Dairy Products Manufactured from Raw Milk Experimentally Inoculated with Toxin

Fate of AflatoxinM1 in soft white cheese and its by-product (whey) and in yogurt locally made from raw sheep's and goat's milk experimentally inoculated with 0.05 and 0.5 µg/l AflatoxinM1 were investigated using ELISA technique. Results reported that AflatoxinM1 was concentrated in cheese at levels significantly higher than that recorded in the raw milk that used for its processing, with a significant decrease in AflatoxinM1 levels in its by-product (whey) comparable to the raw milk used in manufacturing at both inoculated levels. Yogurt produced from raw sheep's milk at second inoculated level exerted AflatoxinM1concentration significantly lower than that present in the milk. Significant differences in AflatoxinM1distribution in cheese and whey produced from sheep's milk comparable to their counterparts produced from goat's milk were recorded. Finally, results revealed the efficacious role of the various dairy manufacturing processes in AflatoxinM1 distribution and the necessity to issue of local legislations concerning the maximum permissible limits for AflatoxinM1 in milk in order to stay within the universal permissible levels for AflatoxinM1 in dairy products to provide greater protection for consumer health.

Effects of technological settings on yield, curd, whey, and cheese composition during the cheese-making process from raw sheep milk in small rural dairies: Emphasis on cutting and cooking conditions

The technological conditions of cheese-making affect cheese yield and compound losses in the whey, especially the processes of cutting and cooking. Although significant compositional and functional differences have been reported among animal species, there is a lack of studies on the effects of cheese-making technology on cheese yield and losses for sheep milk. Thus, we examined the cheese-making settings in 8 small rural dairies working with raw sheep milk and their effects on cheese yield and compound losses in whey during the cheese-production season. Actual cheese yield varied in 2 to 3 kg of cheese/100 kg of milk among dairies due to the cheese-making conditions, particularly the duration of cutting and cooking and the final cooking temperature. The combination of the conditions used during cutting and cooking, especially, determined fat losses in the whey. Fat losses were increased with high-speed and short cutting time settings together with high stirring speed and long duration of cooking. Additionally, cheese-makers should adapt the cutting and cooking conditions to the seasonal variations of milk composition, especially during early summer, when fat losses in the whey are higher. Our results suggest that it could be useful to use approximately 10 to 15 min of cutting time and moderate cooking speed and duration. The data reported in this study may assist the improvement of the cheese-making process in small rural dairies using sheep milk, where facilities are limited and the role of the cheese-maker is crucial.

Technological characterization and sensory evaluation of a traditional Algerian fresh cheese clotted with Cynara cardunculus L. flowers and lactic acid bacteria.

Jben is an Algerian traditional fresh cheese produced on a small scale in a limited area of east and west Algeria, in Maghnia and Nadrouma. It is manufactured from raw sheep, cow or goat milks, coagulated with dried flowers of wild thistle Cynara cardunculus L. without starter culture addition. In this work, Jben was made using cow and goat pasteurized milks to improve the microbiological quality. Milk was clotted with crude enzymatic extract of dried flowers of wild thistle C. cardunculus L. In order to obtain a better organoleptic characteristic, the assays of cheese making were realized with adding strains of lactic acid bacteria isolated from traditional cheeses. Physico-chemical and microbiological analyzes were carried out on the manufactured cheeses. Milk was clotted with 0.5% v/v by aqueous extract (40g/L) of dried flowers of C. cardunculus L. Better organoleptic quality and higher cheese yield were obtained with goat milk. Cheese made from pasteurized goat's milk added with Lactococcus lactis subsp. lactis, and that added with the mixture of lactic acid bacteria strains L. lactis subsp. lactis, Lactococcus raffinolactis, Leuconostoc mesenteroïdes ssp. mesenteroïdes, were the most appreciated. It is believed that the activity of L. raffinolactis in dairy products may contribute to their final sensory characteristics.

Hygienic quality and composition of raw sheep's bulk milk samples on selected Slovak farms during year 2018

At the control of raw ewe's milk (REM) quality is a major microbiological criterion to the total bacterial count (TBC). The aim of our work was to determine the incidence of technologically important species of microorganisms in REM in Slovak Republic. At the monitored 28 ewe´s farms, we took bulk milk samples from evening or morning milking in spring, summer and autumn during year 2018. We analyzed nutrients (fat, protein, lactose and urea) and somatic cell count (SCC). We established technologically important microorganisms (MO) of psychotrophic MO, coliform MO, thermoresistant MO, spore-forming anaerobic MO. We have found a gradual increase in milk components, except for lactose, which is apparently related to the increasing cont of somatic cells during the milking period. We found that the TBC in raw sheep's milk complied an average of 132 x 103 CFU.mL-1 per spring (min 34 x 103 CFU.mL-1, max 501 x 103 CFU.mL-1), 300 x 103 CFU.mL-1 in summer (min. 31 x 103 CFU.mL-1, max 640 x 103 CFU.mL-1) and in autumn with an average value of 147 x 103 CFU.mL-1 (min 52 x 103 CFU.mL-1, max 276 x 103 CFU.mL-1). The enormous occurrence of psychrotrophic bacteria was found in one farm in northern Slovakia during spring and summer, in the summer we increased our number to 3 farms, in the autumn of 2 farms. At the other farms we evaluated the average value of 12 x 103 CFU.mL-1 per spring and 28 x 103 CFU.mL-1 in summer, 130.5 x 103 CFU.mL-1 in the autumn. The count of thermoresistent MO achieved 57 CFU.mL-1 per spring, 15 CFU.mL-1 in summer and 33 CFU.mL-1 in the autumn. The presence of spore-forming anaerobic MO in raw ewe´s milk was found during spring at six farms out of 15, but in the summer at just one in 9, in the autumn two farms.

Strategies for raw sheep milk storage in smallholdings: Effect of freezing or long-term refrigerated storage on microbial growth

We assessed the effects of freezing and refrigeration over long periods on the microbiological quality of sheep milk. The raw milk was frozen in 1-L plastic bags or 5-L milk buckets and, after 1 mo, thawed at 7 or 25°C. We evaluated these samples immediately after thawing (d 0) and after 1 d of storage at 7°C. Furthermore, we stored fresh raw milk at 7°C for 10 d in the same packages and in a bulk milk cooler at 4°C (adding 10% of fresh raw milk daily). The total bacterial, total psychrotolerant, and proteolytic psychrotolerant counts were evaluated before and after thawing (for previously frozen milk) and daily (for refrigerated milk). The frozen-thawed milks showed no significant increase in bacterial counts immediately after thawing for all samples (<0.7 log cfu/mL), but only the samples packaged in 1-L bags and thawed at 7°C remained microbiologically adequate after 1 d of storage. Findings of the refrigerated samples were modeled using a modified Gompertz equation, obtaining a lag phase of around 0.5 (5-L bucket), 2.6 (1-L bag), and 7.0 (bulk milk cooler) d for total bacterial and total psychrotolerant counts. Maximum growth rates (µmax) were 1.0 and 1.0 (5-L bucket), 1.2 and 1.3 (1-L bag) and 3.0 and 1.5 (bulk milk cooler) ln(cfu/mL) per day for total bacteria and total psychrotolerant counts, respectively. Compared with total bacteria and total psychrotolerant bacteria, psychrotolerant proteolytic bacteria grew slowly, reaching unacceptable counts only after 9 to 10 d of storage. The studied methods are interesting alternatives for preserving raw sheep milk on smallholdings.

Salt Distribution in Raw Sheep Milk Cheese during Ripening and the Effect on Proteolysis and Lipolysis.

The salt distribution process in artisanal sheep cheese with an innovative shape of eight lobes was investigated. The cheese was subjected to two brining conditions: 24 h with brine at 16°Baumé and 12 h at 22°Baumé. The chemical composition (pH, water activity, dry matter, fat, and protein content), proteolysis (nitrogen fractions and free amino acids), and lipolysis (free fatty acids) were evaluated in two sampling zones (internal and external) at 1, 15, 30, 60, 90, 120, 180, and 240 days of ripening. The whole cheese reached a homogeneous salt distribution at 180 days of ripening. Brining conditions did not have an influence on the rate of salt penetration, but on the final sodium chloride (NaCl) content. Cheese with higher salt content (3.0%) showed increased proteolysis and lipolysis as compared to cheese with lower salt content (2.2%). Proteolysis index and total free fatty acids did not differ significantly (p > 0.05) between internal and external zones of cheese. It is suggested that producers start marketing this artisanal cheese at 6 months of ripening, when it has uniform composition and salt distribution.

Glycolysis, lipolysis and proteolysis in raw sheep milk Tulum cheese during production and ripening: Effect of ripening materials

In this study, variations in basic chemical constitutes, organic acids (OAs), free amino acids (FAAs) and free fatty acids (FFAs) during ripening of raw sheep’s milk Tulum cheeses in goat’s skin bag (GST) or plastic barrel (PBT) were investigated. Ripening in goat’s skin caused the differences in chemical compositions of Tulum cheese. Moisture loss, salt-in-moisture, fat and protein contents increased. No residual lactose was observed after 90 day. Lactic acid was principal organic acid, followed by propionic acid, acetic acid, formic acid, succinic acid and citric acid. The majority of amino acids were composed of Val, Pro, Tyr, Met, Leu, Trp, Phe, Lys and Glu. Hexadecanoic acid was the most abundant free fatty acid in the cheeses, which followed by cis-9-octadecenoic, octadecanoic, tetradecanoic, decanoic and trans-9-octadecenoic acids. The levels of total FFA and total OA were higher in GST-cheese in comparison to PBT-cheese but total FAAs were lower.

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.

Milk from different species on physicochemical and microstructural yoghurt properties

ABSTRACT: The aim of the present research was to evaluate differences in chemical properties and physical structure of yoghurt produced with milk from different species (sheep, cow, and goat). For each trial, whole raw sheep (S), cow (C), and goat (G) milk were used to manufacture 4L of yoghurts (Y) from each species (SY, CY, and GY, respectively). The SY demonstrated the greatest (P&lt;0.05) values of total solids, protein, and lipid contents, reflecting on greater (P&lt;0.05) firmness, apparent viscosity and water-holding capacity, and lower (P&lt;0.05) syneresis index than CY and GY. Consequently, SY exhibited a more compact microstructure and homogeneous matrix with fewer pores. Furthermore, CY and GY microstructure contained a greater number of pores, which exhibited greater size heterogeneity than SY. Therefore, based on the evaluated physicochemical and microstructural properties of yoghurt, SY demonstrated the most desirable parameter values for dairy industry representing an alternative substitution for cow’s milk yogurt.

Effect of Sheep's Milk Composition on Strength and Syneresis of Rennet-Induced Milk Gel During Lactation.

SUMMARYThis study investigates the effects of raw sheep’s milk composition on the strength and syneresis of obtained gels throughout the lactation. Casein, fat and total solids content, as well as ionic calcium mass fraction significantly (p<0.05) increased during lactation. As lactation progressed, milk formed firmer gel with higher syneresis ability. Increasing casein to fat ratio in sheep’s milk significantly increased (p<0.05) gel strength and syneresis. On the other hand, gel strength and syneresis were significantly reduced as a result of increased fat content in sheep’s milk. Ionic calcium mass fraction affected gel strength but not syneresis. Neither gel strength nor syneresis were affected by casein and urea content or by somatic cell count in sheep’s milk. Correlation coefficients between milk components and gel strength, as well as syneresis, were significant (p<0.01, p<0.05) but never higher than 0.35.