The quality of Valle del Belice sheep’s milk and cheese produced in the hot summer season in Sicily

In response to the growing consumer demand for fresh cheese in summer, this investigation was aimed to evaluate the chemical and microbiological characteristics of sheep’s milk and cheese produced in Sicily in the hot summer months. A total of 810 bulk milk samples collected from 17 farms rearing ewes of the Valle del Belice breed were analysed for chemical composition, somatic cell count, total bacterial count and clotting parameters. Samples (n=18) of Protected Designation of Origin Vastedda della valle del Belice cheese produced in six dairies were collected in summer, autumn and spring and analysed for chemical composition, microbiological profile and fatty acid (FA) composition. Univariate and multivariate analyses were performed to assess variations by season. Sheep’s milk produced in the summer had higher fat and casein contents, less lactose and urea and slightly higher total bacterial count and, similar to milk produced in winter, had a weaker clotting ability. Vastedda cheese produced in spring had less thermophilic lactococci and a high rumenic acid content. Cheese produced in summer had more fat; less saturated FA; and more linoleic acid, monounsaturated FA and omega-3 polyunsaturated FA. A dual approach to data analysis revealed a strong influence of production season on bulk milk and Vastedda cheese characteristics due to climate conditions and ewes’ feeding regimen. Although this study provides evidence of the good nutritional properties of summer sheep’s cheese, management and feeding strategies could aim to further improve the quality of milk and cheese produced in the summer months

Multivariate factor analysis of Girgentana goat milk composition

The interpretation of the several variables that contribute to defining milk quality is difficult due to the high degree of correlation among them. In this case, one of the best methods of statistical processing is factor analysis, which belongs to the multivariate groups; for our study this particular statistical approach was employed. A total of 1485 individual goat milk samples from 117 Girgentana goats, were collected fortnightly from January to July, and analysed for physical and chemical composition, and clotting properties. Milk pH and tritable acidity were within the normal range for fresh goat milk. Morning milk yield resulted 704 ± 323 g with 3.93 ± 1.23% and 3.48±0.38% for fat and protein percentages, respectively. The milk urea content was 43.70 ± 8.28 mg/dl. The clotting ability of Girgentana milk was quite good, with a renneting time equal to 16.96 ± 3.08 minutes, a rate of curd formation of 2.01 ± 1.63 minutes and a curd firmness of 25.08 ± 7.67 millimetres. Factor analysis was performed by applying axis orthogonal rotation (rotation type VARIMAX); the analysis grouped the milk components into three latent or common factors. The first, which explained 51.2% of the total covariance, was defined as “slow milks”, because it was linked to r and pH. The second latent factor, which explained 36.2% of the total covariance, was defined as “milk yield”, because it is positively correlated to the morning milk yield and to the urea content, whilst negatively correlated to the fat percentage. The third latent factor, which explained 12.6% of the total covariance, was defined as “curd firmness,” because it is linked to protein percentage, a30 and titatrable acidity. With the aim of evaluating the influence of environmental effects (stage of kidding, parity and type of kidding), factor scores were analysed with the mixed linear model. Results showed significant effects of the season of kidding and parity on common factors, while no differences were found between goats with one or more kids. The multivariate factor analysis technique was effective in describing the quality of Girgentana milk with a low number of new latent variables. These new variables have been useful in the study of the effect of some technical factors such as parity and season of kidding on the quantitative and qualitative aspects of milk production in this goat breed

Analysis of microbiological variation in PDO Vastedda della valle del Belìce cheese during the storage period

The PDO “Vastedda della valle del Belìce” is a Sicilian pasta filata sheep cheese, made from raw milk without starter addition. It is a small round cheese without rind, weighing about 500-700 g. It is cheese is marketed also out of Sicily to allow its marketing and to prolong its shelf-life. The aim of this work was to evaluate the variation of microbiological parameters during the shelf-life period. Then 162 Vastedda cheeses from 18 cheese-making processes in 7 farms have been analysed at different times of storage at 4°C (0, 15, 30, 45, 60, 75, 90, 105, 120 days). Coliforms and E. coli were detected into 7/18 cheese-making processes and their count decreased during the storage period. Enterococci were more resistant to high temperature achieved during the stretching and their were rather stable during storage period (105 cfu/g). The concentration of total Bacterial Count and Mesophilic Lactococci were around 107 cfu/g, while the concentration of Thermophilic Lactococci was higher (108 cfu/g) probably due to the stretching at 90°C. In conclusion, this study shows the good sanitary conditions of cheeses. Overall, the lactic flora was kept alive and vital at high concentration (> 107 cfu/g) until 120 days of storage

factors associated with milk urea concentrations in girgentana goats

A total of 1,481 milk samples of 166 Girgentana goats, taken along the entire lactation, were utilised to evaluate the effect of non nutritional factors on milk urea (MU). Parity, stage of lactation and month of sampling significantly influenced MU, while no effect was found for born kids number. The first kidding goats produced lower MU than multiparous goats. Trend of MU was similar to milk production course with a peak found at 60 DIM. The different MU levels between several months of production are often linked to pasture chemical variations

The influence of somatic cell count on sheep milk composition and cheese-making properties

Somatic cell count (SCC) is an important tool for monitoring intramammary infections in dairy cows. However, systematic generalization of this decision rule is not easy in small ruminants. Determination of SCC in sheep milk is important for the processors of milk (indicator of quality), for breeders (mastitis indicator) and could be useful for selection as well. SCC value can be affected by some non-infective factors such as breed, stage of lactation, parity, type of lambing, type of milking, etc. (Bergonier et al., 1994), as well the health status of the udder (Fruganti et al., 1985; Ranucci et al., 1988). In addition, EC Directive 92/46, which regulates the production and commercialisation of milk and dairy products, imposes strict limits on SCC from dairy cattle but it does not dispel the uncertainty over recommended SCC levels in small ruminants.With the aim of knowing more about somatic cells count and their effects on milk quality and cheese-making properties an experimental trial was carried out

Cellule somatiche in latte ovino: analisi e applicazione delle curve ROC

Negli ovini da latte le mastiti costituiscono una delle principali cause di perdite economiche per la ridotta produzione e soprattutto per la scarsa qualità tecnologica del latte. Diversi studi hanno dimostrato che il contenuto in cellule somatiche (SCC) del latte può essere impiegato sia come metodo diagnostico sia come criterio di selezione nei programmi di miglioramento genetico per la resistenza alle mastiti. Obiettivo di questo lavoro è stato applicare la metodologia delle Receiver Operating Characteristics curves (ROC) per valutare la capacità diagnostica del SCC nel discriminare le mammelle infette da quelle sane e per individuare un valore soglia discriminante in ovini da latte. In totale sono stati analizzati 14.072 campioni di latte individuale da 720 pecore di razza Valle del Belice in 5 allevamenti. L’isolamento e l’identificazione batterica sono stati effettuati tramite semina di 10 μl di latte su Agar Sangue incubato a 37°C per 24 - 48h in aerofilia e, se necessario, in microaerofilia e la determinazione delle SCC mediante citometria di flusso. In base al risultato dell’esame batteriologico sono stati identificati 9 gruppi. La media aritmetica del SCS per i test negativi e positivi è risultata rispettivamente di 5.17 ± 0.008 e 5.80 ± 0.010, la media geometrica del SCC per i test negativi e positivi è risultata rispettivamente di 146.96 x 103 e 630.85 x 103 cells/ml. Complessivamente sono risultati positivi all’esame batteriologico 6207 campioni con una prevalenza pari al 44,1%. L’AUC è risultata pari a 0.73 ± 0.004 (P 0.0001). Il POO è risultato essere >427x103 cells/ml, in corrispondenza di tale punto la sensibilità è pari al 59,2% mentre la specificità si attesta all’80,9%. In corrispondenza di tale valore il 71% dei soggetti positivi ed il 72% dei soggetti negativi sono classificati correttamente. L’approccio di tipo non parametrico per la stima delle ROC ha dimostrato che il SCC può essere validamente utilizzato per discriminare gli animali infetti da quelli sani. Tuttavia ulteriori studi si ritengono necessari per una più precisa valutazione economica dei costi delle mastiti in considerazione del fatto che il POO sulle ROC tende a spostarsi verso valori con più alta Se e più bassa Sp man mano che i costi dei falsi positivi si riducono rispetto a quelli dei falsi negativi o quando aumenta il valore della prevalenza

The use of Brix refractometer as a simple and economic device to estimate the protein content of sheep milk

In this study, 737 individual sheep milk samples were collected 2 times from morning milkings to evaluate the relationships between Brix refractometer measurements and milk constituentsd protein and fat percentages to verify its ability to predict milk constituents. The Pearson's simple (rSP) and partial (rPP) correlations between milk constituents were calculated, and several first- and second-order regressions were tested to predict the protein and fat percentages. The rSP coefficients between the Brixrefractometer measurement and fat (rSP 1⁄4 0.46) and protein (rSP 1⁄4 0.87) contents were different fromthe rPP coefficients, particularly for fat percentage (rPP 1⁄4 0.04 and rPP 1⁄4 0.82, for fat and protein per-centages, respectively). The results of the forecasts can be considered satisfactory only for the first order regression that predicted the percentage of milk protein, while the regression that predicted the percentage of fat milk protein presented a weak forecasting capacity

Cellule somatiche ed isolamento di agenti mastidogeni in ovini di razza Valle del Belice

Il conteggio delle cellule somatiche nel latte ovino si è dimostrato un valido strumento per la determinazione dello stato sanitario della mammella. Oggetto del presente studio è stato valutare eventuali relazioni fra il contenuto in cellule somatiche (SCC) e le infezioni mammarie (IMI) negli ovini. L’indagine è stata condotta nel periodo 2006-2012 su n.14072 campioni di latte individuale. In base al tenore i campioni sono state inseriti in 4 classi: 300.000; da 301.000 a 500.000; da 501.000 a 1.000.000 e ≥1.001.000 cellule/ml. Per l’isolamento colturale sono stati seminati 10 μl di latte su piastre di Agar Sangue incubate per 24-48 h a 37 °C in aerofilia e, se necessario, in microaerofilia. Sono stati distinti 10 gruppi: nessun isolamento, isolamento di stafilococchi coagulasi positivi (S. aureus, S. intermedius e S. hyicus), stafilococchi coagulasi negativi (CNS), streptococchi patogeni (S. agalactiae, S. dysgalactiae e S. uberis), altri streptococchi o enterococchi (S. acidominimus,S. canis, S. viridans, S. mitis, S. mitior ed E. faecalis), Corynebacterium, Mannheimia haemolithyca, Bacillus spp, altri germi (Proteus spp., E.coli e Pseudomonas spp.) ed associazione di CNS ed altri streptococchi. Per ogni gruppo è stata calcolata la media geometrica del SCC. Il 44% dei campioni analizzati mostrava positività all’esame microbiologico con percentuali crescenti in funzione della classe di SCC d’appartenenza. Si riportano i microrganismi isolati e le relative prevalenze: CNS 80%, stafilococchi coagulasi positivi 11,76% di cui 677 S. aureus (10,9%), 43 S. intermedius (0,69%) e 10 S. hyicus (0,16%), Streptococcus spp. 3,09%, streptococchi patogeni 2,64%, M. haemolytica 0.63%, Corynebacterium 0,18%, Pseudomonas 0,10%, Bacillus 0,68%, E. coli 0,06% e Proteus 0,34%. La media geometrica del SCC mostra differenze statisticamente significative fra i vari gruppi di batteri. Nell’allevamento ovino gli CNS si confermano i principali agenti di mastite subclinica con tendenza alla cronicizzazione pertanto ulteriori approfondimenti sono necessari per indagare il loro ruolo patogenetic

In vitro evaluation of bacteriocinlike inhibitory substances produced by lactic acid bacteria isolated during traditional sicilian cheese making

Bacteriocins are antimicrobial proteins produced by bacteria that inhibit the growth of other bacteria with a bactericidal or bacteriostatic mode of action. Many lactic acid bacteria (LAB) produce a high diversity of different bacteriocins. Bacteriocinogenic LAB are generally recognised as safe (GRAS) and useful to control the frequent development of pathogens and spoilage microorganisms. For this reason they are commonly used as starter cultures in food fermentations. In this study, the authors describe the results of a screening on 699 LAB isolated from wooden vat surfaces, raw milk and traditional Sicilian cheeses, for the production of bacteriocin-like inhibitory substances, by comparing two alternative methods. The antagonistic activity of LAB and its proteinaceous nature were evaluated using the spot-on-thelawn and the well-diffusion assay (WDA) and the sensitivity to proteolytic (proteinase K, protease B and trypsin), amylolytic (a-amylase) and lipolytic (lipase) enzymes. The indicator strains used were: Listeria monocytogenes, Staphylococcus aureus, Escherichia coli, Salmonella enteritidis. A total of 223 strains (belonging to the species Enterococcus spp., Lactobacillus spp., Pediococcus spp., Streptococcus spp., Leuconostoc spp. and Lactococcus lactis) were found to inhibit the growth of Listeria monocytogenes by using the spot-on-the-lawn method; only 37 of these were confirmed by using the WDA. The direct addition of bacteriocin-producing cultures into dairy products can be a more practical and economic option for the improvement of the safety and quality of the final product