Season and altitude effects on milk fatty acid profile in Sarda dairy sheep flocks

Diet plays a major role in modulating the fatty acid composition of ruminant milk. It is also well known that the intake of fresh forages has a positive influence on polyunsaturated fatty acid (PUFA), particularly CLA and omega- 3, compared with diets based on dry forage and concentrates. Altitude influences, directly, grass availability and botanical composition of the pasture, and, indirectly, the amount of concentrate supplemented to the diet. Therefore, the altitude where farms are located at may give indirect information about the type of feeding system trough analysis of milk fat. The objective of this survey was to investigate variations in the milk fatty acid profile, focusing on the content of vaccenic acid (VA), conjugated linoleic acid (CLA) and n-3 fatty acid (FA), of Sarda dairy ewes flocks located at different altitudes throughout Sardinia. Bulk milk samples were collected in spring (April) and in summer (July) from 36 flocks located at different altitudes: 3 flocks in the lowlands (Low), 3 flocks in the hills (Hill) and 3 in the highlands (High) in 4 provinces (Sassari, Nuoro, Oristano and Cagliari) of Sardinia (Italy). Milk fatty acid profile was analyzed by gas-chromatography. Data were analyzed with a linear model with altitude (A), season (S), province (P) and altitude x season as fixed factors. The interaction was never significant. The season influenced significantly almost all fatty acids analyzed. The proportion of short chain FA (C4-C10) decrease (10.0 vs 7.0 mg/100 mg FA; P<0.01) and that of medium chain FA increase (43.2 vs 45.5 mg/100 mg FA; P<0.10) from spring to summer. The long chain FA did not vary between spring and summer but the concentration of oleic acid (C18:1 cis9) increased significantly from spring to summer (22.3 vs 25.1 mg/100 mg FA; P<0.01). The proportion of n-3 FA was higher in spring than summer (1.2 vs 0.7 for n- 3 FA; P<0.01). The variation in n-3 FA in milk fat was mainly due to the variation in a-linolenic acid (ALA; 18:3n- 3) which decrease from 1.0 to 0.5 mg/100 mg FA from spring to summer. The same pattern was showed by vaccenic acid (VA; trans-11 18:1) that decrease from 1.6 vs 0.8 mg/100 mg FA. No variation in cis9, trans11 CLA has been observed between spring and summer (1.0 vs 0.8 mg/100 mg FA). A reduction of PUFA (5.64 vs 5.10; P<0.10), n3/n6 ratio (0.38 vs 0.21) and content of C20:5 n-3 (0.13 vs 0.07 mg/100 mg FA) from spring to summer has been observed. Unexpectedly, the milk FA profile was not affected by altitude, except for C18:1 c9, probably because of the low number of samples analyzed

Preliminary microbiological and chemical characterisation of edible goat's rennet, a unique product of Sardinian food tradition

The edible goat rennet (EGR) namely Caggiu de crabittu, is a traditional Sardinian foodstuff deriving from the stomach of a weaned (breastfed) kid whose edible part is represented by the milk coagulated inside the abomasum that, before consumption, is subjected to a suitable ripening time. In this study, a preliminary investigation into the microbiological characteristics and physicochemical parameters of different EGRs manufactured by distinct Sardinian farms was conducted. Results showed that the edible goat rennet was free of spoilage/pathogenic bacteria and was characterised by a significant presence (6–7 log cfu/g) of mesophilic lactic acid bacteria (i.e. Lactococcus lactis, Lactobacillus plantarum, Lactobacillus paracasei, Lactobacillus brevis) and Enterococci. Oleic, linolenic, palmitic and myristic acids were the most abundant free fatty acids (FFA) in all samples, while both caprylic and butyric acid contents resulted the lowest. Long chain FFA (≥C18:0) represented about 50% of total FFA. Among the polyunsaturated FFA, high content of linoleic (C18:2n-6) and alpha-linolenic (C18:3n-3) acids have been detected. In this study, EGR is shown to be microbiologically safe, with a high number of live lactic bacteria and an FFA content that is attractive from a nutritional point of view.Highlights Edible goat's rennet (EGR) resulted microbiologically safe with a high number of viable mesophilic lactic acid bacteria. In the EGR an intense process of lipolysis has occurred. EGR had a high content of linolenic acid

Microbiologia e valutazione igienico-sanitaria della salsiccia sarda

In this study we evaluated the microbiological status of the Salsiccia sarda with special emphasis on the microbial indicators of the hygienic and sanitary conditions. Moreover, the evolution of the autochthonous microflora has been monitored during the entire production process. For these aims, microbiological analyses were carried out on different samples of minced meat and sausages at different ripening times. Despite the results showed some critical points in the hygienic and sanitary conditions, substantiated by a significant presence of Escherichia coli, Salmonella and Listeria spp. were not found in any sample. The dominant microflora of Salsiccia sarda was composed by Lactobacillus curvatus, L. plantarum, Staphylococcus xylosus and Debaryomyces hansenii. The knowledge of the microbial ecology of this typical sardinian food-stuff is a significant baseline for the development of autochthonous starter cultures to be employed in the production process. The use of such cultures may allow a better management of the process and guarantee suitable qualitative traits of this traditional ripened sausage. Nel presente lavoro sono stati valutati i microrganismi di interesse igienico-sanitario e l'evoluzione della microflora della Salsiccia sarda. Prelievi e analisi microbiologiche sono stati effettuati sulla carne macinata e sulla salsiccia a tempi diversi di maturazione. I risultati hanno mostrato che, nonostante le criticità inerenti le condizioni igienico-sanitarie rilevate in alcune fasi tecnologiche e confermate dalla presenza di Escherichia coli, non sono stati ritrovati batteri ascrivibili ai generi Salmonella e Listeria. Le specie microbiche risultate predominanti sono state Lactobacillus curvatus, L. plantarum, Staphylococcus xylosus e Debaryomyces hansenii. La conoscenza dell'ecologia microbica di questo prodotto tipico costituisce un punto di partenza per la messa a punto di colture starter autoctone da impiegare nei processi di trasformazione. L'utilizzo di tali colture consentirebbe una migliore gestione del processo garantendo adeguati standard qualitativi ad un prodotto tradizionale come la Salsiccia sarda

PCR-based methods to discriminate Bacillus thuringiensis strains

Bacillus thuringiensis is a Gram positive bacterium that is used for the production of biopesticides. The toxic action of different strains and serovars ofB. thuringiensis can be extremely selective towards specific pests, or, in contrast, it can affect a wide variety of non-target organisms such as insects, vertebrates or humans. A reliable characterization of the cultivated strains is of primary importance for the biopesticide industry, in order to assess the contamination of the final product with strains with different pesticide actions or that might be dangerous for human health. The aim of this study was to develop useful methods for the typing of differentB. thuringiensis strains using two PCR-based methods, RAPD and Rep-PCR with BOXA1R and ERIC2 primers. The molecular fingerprints obtained using ERIC2-PCR showed a reliable ability to discriminateBacillus thuringiensis strains

Selection of folate-producing lactic acid bacteria for improving fermented goat milk

Goat milk is a complete food but its low level of folic acid diminisches its nutritional efficacy. In this study, Streptococcus thermophilus, Lactobacillus delbrueckii subsp. bulgaricus, Lb. delbrueckii subsp. lactis and Lb. helveticus strains were selected for folate production in goat milk to improve its quality. A suitable HPLC method was developed to directly determine both total folate and its biologically active derivatives such as 5-methyl-tetrahydrofolate (5- CH3-H4-PteGlu), tetrahydrofolate (H4-PteGlu) and 5 formyl-tetrahydrofolate (5-CHO-H4-PteGlu). Results showed that S. thermophilus, Lb. delbrueckii subsp. lactis and Lb. helveticus strains produced higher amounts of total folate than Lb. delbrueckii subsp. bulgaricus, especially 5-CH3-H4-PteGlu and H4-PteGlu. Moreover the use of selected S. thermophilus strains in association with Lb. delbrueckii subsp. bulgaricus resulted in yoghurt with a significant quantity of folate and good organoleptic features

Comparison of bacteriocins production from Enterococcus faecium strains in cheese whey and optimised commercial MRS medium

The production of bacteriocins from cheap substrates could be useful for many food industrial applications. This study aimed at determining the conditions needed for optimal production of enterocins SD1, SD2, SD3 and SD4 secreted by Enterococcus faecium strains SD1, SD2, SD3 and SD4, respectively. To our knowledge, this is the first use of cheese whey—a low-cost milk by-product—as a substrate for bacteriocin production by E. faecium; skimmed milk and MRS broths were used as reference media. This cheese manufacturing residue proved to be a promising substrate for the production of bacteriocins. However, the levels of secreted antimicrobial compounds were lower than those achieved by E. faecium strains in MRS broth. Bacteriocin production was affected strongly by physical and chemical factors such as growth temperature, time of incubation, pH, and the chemical composition of the culture medium. The optimal temperature and time of incubation supporting the highest bacteriocin production was determined for each strain. Different types, sources and amounts of organic nitrogen, sugar, and inorganic salts played an essential role in bacteriocin secretion. E. faecium strains SD1 and SD2—producing high bacteriocin levels both in cheese whey and skimmed milk—could be of great interest for potential applications in cheese-making

Aspetti igienici e qualità nutrizionale dei formaggi freschi tradizionali prodotti in Sardegna

Nutritional and hygienic quality of traditional fresh cheeses produced in Sardinian - Fruhe is the name of a fresh cheese traditionally manufactured in Sardinia (Italy) from sheep or goat milk. Fruhe is characterized by a compact coagulum and manufactured from whole milk, raw or heat-treated, deriving from Sardinian farms. With the aim to improve the quality and the value of the Sardinian sheep soft cheese, the chemical and microbiological features has been studied. In this study ten samples (5 artisanal and 5 industrial) of Fruhe, manufactured from sheep milk using different cheese-making technologies, have been investigated for their chemical and microbiological composition. Microbiological analyses showed that total mesophilic bacterial counts were between 8,86E+08 and 3,24E+08 CFU/gr. Lactobacilli and lactic streptococci were constantly present in high number in a 1:1 ratio, that constitute a guarantee for the quality and shelf-life of the product. A prominent presence of total coliforms and SCN, showed some critical points in the hygienic and sanitary conditions, particularly in traditional cheese, the presence of this microbial groups suggests a better management of the process. Listeria and SCP were not found in any cheeses. All samples were characterized by a balanced ratio of the protein, fat and lactose without important difference between traditional and industrial Fruhe. Moreover, the use of natural starter culture in industrial technology may allow to obtain a cheese with safety and traditional features

Influence of autochthonous lactic acid bacteria on cheese microflora and free amino acids of sweet Pecorino Sardo PDO

Pecorino Sardo Protected Denomination of Origin (PDO) is a half-cooked paste cheese produced only with full cream ewes’ milk that can be thermised if necessary. Pecorino Sardo PDO is a cylindrical-shaped cheese with flat faces and a straight or slightly convex rim. Two typologies of Pecorino Sardo PDO are currently produced: "sweet" when the ripening time is short (20-60 days), and "ripened" when the ripening is longer than 2 months. In this study we evaluated the influence of autochthonous lactic acid bacteria (LAB) on the microbiological and nutritional characteristics of the “sweet” type of Pecorino Sardo PDO. For this aim two cheese-making trials (experimental and control) were carried out on an industrial scale. Experimental Pecorino Sardo cheese was manufactured with the addition of an autochthonous starter culture prepared with Streptococcus thermophilus + Lactobacillus plantarum + Lactococcus lactis subsp. lactis + Lactobacillus casei subsp. casei while control cheese was manufactured with the addition of a commercial starter including Streptococcus thermophilus + Lactococcus lactis subsp. lactis + Lactococcus lactis subsp. cremoris. The evolution of free amino acids (FAAs) and cheese microflora were then monitored in both cheeses at different ripening times. The addition of the selected autochthonous starter resulted in a substantial increase of the mesophilic lactic microflora, lactobacilli in particular, in the experimental curd and cheeses. The presence of spoilage microorganisms in the experimental cheeses, such as total and fecal coliforms, was significantly reduced compared to the control indicating a suitable activity of the starter during the fermentation phase. Moreover, the use of the selected autochthonous LAB allowed the production of experimental cheeses with a significantly higher amount of FAAs compared to Pecorino Sardo control cheeses. It is concluded that the selected starter used in the experimental trials is suitable for the production on a industrial scale of the “sweet” type of Pecorino Sardo PDO

Microbiological and physicochemical properties of Pecorino Romano cheese produced using a selected starter culture

The effect of a selected autochthonous starter culture made up by Streptococcus thermophilus,Lactobacillus delbrueckii subsp. lactis and Lactobacillus helveticus on the microbiological and physicochemical properties of Pecorino Romano cheese during ripening was investigated. The suitability of the experimental starter culture was tested at industrial scales in cheese-making trials of Pecorino Romano. Pecorino Romano cheese manufactured by use of scotta-fermento served as control. The lactic microflora increased significantly in experimental cheeses as compared to the control and this was also accompanied by a substantial decrease of spoilage microorganisms in experimental cheeses. Free amino acids (FAAs) were more abundant in experimental cheeses, arginine+g-aminobutyric acid and leucine in particular. These differences could be likely due to a different enzymatic activity of the selected starter culture as compared to the scotta-fermento used in the control trials. Oleic (C18:1), palmitic (C16:0), butyric (C4), stearic (C18:0) and myristic (C14:0) acids were the most abundant Free Fatty Acids (FFAs) detected in both brand of cheeses at the end of ripening. Overall, the level of FFAs in experimental and control cheeses did not show significant differences, even if the average values in experimental cheeses were always slightly higher than those recorded for the control. Moreover, the average content of FFAs of Pecorino Romano was found the lowest when compared with the other Sardinian PDO cheeses; most likely the high content of sodium chloride and the low aW of Pecorino Romano influenced all the lipase activities, even those present in the rennet paste. Despite this, the employment of the selected starter culture revealed useful to improve the physico-chemical features of Pecorino Romano while preserving its tipicity

Microbiological characterization of Fruhe cheese

“Fruhe” is the name of a fresh cheese traditionally manufactured in Sardinia (Italy) from sheep or goat milk. When the cheese is stored for long time in brine it is called “Merca”. The Fruhe is a fermented curd characterized by a compact coagulum, a white shining paste and a soft texture. The taste is slightly sour and aromatic. The Fruhe is manufactured from whole milk, raw or heat-treated, deriving from Sardinian farms. It is produced using the following general manufacturing process: - the milk, brought at 36-38 °C, is inoculated with autochthonous lactic acid bacterial (LAB) cultures and coagulated with calf or lamb liquid rennet; - this milk is now distributed in plastic containers that can have a variable volume; - the cheese ripening takes place in 12-24 hours; - the coagulum within the container can be cut in cubes of approximately 4 cm and the whey is usually partially discarded; - the cheese is stored at 4 °C. In the present study we investigated the microbial populations associated with this traditional product. For this aim twenty samples of Fruhe, manufactured from sheep and goat milk by using different cheesemaking technologies, have been investigated. Microbiological analyses showed that total mesophilic bacteria counts of Fruhe samples were between 1.00E+06 and 2.70E+09 CFU/g. Lactobacilli and lactic streptococci were constantly present in a 1:1 ratio and in a few samples they reached significant numbers (around 1.00E+09 CFU/g) while in general the size of these populations was more limited (around 1.00E+06 CFU/g). This was attributed to an excessive acidification and post-acidification of the cheese. It is important to mention that the presence of a suitable number of LAB (at least 1.00E+07 CFU/g) is crucial for the nutritional quality of fresh dairy products. The presence of total coliforms and coagulasenegative staphylococci was limited and related to some extent to the reduced number of LAB in most of the samples. Heterofermenting LAB, faecal coliforms and coagulase-positive staphylococci were always absent while yeasts were isolated only from three Fruhe samples. The study showed that lactic microflora associated to Fruhe cheese was substantially homogeneous in all the samples analyzed. However, the number of LAB was globally low in the majority of samples and quite different from other fresh cheeses