Nicoletta Pasqualina Mangia

Influence of selected lab cultures on the evolution of free amino acids, free fatty acids and Fiore Sardo cheese microflora during the ripening

Fiore Sardo Protected Denomination of Origin is a traditional Sardinian (Italy) hard cheese produced exclusively from whole raw ovine milk and coagulated with lamb rennet paste. Currently, Fiore Sardo is still produced by shepherds at the farmhouse level without the addition of any starter culture and the cheese-making process is characterized by significant waste. The first objective of the present work was to investigate the autochthonous microflora present in milk and Fiore Sardo cheese in order to select lactic acid bacterial (LAB) cultures with suitable cheese-making attributes and, possibly reduce the production waste. Secondly, the ability of selected cultures to guarantee cheese healthiness and quality was tested in experimental cheese-making trials. In this study, we show that the typical lactic microflora of raw ewes milk and Fiore Sardo cheese is mostly composed of mesophilic LAB such as Lactococcus lactis subsp. lactis, Lactobacillus plantarum and Lactobacillus casei subsp. casei. Moreover, strains belonging to the species were selected for cheese-making attributes and used in experimental cheese-making trials carried out in different farms producing Fiore Sardo. The evolution of the cheese microflora, free amino acids and free fatty acids during the ripening showed that the experimental cheeses were characterized by a balanced ratio of the chemical constituents, by a reduced number of spoilage microorganisms and, remarkably, by the absence of production waste that were significant for the control cheeses.

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.

Antimicrobial Activity against Beneficial Microorganisms and Chemical Composition of Essential Oil of Mentha suaveolens ssp. insularis Grown in Sardinia

UNLABELLED The aim of this work was to determine the chemical constituents and in vitro antimicrobial activity of the essential oil (EO) of the aerial parts of Mentha sueveolens spp. insularis grown in Sardinia (Italy) against probiotic and starter microorganisms. The gas chromatography-mass spectrometry (GC-MS) analysis allowed to identified 34 compounds, most of oxygenated monoterpene compounds (82.5%) and among them, pulegone was found as major compound (46.5%). The agar diffusion test carried out employing the EO of Mentha suaveolens spp. insularis showed a low antibacterial activity, in particular no action was noticed for probiotic bacteria belonging to lactic acid bacteria groups, whereas almost all yeasts strains tested were inhibited. The automated microtitter dilution assay showed a clear effect at increasing concentration of EO on the specific growth rate (μ) and extension of the lag phase (λ) only for S. xylosus SA23 among bacteria and for Saccharomyces cerevisiae, Tetrapisispora phaffii CBS 4417, Metschnikowia pulcherrima, and Candida zemplinina among yeasts. Results obtained in this work allow us to broaden the knowledge on the effect of EOs on probiotic and food-related microorganisms. PRACTICAL APPLICATION Mentha suaveolens spp. insularis may be used in combination with probiotic bacteria into the food matrix or encapsulated in coating and edible films for food preservation.

Microbiological characterization using combined culture dependent and independent approaches of Casizolu pasta filata cheese.

Casizolu is a traditional Sardinian (Italy) pasta filata cheese made with cow raw milk belonging to Sardo‐Modicana and/or Bruno‐Sarda breeds added with natural whey starter. This work aims to describe the traditional technology of this product and to evaluate the microbial groups/species involved in the first month of ripening.

Influence of Myrtle Juice and Syrup on Microbiological, Physicochemicaland Sensory Features of Goat?s Milk Yogurt Made with Indigenous StarterCulture

This study evaluated the effect of Myrtle Juice (MJ) and Syrup (MS) on microbiological, physicochemical and sensory features in goat milk yogurt fermented by indigenous Streptococcus thermophilus and Lactobacillus delbruekii subsp. bulgaricus during 30 days of storage. Generally, in all samples, the high LAB number at the end of incubation and the pH values ranging from 4.1 to 4.6 indicates a good effectiveness of the used starter on fermentation process. L. delbrueckii subsp. bulgaricus compared to S. thermophilus was the most abundant in yogurt with MJ (YMJ) after 30 days of storage compared to YMS. On the contrary, S. thermophilus demonstrated the highest viability (7 log cfu/g) in the yogurt with MS throughout the storage period. Spoilage and pathogens microorganisms were absent in fresh products and during the storage period. Overall, physicochemical where very similar in all samples, Myrtle juice addition has positively influenced the increase of the lactic acid L(+), acetaldehyde and Free Fatty Acids (FFAs) content. All samples resulted well for flavor and acidity attributes as well as astringency parameter is highly expressed in the YMJ.

PCR-based methods to discriminateBacillus 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.