Silvia Viale

A NMR metabolomics study of the ripening process of the Fiore Sardo cheese produced with autochthonous adjunct cultures

Fiore Sardo (FS) is a traditional Italian raw ewes milk cheese carrying a Protected Designation of Origin (PDO). This study investigated the kinetics of FS cheese ripening by physicochemical parameters, microbial counting, and NMR metabolomics using aqueous extracts. Four Fiore Sardo cheeses, manufactured from milk with deliberately added autochthonous lactic acid bacteria (LAB) or commercial starters were studied during a period of 90days of ripening. Major differences in the metabolic profiles were observed amongst the samples as a function of the adjunct culture utilised. (1)H NMR metabolomics in combination with multivariate data analysis was able to classify cheese samples on the basis of their maturation age and the type of added cultures. These findings lay the metabolic basis for the authentication of Fiore Sardo cheese produced in compliance with PDO specifications which allow the use of only native LAB cultures.

Characterization of yeast population and molecular fingerprinting of Candida zeylanoides isolated from goat's milk collected in Sardinia

The occurrence of yeast microflora in raw goats milk collected from 62 dairy farms located in different areas of Sardinia was evaluated. Candida zeylanoides was the most frequently occurring species followed by different Basidiomycetous species. In the strains isolated some biochemical characteristics of technological interest were investigated and a predominance of lipolytic yeast species was found. We employed a simple method of DNA extraction that in a minimal time and with low-cost provided a high quality of DNA for RAPD analysis of 32 isolates of C. zeylanoides. The primers M13 and CDU were used and at 40% of similarity, two distinct clusters were observed. The presence of C. krissii species was supposed but further molecular studies are needed to exclude the presence of an as-yet-undescribed species.

Preliminary Evaluation of Probiotic Properties of Lactobacillus Strains Isolated from Sardinian Dairy Products

Twenty-three Lactobacillus strains of dairy origin were evaluated for some functional properties relevant to their use as probiotics. A preliminary subtractive screening based on the abilities to inhibit the growth of microbial pathogens and hydrolyze conjugated bile salts was applied, and six strains were selected for further characterization including survival under gastrointestinal environmental conditions, adhesion to gut epithelial tissue, enzymatic activity, and some safety properties. All selected strains maintained elevated cell numbers under conditions simulating passage through the human gastrointestinal tract, well comparable to the values obtained for the probiotic strain Lactobacillus rhamnosus GG, and were able to adhere to Caco-2 cells to various extents (from 3 to 20%). All strains exhibited high aminopeptidase, and absent or very low proteolytic and strong β-galactosidase activities; none was found to be haemolytic or to produce biogenic amines and all were susceptible to tetracycline, chloramphenicol, erythromycin, ampicillin, and amoxicillin/clavulanic acid. Our results indicate that the Lactobacillus strains analyzed could be considered appropriate probiotic candidates, due to resistance to GIT simulated conditions, antimicrobial activity, adhesion to Caco-2 cell-line, and absence of undesirable properties. They could be used as adjunct cultures for contributing to the quality and health related functional properties of dairy products.

Biological activities of aerial parts extracts of Euphorbia characias

The aim of the present study was to evaluate antioxidant, antimicrobial, anti-HIV, and cholinesterase inhibitory activities of aqueous and alcoholic extracts from leaves, stems, and flowers of Euphorbia characias. The extracts showed a high antioxidant activity and were a good source of total polyphenols and flavonoids. Ethanolic extracts from leaves and flowers displayed the highest inhibitory activity against acetylcholinesterase and butyrylcholinesterase, showing potential properties against Alzheimers disease. Antimicrobial assay showed that leaves and flowers extracts were active against all Gram-positive bacteria tested. The ethanolic leaves extract appeared to have the strongest antibacterial activity against Bacillus cereus with MIC value of 312.5 μg/mL followed by Listeria monocytogenes and Staphylococcus aureus that also exhibited good sensitivity with MIC values of 1250 μg/mL. Moreover, all the extracts possessed anti-HIV activity. The ethanolic flower extract was the most potent inhibitor of HIV-1 RT DNA polymerase RNA-dependent and Ribonuclease H with IC50 values of 0.26 and 0.33 μg/mL, respectively. The LC-DAD metabolic profile showed that ethanolic leaves extract contains high levels of quercetin derivatives. This study suggests that Euphorbia characias extracts represent a good source of natural bioactive compounds which could be useful for pharmaceutical application as well as in food system for the prevention of the growth of food-borne bacteria and to extend the shelf-life of processed foods.

Application of Autochthonous Lactobacillus Strains as Biopreservatives to Control Fungal Spoilage in Caciotta Cheese

Fungal spoilage is one of the main causes of economic losses worldwide in the food industry. In the last years, consumers demands for preservative-free processed foods have increased as a result of growing awareness about the health hazards associated with chemicals. Lactic acid bacteria have been extensively studied for their antibacterial and antifungal potential in order to be used as biopreservatives. The first objective of this study was to investigate in vitro the antifungal activity of autochthonous Lactobacillus strains against moulds commonly associated with cheese spoilage. Then, the Lactobacillus strains with the highest inhibitory effect and broadest spectrum were tested in single or mixed cultures against Penicillium chrysogenum ATCC 9179 and Aspergillus flavus ATCC 46283 on miniature Caciotta cheese produced at laboratory scale to evaluate in situ their ability to prevent mould growth and to determine their impact on cheese organoleptic properties and starter culture activity. The growth of the starter lactococcal population exhibited similar trend and values during ripening, suggesting that the addition of lactobacilli did not influence its growth and survival. Inhibition of P. chrysogenum inoculated in the milk was determined in cheeses produced with single or mixed Lactobacillus adjuncts as compared to cheeses without adjunct. The mixed adjunct cultures resulted in more effective, significantly reducing mould counts of more than 2 log units at the end of ripening. The application of the adjunct cultures resulted in a delay in mycelial growth of P. chrysogenum and A. flavus inoculated on the cheese surface as well. Finally, we found no significant differences among samples for the sensory parameters evaluated that received similar ratings. Our results indicate that the selected Lactobacillus strains may have a potential effect in controlling mould contamination on cheeses. Further studies are currently being carried out to identify the molecules responsible for the antifungal activity.