Simona Belviso

Phenolic Content, Antioxidant Potential, and Antimicrobial Activities of Fruit and Vegetable By-Product Extracts

The use of fruit and vegetable by-products as natural food additives has recently been suggested, due to their richness in polyphenols. The aim of this research study was to determine polyphenolic content and the antioxidative and antimicrobial activities of 13 fruit and vegetable by-product extracts obtained with three solvent mixtures. The Folin-Ciocalteu method was employed to calculate the total phenolic content, while antioxidant capacity was assessed with DPPH· and ABTS ·+. The highest total phenolic content and antioxidant capacity values were obtained for the acetonic extracts. Pomegranate peels and hazelnut skins showed the highest values of total phenolic content (212.3 and 166.3 mg GAE/g dw, respectively) and antioxidant capacity (95.7 and 92.9 of inhibition percentage, respectively, for DPPH· assay). The antimicrobial activity against twelve foodborne pathogens and spoilage microorganisms was evaluated. Pomegranate and apple peels showed the highest inhibition of Staphylococcus aureus and Pseudomonas fluorescens. The results obtained demonstrated that by-products could be used as natural food additives with beneficial health properties.

Microbiota of Minas cheese as influenced by the nisin producer Lactococcus lactis subsp. lactis GLc05.

Minas cheese is a popular dairy product in Brazil that is traditionally produced using raw or pasteurized cow milk. This study proposed an alternative production of Minas cheese using raw goat milk added of a nisin producer Lactococcus lactis subsp. lactis GLc05. An in situ investigation was carried on to evaluate the interactions between the L. lactis subsp. lactis GLc05 and the autochthonous microbiota of a Minas cheese during the ripening; production of biogenic amines (BAs) was assessed as a safety aspect. Minas cheese was produced in two treatments (A, by adding L. lactis subsp. lactis GLc05, and B, without adding this strain), in three independent repetitions (R1, R2, and R3). Culture dependent (direct plating) and independent (rep-PCR and PCR-DGGE) methods were employed to characterize the microbiota and to assess the possible interferences caused by L. lactis subsp. lactis GLc05. BA amounts were measured using HPLC. A significant decrease in coagulase-positive cocci was observed in the cheeses produced by adding L. lactis subsp. lactis GLc05 (cheese A). The rep-PCR and PCR-DGGE highlighted the differences in the microbiota of both cheeses, separating them into two different clusters. Lactococcus sp. was found as the main microorganism in both cheeses, and the microbiota of cheese A presented a higher number of species. High concentrations of tyramine were found in both cheeses and, at specific ripening times, the BA amounts in cheese B were significantly higher than in cheese A (p<0.05). The interaction of nisin producer L. lactis subsp. lactis GLc05 was demonstrated in situ, by demonstration of its influence in the complex microbiota naturally present in a raw goat milk cheese and by controlling the growth of coagulase-positive cocci. L. lactis subsp. lactis GLc05 influenced also the production of BA determining that their amounts in the cheeses were maintained at acceptable levels for human consumption.

Oxygen is required to restore flor strain viability and lipid biosynthesis under fermentative conditions

To further elucidate the biosynthesis of lipids in flor strains under fermentative conditions, the transcription levels of the lipid biosynthetic genes ACS1, ACS2, ACC1, OLE1, ERG1, ERG11, ARE1 and ARE2, as well as the lipid composition and cell viability of a flor strain were compared with that of a non-flor strain during hypoxic and aerobic fermentations in the absence of lipid nutrients. While no significant differences in transcription levels or lipid compositions were observed between the two strains when oxygen was not limiting, significant differences were seen during hypoxic fermentation. In this last condition, the flor strain, in spite of higher levels of transcription of hypoxic genes, lost the abilities to desaturate fatty acids and complete ergosterol biosynthesis, and showed a dramatic loss of viability. In contrast, the non-flor strain, which showed lower transcription levels, was able to reach a balanced lipid composition and maintained a higher cell viability. One possible explanation is that the flor strain requires a higher amount of oxygen than the non-flor strain in order to carry out the oxygen-dependent steps of lipid biosynthesis under fermentative conditions.

Correlation between cell lipid content, gene expression and fermentative behaviour of two Saccharomyces cerevisiae wine strains

Aim:  To verify a possible correlation between cell lipid composition, expression of key genes in lipid metabolism and fermentative behaviour of Saccharomyces cerevisiae wine strains.

Chemical, mechanical and sensory monitoring of hot air- and infrared-roasted hazelnuts (Corylus avellana L.) during nine months of storage

Roasted hazelnuts can be consumed as whole nuts, or as an ingredient in the confectionary and bakery industries and are highly appreciated for their typical taste, aroma and crunchy texture. In this work, two hazelnut types (TGT, Ordu) from two harvests were roasted using two different systems (hot air, infrared) at different time/temperature combinations, and the evolution of oxidative stability, the total phenolic content (TPC), the antioxidant capacity, the mechanical and acoustic properties and the sensory perception were determined during storage. The results showed that the oxidative stability was increased by roasting hazelnuts at 120°C for 40min with hot air system. Similar overall trends were not found for the TPC, the antioxidant capacity and the mechanical-acoustic properties. However, for the maintenance of high antioxidant activity, a storage time of 6months at 4°C is recommended. The two roasting systems gave hazelnuts with significant sensory differences only at high roasting temperature.

Technological properties and biogenic amines production by bacteriocinogenic lactococci and enterococci strains isolated from raw goat's milk

Technological properties and biogenic amine production were analyzed in 56 bacteriocinogenic lactococci and enterococci strains isolated from raw goats milk. Fifteen lactococci strains were able to reduce milk pH to 5.3 or lower after 6 h, while enterococci strains were initially slow in producing acids. Lactococcus lactis subsp. lactis GLc06 and three strains of Enterococcus faecalis (GEn20, GEn22, and GEn23) presented high proteolytic activity. L. lactis subsp. lactis GLc06 and E. faecalis GEn22 also showed a high percentage of autolysis after only 4 h, reaching 71.11 and 97.67%, respectively, after 24 h. No strain was able to secrete exopolysaccharides, and L. lactis subsp. lactis GLc22 and 25 of the Enterococcus strains were able to produce diacetyl. L. lactis subsp. lactis GLc05 and 23 of the Enterococcus strains presented a high tolerance to NaCl at 10% (wt/vol). Regarding biogenic amine production, 12 strains (5 lactococci and 7 enterococci) were capable of forming tyramine and 4 strains (1 lactococcus and 3 enterococci) were capable of forming 2-phenylethylamine, but in very low amounts. GLc06 presented great acidifying, proteolytic, and autolytic activities, and GLc05 was capable of growing at high NaCl concentrations (10%, wt/vol), possessing medium autolytic and proteolytic activities. Some enterococci strains produced diacetyl and high autolytic and extracellular proteolytic activities and also presented resistance to high NaCl concentrations. The interesting technological properties presented by some bacteriocinogenic strains can justify their use by the dairy industry, with the aim of ensuring both safety due to bacteriocin production and technological transformations in fermented products.