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Plant polyphenolic compounds are considered a promising source for new antibacterial agents. In this study, we evaluated the antimicrobial activity of a collection of resveratrol-derived monomers and dimers screened as single molecules against a panel of nine foodborne pathogens. The results demonstrated that two monomers (i.e., pterostilbene 2 and (E)-3-hydroxy-4′,5-dimethoxystilbene 9) and three dimers (i.e., δ-viniferin 10, viniferifuran 14 and dehydro-δ-viniferin 15) were endowed with significant antibacterial activity against gram-positive bacteria. The exposure of gram-positive foodborne pathogens to 100 µg/mL of 2, 9 and 15 induced severe cell membrane damage, resulting in the disruption of the phospholipid bilayer. The most promising dimeric compound, dehydro-δ-viniferin 15, was tested against Listeria monocytogenes, resulting in a loss of cultivability, viability and cell membrane potential. TEM analysis revealed grave morphological modifications on the cell membrane and leakage of intracellular content, confirming that the cell membrane was the principal biological target of the tested derivative.

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Casein phosphopeptides (CPP) which develop in Grana Padano cheese at different ages were isolated by precipitation with Ba2+ and analysed by HPLC. Profiles were complex throughout the period between 4 and 38 months. CPP in a cheese sample 14 months old were identified by a combination of fast atom bombardment–mass spectrometry and Edman degradation. They were found to consist of a mixture of components derived from three parent peptides, β-CNf(7–28)4P, αs1-CNf(61–79)4P and αs1-CNf(7–21)4P. In total, 45 phosphopeptides were identified: 24 from β-CN, 16 from αs1-CN and 5 from αs2-CN. The presence of aminopeptidase activity during cheese ripening was deduced from the presence of a number of CPP of different lengths with the loss of one or more residues from the N-terminus. The longest had C-terminal lysine and seemed to be progressively hydrolysed by carboxypeptidases A and B to shorter peptides. CPP in cheese appeared to be shortened plasmin-mediated products. Moreover, those most resistant to further hydrolysis contained at least three closely located phosphoserine residues. The anticariogenic activity of CPP is also discussed.

Background and Aims: The light-struck taste is a fault occurring in light-exposed white wine containing methionine and a high concentration of riboflavin (RF) and bottled in clear bottles. These conditions induce the formation of methanethiol and dimethyl disulfide, responsible for a cabbagelike aroma. In order to decrease the risk of wine spoilage, a low concentration of RF should be obtained in wine either by preventing RF release from yeast during winemaking or by removing RF from wine. Methods and Results:Fifteen commercial Saccharomyces strains intended for the wine industry were tested for RF production which was also evaluated when two yeast-based nutrients were added into the must for one of these strains. The RF released during vinification was straindependent and a concentration from 30 to 170 g/L was found in wine. A high concentration of RF was released in presence of the yeast-based nutrients due to either the yeast metabolism or the RF contained in the nutrient itself. The ability of different inorganic (bentonite, charcoal, zeolite, kaolin) and organic adjuvants (egg-white proteins, polyvinylpolypyrrolidone) to deplete RF in wine was evaluated. A relatively low level of charcoal (50 mg/L) removed up to 60% of RF in wine, though its effectiveness was related to the charcoal source. A high concentration of bentonite (1 g/L) was needed to effectively decrease the risk of wine spoilage. Conclusion:A critical RF concentration in white wine can be prevented by applying one or more approaches in winemaking: using low RF-producing yeast strains in fermentation, selecting suitable yeast nutrients or adsorbing RF by insoluble charcoal or bentonite. Significance of the study:The research highlights suitable tools to prevent light-struck taste in white winemaking.

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