Abstract Green bactericides are excellent strategies for reducing food spoilage. Phloretin was regarded as efficient, broad-spectrum and safe preservative, which showed enormous potential in food industry. Inhibitory mechanism of phloretin on Listeria monocytogenes was systematically elucidated through integrity of cell membrane, intracellular protein content, energy level, and nucleic acid morphological character. SEM and TEM results showed minimal injury of cell membrane, which was further proved by a leakage of potassium ions, ATP and little protein and nucleic acid. There were drastic reduction of intracellular or total protein and ATP compared to cell without phloretin treatment. However, the specific activity of hexokinase and isocitrate dehydrogenase were unaffected after phloretin treatment. From these results, we concluded that phloretin’s bacteriostatic mechanism is decreasing the intracellular protein content and energy level resulting from DNA aggregation. This finding was prospective to fully illustrate the phloretin’s mechanism and develop it into a natural preservative in food industry.

Abstract Since the grape skin and seed contain different phenolic substances, the proportion of the skin and seed will affect the wine mouthfeel during the wine making process. During the wine ageing, the interaction between flavanols with anthocyanins is an important reaction and considered linked to astringency. Hence, a major question is whether changing the skin-seed ratio will affect the polymerization of phenolic substances in wine, thus affecting the astringency of wine. To answer this, astringency of wine was studied by changing the content of grape skins and seeds by SDS-PAGE, fluorescence quenching and sensory taste. Besides, acetaldehyde-mediated condensation reaction between different flavan-3-ols and malvidin-3-glucoside were studied in model solution. The result showed that grape skins and seeds contribute differently to astringency sensation, mainly because of the difference in the type and content of flavanols and anthocyanins contained in them. In addition, acetaldehyde-induced flavan-3-ols: anthocyanin mixture presents a strong effect toward the interaction with BSA when compared to other phenolic combinations. Furthermore, it was observed that the protein-binding ability of the polyphenols in red wine has a strong correlation with the wine astringency intensity.