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The quantitation of the main polyphenols and the assessment of the total polyphenolic content (TPC) in polyphenol-rich extracts of grape berries and vinification byproducts, obtained from Vitis vinifera cultivars of the Greek islands, are presented. The results indicated that seed extracts contain high concentrations of flavan-3-ols and their derivatives, whereas pomace and stem extracts consist of significant amounts of flavonoids, stilbenes, and phenolic acids. In particular, stemsa scarcely studied class of grape byproductwere also characterized by high trans-resveratrol and epsilon-viniferin content. The evaluation of their in vitro antilisterial activities revealed as most potent the seed and stem extracts of the red variety Mandilaria. Their minimum inhibitory concentrations (MICs) were assessed using a Malthus apparatus by two methods, a plate count technique and an automated technique that combines the conductance measurements with the common dilution method. The results revealed the usefulness of the conductance method as an alternative rapid means for the MIC estimation, whereas the respective values (0.26 and 0.34 for seeds and stems) indicated that both extracts represent an inexpensive source of potent natural antilisterial mixtures, which may be incorporated in food systems to prevent the growth of Listeria monocytogenes .

A sensitive and simple method was developed for the classification of wines according to variety, geographical origin, and vintage using NMR-based metabonomics. Polyphenol-rich extracts were prepared from 67 varietal wines from the principal wine-producing regions of Greece, using adsorption resin XAD-4. 1D (1)H NMR spectra obtained from the corresponding extracts were segmented, integrated, and normalized, and the data were subjected to principal component analysis. The chemometric classification of wines according to their phenolic profile allows discrimination between wines from different wineries of the same wine-producing zone and between different vintages for wines of the same variety.

Aims:  The fate of Listeria monocytogenes Scott A, was studied in broth, at different aws (by adding NaCl or KCl from 0·0 to 1·4 mol l−1), pHs (from 4·0 to 7·3 by adding lactic acid), and nisin concentrations (from 0 to 100 IU ml−1). Methods and results:  Increasing salt and nisin concentrations and decreasing pH resulted in lower growth rates and extended lag phases. At pH 4·5 no growth was observed while in presence of nisin and/or 1 mol l−1 salts of both kinds, L. monocytogenes Scott A was inactivated. Equal‐molar concentrations of NaCl or KCl (similar aw), exerted similar effects against L. monocytogenes in terms of lag phase duration, growth or death rate. The growth boundaries of L. monocytogenes Scott A at 5°C were also estimated by growth/no growth turbidity data, modeled by logistic polynomial regression. The concordance of logistic models, were 99·6 and 99·8% for NaCl and KCl, respectively. Conclusions:  The growth interfaces derived by both NaCl and KCl models were almost identical. Hence, NaCl can be replaced by KCl without risking the microbiological safety of the product. Increasing nisin concentrations markedly affected the interface resulting in a more inhibitory environment for L. monocytogenes Scott A. Low to medium salt concentrations (0·3–0·7 mol l−1 of either NaCl or KCl) provided a protective effect against inhibition of L. monocytogenes Scott A by nisin. Significance and impact of the study:  Modelling the growth boundaries not only contributes to the development of safer food by providing useful data, but can also be used to study interactions between factors affecting initiation of growth of pathogenic micro‐organisms.