Purification method for the isolation of monophosphate nucleotides from Champagne wine and their identification by mass spectrometry.

Monophosphate nucleotides are difficult to identify in Champagne wine because they are present in small concentrations in a complex mixture. A method for the isolation, separation and identification of reference compounds, which achieved on average 79% recovery (except for cytidine derivatives), was developed and applied to wine. Some monophosphate nucleotides were then isolated from a Champagne wine aged on lees for 8 years, by ultrafiltration followed by a semi-preparative HPLC step using a strong anion-exchange column. The fraction obtained was subjected to HPLC in a reversed-phase column to remove the salt previously introduced, before identification of compounds by HPLC coupled to a mass spectrometer. For the first time in wine, 5'-IMP, 5'-AMP, 5'-CMP, 5'-GMP, 5'-UMP and the 3'- and/or 2'-isomers of the four latter compounds were identified by comparing their HPLC and electrospray ionization mass spectrometry data with those of reference nucleotides.

Liquid chromatographic fractionation of small peptides from wine.

Peptides are difficult to isolate from wine because they are present in a complex mixture together with non-peptidic compounds. A method for the isolation, separation and purity assessing of small peptides is proposed. Small peptides (Mr<3000) were isolated from wine by hollow fibre ultrafiltration followed by column chromatography using the gel matrix Sephadex LH20. Fractions obtained by gel filtration on Sephadex LH20 were subjected to HPLC on a porous graphitic carbon column in order to isolate small peptides. Peak purity was then analysed by capillary electrophoresis.

[Characterization of cell wall constituents involved in the flocculation of Saccharomyces uvarum yeast strains]. / Caractérisation des constituants pariétaux impliqués dans la floculation de levures Saccharomyces uvarum.

Cell walls of flocculent strains (0006) and non flocculent strains (0019) of Saccharomyces uvarum (Carlsbergensis), grown in different media and taken in both growth and stationary phases, were treated with water and with 2 per cent (W/V) potassium hydroxide. This treatment yielded four fractions (FI, FII, FIII and FR). The fractions FI isolated from the flocculent cell walls contained more mannose and less protein than the corresponding fractions FI isolated from the non flocculent cell walls. The amino-acid composition was also different between the two types of fractions. A radioactive labelling technique revealed that the FI and the walls from flocculent cells bound on average two to three times as much 45Ca as did the FI and the walls from non flocculent yeast. The substitution of carboxyl groups in FI and walls with glycine methyl ester led to a great drop of the 45Ca binding capacity. This result suggests that carboxyl groups of the cell walls are involved in the flocculation process. But flocculation seems to be a phenomenon more complex than the simple formation of a Ca2+ bridge, the involvement of "lectin like" components easily removed from the cell walls, should not be rejected.

Use of [14C]lysine to detect microbial contamination in liquid foods.

A radiometric method for microbiological control in food industries is suggested. This method, based on the labeling of cells by [14C]lysine, was tested by using nine species of yeast and two species of bacteria.