Proteins have proven to play a major role in the stabilization of foam in Champagne wines despite their low concentration that ranges from 4 to 20 mg/L. The aim of this study was to evaluate the effect of fining on total protein and grape invertase contents of champenois base wines and their foaming properties. Data showed that fining and especially the use of bentonite at doses ranging from 10 to 50 g/hL leads to a significant decrease in the total protein content of wines together with that of the grape invertase content, with such a decrease being very detrimental to the foaming properties of the treated wines in terms of foam height (HM) and foam stability (HS). Only a slight decrease in the total protein content, in the grape invertase concentration, and in the foam quality of wines was observed when using casein (10 and 20 g/hL) or bentonite combined with casein (both at 20 g/hL). Our study thus clearly establishes the good correlation existing between the wine protein concentration and its foaming properties. A remarkable correlation was observed between the decrease in the grape invertase content and the total protein content of wines, following bentonite treatments, suggesting that the grape invertase (which represents at least 10-20% of the wine proteins) follows a similar behavior upon fining to other proteins of Champagne wines, despite the high molecular mass and the highly glycosylated structure of this particular protein. Moreover, the decrease in total protein and grape invertase contents of wine after fining with bentonite was found to be correlated with a decrease in the foaming properties of the corresponding wines (with respectively R(2) = 0.89 and 0.95).

We report in this paper measurements of the rising velocity of champagne bubbles, investigated by using a camera and a stroboscopic light. It is shown that the velocity of bubbles during ascent is intermediate between that of a rigid sphere and that of a fluid sphere free from surface-active compounds. We show that our experimental results are compatible with a model of surfactant diffusive flux toward a moving sphere, suited to the case of rising and expanding gas bubbles. The critical surface concentration of contaminants needed to completely rigidify the bubble interface may not be reached in real conditions, i.e., in a flute. The rising velocity of champagne bubbles is then compared with the velocity of bubbles in beer. Contrary to champagne bubbles, beer bubbles are found to behave hydrodynamically as rigid spheres.

A method was developed for the determination of putative lectin activities of cytokines. It involved the immunoblotting measurement of the quantity of these cytokines unbound to a series of different immobilized glycoconjugates and displacement of the bound cytokines with oligosaccharides of known structures. This method allows demonstrating that the following interleukins specifically recognize different oligosaccharide structures in a calcium-independent mechanism: interleukin-1␣ binds to the biantennary disialylated N-glycan completed with two Neu5Ac␣2-3 residues; interleukin-1␤ to a GM 4 sialylated glycolipid Neu5Ac␣2-3Gal␤1-Cer having very long and unusual long-chain bases; interleukin-4 to the 1,7 intramolecular lactone of N-acetyl-neuraminic acid; interleukin-6 to compounds having N-linked and O-linked HNK-1-like epitopes; and interleukin-7 to the sialyl-Tn antigen. Because the glycan ligands are rare structures in human circulating cells, it is suggested that such activities could be essential for providing specific signaling systems to cells having both the receptors and the oligosaccharide ligands of the interleukin at their cell surface.Cytokines are modulators of the activity of the immune system, their mechanism of action remaining, for the most part, not decrypted. As a general rule, the action of a cytokine results from its binding to membrane receptors, a series of molecules coupled to signaling systems involving kinases and/or phosphatases (1-5). The binding of a cytokine to its receptor(s) generally results in the phosphorylation/dephosphorylation of the intracytoplasmic domain of the receptor(s), the first step of the signaling. In general, the phosphorylation/dephosphorylation mechanism is cell type-specific, the kinases/phosphatases involved in these processes being quite specifically associated with surface molecular complexes different from the cytokine receptor complex (3, 6). Even when two different cytokines use the same receptor, the signal transduction pathways may be specific of the cytokines (7).We made the hypothesis that the specific association of interleukin receptors with other surface complexes could be due to carbohydrate-binding properties of these cytokines, a property already suggested in the literature (8 -14). The lectin activity of interleukin-2 (IL-2) 1 for specific oligomannosides (15) appeared to be essential, because IL-2 behaves as a bifunctional molecule able to extracellularly associate its ␤ receptor (IL-2R␤) to other surface receptor complexes bearing N-glycans recognized by IL-2. This is the case for the CD3⅐TCR complex in which a N-glycosylated form of CD3 is an IL-2 ligand. This specific extracellular association is responsible for the specific phosphorylation of the IL-2R␤ by the CD3⅐TCR-associated kinase p56 lck (15), considered as a first step in the antigenspecific activation process of CD4 ϩ T cells. As a consequence of this carbohydrate-binding property, it was suggested that oligomannosides accumulated in specific diseases or bound to specific microor...

The objective of this study was to analyze the origin of proteins of a Chardonnay wine. Three various polyclonal antibodies raised against must, yeast, and bacteria proteins were produced. For microorganisms, only the secreted macromolecules were used. To this end, yeast and bacteria were cultured in a model medium under conditions close to those of winemaking. Results obtained using these specific antibodies indicate that most of the wine proteins came from grapes and many of them were glycoproteins. Some proteins of this Chardonnay wine came from the yeast; they were released during the alcoholic fermentation and consisted of high molecular weight mannoproteins. In contrast, no bacteria proteins were detected in this Chardonnay wine.