Potassium hydrogen tartrate (KHT) crystallization induction times were measured at 11.5 degrees C using hydroalcoholic solutions with and without polysaccharides. The effect of well characterized natural wine polysaccharides (mannoprotein (MP), arabinogalactan-protein (AGP) and two types of rhamnogalacturonan (RG-I and RG-II)) was tested on KHT crystallization. A carboxymethylcellulose was also tested because of its strong nature as an efficient inhibitor of KHT crystallization. Wine polysaccharides showed the following effects: no influence with AGPs; a slight increase of KHT induction time when concentration of MPs or RG-I increases, RG-I being more efficient than MPs; and RG-II displays a concentration dependence effect changing from a reduction of induction time to an increase as concentration rises. These features do not bear any relation to the charge per molecule of the polysaccharides, but seemed to be related to their structural characteristics. Further measurements of induction time al different supersaturation values were performed for solutions without polysaccharide, with RG-I and with RG-II, A recent theory of crystallization phenomena in the presence of an additive was used. It takes into account the growth of nuclei to a detectable size and postulates that nucleation occurs heterogeneously and that additive molecules act as secondary nucleation centres. Specific surface energy and specific edge energy values were obtained: 8.1 mJ m(-2) and 1.1 x 10(-12) J m(-1), 10.0 mJ m(-2) and 1.6 x 10(-12) J m(-1), 7.0 mJ m(-2) and 3.1 x 10(-12) J m(-1) for solutions without additive, with 30 mg l(-1) of RG-I and with 60 mg l(-1) of RG-II respectively. According to the theory, RG-I has almost no effect on nucleation whereas RG-II accelerates nucleation. Both rhamnogalacturonan I and II induce a decrease of the growth rate as concentration increases.