Aims: Inhibition of potassium hydrogen tartrate (KHT) crystallization by carboxymethylcellulose (CMC) is tested in a model solution and in wines. Tartaric acid salt crystallization risk is assessed by computing the supersaturation, saturation temperature and excess KHT with respect to the saturation equilibrium using MEXTAR® (Mesure de l’EXces de TARtre) software.
Materials and results: Firstly, the time for crystals to appear was recorded by monitoring the conductivity in a model solution and in a wine, and the inhibition ratio was computed. At 11,5 °C, 0,5 mg.L-1 CMC inhibited KHT crystallization. The inhibitory effect increased exponentially with increasing CMC concentration and was several times greater than that of polysaccharides and polyphenols, the protective colloids in wine (Gerbaud et al., 1997). At 2 °C, 30 mg.L-1 CMC had the same inhibitory effect than 10 mg.L-1 at 11.5°C.Secondly, 20 red and white wines were refrigerated for 3 weeks at -4 °C with CMC or metatartaric acid. Results show that the addition of 20 mg.L-1 CMC has an inhibitory effect at least equivalent to 100 mg.L-1 metatartaric acid. Furthermore, for 10 wines preheated for 8 days at 30 °C and then refrigerated for 2 months at 0 °C, 5 and 20 mg. L-1 CMC maintains its inhibitory efficiency, unlike metatartaric acid which is hydrolysed
Significance and impact of the study: The OIV-OENO 366-2009 and OIV-OENO 02/2008 resolutions recently authorized the use of CMC to prevent tartaric acid salt precipitation. With no impact on health, and stable under heating and in acid solution, CMC is an efficient candidate for tartaric stabilization. The optimal concentration of 20 mg.L-1 (2 g.hL-1) should however be adapted to local wine storage conditions and KHT crystallization risk.
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