Metatartaric acid effectiveness

The spontaneous crystallization temperature of each sample of treated wine (Table 1.16) was also determined using the same procedure. Examination of the results shows that a wine filtered on a 10 Da Millipore membrane, i.e. a wine from which all the colloids have been removed, has the lowest value for the supersaturation field (Tsat - Tcso), closest to that of the model dilute alcohol solution. Therefore, the difference between the results for this sample and the higher values of the supersaturation fields of fined samples define the effect of the protective colloids. It is interesting to note that the sample treated with metatartaric acid had the widest supersaturation field, and cold stabilization was completely ineffective in this case. This clearly demonstrates the inhibiting effect this polymer has on crystallization and, therefore, its stabilizing effect on wine (Section 1.7.6). Stabilization by this method, however, is not permanent. 

There are many laboratory tests for assessing the effectiveness of a metatartaric acid preparation. Table 1.19 presents an example of a procedure where a saturated potassium bitartrate solution is placed in 10 ml test tubes and increasing quantities of metatartaric acid preparations with different esterification numbers are added. This inhibits the precipitation of potassium bitartrate induced by adding 1 ml EtOH at 96% vol and leaving the preparation overnight at 0°C. Only 1.6 mg of a preparation with an esterification number of 10 is... 

With this in mind, its effectiveness has been compared to that of two other tartrate stabilization methods continuous contact cold stabilization and the addition of metatartaric acid (Table 1.21). This comparison was carried ont by measuring spontaneous crystallization after the addition of KHT (Section 1.6.4). The values obtained indicate the effectiveness of protective colloids, even if they do not necessarily correspond to the instability temperatnres. The addition of 15 g/hl of Mannostab to wine 2 and 25 g/hl... 

However, metatartaric acid is hydrolyzed in wine, and loses its effectiveness, while adding tartaric acid may even facilitate potassium bitartrate crystallization. Under the same conditions, manno-proteins are stable and have a durable protective effect on tartrate crystallization. To demonstrate this difference, white wines treated with metatartaric acid or Mannostab and kept at 30°C for 10 weeks were then subjected to a cold test. Crystallization occurred in the sample treated with metatartaric acid, while the Mannostab sample remained stable (Table 1.22). 

These results demonstrate comparable effectiveness for metatartaric acid (10 g/hl) and CMC (4 g/hl). Furthermore, a comparison of the stability and effectiveness of these two additives, following prolonged heat treatment at 55-60°C for... 

Fig. 1.25. Comparison of the effectiveness of metatartaric acid and carboxymethylcellulose on turbidity due to tartrate crystals (Crachereau et al., 2001) (See Table 1.23 for treatment conditions)...

Cold stabilization is not always totally effective and the following additional treatments may be used to ensure complete stability metatartaric acid (Section 1.7.6), mannoproteins (Section 1.7.7), carboxymethylcellulose (Section 1.7.8), ion exchangers (Section 12.4) and electrodialysis (Section 12.5). 

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