Tartrate stability test

Tartrate Stability Test Used to Determine Process Settings... 

Although early ED tests for tartrate stabilization of wines had been performed by Paronetto (1941), more systematic experiments were carried out in the 1970s (Audinos et al., 1979 Paronetto et al., 1977 Wucherpfennig and Krueger, 1975) and led to the automatic method and device for tartaric stabilization of wines developed by Escudier et al. (1995) at the French National Agronomic Research Institute (INRA) in cooperation with Ameridia (Moutounet et al., 1997). 

Paronetto, L., Paronetto, L., and Braido, A. 1977. Some tests on tartrate stabilization of musts and wines by electrodialysis. Vignevini 4, 9-15. 

First, laboratory testing is conducted to ascertain the stability of the wine. Like tests for protein stability, tests for determining stability and method for correcting instability vary from winery to winery. Berg (34) suggested that a wine stored at — 4° C for four days, without a bitartrate crystalline deposit, may be considered stable. The wines usually are allowed to warm to room temperature before test results are read. Absence of crystals indicates stability. A quantitative method, the concentration product (36), also can be used to evaluate tartrate stability. 

The first indnstrial electrodialysis nnit with a 45 m membrane surface went into operation in 1996. Its resnlts, consistent with those of the many earlier pilot tests, showed that electrodialysis can be applied on an industrial scale for the tartrate stabilization of wine. The optimnm effectiveness of this techniqne is subject to choosing a pair of (anion and cation) membranes that best preserve the wine s natnral balance, and combining it with an antomatic testing system to restrict the treatment to the minimum required to achieve tartrate stability. 

The mini-contact test is based on homogeneous induced nucleation, which is faster than primary nucleation. However, this test does not take into account the particle size of the seed tartrate, although the importance of its effect on the crystallization rate is well known. The operative factor in this test is the surface area of the liquid/solid contact interface. Furthermore, this test defines the stability of the wine at 0°C and in its colloidal state at the time of testing. In other words, it makes no allowance for colloidal reorganization in wine, especially red wine, during aging. 

It should be noted that mini-contact test results tend to overestimate a wine s stability and therefore the effectiveness of prior treatment. This statement is based on work by Boulton (1982). After 2 hours contact, only 60-70% of the endogeneous tartrate has crystallized and therefore the increase in weight of the crystal precipitate is minimized. These results are interpreted to mean that the treatment was more effective, or the wine more stable, than was actually the case. In order to make the mini-contact test faster, more reliable and compatible with the dynamic contact process, the Martin Vialatte Company proposed the following variant in 1984 seeding a wine sample with 10 g/1 of cream of tartar and measuring the drop in conductivity at 0°C. 

Modeling this phenomenon over a 4-honr period makes it possible to assess the theoretical drop in condnctivity over an unlimited period. The test resnlts, therefore, indicate the final condnctivity valne at which the wine no longer presents a risk of tartrate precipitation. The drop in condnctivity reqnired for the wine to be stabilized is monitored using an automatic system controlled by a PC (Escndier et al., 1998). 

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