On 3/29/04 6:35 PM, in article
, "Ben Rotter"
> wrote:

> Greg Cook > wrote:
>
>> I think the difference between pH 7 and 8.2
>> during the titration is a matter of just a few drops anyway (the titration
>> curve is very very steep at the point of neutralization of the acids).
>
> Theoretically, that's true and I always assumed there'd be little
> difference. I haven't done enough comparisons to accurately judge, but
> I actually just read a paper recently which suggests this difference
> *is* significant.
>
> In the paper [1], they compared the OIV method (titrate to pH 7.0, 50
> ml wine) and the AOAC method (titrate to pH 8.2, 10 ml wine diluted
> with water to 100 ml) for 30 wines. They found no significant
> difference due to operative technique (i.e. the dilution and sample
> sizes), but they did find a difference due to pH end-point. This
> difference correlated to a TA difference of 0.6 g/l (as tartaric) for
> reds and 0.5 g/l for whites. Well, I consider that significant.
>
> BTW, if the standard was to titrate to the actual equivalence point
> for wines, we'd all be titrating to pH's of around 10. In the purely
> practical sense, I'm glad we have a standard at pH 7/8.2. Certainly
> saves on the NaOH ;-)
>
> Ben
>
> [1] Darias-Martín, J. et al. (2003). Comparative study of methods for
> determination of titrable acidity in wine. J. Food Composition and
> Analysis 16, 555-562.


Ben --- thanks for the reference. This is very interesting.

--
Greg Cook
http://homepage.mac.com/gregcook/Wine

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