K-meta reduction over time by container

4score · Mar 30, 2015

Just some observations of the reduction of free SO2 from the last testing. These observations are for various varietals with relatively high (~3.8 to 4) pH wines stored in a air-conditioned 64 degrees.

Container------------------------K-Meta PPM loss/day

2nd year 8-gallon barrel------------------1.7 ppm/day

New 30 gal barrel------------------------1.6 ppm/day

30-gal Flex tank--------------------------0.7 ppm/day

5-gal glass Carboy------------------------0.27 ppm/day

NorCal · Mar 30, 2015

Very interesting 4score.

acorn · Mar 30, 2015

Interesting indeed. How would the higher and lower temperatures affect the rate of SO2 loss/binding? I have a couple of hypothesis, yet unproven to myself, in regard to the effect of the temperature. I would appreciate if you could possibly elucidate a bit on the subject.

4score · Mar 31, 2015

I'm not sure "why"....but I found the following abstract....

White and red table wine samples, under simulated transit or storage conditions, were held at five different temperatures (28°, 32°, 38°, 43°, and 47°C) at low and medium SO2 levels for 21 days. Changes in composition during the storage period and wine quality afterward were measured and evaluated. The need for the use of SO2 was verified if quality of the wines was to be maintained. The problems caused by the failure to use SO2 are increased dramatically by increasing temperature. SO2 and color changes were related to temperature. Red pigment was lost for the red wine at about the same rate the white wine browned for the low SO2 wines. The loss in SO2 was more rapid with increasing temperature for the red wine than for the white.

Copyright 1985 by the American Society for Enology and Viticulture

acorn · Mar 31, 2015

Well, I am wondering then, is the effect of temperature on SO2 expiration direct (e.g. like pH, where higher pH makes free SO2 less effective, and vice versa), or is it more indirect, such as when the temperature affects the headspace air or rate of multiplication of bacteria, etc., whereby K-meta will be expended to counteract these events?

sour_grapes · Mar 31, 2015

4score said:
I'm not sure "why"....but I found the following abstract....

White and red table wine samples, under simulated transit or storage conditions, were held at five different temperatures (28°, 32°, 38°, 43°, and 47°C) at low and medium SO2 levels for 21 days.

Interesting stuff.

It may be worth noting to the USA crowd that these temperatures are:
82, 90, 100, 109, and 117 F, respectively. Obviously, they used high temperatures to speed up the degradation to investigate the effect. Clearly, no one would intentionally store at these temps.

Here is the article that 4score kindly found: http://ajevonline.org/content/36/1/18.abstract

codeman · Mar 31, 2015

Was that a heavy weight or thin walled flextank?

stickman · Apr 1, 2015

Keep in mind that there are many factors involved and the so2 loss isn't usually constant over time. For example a young red being racked to a barrel or a Flextank after malolactic fermentation will consume sulfite at a greater rate than the same wine 6 months later in the same vessel. A lot of so2 binding occurs early and this has to do with how dirty the wine is and the microbial load, as well as other factors like the amount of new oak addition. I have 3 of the 30 gallon light weight Flextanks and for a heavy red I typically use 4 to 5 of the 36" French oak tank staves. Everyone will have their own method, but I adjust the so2 a couple of times during a two week period after the malolactic completion racking; there is a lot of binding going on at this point. My A/O measurements starting a month after this have been around 6 to 7 ppm per month for a few months and less than this later on. My cellar temperature is maintained at 59F.