Author Topic: Does freezing sulfited fruit puree dissipate so2?  (Read 2159 times)

Offline brewsumore

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Does freezing sulfited fruit puree dissipate so2?
« on: September 19, 2017, 04:12:54 PM »
I realize that when using sulfite that the recommended process is to sulfite fruit or puree, say to 50 ppm, let sit overnight (12 - 24 hrs) to dissipate the so2 and then add the fruit to primary or rack on top of it in secondary fermenter.

In this instance I pureed ripe plums (minus pits) when available and added sulfite to 50 ppm (.33 g pot meta per gallon of puree) to protect color, reduce wild yeast, and prevent browning, and then put it in gallon zip locks and immediately froze it for later use.

I'm wondering if upon thawing the puree if I need to open the bag tops and let the puree "breathe" for let's say 12 hrs, before fermenting, or if having frozen it for a few days that the so2 will already have dissipated.

The fruit puree will be added to actively fermenting saison in primary fermenters, so sacchromyces yeast tolerance of so2 is at the center of the question, and whether it dissipates during freezing so becomes a non-issue.

My hunch and general inclination is that I could thaw the full bags, open their zip tops for a few hours to let the puree breathe, and then add the puree to primary, but I wonder if the sulfite already dissipated during the few days in the freezer.

Thanks for any insight here.

Offline kramerog

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Re: Does freezing sulfited fruit puree dissipate so2?
« Reply #1 on: September 19, 2017, 05:26:56 PM »
No need to let the fruit breathe while thawing.  An active fermentatation removes the SO2.

Offline brewsumore

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Re: Does freezing sulfited fruit puree dissipate so2?
« Reply #2 on: September 19, 2017, 08:09:34 PM »
No need to let the fruit breathe while thawing.  An active fermentatation removes the SO2.

Cool!  I had pondered it from that angle, namely that active yeast in large numbers (active ferment) is enough to compensate for yeast shock, that would otherwise occur if the scenario was pitching at standard pitch rate at the beginning of fermentation in the presence of sulfited puree.

Thank you!  This means less exposure and fuss.  Once the puree is thawed and at room temp I'll just spritz the ziplock bags with star san, open them and dump in the fruit puree.
« Last Edit: September 19, 2017, 08:12:23 PM by brewsumore »

Offline brewsumore

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Re: Does freezing sulfited fruit puree dissipate so2?
« Reply #3 on: September 19, 2017, 11:14:19 PM »
Huh!  A very knowledgeable winery owner / wine maker on my winemaking forum just shared that Saccharomyces yeast isn't inhibited by so2 until at least 200 ppm.  That is very interesting.

Offline natebrews

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Re: Does freezing sulfited fruit puree dissipate so2?
« Reply #4 on: September 19, 2017, 11:34:25 PM »
It may not be inhibited, but does it produce undesirable bi-products when it is in an SO2 environment?  If the yeast works on it and produces a bunch of H2S, it might be plenty happy to be there but the results might be a bit  unwelcome to the human olfactory system.       

I would imagine this is fairly strain dependent, with results varying from fart bomb to nothing.  Then again, maybe it doesn't matter at all.
« Last Edit: September 20, 2017, 12:17:00 AM by natebrews »
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Offline brewsumore

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Re: Does freezing sulfited fruit puree dissipate so2?
« Reply #5 on: September 19, 2017, 11:56:20 PM »
Hmm, that's thought provoking.  Especially given that when fermenting on fruit it's recommended to keep the fermenter lid snapped down to prevent staling by 02 - of course with airlock or blowoff tube in place.  Meaning less ability for any gasses to easily off gas.

Offline brewsumore

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Re: Does freezing sulfited fruit puree dissipate so2?
« Reply #6 on: September 20, 2017, 03:11:25 AM »
I ended up nice and tightly fitting the 6 thawing bags into a clean and sanitized sausage tub, of course faced with the zip lock up, and partly opened each bag tucked away in the basement where there's no cross breezes from heater vents, etc..  Come morning the puree will be room temp and unspilled and ready to go into the two awaiting fermenters, and I have basically no worry that they will have collected any significant off-flavor causing microbes.

One can think things through, but one shouldn't overthink things.

Offline brewsumore

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Re: Does freezing sulfited fruit puree dissipate so2?
« Reply #7 on: September 21, 2017, 02:31:17 AM »
I thought I'd cap this little wandering mini-drama.  As with many things, finesse makes the difference between "works" vs. "I think it's broke".

So, since yesterday when I opened the ziplock on each still-partially-frozen bag about 2 inches to allow any of the retained so2 to diffuse out as they fully thawed and came to room temp, it took a lot longer for them to warm up than I expected.

Had I re-zipped the bags after 10 hrs exposure and let them fully warm up I'd have been ok.  Instead I let them go closer to 20 hrs since they were still cold - not ready to pitch.  When I last looked at them, the bits of pureed fruit near the opening had discolored/darkened from air ingress which made me wonder if they weren't also a bit microbially impacted.

My fix, as I have done in the past with homemade puree, was to pour all the bags (total 3 gallons) into a clean SS canning pot, heat the puree at just over medium heat to 150F, while stirring constantly so as not to set pectins at the bottom of the pot, and then held the puree at 150 - 151F for 15 minutes, again while stirring.
 Then I chilled down the pot of puree while stirring to the beer ferment temp (80F) in an ice water bath in the sink, and pitch it via a sanitized 1-pint measuring cup.

All is well at least.
« Last Edit: September 22, 2017, 02:47:02 AM by brewsumore »