Alternative Methods to SO2 for Microbiological Stabilization of Wine

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winemaker81

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I have posted the link to the The Australian Wine Research Institute's FAQ on fining agents, as they provide a very good description of the effects of common fining agents. One they leave out is kieselsol/chitosan, so this morning I emailed, asking if they had any plans for updating the FAQ to include kieselsol/chitosan.

I receive a reply a few hours later, stating they are in the process of updating the FAQ (no time frame specified) and pointing me to this article as potentially relevant:

Alternative Methods to SO2 for Microbiological Stabilization of Wine - Lisanti - 2019 - Comprehensive Reviews in Food Science and Food Safety - Wiley Online Library.

I breezed through the article for highlights, and spotted a list of benefits to chitosan:
  • a) Clarifying agent
  • b) Reduction in the heavy metal content particularly iron, lead, cadmium and copper
  • c) Prevention of ferric casse and copper casse
  • d) Reduction of possible contaminants, especially ochratoxin A
  • e) Reduction in the populations of undesirable micro‐organisms, in particular Brettanomyces
#a is known, but the others are things I did not know.

This article is technically detailed, in the "puts the reader into a coma" detailed arena. I'm going to risk all and read it carefully.
 

my wine

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Wow, lots of big words. Good to know that chitosan is more than just a clarifier.
 

winemaker81

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Wow, lots of big words. Good to know that chitosan is more than just a clarifier.
I'm reading through it. I recall enough of my college sciences background to understand the majority, although I'm looking for practical information, e.g., chitosan precipitates heavy metals AND it reduces (sanitizes) a potential toxin and at least one undesired organism.

On the plus side, I now have a basic understanding of what ochratoxin A and Brettanomyces are, and why we don't want them. Some folks claim wikipedia is useless, but it's a great place to start. Regarding these terms, I got what I needed without having to look further.
 

NorCal

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While not eliminating SO2, I try to minimize how much I add. What I take into account when deciding how much SO2:
pH
alcohol %
cleanliness of grapes/ferment
amount of tannin
length of time until I’ll drink
did I filter

With wines that check a number of these boxes I’ll back off the pH vs free SO2 curve. The only wines I’ve had that have not survived the test of age are very few corked bottles (like 5 out of 5,000).
 

winemaker81

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I read part of the study last night. Enough that my eyes started to bleed. I understand most of what is written, but I keep in mind this is NOT written for laymen, e.g., home winemakers. I am not the designated audience, so it gets very far into the weeds. My take on the abstract is:

Industry wants to reduce or eliminate SO2 as an additive. Alternate products to meet the antioxidant and antimicrobial effects have been examined. The examined alternatives cannot replace SO2 in this regard, but may be used to complement SO2 and reduce the amount of SO2 used.

I'm making notes as I go, which include recording points of interest and my take on those points. My posts in this regard are stream of consciousness, meaning that I'm recording what strikes me at that moment. A second read through might find other points.

Interesting point:

"SO2 addition to the must, prior to alcoholic fermentation, shortens the fermentation time by repressing non‐Saccharomyces yeasts and promoting the growth of sulfite‐tolerant Saccharomyces yeasts"

I suspect this indicates that the suppression of unwanted yeast means the cultured yeast has to spend less time fighting for market share and more time reproducing. This makes sense, unless MLF is desired.

About 1% of the population is "sulfite-sensitive".

I've read different figures on sulfite sensitivity. Oddly enough, in the last 40 years I cannot recall meeting anyone who was sulfite sensitive. This is not to say sensitivity doesn't exist, just that I haven't met anyone who is. Which may make sense, as it's not a topic for normal conversation and sulfite sensitive folks are less likely to be at a wine tasting.

SO2 is more active at higher temperature and higher alcohol concentrations.

This may explain why high alcohol wines have a longer shelf life

"Wine microfiltration of high‐quality wines, especially red wines, has always been a controversial subject regarding the possible negative effects on wine quality. However, existing studies indicate that, in spite of small but significant decreases in flavor or color compounds, microfiltration has only a minimal impact on the sensory profile of red wines, even over 18 months bottle‐aging"

Interesting. I recall an article in the Wine Spectator, sometime in the early 90's, about a professional wine critic who could identify when a producer started filtering their wines, by the taste. This guy had a highly trained palate, so it's likely he smelled and tasted things most don't.
 

winemanden

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Personally I think a lot of people who claim to be Sulphite sensitive are excess alcohol sensitive. It's easier to claim that your bad headache is caused by Sulphite than to admit that maybe you've supped too much the night before.
Been there. Done it. Learned to take it easy, but sometimes at my age I do get a bit forgetful.
I only drink for medicinal reasons, but often the medicine tastes so good, I have to increase the dose.
 

winemaker81

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@winemanden, I fully agree with your point. I have a few acquaintances that jump on whatever the current bandwagon is.

OTOH, my understanding is that sulfite doesn't cause headaches, although it may cause allergic reactions. If someone is not over-indulging, it's likely they are histamine sensitive.

I LOVE bourbon. But about 4 years ago I started getting headaches when I had a glass. Didn't matter how much, I got a headache within 20 minutes. I suspect it's histamines or something related to the oak, as bourbon must be aged 2 years in new oak. This really sucked for me.

Fortunately, I discovered that Irish whiskey doesn't bother me, and very recently I discovered Scotch doesn't either, so it's not like my life is all doom-n-gloom. Gin, tequila, and cognac also work fine for me.

If I find myself having a bad reaction to red wine? Ok -- at that point life would truly suck.
 

winemaker81

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Not sure it was the oak aging causing your issues with bourbon. Both Irish whisky and Scotch whiskey are aged in oak barrels and for longer than bourbon.
Bourbon requires new oak. Can't reuse a barrel, so the amount of oak character extracted is high.

At one point, the biggest purchaser of used bourbon barrels was Ireland and Scotland. Neutral barrels are the norm, while new barrels are not the requirement.
 

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