Aging Fail: Temperature

[dr9]

I know the rules. Search it out before you ask. Well, again, I searched, advanced, and every topic included a reply that said "Use the search function".



Why/how does 60 degrees make aging better than, say, 38 or 70?

In other words, I have things aging at room temp now because it's too cold for the shed. I have other things in the fridge, really cold. In Georgia, we get 3 weeks of spring and 3 weeks of fall. All other times it's really hot or really cold. LSSTL, how important is it to keep 60 degrees and why?

 

[AToE]

From what I gather, cold will slow down aging, hotter will accerate it (but not in the best way??? unsure...) and it's actually temp fluctuations that do most of the damage.

Take that with a BUCKET of salt though, I don't know what I'm talking about!

 

[dr9]

The newbee guide verifies your comment about fluctuations.

I am interested in the science behind it. How/why.

 

[AToE]

The newbee guide verifies your comment about fluctuations.

I am interested in the science behind it. How/why.

I'm curious about that too...

 

[GeorgiaMead]

Interesting reading below.

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2293160/



http://www.howtobrew.com/glossary.html Defines fusel alcohols as...

Fusel Alcohol - A group of higher molecular weight alcohols that esterify under normal conditions. When present after fermentation, fusels have sharp solvent-like flavors and are thought to be partly responsible for hangovers.

Also, i know that fusel alcohol is an oil based substance. ::insert speculation::

Maybe the fusel oils break down easier in heat, polluting the rest of the batch? Aging in lower temps allows a molecular encapsulation?

i dunno.
::end speculation::

 

[trennels]

Interesting reading below.

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2293160/



http://www.howtobrew.com/glossary.html Defines fusel alcohols as...

Fusel Alcohol - A group of higher molecular weight alcohols that esterify under normal conditions. When present after fermentation, fusels have sharp solvent-like flavors and are thought to be partly responsible for hangovers.

Also, i know that fusel alcohol is an oil based substance. ::insert speculation::

Maybe the fusel oils break down easier in heat, polluting the rest of the batch? Aging in lower temps allows a molecular encapsulation?

i dunno.
::end speculation::

I would think fusel production is going to take place in fermentation rather than in aging. Storing your mead or wine at 38 degrees shouldn't hurt anything at all, but it will slow the aging process. Higher temps can produce off flavors. There's a great article about the process here:
http://www.wineperspective.com/STORAGE TEMPERATURE & AGING.htm

 

[Medsen Fey]

As one of Lady Vicky's Royal Fuseliers, I can confirm that fusels are a production issue during fermentation. Once they are created, significant aging is required for them to bind and dissipate. Even cooking them (see the Meadeira Brewlog) doesn't speed their elimination.

Aging at higher temperature allows oxidative process to proceed at a faster rate, and wines/meads will tend to fade much soon and may develop frank sherry-like character. This can be good or bad depending on your taste preferences, but it is universally considered a flaw in table wines.

This article from Am. J. Enol. Vitic. 48:3:310-316 (1997) shows the significant impact high temperature impact can have:

Effect of Storage at Elevated Temperatures on Aroma of Chardonnay Wines

[SIZE=+1]C. De LA Presa-Owens and A. C. Noble [/SIZE]

The effect of elevated temperatures during storage on wine aroma was determined for commercial Chardonnay wines with and without oak aging. A significant difference in aroma was detected between the control wine (held at 5°C) and the unoaked (94-U) and oaked (94-O) 1994 wines, after they were held at 40°C for five and seven days, respectively. The 1993 oak-aged wine (93-O) was more resistant to the storage treatment, with a significant difference produced only after nine days at 40°C. After five to nine days of heated storage, only very small decreases in glycosyl glucose (GG) level were observed, suggesting that the initial changes affecting aroma were not a result of hydrolysis of glycosides. To characterize the changes in aroma produced by heating, wines stored at 40°C for 0, 15, 30, and 45 days were profiled by descriptive analysis using trained judges. Upon heating of all wines (93-O, 94-O, 94-U), the intensity of floral and fruity notes decreased, while aromas associated with oak and aging increased: honey, butter/vanilla, oak, tea/tobacco and rubber. The first 15 days of heating resulted in significant increases in the honey, rubber and tea/tobacco attributes and decreases in citrus, tropical fruit, green apple and floral aromas. Increasing the storage time to 30 days resulted in a further decrease in fruity aromas and increase in honey, rubber, tea/tobacco, butter/vanilla, and oak. Few further changes in aroma occurred when storage was extended to 45 days. Although larger decreases in GG concentration occurred upon heating for 15 to 45 days, no consistent relation between GG and the attributes was found.

In another study Am. J. Enol. Vitic. 36:1:18-22 (1985) also found that even short times at high temperature can alter wines. The study also supports the use of Sulfites for protection.

Some Effects of Temperature and S02 on Wine
During Simulated Transport or Storage
C. S. OUGH ​

​

​

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 SO 2 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 SO 2 was verified if quality of the wines was to be maintained. The problems caused by the failure to use SO 2 are increased dramatically by increasing temperature. SO 2 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 SO 2 wines. The loss in SO 2 was more rapid with increasing temperature for the red wine than for the white. ​

The graphs below were taken from the article and interestingly, the white wine showed some improvement with temps of 90 F - go figure. But I suspect long aging would show it subsequently deteriorates more rapidly. In the other cases, the deterioration is already apparent - especially in the wines without SO2.

The question of exactly what chemical reactions are occurring during the aging process is not one that I can answer, and in fact, I don't think the answers are really well understood at this point. It seems hydrolysis of acetate esters is a big factor (and heating speeds this up). There is also polymerization of tannins and anthocyanins (in reds) and that also increases during heating, but some studies have shown that the results from aging at higher temperatures are more bitter, rather than the smoothing that develops from the slower polymerization that occurs with aging at cooler temps.

The general trend to all the data is that storage at higher temps is bad for wine. As for exactly what chemical reactions are making it bad - the questions still remain. How does all this relate to mead? No one is even studying it as far as I know, so I don't anticipate any sudden breakthrough of knowledge.

The good news is that from a practical standpoint, even with crappy room-temperature storage conditions, mead can be stored long enough to become good. I haven't yet aged anything long enough to be able to say what (if anything) will survive for decades in such conditions, but each year that goes by should give me more insight. I hope some of the folks who've aged some for a decade will chime in.

 

[GeorgiaMead]

I would think fusel production is going to take place in fermentation rather than in aging. Storing your mead or wine at 38 degrees shouldn't hurt anything at all, but it will slow the aging process. Higher temps can produce off flavors. There's a great article about the process here:
http://www.wineperspective.com/STORAGE TEMPERATURE & AGING.htm

agreed, but i was trying to get across that maybe since the viscosity is so low that the oil breaks down in lower temps. i'm talking on a whole other level that the post, i'll shaddup

 

[akueck]

It's not "oil" in the sense of motor oil. The "higher" in higher alcohol means more CH2-type groups, i.e. longer chains. These chains are oil-like but it's still alcohol and "longer" in this sense means like 5-10 or so carbons. Still soluble so you're not going to see, for example, a slick of fusels coming out under normal storage conditions (unless you make A LOT of them). Take away that -OH and then you'd definitely see solubility vs. temperature effects come into play. Or make the chain say 20 carbons long, etc. The viscosity of the mead itself probably changes very little over the range of 40-80 F.

 

[wayneb]

However it is a mixture of higher order hydrocarbons (albeit alcohol based in this case) that is smelly and slippery to the touch, and that's one reason why the term "oil" is associated with it. Fusel is a German term for low quality distilled alcohol (i.e. "hootch"). It was discovered during experiments with fermentation and distillation in the late 1800's that these higher order compounds were the classic causes of those bad flavors, and many hangovers, resulting from consumption of liquors containing fusels.

 

[Angelic Alchemist]

Good stuff guys! What about the other end of the spectrum - cold storage? I have a buddy who is using a fridge to "cellar" his brews well under 57F degree mark, which is better than 100+ Houston summers, but I'm curious about the aging process in that scenario.

 

[Medsen Fey]

With cooler temperatures, the rate of chemical reactions that produce the changes of aging is retarded (and don't call Sarah Palin on me, I'm not referring to an individual). That may mean a longer time for things to become smooth and drinkable, but a longer life as well.

As a Counter point, Luc Volders has done some experimentation with his fruit wines and had found that freezing them may actually improve some of them. I am not sure about the mechanism.

 

[icedmetal]

It was discovered during experiments with fermentation and distillation in the late 1800's that these higher order compounds were the classic causes of those bad flavors, and many hangovers, resulting from consumption of liquors containing fusels.

While doing some research on the safety of freeze distillation, I found this article on Wikipedia. It suggests that fusels actually aren't responsible for hangovers afterall; I checked out the research, but don't know enough about science to comment on its veracity.

Seems to me like this should be fairly easy to prove or disprove. Have a test group drink pure fusel alcohol, observe effects and measure the number of hangovers. Have a second group drink everclear (190 proof), observe and measure.

If anyone wants to volunteer to do this study on themselves, I'll totally cheer you on and provide little/no scientific rigor...

Chris

 

[dr9]

It should also be noted that the Appalachian moonshiners used hardwood coals as a final filter to extract a deadly-ish film that would form on the final product.

 

[wayneb]

While doing some research on the safety of freeze distillation, I found this article on Wikipedia. It suggests that fusels actually aren't responsible for hangovers afterall; I checked out the research, but don't know enough about science to comment on its veracity.

Chris

Yeah, but vomiting is only one possible symptom of a hangover, and the hangover has to be a "real mutha" to induce the dry heaves. Lack of "emetic response" in mice isn't a high enough correlation, IMO. I do think that your suggestion for a more controlled, human study, is warranted.

The fact that fusels suppress a learned aversion to the taste of ethanol in mice is intriguing, though. That suggests that some whisky's "smoothness" or other desirable flavor properties may come from the very stuff we've been led to believe causes the harsh tastes in poorly distilled samples.

Definitely, more study is indicated here!