Fermenting Fruit Causes Methanol?

[Duncs]

I read somewhere (can't remember where) recently that fermenting fruit produces more methanol than fermenting grains. I seem to recall they mentioned 3% methanol by volume! I read that it was due to the pectin and the use of pectolase. At the time I thought that this was a load of BS, but is there any truth in it? What does pectolase break pectin down into and would that be the cause?

Whatever, it's not going to stop me making and enjoying wine, but I may have to make more beer :drink:

 

[oldbloke]

As I understand it, almost all brewing creates small amounts of methanol, but it's insignificant. The more pectin, the more you get, as far as a quick Google can reveal, but it's still tiny: 3% sounds stupidly high. Although... unfermented apple juice can have 0.3% methanol.
My bit of Googling doesn't really clear up the role of pectolase. I've seen a couple of people saying it would reduce methanol production by getting rid of the pectin, but more saying it mimics the process that produces methanol so you get just as much, maybe more, if you use it. I can see what I'll be researching tonight!

 

[oldbloke]

http://technology.kku.ac.th/food-technology/AFC2011/index.asp_files/Full_Paper/Oral/OH_306.pdf
definitely shows use of pectic enzymes increases methanol production but still no figures for actual concentrations

Also found a paper about plum brandy showing the methanol produced by various yeasts working on plum must is well under 1%

 

[Duncs]

http://technology.kku.ac.th/food-technology/AFC2011/index.asp_files/Full_Paper/Oral/OH_306.pdf
definitely shows use of pectic enzymes increases methanol production but still no figures for actual concentrations

Also found a paper about plum brandy showing the methanol produced by various yeasts working on plum must is well under 1%

That's some reading! :ugeek:

This bit worried me a little

Although methanol content of carambola wines increased slowly reaching 250 ppm at day
14 fermentation without the addition of pectic enzymes, in the presence of added pectic
enzymes methanol increased rapidly and reached 400 ppm which is equivalent to 3333
mg/L ethanol, a value higher than the legal standard limit posing toxicity.

But that was mainly talking about pectin methylesterase. We use Pectolase (PL) so this was more reassuring (bolding mine)

In reviewing the methods for methanol reduction, it is found that the addition of PMEI,
gallic acid or coumaric acid with CPE or using PL for CPE replacement are effective in
reducing methanol content of fruit wines.

 

[oldbloke]

So, at least some naturally occurring pectic enzymes put methanol up, but the pectolase we buy and use brings it down? That's handy.

I did see something about some Italian wines that breach the legal limits but have been drunk for ages with no ill effects so that they were thinking of upping the legal limit for at least some classes of wine. The limits are set pretty conservatively, usually, with this kind of stuff. I think you'd have to get through an awful lot of iffy wine for the methanol to do more than give you a stonking headache with your hangover and maybe a bit of gutrot. AFAIK the only genuine poisonings have been from booze that was deliberately cut with methanol.