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Jun 08, 2022 View:

Methanol Reduction

I have read that more methanol forms while fermenting fruits high in pectin. One suggestion on reducing the amount of methanol produced, was by heating the mash in order to deactivate some of the enzymes responsible. What temperatures would the enzymes break down at? Are there any other ways to reduce the amount of methanol?


Reply:

Apple is the one fruit that you really have to worry about. I have notes somewhere of which fruits, produce what amounts, of methanol from pectin.

I will post more when I dig up my notes from some cider and distilling seminars I went to last year at Cornell University.

Jonathan

I have read that more methanol forms while fermenting fruits high in pectin. One suggestion on reducing the amount of methanol produced, was by heating the mash in order to deactivate some of the enzymes responsible. What temperatures would the enzymes break down at? Are there any other ways to reduce the amount of methanol?
Reply:

The type of distillers yeast used can also have an impact on the amount of higher alcohols. Make sure your yeast is compatable with your additives. Red wine distillation has the same problem, so watch for compatability there, as there is less data on apple distillations than grape distillation's. Classical high cuts are the rule in a case like this and might be the best answer.

PS never use pectic enzyme in distillation fermentations.

Best regards,

Donald R Outterson


Reply:

Donald- why shouldn't you use pectin enzymes? Do you mean pectinase?

The type of distillers yeast used can also have an impact on the amount of higher alcohols. Make sure your yeast is compatable with your additives. Red wine distillation has the same problem, so watch for compatability there, as there is less data on apple distillations than grape distillation's. Classical high cuts are the rule in a case like this and might be the best answer.

PS never use pectic enzyme in distillation fermentations.

Best regards,

Donald R Outterson


Reply:

Kris Berglund's (MSU) book (please forgive any misspelling) has info on methanol levels in pome fruit brandies and a bit about heat deactivation of the enzymes involved. It's not an issue limited to pome fruit. And you don't want _no_ methanol in brandy - just not too much. The legal limit is really quite high.

Most people using 'pectinase' usually mean a pectolytic enzyme. It's used by some pressers for apples/pears to increase pressing yield. If you're running whole mash, there's no real need to use it up front, as it will just make the pomace slimier. (IMHO) We don't use it when pressing anyway - we just press a bit more slowly. Depending on the varieties, we run from about 3.7 to 4+ gal/bushel of apples. Common pear come in at about 2.8 gal/40 lbs.

Using pectolytic enzymes in wine making post pressing is pretty common, too. it's uses to help clear hazes and speed settling. Also, not needed for distilling stock.

I believe pectolytic enzymes generate some methanol as they chew up the pectine polysaccharide, but they are not the main concern.

There's another enzyme called PME, or pectin methyl esterase. It skims along the pectin polysaccharaide chain and lops off the occasional methyl group (making methanol). It occurs to some degree naturally in apples. Cidermakers in UK and France use commercial preparations to aid a process called 'keeving'. The idea behind keeving is to strip the must of available nitrogen, thiamin and wild organisms by entraining them in a pectin gel. The 'bright cider' is racked out from underneath the gel and ferments very slowly - usually sticking at just a few percent alcohol. A good trick if you can pull it off.

Anyway, the pectin gel is formed by pectin, the PME enzyme and Ca2+ ions. The PME kicks methanol off the pectin (but leaves the chain intact) leaving a charged site. The Calcium binds at the charged site - and cross binds to other chains. CO2 from early in the ferment lofts the gel.

Anyway, pectolytic enzymes are either pressing aids or clarification aids, which distillers shouldn't _usually_ need.

PME is a cidermaking tool, and isn't even available in the States.

If you're worried about it, throw the pomace in the still, cook it a bit, and _then_ ferment it. Kris's book gives some details about time and temp.

BTW, some pectolytic enzymes have a side activity. Glucosidase - alpha or beta, I can't recall which. It releases a glucose moluecule from aroma precursors, freeing up a terpene. Not all fruit have them, but it might be an interesting use of AR2000 (for example) for distillers - especially for brandy and grappa.


Reply:

Here's a link to an online edition of Berglund's book on Bill's ADI site.

http://www.distilling.com/PDF/artisan.pdf

Kris Berglund's (MSU) book (please forgive any misspelling) has info on methanol levels in pome fruit brandies and a bit about heat deactivation of the enzymes involved. It's not an issue limited to pome fruit. And you don't want _no_ methanol in brandy - just not too much. The legal limit is really quite high.

Most people using 'pectinase' usually mean a pectolytic enzyme. It's used by some pressers for apples/pears to increase pressing yield. If you're running whole mash, there's no real need to use it up front, as it will just make the pomace slimier. (IMHO) We don't use it when pressing anyway - we just press a bit more slowly. Depending on the varieties, we run from about 3.7 to 4+ gal/bushel of apples. Common pear come in at about 2.8 gal/40 lbs.

Using pectolytic enzymes in wine making post pressing is pretty common, too. it's uses to help clear hazes and speed settling. Also, not needed for distilling stock.

I believe pectolytic enzymes generate some methanol as they chew up the pectine polysaccharide, but they are not the main concern.

There's another enzyme called PME, or pectin methyl esterase. It skims along the pectin polysaccharaide chain and lops off the occasional methyl group (making methanol). It occurs to some degree naturally in apples. Cidermakers in UK and France use commercial preparations to aid a process called 'keeving'. The idea behind keeving is to strip the must of available nitrogen, thiamin and wild organisms by entraining them in a pectin gel. The 'bright cider' is racked out from underneath the gel and ferments very slowly - usually sticking at just a few percent alcohol. A good trick if you can pull it off.

Anyway, the pectin gel is formed by pectin, the PME enzyme and Ca2+ ions. The PME kicks methanol off the pectin (but leaves the chain intact) leaving a charged site. The Calcium binds at the charged site - and cross binds to other chains. CO2 from early in the ferment lofts the gel.

Anyway, pectolytic enzymes are either pressing aids or clarification aids, which distillers shouldn't _usually_ need.

PME is a cidermaking tool, and isn't even available in the States.

If you're worried about it, throw the pomace in the still, cook it a bit, and _then_ ferment it. Kris's book gives some details about time and temp.

BTW, some pectolytic enzymes have a side activity. Glucosidase - alpha or beta, I can't recall which. It releases a glucose moluecule from aroma precursors, freeing up a terpene. Not all fruit have them, but it might be an interesting use of AR2000 (for example) for distillers - especially for brandy and grappa.