Off smelling steam

[Urban Sugarmaker]

I collected over 100 gallons of fresh sap today after boiling about the same amount yesterday. I decided to clean my pan and the niter was really bad on the draw-off side, so I'm glad I cleaned. I boiled for about 6 hours this evening and I was noticing a kind of burnt smell to the steam. Definitely not the nice sweet maple smell we are all so fond of. Sap was clear and fresh and the buds are still squeezed tight. The syrup I drew off tasted very good and is probably medium in color. I kept the pan depth normal and there was no problem with foaming. Any ideas? I'll finish the rest tomorrow and see what happens.

[PerryW]

are you sure that you didn't spill some sap on the side of the evaporator?

[MapleMark753]

Niter got bad on me too last couple of runs, man I hate that. You cleaned the pan of the niter build up? Couple of thoughts on an off/burnt smell. If you used vinegar and didn't get it all out really well, that could contribute to an off smell or taste too. Or, if you didn't quite get all the niter out, but it was loosened, there could be a small scorch/burnt area under what remained. Hate to say it, but I have had that happen from a partial incomplete mid season "clean". I don't think its your sap, too early for buddy sap I think, unless they're silvers or reds. Or if the sap sat for just a day too long... lots of possibilities, all of em frustrating! take care, Mark

[markcasper]

I collected over 100 gallons of fresh sap today after boiling about the same amount yesterday. I decided to clean my pan and the niter was really bad on the draw-off side, so I'm glad I cleaned. I boiled for about 6 hours this evening and I was noticing a kind of burnt smell to the steam. Definitely not the nice sweet maple smell we are all so fond of. Sap was clear and fresh and the buds are still squeezed tight. The syrup I drew off tasted very good and is probably medium in color. I kept the pan depth normal and there was no problem with foaming. Any ideas? I'll finish the rest tomorrow and see what happens.The sap is changing whether we like it or not. I have the same thing every year. It will go on for a few times the smell getting more pronounced and then will start showing up in the taste and its called "metabolism". You don't have to see the buds expanding to be getting this already. Lighter syrup really gets ruined by it, while the darker syrup will mask some of it to a point.

[DrTimPerkins]

The sap is changing whether we like it or not. I have the same thing every year. It will go on for a few times the smell getting more pronounced and then will start showing up in the taste and its called "metabolism". You don't have to see the buds expanding to be getting this already. Lighter syrup really gets ruined by it, while the darker syrup will mask some of it to a point.

"Metabolism" (also called "woody") is an off-flavor that, when it occurs (it tends to be found regionally some seasons, especially long-cold seasons without a thaw), is typically found in the early to mid-season. You can't detect it in the sap. We have heard several reports of this problem already this season.

The late-season, progressive off-flavor that is found and is associated with the tree ramping up growth coincident with budbreak is called "buddy". These are very distinctly different phenomenon, but both have their origins in amino acids produced within the tree.

There are a few papers on "metabolism" available at http://www.uvm.edu/~pmrc/?Page=publications.html and there will be another in the next issue of "The Maple News."

[saphound]

Very interesting info Dr. Tim. But Urban Sugarmaker isn't detecting an off flavor..just an off smell to the steam. Says the syrup tasted "very good". Wouldn't that be something other than metabolism?

[Sandersyrup]

Very interesting info Dr. Tim. But Urban Sugarmaker isn't detecting an off flavor..just an off smell to the steam. Says the syrup tasted "very good". Wouldn't that be something other than metabolism?

I have been getting a few batches with off smelling steam, half finished syrup even has an off something to it. but when finished its completely gone. I have attributed it to a mix of sap that is perhaps one or more days old, possibly burnt niter.

[DrTimPerkins]

Very interesting info Dr. Tim. But Urban Sugarmaker isn't detecting an off flavor..just an off smell to the steam. Says the syrup tasted "very good". Wouldn't that be something other than metabolism?

It could definitely be something other than metabolism. Flavors are pretty difficult to diagnose without actually tasting. I mention it only because we've already heard of a few instances of it so far this season, some of which have been verified by tasting. One oddball characteristic of metabolism though is that sometimes you don't really notice it when the syrup is first made, but after you open the barrel to reheat and pack it, the off-flavor comes through.

[DrTimPerkins]

I have been getting a few batches with off smelling steam, half finished syrup even has an off something to it. but when finished its completely gone. I have attributed it to a mix of sap that is perhaps one or more days old, possibly burnt niter.

Did you retube much of your woods this year? Or replace a lot of drops?

[wnybassman]

I can't drink beer while boiling, it changes my sense of smell and makes good syrup smell bad. Took me a few years to figure that out and even dumped some batches of syrup thinking it was bad. Decided to save some of the bad smelling syrup and it was just fine the next day. No beer, no bad smell for me. Weird. Not sure if this has any bearing on what is going on with you or not, but something to consider if you do like to enjoy a beer or three while boiling.

[markcasper]

It could definitely be something other than metabolism. Flavors are pretty difficult to diagnose without actually tasting. I mention it only because we've already heard of a few instances of it so far this season, some of which have been verified by tasting. One oddball characteristic of metabolism though is that sometimes you don't really notice it when the syrup is first made, but after you open the barrel to reheat and pack it, the off-flavor comes through.

Exactly right. I had some from 2013 and had it marked as light amber extra and thought it was #1. Upon bottling it turned out that 3 drums from that date were off flavor. It wasn't horrid, but I could definately notice it. The funny thing is, syrup produced two days later from 2013 was definately noticable and was marked as such, so already those 3 drums were getting it.The smell from the steam two days ago wasn't the same as the time before, but tasted great. Will see what tonights syrup is like. One thing as mentioned, if the syrup were darker it would be undetectable at this point in the game. No need to worry about darker syrup as by mid next week it is to be in the 60's again.

[Sandersyrup]

Did you retube much of your woods this year? Or replace a lot of drops?

All new everything.


~ John 3/16th"

[Sandersyrup]

No beer, no bad smell for me. Weird. .

This is funny. I'm sure it's true as well. Our sense of taste is tied to our sense of smell. I wonder if we ate maple candy in the shack every batch would smell perfect?


~ John 3/16th"

[Urban Sugarmaker]

So here's the update:

I finished the last of my sap today and the smell seemed to be dissipating by the end. Overall the shack smells like it should, but when I put nose over the syrup section of the pan, that's when I smell it most. Yes, the niter has been really bad for the last two boils but I reversed flow for today and it was a big help. When I cleaned the pan I was literally scraping it off the bottom but none of it looked burned. The smell of the steam is described by my wife as "corn chips". I guess it has somewhat of corn smell, but again, the finished syrup tastes and smells good and normal. As discussed above, if an off-flavor develops it will be after bottling. Time will tell.

WNYbassman - yes I do sometimes have a beer during the shutdown, but that hasn't seemed to affect my sense of smell.

Dr. Tim - we talked about metabolism in another thread in reference to my first batch this year which I bottled on 3/17. After getting some other opinions and tasting it often myself, its flavor does not match any of the descriptors of metabolism (woody, peanut butter, popcorn, or cardboard). Its flavor is noticeably different than subsequent batches but not unpleasant to anyone who's tasted it. Originally I thought it was woody, but it's actually a more delicate maple flavor. I just opened another container from that batch and the taste has not changed or intensified.

So the question now is, do I finish all the sweet in the pan in hopes that whatever caused this doesn't taint the next batch? Probably only 1 week left here.

[MapleMark753]

We had two boiling sessions with off (woody) smelling steam this season. Had heard that it could be metabolism, and drained all the sap and near syrup both times, segregating it and rinsing out the evaporator. (didn't want to waste anything!) Boiled it (each batch) to syrup at about 66.7 brix. Then, boiled it down to near half that volume about. Refilled with permeate. Smell seemed to dissipate a bit. Boiled it down to half (approx.) again, and refilled with permeate. Bad smell was almost gone, but faint chocolately smell. Boiled it down again to half, and refilled. The off smell was gone both times, and the syrup tasted fine, both hot, and when cooled later.
I don't know if three times boiling down is THE recipe, but it did work for us. Only issue really was a lot of foaming, but it was manageable. Didn't expect the faint chocolate odor near the end, maybe others have had a similar experience. If somebody has the time and wants to, I'd say the re-boiling a few times is worth it, or at least worth a try.
take care, Mark

[Urban Sugarmaker]

I actually found that the off smell was coming from defoamer. I think I had a day when I used too much. I was boiling yesterday and noticed it even after adding just a drop or two. This time though, it went away after a few minutes. Lesson learned on too much defoamer. Fortunately I'm not tasting anything different in the syrup as defoamer can supposedly create an off-flavor.