The taste of my latest syrup/is it tubing related

[buckeye gold]

Ok, We all have new experiences in life and it's my turn. I am near the end of my fall tapping and I had three pretty good runs this week. I made a little over 2 gallons of syrup and I'm kind of perplexed by it's taste/grade. I have made darker syrup before, but this is different in taste. this is all off new 3/16th tubing. I collected fresh and boiled promptly. Early in my fall season everything worked just as always, but the only difference being I was on tubing. I had a prolonged down period where my lines were frozen, then it warmed. In the mean time I drained my evaporator and emptied tanks. In other words i had no stored sap, except what was in the lines. when it warmed up last week I had about three days before sap ran, but lines thawed and emptied. I dumped all that. My lines do not hold sap they are 100% on slope. So when i got runs I gathered and cooked. The temps did go rather high, in the high 50s and low 60s. When I finished syrup it had a good bit of Nitre and a taste I have never encountered in my syrup. It is all dark and does not have a pure maple profile like I'm used to. It is more of a vanilla to butterscotch taste, with perhaps a bit of earthyness. It is not bitter. I figure it is due to microbial activity, but I'm not sure. My process has not changed for 10 years, the only difference is tubing. Does tubing lend more to microbial activity during warm spells. I know i used to be able to tell when my buckets would get a sheen I needed to wash. Do I need to flush or clean my tubing after warm spells? This has me perplexed as I don't know whether to sell this syrup, my customers are used to my light to medium rich Maple flavor.....I am afraid it will turn them off. am I to expect this to happen come spring? If so I'm not sure I'm going to like tubing. As soon as I get a warm spell I am going to wash everything thoroughly. Right now I am letting sap run on the ground as I want no more of this. I let some friends taste it and they new it was different, but said it was good. Any thoughts. Don't get me wrong, I know what buddy or spoiled sap syrup is like...this is not that.

[maple flats]

If you read about the typical tastes associated with maple syrup, Vanilla and butterscotch are c2 very typical tastes described by professional taste testers.

[n8hutch]

Maple syrup can take on many flavor profiles, I would go with your gut when it comes to selling syrup that you think tastes off, only you can decide that, I have bought some syrup in the past from a packed that I thought didn't taste quite as good as some of my syrup but most of the people that tried it found no noticeable difference. When you say your 3/16 lines all drain I presume you mean after the taps are pulled? If not you have some leeks and are not getting the desired benefit from 3/16.

[buckeye gold]

n8hutch, yeah what I meant was I have no traps or severe swags. That if sap runs it doesn't build up anywhere a drop in and a drop comes out the discharge end, more or less. I guess what I'm getting at is the sap more prone to heat up and start to break down in tubing? It has been a crazy fall with extreme cold and then extreme warm, so I'm hoping a good cleaning is all I need.

[Super Sapper]

I do not think it is due to your tubing. If your tubing is new it should have less exposure to bacteria than pails or bags. It is probably from the trees but I would not expect it to be a problem in the spring. They say you can get this off flavor at any time and can disappear just as fast. Metabolic is a term that is sometimes used. If it is just a vanilla or butterscotch enjoy it as a different flavor or use it for making sugar or nuts.

[MapleMark753]

https://www.ams.usda.gov/sites/default/files/media/VT%200899.pdf
If this doesn't come through as a link, maybe copy and paste into your browser
You might already have the above info or have read the PDF, but here it is again if you have! I've had those flavors too from time to time (not usually, once in a while). I guess you could consider them an off flavor (metabolism?), or part of the normal if not usual flavor profile. I have people who like the vanilla flavor BETTER, and need some convincing that its pure maple syrup. I don't have info re your direct tubing question. Great to hear you were late fall tapping. We tried, but the trees did not give (first time in six years).