Off flavor permeate?

[sapman]

I'm concentrating for the first time, and it sure seems like the permeate has a little glycol taste to it. Maybe I'm just being paranoid. Hydrometer tests 0. Washed and rinsed with 1800~ gallons of soft water a couple weeks ago. Running it on the ground for now, but hate to. Does anyone think that's just the normal taste of permeate?

Concentrate seems fine.

[wiam]

Have you tasted permeate before? It tastes different anyways. Also a hydrometer is not very accurate close to 0% I have been told.

[VTFarmer]

There are a lot of reasons your permeate will "taste funny". If you're just getting started for the season, the most likely reason is all the stale nastiness that's been sitting in your lines all summer. There are always a few days of off-flavored everything (raw sap, concentrate, permeate, and even syrup) at the start of the season. If your concentrate is yellow or milky looking, chances are that's what's going on.

That being said, there are some other factors that can affect the taste of your permeate. Not all membranes are created equal. Some retain much higher levels of solids than others. If you have a "loose" (low retention) membrane, you can pass as much as 40% of the total solids in your raw sap into the permeate. Most of these solids are what amounts to niter in your finished product but loose membranes almost always pass some amount of sugar as well...but not enough to show up on a hydrometer or refractometer. The idea here is that your permeate isn't "pure water" unless your particular membrane has a retention rate that approaches 100%. Temperature can play a role in off-flavor as well...not usually till the end of the season when it starts to get warm but this year, who knows. Warm sap is more easily affected by bacteria, bacteria "eat" the sugar in your sap, and their by-products (waste) will affect flavor.

Chances are you don't really need to worry about how loose/tight your membrane is if it works and you don't detect any sugar in the permeate...the short skinny version is don't get nervous just yet. If, when the season shapes up, your lines have had a chance to clean themselves out, and the sap is running every day, you still have off flavored permeate; you might want to look into why. I just started my ro for the first time this morning so I'll taste the permeate when I go back to check on it. With all the weird weather this year it could just have something to do with the ground water your trees are picking up.

[sapman]

Yeah, I think I was being paranoid. Might have been a little stronger than when I concentrated yesterday, but pretty much typical, I guess. I forgot what it tastes like, apparently! The filters were filthy after just the one use.

Thanks,
Tim