I have been siphoning off the juice from my fresh caught beaver and using it to catch more beaver but I notice that it taints after a couple of days and doesn't work very well at all. What would be the better preservative to keep that fresh castor smell going?

Works great when it is fresh.

I'm wondering whether sodium benzoate or methyl paraben would be candidates?

Vodka

MP is mold retardant

I wonder if citric acid would stabilize the stuff? It certainly would bring the pH way down.

Freeze It and thaw as needed.

I think you may be talking about sac oil ? Castor does not go bad , or at least I’ve not seen it go bad over a three year period. Sac oil gets rancid in short order .

I have never had sac oil good bad unless it was blood contaminated or with some other bacteria. Have had some for 15-20 years now Just as good as fresh. It can separate over time if sitting in a jar or bottle for a long period. Just shake it and it mixes quickly.

What Beav said.

Well there must be something different when you actually milk a beaver at a set. Since that fluid that comes out Isn't In the oil form it's more like water. It must be a mixture of oil and urine. But I'm only guessing.

Bob I haven’t ever separated the oil from the sac . I make a coyote bait / lure from it and use the oil and sacs together, gets a rancid smell very quickly. Did not realize the oil would keep if separated, thanks !

I will remove the oil from the sacs then let the empty oil sacs taint a bit and use them as bait/lure.

Most any tissue/meat or membrane is prone to spoilage in the right temp conditions. Oil alone should not sour or degrade if it is pure.

I’ve seen this stuff look like an oil and I’ve seen it very runny . Would it be safe to assume the runny version should not be mixed in with the thicker oil ?

If you're referring to the sac oil, the females tend to have a real light runny oil and the males tend to have more of a pasty oil.

Rub that oil into your leather boots real good.It will make them waterproof and you'll be like the pie eyed piper,all the animals will follow you around.
A sucessful trapper takes on the stink of the animals he's catching.

Remind me not to ride far with you Boco , lol . Paul do you keep the two separate when using on beaver sets ?

I tried using them separately and noticed no difference in their effectiveness.

Just kidding Boco, thank you Paul.