I'm not hard and fast "sold" on most bait scents, especially the oils that get cooked into the plastics we use. Baits that get scent applied to them or are in bags having scent added to them are more effective if they work at all. I use an anise oil in my plastics when I sell any but only because I think that customers are so engrained with the scent idea doing more than it actually does. Then enter a few baits that I think work....due to chemistry.
Berkley of Spirit Lake Iowa has done, what I consider, a superb job of chemically enhancing and tweaking things to make plastics perform better for the angler in their PowerBait and Gulp products. There are a couple other product lines that do well too, but Berkley has always been at the forefront of this business and I honestly feel that they research what they claim thoroughly before making claims. What I describe doing with my own baits in the Gulp juice is as much research as I have put into the matter, however I do pay attention to whether little trials like this do better, worse, or stay the same when it comes to use in my crappie plastics and I do feel that the plastics being soaked in the Gulp juice have an edge IF at the time Gulp is what the fish want. I do similar things with PowerBait and my plastics by placing my walleye plastics in freshly opened packages of PowerBait of similar colors then re-sealing and let set for a month at least and I have noticed similar positive results. PowerBait will not opaque a bait like Gulp will, but I haven't seen where the fish mind a clouded bait at all since the factory stuff is far from transparent.
Why the PowerBait and Gulp work in my opinion is because Berkley has been able to chemically replicate either feeding pheromones or fear pheromones given off by forage fish that prey fish can sense thru smell, taste or lateral line. In order for that to work with a fish the scent has to be water soluble because fish live in what? Both of these products will go to pot if the packaging is left open to air exposure, with the Gulp being the king-pin of misery should it dry out.....especially on a hook or jig. Granted, neither of these products will be a preferred bait by the fish all the time, but they certainly have proven themselves to me by working even when bait falls flat on its face. The Gulp juice can be purchased on a spray bottle for topical use while fishing. I buy a couple of these a year and use the juice to recharge my individual bottles. There's plenty of room in those tubs of Gulp minnow that walleye anglers would use to put in a pile of plastics in colors walleye like. I'd do it a month ahead of a planned trip and I'd save any juice left upon return or taken out to make room for more plastic. I'd bet you a donut that doing this will open your eyes a little.