This is exciting! I added 360 mg of ethylvanillin powder (which should equate in strength to about 1.8 g of “normal” (methyl) vanillin powder) to 2 L of Soylent 1.4 and it eradicated the taste. It doesn’t even have a strong vanilla flavor. It’s more, day I say it, neutral. I think vanillin may have been the key masking flavor for the people who liked 1.0-1.3 but don’t like 1.4 or 1.5; sunflower oil was drastically reduced from 1.4 to 1.5, so that can’t be the whole story.
I also added extra sucralose (1/64 tsp), so what I ended up with tastes a lot like a melted vanilla milkshake. Probably not quite that sweet, but sweeter than I wanted. Next time I’ll try adding vanillin without any extra sweetener to see how that turns out.
I had previously only experimented with much smaller amounts of vanillin. If you experiment with a single serving, which is smarter than what I did, I’d keep adding it until the offensive flavor is undetectable. If you keep track of how much you add, then it should be easy to scale it up to a whole pitcher.
I’ve got about two boxes of 1.4 left, so I’ll probably sacrifice a few bags to experiment with different vanillin blends.
Edit: I’m halfway through the pitcher and 360 mg is too much per pitcher, for me at least. I find myself missing plain old 1.4.