I just harvested some scallions from the garden, where it's getting bit chilly (late November in Seattle).
After chopping them, I realized that their insides were covered in a gelatinous, slippery, viscous goo!
What is it? Is it safe to eat?
Normally, people associate slime with "inedible" because some bacterial colonies can build up slime on spoiled food. But there are plants which naturally produce slime, and it is as edible as any other part of the same plant. Slimes are most common in algae, but I have also seen them in other plants such as hyacinth greens, and scallions have it too, although in normally not that much. But if you mash a "dry" scallion or the greens of a typical yellow onion, they still feel slimy, while other alliums become slimy on cooking, for example leeks.
Physically, slime is just a special kind of gel. As long as it is not of bacterial origin, it is not a sign of spoilage, and it is highly improbable that a living green plant without signs of sickness will be full of colonies of spoilage bacteria. So, I would declare it good to eat.
I found an interesting discussion on the subject that is more anecdotal than hard facts but the consensus is that if the onions are fresh and not wilted or obviously spoiled, the goo is normal and edible, albeit a bit gross, and you can try just rinsing them thoroughly.