How do I store mandolins-sliced yams two days before baking?

I wouldn't brine them, since that might interfere with the recipe, and they don't need softening. I would keep them in a bowl in the fridge, covered with an inch of water and plenty of ice. Every couple hours, when the ice melts and water evaporates, drain some water and refresh the ice/water to 1 inch above the potatoes.

If they are paper thin slices from your mandoline, you might be better off making the dish right away and freezing it.

i sliced too many yukon golds for my potatoes au gratin and didn't want to waste them. i put them in some salty water (basically brined them) in the fridge and 36 hours later i fried them up for brunch and they were fine and not salty. try that.

Thank you so much!

How do you plan to cook them? Five days is a long time for sliced veg. I would probably peel them ahead of time and store in the fridge in a bowl tightly sealed with plastic wrap. Then on day 5 it would take very little time to slice 5 pounds of sweet potatoes on a mandoline. If you put them in water, they may be very soggy five days later. If you just refrigerate them, they will probably dry out. If you are making a puree or soup, it doesn't matter much, but if you mean to sauté them or roast them its tricky.

I don't think they brown, but I have not stored them longer than one day. I sliced them, layed them on a cookie sheet on paper towels and wrapped the sheet pan tightly with plastic wrap and stored them in my fridge until the next day. I have known people to store them in water, but I am not sure it's necessary.