no such thing as too much "starch", not sure why you think they didn't "particularly like it", altho' I assume you think it didn't 'disappear' fast enough

ANY organic material makes for good worm feed, providing it's in a form that readily becomes microbially active, because it's really the microbes the worms are eating, but a clump of mashed potato might take awhile because it'd be too dense [low oxygen] for the bacteria to work on

all food waste is made of the basics carbon and nitrogen - what you think of as 'starch' is simply something with higher carbon content [carbohydrates], slightly more complex sugars than found in fruit ... fruit [especially melons] gets microbially active faster than most other food waste, so disapears [decomposes] faster

no need to cook up the rice, it'll decompose raw, or you could soak it awhile to speed it up, but anything will work in time, overall quantity determining how fast the given population can deal with it

Bill

Thanks Bill. I was sorely tempted just to put some rice raw in the bin, but wasn't sure. You've confirmed my thoughts that I can; or I will at least cook it to soften. I guess the mashed potato isn't breaking down fast enough, I see it all the time. So they will eat it in time....

Sherry