How to spot the "rock hard" mung bean

[MysticTree]

I eat my mung beans only just sprouted and whilst they are usually ok, the packet of seed I have at the moment seems to have a higher than usual amount of un-viable seeds. The result is, if I don't spot and remove them, that they cause almost tooth-breaking moments in the mouth.

I can sift through picking out the ones that look small and hard but I do miss some most times.

Is there an easier way ... and I will not be buying from this source again :(

Georgina