The arm reaching into the sink does not add anything to the photo in fact it detracts from the subject ... mechanical machine! Need more action in the photo. Perhaps a low shot with the potatoes streaming out of the holes would have been more dramatic. Good subject but needs work.
I think this photo would be soooo much better if you had left the hand out of the shot. Its a neat devise and looks like it would be interesting with a tight crop. Nice job though.
you've got a few too many elements in your shot -- going for the potato thing as your main subject? bright blue pulls my eye off your subject as does the white grid thing. Suggest creating more of a setup shot to highlight your point (use the device) or object can't really tell too much about it because it's covered in potatoes)
the ricer is certainly mechanical. Would have tried a diffeent composition though getting in closer to the potatoes and excluding the arm. On-camera direct flash creates rather ugly lighting. Perhaps shooting from below as the potato is forced through the ricer would have created a more powerful shot?