How do I delicately tell my mum to wash her hands?

Almost every day my mother cooks some meal for my family. It's normal that she's touching the food and all. But sometimes she doesn't wash her hand. Today she was outside with some friends, came back and started cooking and mashing potatoes with a fork and a hand.

I didn't really notice it until like couple months ago but it bothers me a lot now. I wash my hands probably over 6-7 times a day. And every time she's around I'm telling her I'm washing my hands (like a casual remark) but I just hope to get this in her head. I may sound like a jerk, you know, being squeamish but all I can think about is how her hands are all dirty (not obviously cuz she's wash them then of course) and she touches left and right.

Any advice on how to tell her so that she is not offended? I know it's up to the person's personality if she'll feel bad but believe me my mother gets offended all the time for non sense things (like when I eat in front of my PC while watching a movie she instantly thinks I hate her and feel offended??)