I can completely relate, OP. There are some people I would trust enough to eat their food, but some of it goes straight in the bin and I just pretend I enjoyed it at home. My boss for instance LOVES bringing in food to the office, but she has what I consider appalling standards of food hygiene.
She'll buy a packet of biscuits, then leave the pack open on a table going soft for a week. She will continue to eat them and offer them to people in this condition. It's been years and it never occurs to her to just put them in a bloody biscuit tin. I would never eat bikkies that had been open to the flies and going soft for a week, but she thinks nothing of it!
Also thinks nothing of buying chicken, milk, cream etc for her dinner in the evenings and leaving it to sit out on the counter all day instead of putting it in the fridge. Attributes her constant stomach upsets to "IBS" 
Never covers food when putting in the fridge or microwave either. Fish, eggs, ham, whatever. All just sit there open and stinking to contaminate the food around them. Again, it'd be a two minute job to pop another plate or a bit of cling film on top to prevent cross-contamination, but does she? Never. She'll leave the butter open beside last week's ham and a big uncovered hunk of cheese and beetroot, and then complain the butter tastes funny. Gosh, does it? I can't imagine why . . .
I once made the mistake of alerting her to the fact that the milk she was about to pour on her cereal was two days past the use by. She insisted it was "fine" and she "always does it" and then quite happily poured away! Sour milk in baking is one thing but on your breakfast? 
I haven't been able to keep food in the work fridge for years because of her. I feel nauseous even opening it, it's such a horrible combination of strong overlapping smells.
She's the sort of woman who likes to make fun of others for being "OCD" and insists that "a few germs never did anyone any harm" and that younger generations are being too precious and need to toughen up our immune systems. The fact that she has the runs on a daily basis and keeps a permanent stash of Immodium in her handbag is completely unrelated, of course. I bite my tongue so hard I nearly bloody bite it off sometimes.