I would approach it differently than most of these if you were trying to recruit someone who doesn't have experience in the qaqc of food industry... Are you hoping to get experienced applicants? I came into my position after being a food microbiologist and had to go through SQF and HACCP training so I would not have been able to answer these questions and I would recommend different ones.
I agree; as I came from a food chemistry background prior to joining this side of the food industry. I understood what HACCP was but had no formal training, and I did not know exactly what is entailed in GFSI certification. I knew that it had to be a high tier certification, and I had done some reading, but you don't fully understand until you're actually waist deep in it.
The GFSI related questions are great for someone with more of a food production/QA background.
For applicants who have a somewhat different work history, I'd ask something along the lines of "how can you correlate your previous position(s) with this one? What can you bring to the QA Manager position here?" "If you're working on Project A (a complex project), and someone calls you about Project B (in which the deadline is tomorrow), and you have to deal with an issue on the floor, what would you do first?" or "If you have two tasks you're working on, and you feel you may not be able to meet a deadline for one or both, what would you do?"
For applicants with the QA work history in food, I totally like the GFSI related questions. I also like the questioning related to company culture change. I've also been asked scenario-based questions about working with someone you may not agree with; like Martha discussed above. You end up sort of role playing with the applicant, and that can show you a lot about the applicant in a short time. As far as asking questions about multi-tasking, most anyone who works in Quality has the proper skill set. A question to ask is "If/When hired, what would be your process to get acclimated?" A lot of hiring managers want to know whether you will meet with the team and learn what each person does, or if you want to jump right in without getting a good understanding first. Another question would be: "How do you plan on communicating with supervisors and necessary individuals about issues, projects, etc.?"
As far as the management portion: "What does it take to be a good manager?" "What do you do in the event one of your employees is not doing their job properly?"