People can help themselves whenever they want it. If they genuinely don't like it that's their problem. Food is food. It's a film set, not a five star restaurant. The flip side to all this is that you want to keep everyone happy, especially if things are quite slow.
Food makes people happy.
The best solution is to persuade someone who you know can cook to make a big bowl of pasta salad, or similar, each night. This costs nothing, and at least it shows a bit of effort. As far as getting free food goes, don't waste the time trying. All the big supermarkets have a simple policy - they have to throw out stuff as soon as it's out of date. The reason is that they can't risk getting sued.