Do not worry about finding 5 different food buffs in a single level until you get the Corruption Card: Ravenous at the beginning of a level. Ravenous forces a hunger status on the Cleaners and every 15 seconds you either take or heal 1 Trauma. To make this fair, food items are placed EVERYWHERE. It would be more impressive to finish a level and not get this achievement, somehow.
Seriously, don't worry about it if Ravenous isn't on. For me, I went a couple levels triple-checking everything and got 4 food items at most. The third level had Ravenous on, and I picked up:
39x Green Beans
34x Cereal
40x Peaches
37x Peanut Butter
43x Power/Protein Bars
You can't miss it with Ravenous on.
Ravenous can appear as early as the 1st mission on Act 5. I haven't tested it on non-DLC missions.