Sorry for my late reply,
I would carry food items especially liquid stuffs like juice, milk etc in addition to this I'll also prefer to carry beaf as well.
I think we may need a bit more information if you are planning to carry enough food for 5-6 days!
Is the juice & milk fresh(raw), pasteurised or UHT?- only UHT will be safe for 5-6 days if kept unopened in original container
Cooked beef should be kept below 8 degrees celsius to slow down growth of pathogens (afetr 4hrs or so at room temp- I wouldn't eat it never mind 5 days!)
You can get cool boxes that claim to maintain tempo using ice packs for up to 48hrs as long as you don't open the lid too many times- or 12v one's which plug into your car lighter socket and are good for as long as they are plugged in
Also are you travelling to a different country- at many border crossings you will be told to dispose of any food you are carrying anyway!