There are elements that are free marketish and there are elements that aren't. The ones that aren't have already been noted in the thread, but if you missed them we can start with first principles.
Or instead of playing 20 questions you could be nice enough to point out the posts where the non-free market elements were posted.
Why do free market advocates believe free markets produce good outcomes for society?
Always?
What elements are necessary?
Guns and Fox News.
He who knows only one side of the argument knows neither.
OK, a few quickies:
1) The end customer, prisoners, are not free to contract on their own
2) The end customer, prisoners, are not free to pursue other food sources if they find their current food unsatisfactory
3) The people who enter the contract, government officials, are not going to be the ones eating the food
4) The people who enter the contract, government officials, do not necessarily have the correct incentives to get the highest quality food service
5) The people who enter the contract, government officials, maybe quite happy with food running out or generally sucking so long as the consequences do not stick to them
6) The people who enter the contract, government officials, may just care about hitting some budget number or not care much at all. We don't really know what they care about.
7) The people who oversee the contract, government officials, may not have much incentive or ability to see that the service is being provided at the levels they contracted for.
8) The people who enter and oversee the contract, government officials, are spending other people's money. No takes as much care with another's money as he does with his own.
9) The people who enter and oversee the contract, government officials, are not likely to be held responsible for how they manage this money. Or did you forget to add the link where the government officials people responsible for hiring and managing Aramark were losing their jobs over this?
10) The end customers, prisoners, have little or no recourse if they are unhappy.