I expect that to some nurseries 'prepared from fresh' means tin immediately emptied into microwave and Angel Delight not prepared in advance. I try not to think what dd is getting and as someone else said, it's not forever and you give good food at home. however, I wouldn't be worried about taking it up with them.
I would be extremely unimpressed with my child being fed the worst sort of synthetic crap, which includes hydrogenated oils which are strongly associated with a risk of lifelong obesity and other horrors. And tinned spaghetti ffs. I wouldn't eat this crap and I wouldn't want my children eating it. Complain vigorously and tell them this:
Top nutritionists at Harvard have stated as follows:
"By our most conservative estimate, replacement of partially hydrogenated fat in the U.S. diet with natural unhydrogenated vegetable oils would prevent approximately 30,000 premature coronary deaths per year, and epidemiologic evidence suggests this number is closer to 100,000 premature deaths annually."
i wouldn't object to the odd portion of spaghetti hoops, so long as the greater proportion of what was offered was fresh and healthy. though am raising eyebrows somewhat at the angel delight (what's wrong with yoghurt fgs?).
that said i really fancy a bowl of butterscotch angel delight right now [hormonal pregnant emoticon] can't have had any of that since 1981
I would ask for a menu from them and then check that they are getting what they say they are.
Tbh I think most nurseries give kids more processed foods than they either let on or than people are generally happy with. Dd1 had more ham sandwiches than I was comfortable with (like most days for tea ) and too many puddings/buns and not enough fruit. However I took the view that she got a good diet at home and it wasn't for ever - she is 9 now and eats a very healthy diet very happily. It's not done her any long term harm.