I would use "The food has been in the fridge for a long time. Don't eat it/It's inedible". A better idea would be to throw the food away so no one is tempted to eat it! Of course, there are lots of foodstuffs which can remain in the fridge for a long time and still be edible.
At least the tense is incorrect, because the present continuous does not agree with 'a long time ago'.
You may consult a dictionary to see the correct usage of 'save'.