https://www.milanomalpensa-airport.com/en/airport/bar-restaurants <-- you can see what the food options in T1 outside of security are

There is also a Carrefour Express on the lower level on the way to the train station/Sheraton.

From my experience, the Sheraton is probably the best quality option without leaving the airport. Alternatively, the Carrefour does provide some picnic type options.