Your space prison will suffer some permanent food supply problems!

Every in-game day, your prison kitchen will receive 20 ingredients for free at 4:30 PM. Those will be divided into 10 rations in the morning and 10 in the evening. So you will be able to feed only 10 inmates with this food. You can permanently check your ingredients left in the description window of your kitchen (wheat spike icon).

You should be able to generate your own food in Space Cooler. You must unlock your Garden Workshop as soon as you can afford it! It will work as all prison workshops, so you will need to hire workshop managers and prisoners will collect the ingredients during the workshop in-game time (3:30 - 9:00 PM).

Upgrade the garden workshop to optimize this feature (reducing harvest times and increasing your ingredient supplies). You could check how the wheat spike icon in your kitchen will grow while you prisoners are working in the garden. Your leftover food will expire every day if it is not used.