I think the answer is
Faucet
(- tough one to come up with coming from europe where we call them taps)
The prefix allows you to eat what is old.
Thaw out frozen food... sounds like Fau
The suffix will make you think it is cold.
cet.... maybe like set - when a jam or jelly is made (fruit preserve) it should 'set' when it is cold (it has cooled down).
The infix is metal, as chemists should know.
Ce - atomic symbol for Cerium, one of the Actinide metals if I remember correctly.
Alternatively, the middle of the word sounds like 'ore' which is a mineral containing a metal.
Alternatively, Au = gold.
Together they are controlling the flow.
A Faucet (or tap) controls the flow of water from a pipe - or other liquid, or gas...