How long does milk last in insulated cool bags?

[1990shopefulftm]

We want to try taking our son to the local park a 20 minute drive away, as we re in a tier 3 area we d want to make it as simple as possible to feed him outdoors however as we ve got him on comfort milk there's no ready made version.

There seems to be disagreement online as to whether a made up milk lasts 2 hours or 4 hours in a cool bag so unsure what to do.

Its 4 hours if in a cool bag with ice packs

NHS advice:

What if I need to transport a made-up feed?

If it is not possible to follow the advice above, or if you need to transport a feed (for example, to a nursery),prepare the feed at home, cool under a running tap or in a bowl of cold water, and cool it for at least 1 hour in the back of the fridge.

Take it out of the fridge just before you leave and carry it in a cool bag with an ice pack, and use it within 4 hours. If you do not have an ice pack, or access to a fridge, the made-up infant formula must be used within 2 hours.

If made-up formula is stored:

• in a fridge–use within 24 hours
• in a cool bag with an ice pack–use within4 hours
• at room temperature–use within2 hours