Mixing 2 different expressed bottles?

[Novia]

Hi - just wondered if anyone could advise me please...?

I expressed 2oz of breast milk today, but didn't have time to do more. I want to add another 3oz tomorrow so my DH can feed the baby at lunchtime.

The first 2oz is in the fridge. Can I just express more into that bottle tomorrow morning? Or if not, can I express separately, cool it and then combine them? Are there any risks around this I should know about?

Thanks in advance for any help!

This Kellymom article on breastmilk storage suggests that it's best to cool the milk you're adding before combining with the milk in the fridge.

When I express I cool each batch before mixing together. Read somewhere that you shouldn't mix room temp milk with chilled, but not sure why!!