I have just been overseas (last month).. This is done just after immigration, so is the same for all airlines, but if you get a nasty security officer they may make you taste it, however tell then what you have for baby, and it should be fine..

Do not take any liquid except what is necessary on the plane cause you will be asked to get rid of it (i.e deodorants, skincare etc).. Duty free will need to be bought once through security checkpoints..

Leaving Brisbane wasn't an issue, we had 3x200 mls bottle cows milk, and a sippy cup of water, and some anchovies.. All were fine and didn't have to test any of them.

Coming back from Christchurch, we weren't allowed to take water through. You could take the empty bottle and fill it up once through (not sure if this was the same for water steralised for formula though as ours was just a sippy cup). We also had cows milk. The girl at the check in looked ever so horrified and said that we would have to sample it.. No big deal on our part, but we just told security what we had, they X-rayed it and all was good, also having a child with you is also a giveaway that you might need to feed them, LOL..

They have to give you the worst possible case of what might happen. Each airline has their own guidlines, but this check is done just after immigration and the security staff don't check to see where you are going..