they will 搜行李, when there is any thing can not be seen under x-ray.
I remember that time, one of our BK mom moved back to hk, she has the cooker inside the lugguage which made by metal, the officer opened the lugguage and took everything out (from the cooker) as they can't see inside.
Just bear in mind they will do it, all powder formula better be sealed not opened before. there will be less trouble.
Also, as I said before in another forum, check if the airline or the travel agency you got your air ticket, ask them about the formula inflight. can you carry powder formula or better have th sealed ready to use bottle.