Hi - new to this. I have been BF ing my DD for nearly 6 months and in the last week have been switching 1 feed a day to formula. I am using ready made cartons until I know which one she will settle with. If I sterlise a bottle before I go out and assemble it, will it then be sterile to use later when I come to fill it with the ready made milk? If this is not correct, how do you take a bottle out and keep it sterile to use with ready made milk? Thank you all in advance and sorry if this is a daft question.