Provide your best answer for the following question. Give ONLY the answer, no other words or explanation.
For example:

Answer: <most likely answer, as short as possible; not a complete sentence, just the answer!>.

The question is: Louis Pasteur discovered a process that allows milk to be stored in sealed containers for long periods of time without spoiling. The process, called pasteurization, involves heating the milk before placing it in the sealed containers.Which is the best explanation of how pasteurization works?
Heat killed microorganisms that could cause spoiling.
Heating milk before sealing to kill bacteria.