There are enough programs, even free, which do what you want. Usually, these are picture managers which allow you to select the files/directories to process and what processing/conversion to do for them.

For example the procedure for the XnView (freeware) is as following:

• select the desired files directories.
• go to Tools > Batch Processing...
• on the first tab of the Batch Processing window (the 'General' tab) set the destination directory (if you don't want to have your files overwritten) and the output format if you want to change it.
• on the second tab (the Transformations tab) select from the List of Available Transformations the Auto Crop feature and click Add to add it to the list of the active transformations on the left. On the Parameters panel at bottom you will choose your desired color (white). Alternatively, if your images must be cropped at exactly same size and offset there is another option (transformation) which will work, perhaps, better.
• press the Go button and check at the end your destination folder if everything went ok.

The entire process is much simpler than it sounds.