Force UTF-8 for description html please

Hello,

Sometimes, some data seems not with utf-8, and in this case, Google shopping will refuse the feeds, and it will show some warning:

Encoding problem in attribute: description:
Some of the characters in your items seem to be invalid. Please verify all the characters in your feed are valid for your selected encoding.
Below are some example items that are affected by this issue.

Screenshot: http://prntscr.com/rre0rd

If copy the description info into a text editor, This kind of characters will show up:” ”.

Thanks