How to define HTTP header for cached pages in public dir

I want it to be
Content-Type: text/html; charset=utf8

now it is just

Content-Type: text/html;

I know, that it is possible to make Apache (lighttpd,..) responsible
for files in public dir.
But sometimes in different development environments i don't want to
define special assets-host and configure Apache.

So is it possible to define HHTP HEADER rules for files in public dir in rails ?

I use Rails 2.0.1, mongrel.