How to remove parent taxonomy name from the title generated by wp_title()?

Hi @Edward:

This is not a generic solution but will probably solve your needs. If you want to get rid of the '| Portfolio Categories' from your site’s title just hook the 'wp_title' filter in your theme’s functions.php file and remove that from the title string. Copy this code to the bottom of that file and modify as need be:

add_filter('wp_title','your_wp_title');
function your_wp_title($title) {
  $title = str_replace('| Portfolio Categories','',$title);
  return $title;
}