Hmm. What you're trying to do is complicated a bit by the fact you can assign a post to multiple categories. Anyway, this bit of code (placed in your template before <title>) will scrape up the first (or only) category:
<?php if(is_single()) {
$post = $wp_query->post;
$categories = get_the_category($post->ID);
$cat_title = $categories[0]->cat_name;
} ?>
You may need to modify $cat_title= to incorporate ">" and whatnot. To display the category:
<?php echo $cat_title; ?>
Note that if you use multiple categories and wanted to display each, you could assign the category names to an array:
<?php if(is_single()) {
$post = $wp_query->post;
$cat_titles = array();
$categories = get_the_category($post->ID);
foreach($categories as $category) {
$cat_titles = $category->cat_name;
}
} ?>
Then to display you could loop them in a foreach().