Google News Keywords, one category only

add_action( 'wp_head', 'thsp_add_google_news_keyword_meta' );
function thsp_add_google_news_keyword_meta() {

    global $post;

    if( is_single() && in_category( 'news-category' ) ) {

        $thsp_post_tags = wp_get_post_tags( $post->ID );
            // Check if post has tags
            if ( !empty( $thsp_post_tags ) ) {

            $thsp_tags_list = '';
            foreach( $thsp_post_tags as $thsp_post_tag ) {
                $thsp_tags_list .= $thsp_post_tag->name . ', ';
            }

            // Insert the meta tag, remove comma and space at the end
            echo '<meta name="news_keywords" content="' . substr( $thsp_tags_list, 0, -2 ) . '">';
        }
    }

}