Divi shop loop subtitle

I am using Divi with Woocommerce for a bookshop and would like to add the name of the author as a subtitle for each book product in the Divi Shop module. However, I cannot seem to get the PHP code right (new to it). What am I doing wrong?

Code:

function woocommerce_shop_loop_item_subtitle() {
global $product;
echo '<p class="add_author_name">' . get_the_terms($product->ID, 'product_cat', true) . '</p>';
}
add_action( 'woocommerce_shop_loop_item_title', 'woocommerce_shop_loop_item_subtitle', 10 );