add_action( 'wpcf7_init', 'yoursite_cf7_new_shortcode',20 );
function yoursite_cf7_new_shortcode() {
    wpcf7_add_shortcode( 'yourshortcode', 'your_site_cf7_new_shortcode_handler' );
}

function your_site_cf7_new_shortcode_handler( $tag ) {
	return '<input type="hidden" value="'. esc_attr(get_field("title")) .  '"/>';
}