[jQuery] client side serialize issue

Hi folks hope I someone can helps with something simple

In my rails project I have a jquery connected sortable that current
sends updates to a hidden field using ajax

$(function() {
$("#sortable1, #sortable2").sortable({
connectWith: '.connectedSortable',

update:function(){
$.ajax({
data:$(this).sortable('serialize',{
key:'clients[]'
}),
dataType:'script',
type:'post',
url:'/users/selected_clients'
})
}
})
});

the above code produces {"selected_clients"=>"89,46"} . However
updating a hidden field with data from a sortable element is something
I would prefer done on the client side, so I came up with this:

$(function() {
$("#sortable1, #sortable2").sortable({

connectWith: '.connectedSortable',
update:function(){
var selected_clients = $(this).sortable('serialize',{
key:'clients[]'
});
$('#selected_clients').val(selected_clients)
}
})
});

Although this does update the hidden field the value is formatted as
{clients[]=89&clients[]=46" }, which is too messy. I would like the
results to make that of the ajax serialized data. How might I fix
this?

Thanks for your help,

Josh