params

Hi, I'm building a database and I need to save all the changes users do.
This means that every time something goes to the method update, create
or destroy I have to save some information in another table. That's
fine, the problem is that I need to store all the new information in one
field, and the old information in another.
I tried to do so doing the following:

ModificacionesEmpresa.create(:empresa_id =>@empresa.id, :usuario_id =>
session[:user_id],:tipo => 'U', :tupla_nuevo => params[:empresa].to_s,
:tupla_antiguo => @tupla)

The problem is that neither params[:empresa].to_s nor :tupla_antiguo =>
@tupla
are save as readable information.... I think I might need to do some
kind of method to get everything in one big string... while I do thata,
Anybody have a smarter solution?