The main enzyme in saliva as far as I know is ptyalin or salivary amylase. It is inactivated as soon as it gets to the stomach. That suggests that its real job is just to clean your teeth of starch that might encourage bacterial growth and plaque or caries. I am pretty sure that is has no use in digesting food as such.
I thought the fact that bread tastes sweet if you much on it for a long time was proof that amylase has this effect? I guess the question then is how long we should be chewing our food for.