Prasadam: Honoring Prasadam

                                                                  Q. I was wondering if you could help me understand something. Could you please explain the exchange of karma/bhakti involved when you take someone's remnants? Could you explain the following scenarios if there is a difference...

                                                                  1) Taking the remnants of a pure devotee - do you get the bhakti of the pure devotee and does the pure devotee get some of your karma?

                                                                  Q: Narada accepted remnants of food left behind by the Bhaktivedantas and just by that act, he was completely purified from all sins. In general, eating remnants of food is considered to be in the mode of ignorance. So what is it that which makes the remnants of prasad of spiritual master or uttama adhikari devotees so special that it removes all kinds of sins? In other words, how does it work and what are some scriptural references that further corroborate this? Is it that by accepting the remnants, one is taking a humble position and thereby able to receive knowledge from the spiritual master?
                                                                  Please see Digest 233 for the answer.

                                                                  Q. 1. If prasadam is spiritual why does it decay like normal food does in a day or so?