Devotees make an offering of food to the Lord and later partake of it as prasaada - a holy gift from the Lord.

All that you do, all that you eat, all that you offer and give away, as well as all austerities that you may perform, should be done as an offering unto Me.” Bhagwat Geeta. So offering what we eat to the Lord is an integral part of bhakti-yoga and makes the food blessed with spiritual potencies. 
"Patram Pushpam Phalam Toyam Yo Me Bhaktya Prayacchati, Tadaham Bhaktyupahritamasanami Prayatatmanah" 
Whoever offers a leaf, a flower, a fruit or even water with devotion, that I accept, offered as it is with a loving heart". Thus, we can see that the Lord does not need anything, but if one offers fruits, grains, and vegetarian foods, He will accept it.
Indians make an offering of food to the Lord and later partake of it as prasaada - a holy gift from the Lord. What we offer to God is Naivedyam. When it comes back to us, it becomes Prasada. Literally, a gracious gift. The prasad has the deity's blessing residing within it. To most of us, prasada means something edible and that is all. But the real meaning of prasada is “purity, cheerfulness, bliss, joy, peace”. This is our true gain upon tuning our minds with the Lord during the worship. The real prasada is the feeling of peace we experience in our hearts while looking at the idol of the Lord after we have performed our daily puja with love and devotion. Experiencing the peace and joy is how we tune our minds to the Lord. There is a Bhavana, an attitude involved in it. This attitude is born of the vision of God. Prasada is not an object. It is purely born of understanding. The understanding of the reality is the basis for prasada. In its material sense, prasada is created by a process of giving and receiving between a human devotee and the divine god. A flower accepted for one’s sense gratification is material, but when the same flower is offered to the Supreme by a devotee, it is spiritual. Food taken and cooked for oneself is material, but food cooked for the Supreme Lord is spiritual prasäda. This means the mercy of the Lord. Thus, the food we eat after it is offered to the Lord becomes a means for our purification and spiritual development.
This is the appreciation of God. We accept that God is the author of the result of our actions. The result thus becomes prasada since it comes from God. Thus result of every action must be looked upon as prasada from the Lord. So we have to be alive to the reality of our being the doer of action and God being the giver of the result. Therefore, even if I do not get what I expected, I still accept the result as prasada and having become wiser, work harder. A person ultimately becomes wiser by the attitude of prasada. We welcome whatever comes to us and our whole life becomes a learning experience. Thus we arrive at the meaning of prasada as the cheerful acceptance of the situation as it comes to me. Thus prasada-buddhi becomes the attitude of glad acceptance. Anything that comes from the Lord is Grace or Prasada. Let us learn to look upon the results of out actions given to me by the Lord as prasada.
Food is a gift from God, it should be treated with great respect. Traditional Hindus offer food to God mentally before eating. “The devotees of the Lord are released from all kinds of sin because they eat food, which is offered first for sacrifice. Others, who prepare food for personal sense enjoyment, verily eat only sin” Bhagwat Geeta. 
Om Namah Shivaya ~ Jai Shri Mahakal!