"The word apavitra anna refers to food that is unacceptable for a Vaisnava. In other words, a Vaisnava cannot accept any food offered by an avaisnava in the name of maha-prasada. This should be a principle for all Vaisnavas. When asked, "What is the behavior of a Vaisnava?" Sri Caitanya Mahaprabhu replied, "A Vaisnava must avoid the company of an avaisnava [asat]." The word asat refers to an avaisnava, that is, one who is not a Vaisnava. Asat-sanga-tyaga,--ei vaisnava-acara (Cc. Madhya 22.87). A Vaisnava must be very strict in this respect and should not at all cooperate with an avaisnava. If an avaisnava offers food in the name of maha-prasada, it should not be accepted. Such food cannot be prasada because an avaisnava cannot offer anything to the Lord. Sometimes preachers in the Krsna consciousness movement have to accept food in a home where the householder is an avaisnava; however, if this food is offered to the Deity, it can be taken. Ordinary food cooked by an avaisnava should not be accepted by a Vaisnava. Even if an avaisnava cooks food without fault, he cannot offer it to Lord Visnu, and it cannot be accepted as maha-prasada. According to Lord Krsna in the Bhagavad-gita (9.26): patram puspam phalam toyam yo me bhaktya prayacchati tad aham bhakty-upahrtam asnami prayatatmanah "If one offers Me with love and devotion a leaf, a flower, a fruit or water, I will accept it." Krsna can accept anything offered by His devotee with devotion. An avaisnava may be a vegetarian and a very clean cook, but because he cannot offer the food he cooks to Visnu, it cannot be accepted as maha-prasada. It is better that a Vaisnava abandon such food as untouchable." Caitanya-caritamrta, Madhya lila 9:53 Purport

In Vedic culture and Vaisnava sastra, we find many references to the protocol one should follow when preparing bhoga, offering foodstuffs to the Lord, and taking Krsna prasadam. These regulations establish how prasada should be handled for both home and temple worship. Srila Prabhupada gave instructions as to how these rules should apply for present time, place and circumstance. For example, he explained how prasada should be handled for those living under shelter of the temples.

Srila Prabhupada provided a great deal of instruction and purport on Vaisnava literatures which explicitly detail how offerings are to be made to the Deities in the temple, and the prasada protocol related thereto. For example, Srila Prabhupada instructed that only twice initiated brahmana disciples were to cook in the temple. Non-brahmanas were permitted to assist, but could not themselves cook. Preparations produced by non-devotees are not to be offered to the Deities, and this regulation should extend, to the greatest degree possible, to ingredients purchased in karmi stores. At the same time, Srila Prabhupada always emphasized a common sense approach to regulative practices. For example, while regulations require fasting for Ekadasi and the observance of various religious and festival events, Srila Prabhupada instructed that one should not allow such practices to interfere with devotional service:

Devotee: You said that if we fast and we can't do our work and we become weak, than this is not so good. Prabhupada: This is not good, "not so" not, absolutely bad. Devotee: So, our devotional service comes first?
Prabhupada: Yes.
Devotee: So if there is, let us say there is grain and rice being offered to the Deities, and one finds that if he eats this, his service is impaired. Like so many times I've seen, practically myself if I overeat grains in the summertime, I drive around doing my service and I'm falling asleep.
Prabhupada: Then which foodstuff suits you?
Devotee: Fruits are more... they keep me more active.
Prabhupada: So you take fruit. Fruit is also offered to the Deity. There are varieties of prasadam. So whichever suits, you can take. Anything artificial is bad.

Srila Prabhupada Morning Walk, 07-01-75, Denver

A great deal of prasada protocol is given within the context of the Varnasrama system, which regulates right living for the varnas and asramas. Different rules are given for those who are brahmana, ksatriya, vaisya, and sudra, each according to their unique station in society. While the pure varnas and asramas do not exist in the age of Kali yuga, these designations are still somewhat delineated amongst those strictly following the path of Bhakti yoga. Grhasthas (householders) are expected to take a practical approach to prasadam for one engaged in family life, whereas one in the renounced order follows a different protocol. For example, a person in the renounced order of life should not cook for himself, but is permitted to cook for the Supreme Lord. A sannyasi may take prasada at the house of a grhastha, and a brahmacari helps in this connection, given that a sannyasi is supposed to be a spiritual master and a brahmacari his disciple. The husband provides for his family, and the wife offers him service, not as a servant, but so that husband and wife work together in a way that encourages spiritual advancement.

"Although she was not accustomed to such difficulties, Queen Arci followed her husband in the regulative principles of living in the forest like great sages. She lay down on the ground and ate only fruits, flowers and leaves, and because she was not fit for these activities, she became frail and thin. Yet because of the pleasure she derived in serving her husband, she did not feel any difficulties.

Purport: The words bhartur vrata-dharma-nisthaya indicate that a woman's duty, or religious principle, is to serve her husband in all conditions. In Vedic civilization a man is taught from the beginning of his life to become a brahmacari, then an ideal grhastha, then vanaprastha, then sannyasi, and the wife is taught just to follow the husband strictly in all conditions of life. After the period of brahmacarya, a man accepts a householder's life, and the woman is also taught by her parents to be a chaste wife. Thus when a girl and boy are united, both are trained for a life dedicated to a higher purpose. The boy is trained to execute his duty in accordance with the higher purpose of life, and the girl is trained to follow him. The chaste wife's duty is to keep her husband pleased in householder life in all respects, and when the husband retires from family life, she is to go to the forest and adopt the life of vanaprastha, or vana-vasi. At that time the wife is to follow her husband and take care of him, just as she took care of him in householder life. But when the husband takes the renounced order of life, namely sannyasa, the wife is to return home and become a saintly woman, setting an example for her children and daughters-in-law and showing them how to live a life of austerity.

When Caitanya Mahaprabhu took sannyasa, His wife, Visnupriyadevi, although only sixteen years old, also took the vow of austerity due to her husband's leaving home. She chanted her beads, and after finishing one round, she collected one grain of rice. In this way, as many rounds as she chanted, she would receive the same number of rice grains and then cook them and so take prasada. This is called austerity. Even today in India, widows or women whose husbands have taken sannyasa follow the principles of austerity, even though they live with their children. Prthu Maharaja's wife, Arci, was steadily determined to execute the duty of a wife, and while her husband was in the forest, she followed him in eating only fruits and leaves and lying down on the ground. Since a woman's body is considerably more delicate than a man's, Queen Arci became very frail and thin, parikarsita. When one engages in austerities, his body generally becomes lean and thin. Becoming fat is not a very good qualification in spiritual life because a person who is engaged in spiritual life must reduce the comforts of the body--namely eating, sleeping and mating--to a minimum. Although Queen Arci became very thin from living in the forest according to regulative principles, she was not unhappy, for she was enjoying the honor of serving her great husband."

Srimad-Bhagavatam 4:23:20

"A sannyasi should be completely detached from fire and any residential quarters. A grhastha has a relationship with fire, either for offering sacrifices or for cooking, but a sannyasi is freed from these two responsibilities. He does not have to cook or offer fire for sacrifice because he is always engaged in Krsna consciousness; therefore he has already accomplished all ritualistic performances of religion. Aniketanah means "without lodging." He should not have his own house, but should depend completely on the Supreme Lord for his food and lodging. He should travel."

Srimad-Bhagavatam 3:24:42 Purport

"After the grhastha-asrama is another asrama, known as vanaprastha, which is midway between grhastha and sannyasa. A person in the vanaprastha order is restricted in eating food grains and forbidden to eat fruits that have not ripened on the tree. Nor should he cook food with fire, although he is allowed to eat caru, grains that have been offered in a sacrificial fire. He may also eat fruits and grains that have grown naturally. Living in a thatched cottage, the vanaprastha should endure all kinds of heat and cold. He should not cut his nails or hair, and he should give up cleaning his body and teeth. He should wear tree bark, accept a danda, and practice life in the forest, taking a vow to live there for twelve years, eight years, four years, two years or at least one year. At last, when because of old age he can no longer perform the activities of a vanaprastha, he should gradually stop everything and in this way give up his body."

Srimad-Bhagavatam 7:12 Summary

Bhaktivedanta Book Trust. HDG A.C. Bhaktivedanta Swami Srila Prabhupada.