Srila Prabhupada writes, "As far as the eatables are concerned, all items should be first-class preparations. There should be first-class rice, dal, fruit, sweet rice, vegetables, and a variety of foods to be sucked, drunk, and chewed. All the eatables offered to the deities should be extraordinarily excellent."
Food items that can be offered
The Hari-bhakti-vilasa lists some of the foods that may be offered: bilva, amalaki, dates, coconut, jackfruit, grapes, tala fruit, lotus root, leafy vegetables, cowmilk products, and items made from grains, ghee, and sugar. Grains, especially rice, should always be offered with ghee. Rice without ghee is considered asuric. The Lord is pleased when offered items made with ghee, sugar, yogurt, guda (jaggery), and honey; chickpea preparations, dals, soups (wet sabjis), varieties of cakes, and other items that can be licked, chewed, sucked, or drunk are all pleasing as well. One may also offer drinks such as sugarcane juice, yogurt drinks, sweetened lemon water, water flavored with cinnamon, camphor, or cardamom, and fruit drinks of various scents and colors. Many passages in the Caitanya-caritamrta describe preparations that please Krsna. Here is a sample, describing what Lord Caitanya’s associates would prepare for Him, "They offered [Him] pungent preparations made with black pepper, sweet-and-sour preparations, ginger, salty preparations, limes, milk, yogurt, cheese, two or four kinds of spinach, soup made with bitter melon [sukta], eggplant mixed with nimba flowers, and fried patola." In a letter Srila Prabhupada described foods in the mode of goodness and how to present them to the Lord, "Foodstuffs in the modes of goodness are wheat, rice, pulse (beans, peas), sugar, honey, butter, and all milk preparations, vegetables, flowers, fruits, grains. So these foods can be offered in any shape, but prepared in various ways by the intelligence of the devotees." In Caitanya-caritamrta, Srila Prabhupada describes the best type of rice for deity offerings, "In India sukla-caval (white rice) is also called atapa-caval, or rice that has not been boiled before being threshed. Another kind of rice, called siddha-caval (brown rice), is boiled before being threshed. Generally, first-class fine white rice is required for offerings to the deity." A devotee may offer bona fide foods considered delicacies by the local people or preferred by him or his family. In commenting on a sloka stating that one may offer his own or local favorites, Sanatana Gosvami writes that this means that even though people in general may not like a certain food, if a person prefers it he may offer it. But this refers to foods the scriptures approves, not those they forbid. Thus if one is fond of a forbidden food, one cannot offer it to the Lord. And thus one cannot eat it. Also, one should not offer even permissible foods that are tasteless, unpalatable, inedible, impure for any reason, or eaten by insects, animals, or people. If nothing else offerable is available, one may offer fruit alone. If even fruit is unavailable, one may offer pure water while meditating on offering elaborate preparations. If even water is unavailable, one should at least mentally make an offering of food.
Food items that can not be offered
Common forbidden foods include meat, fish, eggs, onions, mushrooms, garlic, masur-dal (red lentils), burned rice, white eggplant, hemp (marijuana), citron, saps from trees (if not boiled first), buffalo and goat milk products, and milk with salt in it. Also, one should not offer canned or frozen foods to the deity, and it is best to avoid offering foods containing unhealthy substances such as yeast and white sugar. Srila Prabhupada makes following comments, “Frozen means nasty. I never take frozen…. All rotten, rather the same vegetable, as we have got in India practice, we dry it and keep it. That is tasteful. So far the cucumber pickles: As far as possible we should not offer to the deity things which are prepared by nondevotees. We can accept from them raw fruits, grains, or similar raw things. So far cooking and preparing, that should be strictly limited to the initiated devotees. And aside from this, vinegar is not good; it is tamasic, in the darkness, nasty food. Concerning the use of sour cream in the temple, it should be stopped immediately. Nothing should be offered to the Deities which is purchased in the stores. Things produced by the karmis should not be offered to Radha-Krishna. Icecream, if you can prepare, is O.K., but not otherwise. Unpolished rice which looks like brown can be used… We do not mind polished or unpolished, but doubly-boiled [siddha rice] mustn’t be used. Doubly-boiled rice is considered impure. Sunbaked rice (atapa) is all right. Soya beans and lentils are unofferable. Regarding purchasing things in the market, these items are considered as purified when we pay the price for them. That is the general instruction. But when we know something is adulterated, we should avoid it. But unknowingly if something is purchased, that is not our fault. Things which are suspicious, however, should be avoided. No, it is not very good to use yeast in preparing prasadam. Since it is offensive to offer anything to Krsna that He will not accept, one should be extremely cautious not to offer (or eat) anything questionable.”
After assembling the ingredients for cooking, wash all vegetables and fruits and anything else that can be washed. If something washable falls on the floor or in a sink, wash it off; if it is unwashable, reject it.
The cook should cover all preparations as soon as they are cooked. If an animal sees a preparation before it is offered, it must be rejected. No one except the cook and the pujari should see the unoffered food. Cover the ghee used for frying when it is not in use. Old ghee should be replaced regularly with fresh ghee. See to it that all ingredients are properly stored in closed containers.
Just as we must select pure, excellent foods to offer to Krsna, so we must also prepare them purely. To prepare food for the Lord, one must meticulously observe the rules for cleanliness and take the utmost care to prepare the food properly. The consciousness of the cook enters into the food he prepares, and therefore he should strive to be Krsna conscious while in the kitchen. The kitchen, where the Lord’s food is prepared, is an extension of the deity room, where He eats. So the same high standard of cleanliness should be maintained.
Dress in Kitchen
If possible cover your hair so as to avoid any hair falling into a preparation. Do not wear wool in the kitchen. All clothing must be clean-that is, it must not have been worn in the bathroom, when eating or sleeping, or outside the temple grounds.
You should be freshly showered and wearing tilaka and neck beads. Wash your hands when first entering the kitchen, and wash them again if you touch your face, mouth, or hair, or if you sneeze or cough (having-hopefully-covered your mouth).
Kitchen and Utensil Cleanliness
The kitchen should be thoroughly cleaned regularly, including inside the stoves, ovens, and refrigerators. Do not leave unclean saucepans and utensils lying around in the kitchen. Clean them after they are used (the sooner they are cleaned after use, the easier they are to clean). No one should eat or drink in the kitchen; nor should anyone use the sink for spitting into or drinking from. Remove all garbage from the kitchen at least once a day. If you need to store prasada in the refrigerator store it in such a way that unoffered items will not become contaminated. I.e. store prasada in sealed containers.
Maintaining Proper Consciousness
As far as possible restrict conversation to topics about Krsna. Do not play recordings of popular-style music in the kitchen. Traditional bhajana and kirtana recordings are appropriate. Deep-frying should be done in pure ghee, if possible. Ghee used for frying should be regularly replaced. (Ideally, ghee and other oils should be used only once, since each reheating reduces their digestibility. An expert cook will use a minimum amount of ghee for deep-frying and use the remainder for making halava or mixing into rice.) If ghee is not available or cannot be made, you may use vegetable oil, such as coconut, mustard, sunflower, or peanut oil.