Swami says that there three types of purities are said to be necessary with regard to food :
1. Pathra Shuddhi (purity of vessels): The vessels for cooking must be clean and pure. 2. Paka Shuddhi (purity of the process of cooking): The process of cooking should not bring impurities. The person who prepares the food and serves must not only be clean in dress, but clean in habits, character, and conduct. He should not allow his mind to dwell on wicked or vicious ideas. 3. Pachaka Shuddhi (Purity of food materials): The provisions used for cooking has to be pure and of good quality. They should have been procured by fair means. In the absence of any of the above three qualities or in spite of them, purify the food with Brahmarpanam! - taken from Swami's Summer Course Discourses in Brindavan 1993... Sai Ram
