According to physical concept of Ayurveda both the human body & the food that goes to build it are panchabhautika in structure. In spite of this basic identity of the ultimate components of the food and its consumer, the final and finished protoplasmic matter physically and physiologically (& even psychologically) it’s so different from that of the former, that an agency has to be postulated to initiate the process of metabolism culminating in the conversion of simple constituents of the food into highly complex and specialized human tissues (dhatu). This agency consists of the five agni of the respective five bhutas.
The moistened food is disintegrated by the jatharagni and then acted upon by bhautikagni which brings about the physical transformation. In dhatupaka too, with the assistance of dhatvagnis, bhautikagnis effect the final conversion of respective dhatus according to their character as Cakrapani says - after disintegration by the jatharagni, the five bhautikagni cook their respective portions of the substances, thus bhautikagni also operate in dhatus as the five bhutas are present also in dhatus and thus there too the operation of both dhatvagni and bhautikagnis should be taken as in case of jatharagni (ca. ci. 15/13).
According to Ayurvedika physiology during avasthapaka panchabhutagni derives strength from jatharagni, while during nishthapaka it derives strength from dhatvagnis and converts the parthivadi amshas of food in paka and vipaka process, by which ingested food particles made capable to assimilate to increase bodily tissues parthivadi amshas and gunas.
Acharya Gangadhara put forward the hypothesis that, the five agnis such as parthiva etc are located / present in the food ingredients. They get stimulated and become activated by jatharagni in the GIT. The bhutagnis while disintegrating (paka) the mahabhutas in the food ingredients cause manifestation of their respective attributes.
The ingredients and their attributes in the food are heterogeneous in nature (vijatiya) prior to bhutagni paka. It is because of this paka that these heterogeneous ingredients and attributes becomes homologous (sajatiya) and thus, cause appropriate nourishment of the tissues. Accordingly the parthiva, apya, tejas, vayavya and jaliiya ingredients of tissues in the body. Similarly the attributes of food viz smell, unctuousness, heat, heaviness, etc, provide nourishment to smell, unctuousness, heat, heaviness, etc of the tissue respectively.
Even though, the five categories of mahabhautika ingredients are reacted upon by their respective and inherent agnis, the ultimate product which come out of this reaction are the specific attributes (vishishta gunas) & not only the fine particles of the food.
In context of bhautikagnis, Cakrapani interprets the term dehadravyaguna as dravyagataguna that the nourishment of matter in the tissues is possible by the nourishing ingredients through their respective attributes and the nourishment of attributes (guna) is not possible without the nourishment of matter (dravya).