Ojā: 'nutriment' synonym of āhāra, is one of those 8 minimal constituent parts, or qualities, of all materiality, to wit: the solid, liquid, heat, motion; colour, odour, taste and nutriment. This is the 'octad with nutriment as the eighth factor' ojatthamaka-kalāpa also called the 'pure 8-fold unit' suddhatthaka-kalāpa being the most primitive material combination. For further details, see: rūpa-kalāpa.
Maha Thera Nyanatiloka. Manual of Buddhist Terms and Doctrines, Buddhist Publication Society, first edition 1952.