Śatapatha Brāhmaṇa ("of a hundred paths") 4.2.5.18

4.2.5.18

atha yatpuroḍāśaḥ dhānāḥ karambho dadhyāmikṣeti bhavati yā yajñasya devatāstāḥ suprītā asanniti

And as to why there are a cake, parched barley-grain, a porridge, sour curds, and clotted curds,--it is that those who are the deities of the sacrifice shall be well-pleased.