Rabbi Silber's Daf Yomi shiur on Chullin 36 traces the halachos of hechsher l'kabel tumah - what makes a food item receptive to tumah - working through which types of blood (from shechita, an injury, or an animal killed by another) create that receptivity, and whether the sanctity of a consecrated item (chibas hakodesh) functions the same way as contact with water. This is a dense, highly technical daf with no distinct mussar aside; it works through cases involving a gourd of terumah, a stray clump of mincha flour, and a basket of oozing grapes to sharpen a subtle halachic distinction.
Food becomes receptive to tumah only through contact with a liquid, or through being consecrated (chibas hakodesh) - dry food, however edible, cannot become tumah.
Blood from an animal killed by another animal or from live shechita can function as that liquid-like trigger, but blood from a natural death or a mere wound generally does not.
Sacrificial blood itself does not make an item receptive to tumah, because only blood that could be spilled on the ground - not collected sacrificial blood - carries the halachic comparison to water.
Beis Hillel initially held that grapes oozing juice in a basket are not rendered receptive to tumah, but ultimately deferred to Beis Shammai's view that they are.
When halachic sources are evenly divided over whether an object is receptive to tumah, the status can remain in unresolved suspension (tolin) rather than being decided either way.
