Calories in Mushroom, portabella

What makes mushroom so powerful?

Portabella mushrooms are simply mature specimens of Agaricus bisporus — the exact same species as white button and crimini mushrooms. The difference is entirely a matter of age. White buttons are harvested young, criminis are slightly more mature brown-strain individuals, and portabellas are left to grow until the cap flattens and the veil covering the gills tears open, exposing dark spore-producing structures. This extended growth reduces moisture density and concentrates free glutamate, which is why portabellas taste meatier and more umami-rich than their younger counterparts. The dark gills under the cap release spores and can stain food black, which is why some cooks scrape them out before stuffing. When exposed to ultraviolet light, Agaricus bisporus converts ergosterol in its cell membranes into vitamin D2 (ergocalciferol), making it one of the few non-animal dietary vitamin D sources. Most commercially grown mushrooms are cultivated in dark rooms, so they contain negligible vitamin D unless deliberately UV-treated during processing.