When I make steak, I sear it on the grill at high heat, then transfer to a pan of already cooking onions, mushrooms, butter to finish on low. Sometimes I've left it a little too long in the pan and notice sear marks and some of the color has vanished. I notice something similar if I put sautee'd onions directly on top of steak; after a while, the grill marks disappear. Why?

My assumption is maybe there's an acidic compound in the liquid that leeches out of the onions when cooked, essentially washing away the sear marks. Or, perhaps with the butter for the same reasons.

  • Just a guess but onions have layers and layers of cells, so the sear marks may simply melt off of the outside of the onions.
    – Pointy
    Dec 31, 2022 at 18:12
  • 1
    @Pointy the grill marks are disappearing from the steak, not the onions.
    – brhans
    Jan 2, 2023 at 3:13

1 Answer 1


Grill marks are a product of the Maillard reaction, which is accelerated in an alkaline environment.

Onions are slightly acidic and like mushrooms, also release a lot of water upon grilling. This has a two-fold effect.

  1. The flavour compounds that form the grill marks get washed away by the introduction of moisture. You can emulate this by getting a similarly grilled steak, and then transferring it to another hot pan with some water in it. The mushrooms and onions were simply a vessel for this water.

  2. The acidic environment discourages further Maillard browning from occurring, even if the second pan is at a sufficient temperature for it to occur normally.

The mushrooms and onions in the second pan most likely still had moisture left to release. I am willing to bet that if you had grilled them further and then transferred the steak, the grill marks would have stayed.

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