Just the facts. From the experts.

Have you ever cut into a potato and noticed brown tissue that looks like a small trail or print? What is that brown tissue inside the potato, and is it harmful?

A Best Food Facts reader submitted a question: “I’ve bought russett potatoes (that’s what I use for mashed, baked, etc.), and when I peel them and slice them I’ve seen what appears to be a small trail or print running through them. Often wondered what this is, and is it harmful?” We spoke with Dr. Rich Novy, Small Grains and Potato Germplasm Research Geneticist from the USDA Agricultural Research Service to answer the question.

Dr. Rich Novy told us that potato tubers will sometimes show brown tissue regions interspersed through the normal tuber tissue most often due to the environment in which they were grown, like high heat during tuber formation, or because of a potato-specific virus/fungus. This should not be a worry to humans though, as the virus/fungus isn't harmful to us. All in all, the brown areas of tuber tissue are not harmful.


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