From an article in Fine Woodworking  https://www.finewoodworking.com/2024/10/10/the-best-food-safe-finish-may-be-none-at-all?srsltid=AfmBOoqP2OTnk4rvYLZA1f63Dk10JMGRhKYj5QVdNSYoX3O05Oid4B_O

"Raw wood has an inherent ability to self-clean

To understand why finish is the enemy on food-related woodwork, let’s take a quick look at wood’s anatomy and physics.

Popular wisdom says that microbes multiply in raw wood, growing and waiting until—Whammo!—the listeria army attacks your charcuterie party.

That’s not how raw wood and bacteria interact, and there are decades of research to back this up, as well as centuries of safe contact between food and unfinished wood. Here’s what is actually happening.

Wood is constantly gaining and losing moisture from the air around it. In scientific circles we refer to this as wood’s hydroscopic property. Wood does the same when it comes in contact with any liquid, such as water from a sink or juice from an uncooked steak.

Wood also wants to bring its own moisture content into equilibrium, throughout the board. So when the surface of a relatively dry cutting board or spoon becomes wet, the wood draws that moisture toward the interior, taking bacteria with it.

So if bacteria is drawn into the wood with moisture, why won’t it come back out and wreak havoc? If you give your cutting board or spoon a rinse after use and let it dry on all sides, the drying action will continue to pull bacteria deep into the wood, where it will be trapped and die. Little to none will be left on the surface, at least not enough to transfer. This is what I mean when I say wood is antimicrobial. See “Self-cleaning nature of wood” below to better understand this process.

Study after study has shown this to be true across many wood species, wood thicknesses, and bacteria types. So enjoy this unusual moment when the science is all in agreement!

Raw wood will manage stains too—Go ahead and cut strawberries and blueberries on your unfinished board. Yes, there will be some immediate color left in the wood. But just like the bacteria, it will be drawn progressively inward with each wet-dry cycle. So after every wash, there will be a little less of the stain on the surface. And after seven or eight days of use, the stain will be gone from view.

Don’t polish the surface too much—Because you are not finishing the wood, you might be tempted to sand it to a high polish, which will highlight the beauty somewhat. But I’ve found that sanding ­beyond 400 grit tends to slow the absorption of liquid and moisture, hampering that self-cleaning ability."