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I do not recommend using linseed oil on food preparation surfaces. The reason is that it may contain a number of very nasty substances. To "quote a quote" from our article on linseed oil… https://www.naturalhandyman.com/iip/infpai/inflin.html
"Use of this product will expose you to arsenic, beryllium, chromium, cadmium and nickel, which are known to cause cancer; and lead which is known to cause birth defects and other reproductive harm. I think you will agree that this warning is unambiguous. Don't use linseed oil on surfaces used for food unless it is certified safe for food preparation surfaces!
My recommendation is to use an edible oil, usually called something like "cutting board oil" or "butcher block oil". You can purchase this oil at many hardware and home stores, or online. The oil is safe for all food surfaces, but because it is less stable than drying preservatives it must be occasionally reapplied. (Works great on wooden knife handles, too!)
Regarding bacterial growth, thorough cleaning with hot water and soap is the best way to keep your cutting boards or butcher block safe.