>> from what I have seen in the past, straight oil does seem to chnage colour over time, I assume as the oil oxidises??.
Mineral oil never oxides or dries so it never changes color.
Personally I would not use a standard oil/varnish mixture product like Seal A Cel on a salad bowl. It will always have some odor. Rather, if you want to use a product like that, use one of the "Salad Bowl Finishes" which are made with deodorized mineral spirits and impart not odor to the bowl contents. Behlen makes one as does General Finishes. And, there are others.
My preference is the following for cutting boards and other wood products used for foods.
An excellent treatment for wooden food preparation surfaces like cutting boards and butcher blocks is a mixture of mineral oil and either paraffin or beeswax. This is what is used on many commercial wood surfaces. It will last longer and be more protective than just mineral oil. Mineral oil can be found in most supermarkets in the pharmacy section or in a true pharmacy. Paraffin is found in the canning section of the store or in a hardware store.
Heat the oil in a double boiler and shave in some wax. The exact proportions are not critical--a 5-6 parts of oil to one part of wax will work fine. Stir the mixture until all the wax is liquefied. Apply the mixture heavily and let it set 10-12 hours or overnight. Next day do it again and continue until the wood will no longer absorb the finish. Let it set for 10-12 hours and then lightly scrape off any excess. Then buff it with a rag.
Reapply whenever the wood begins to look dry.
Never put a wood board in the dishwasher and don't soak it in dishwater for long periods.
