The folks at Boyajian, Inc. in Norwood, Mass. say you can use their citrus oils in any recipe calling for citrus zest. They base the ratio on the amount of other ingredients in the recipe: 1/2-tsp of oil per cup of dry ingredients in the recipe plus 1/4-tsp per cup of liquid.
How do I determine how much orange oil to use in place of grated orange peel? What would the ratio be?