1. Pale gray streaks and blotches that appear on the surface of chocolate. Bloom is a result of cocoa butter forming crystals on the chocolate, usually caused by the chocolate being stored in too warm an environment. see also chocolate. 2. The pale gray film found on the skin of fruits such as grapes and plums. Fruit bloom is simply nature's waterproofing and completely harmless. 3. A natural, invisible, protective coating found on eggshells. This covering is washed off when USDA-graded eggs are sanitized; producers then replace it with a thin film of mineral oil.