Encapsulated Citric Acid:
Encapsulated Citric Acid is offered in two different types of coating. One with polymer coating is used mainly in fracturing industry and the one which is coated with hydrogenated vegetable oil is used in bakery or food industries apart from fracturing.
Polymer coated slow release or extended release citric aid is used in shale gas fracturing. It releases slowly with time, like say less than 10% in 1 hour and balance in a day or so.
Citric Acid coated with hydrogenated palm oil or hydrogenated soybean oil will have a sharp release at say 55-60C (about 130-140F) or say 65-70C (about 150-160F). This can be called temperature based release.