The chitosan solution (1%) was prepared as follows: weigh 1 g chitosan and put into a 200-mL beaker, then slowly added 100 mL 1% citric acid solution and meanwhile stirred with a magnetic stirrer until the mixture solution pH 3.5–4.0 became clear and coating formed. The solution was vacuumed for 2 h to remove trapped air bubbles introduced during the mixing. The film forming solution was used for apple slices fruit coatings.