Sodium citrate

Degraded k-carrageenan was made by our laboratory. Anhydrous ethanol and potassium chloride were obtained from Tianjin Yongda Chemical Reagent Co., Ltd. (Tianjin, China). Hydrogen peroxide was obtained from Liaoning Jiacheng Fine Chemicals Co., Ltd. (Fuxin, China). Ferric chloride and sodium citrate were obtained from Tianjin Damao Chemical Reagent Factory (Tianjin, China). Sodium hydroxide was obtained from Tianjin Ruijinte Chemical Co., Ltd. (Tianjin, China). Waterborne epoxy resin was obtained from Hexion Specialty Chemicals, Inc. (Columbus, Ohio, USA).

The Damao Chemical Reagent Factory (Tianjin) provided the analytical grade sodium citrate and citric acid. Polyglycerol polyricinoleate (PGPR, food grade), bacterial cellulose (BC), and Nile red (BR, 98%) were acquired from Yuanye biology company. Food grade soybean oil was purchased from Fulinmen company (China Oil & Foodstuffs Corporation, Shanghai, China) and used without further purification. Beeswax (BW, melting point between 46–60 °C) was purchased from Aladdin (Shanghai, China). Other chemicals, including sodium alginate (viscosity 200 ± 20 mpa.s), 2,3-diacetyl (>99%) were purchased from Macklin company (Shanghai, China). All solutions were prepared with deionized (DI) water purified using a Milli-Q purification system.