Hydroxytyrosol sturgeon skin gelatin film with antioxidant activity and Salmonella detection ability and a method of preparing the same

A method of preparing a hydroxytyrosol sturgeon skin gelatin film with antioxidant activity and Salmonella detection ability comprising the following steps:

• (1) mixing a neutral red indicator solution and distilled water at room temperature in a ratio of 1:65 to 1:70 (v:v) to obtain a mixture solution, and adding 1 mol/L NaHCO3 solution to the mixture solution until discoloration to obtain an alkaline solution;
• (2) adding an amount of the alkaline solution obtained in step (1) to a mixture of Sturgeon skin gelatin and distilled water in a ratio of Sturgeon skin gelatin:
• distilled water=1:8 to 1:12 (w:w) to obtain an alkaline gelatin solution;
• (3) adding hydroxytyrosol and glycerin in a ratio of Sturgeon skin gelatin:hydroxytyrosol:glycerin=1:0.3:0.2 to 1:0.6:0.4 (w:w:w) and propylene glycol to the alkaline gelatin solution to obtain a hydroxytyrosol gelatin solution, and heating the hydroxytyrosol gelatin solution at 40-70° C.;
• (4) ultrasonicating the hydroxytyrosol gelatin solution from step (3), placing the hydroxytyrosol gelatin solution evenly on a plexiglass plate, drying the hydroxytyrosol gelatin solution on a worktable at room temperature to obtain the hydroxytyrosol sturgeon skin gelatin film.