Preparation method and application of nano-emulsion capable of indicating food freshness

The invention belongs to the field of food packaging, and particularly relates to a preparation method of a nano-emulsion with a function of indicating food freshness and application of the nano-emulsion in the aspect of food freshness detection. The method comprises the following steps: preparing a buffer solution with the pH value of 2-12, adding the natural pigment into the buffer solution, recording the colorimetric conditions of the pH-sensitive natural pigment under different pH values, and screening to obtain the pH-sensitive natural pigment, dissolving a solid particle emulsifier in ultrapure water, stirring and dissolving to form an emulsifier water phase; the method comprises the following steps: by taking vegetable oil as a carrier, adding a pH-sensitive natural pigment into the vegetable oil, and uniformly stirring to obtain a pH-sensitive natural pigment oil phase; mixing the pH-sensitive natural pigment oil phase with the emulsifier water phase, and homogenizing for the first time to form a crud