The role of emulsion droplets and their interactions with other components in affecting the properties of active edible films: A review

Edible emulsion films have received increased interest in the research area of food packaging in recent years. However, the impact of the presence of oil droplets on the properties of biopolymer-based films has not been summarized. This paper provides an update on the current knowledge of the filming mechanisms of various biopolymers, the interactions among different components in edible emulsion films, and the impact of adding oil droplets in the physical properties, bioactive functions and applications of biopolymer-based emulsion films. Various polysaccharides and proteins can be used as film matrices to prepare edible films. The filming mechanism of these biopolymer-based films is similar, which mainly involves the strengthened hydrogen bonding and/or covalent interactions between biopolymer molecules during drying process with the decreased water content and bulk volume. The introduced oil droplets show weak hydrogen bonding with biopolymer molecules in films without emulsifiers, while further adding emulsifiers can improve the hydrogen bonding between biopolymer molecules and oil droplets, leading to the improved mechanical and barrier properties of biopolymer-based emulsion films. With the introducing of some oil-soluble, water-soluble, or insoluble functional compounds into the above edible emulsion films, the resultant active emulsion films reveal good antimicrobial and/or anti-oxidative properties, and thus they exhibit fantastic potential applications in food packaging for maintaining food quality and prolonging shelf-life.