Gelatins as emulsifiers for oil-in-water emulsions: Extraction, chemical composition, molecular structure, and molecular modification

Gelatins are important natural amphiphilic macromolecules and can act as emulsifiers in oil-in-water emulsions due to their surface-active properties. However, they are generally weaker emulsifiers than other surface-active substances. In the past two decades, many studies have worked to understand the relationships of gelatins structures with their function properties and to explore the possible molecular modification methods to improve their emulsion stabilization abilities. It is well known that protein structure determines function in natural sciences. Based on this axiom, this review summarizes and discusses the extraction, chemical composition, molecular structure, and molecular modification of gelatins for oil-in-water emulsion development. Finally, the review provides a brief summary and outlook of gelatins as emulsifiers. Gelatin sources/organs and extraction methods/parameter have obvious effects on the chemical composition, molecular structure, and emulsifying properties of gelatin. Many molecular modification methods have shown efficient improvements in the interfacial layer molecular structures and emulsion stabilization abilities of gelatins such as physical, chemical, enzymatic, and complex modifications. However, further studies are still required to better understand the relationships of gelatin sources-extraction methods-chemical compositions-molecular structures-molecular modifications-interfacial layer structures-emulsion stabilization abilities. This work can provide basic information on the structure-function relationships of gelatins and can guide the research and development of gelatins as emulsifiers in the future.