Recent Progress in Agar Extraction and Development of Agar-Based Films for Active and Intelligent Packaging Applications: A Review

Seaweed-derived agar has attracted increasing attention in the food industry owing to its promising functional properties and broad application potential. Known for its excellent film-forming ability, high compatibility, and favorable carrier properties, agar is considered a promising polymeric base material for food packaging films. Accordingly, this review discusses various agar extraction methods and their applications in agar-based films for active and intelligent food packaging. Particular emphasis is placed on the structural influence of agar on film properties, beginning with how different extraction methods affect the gelling properties of the polymer. Extraction techniques, including hot water, microwave-assisted, enzymatic, and autoclave methods, with or without ultrasonication and pretreatment, are comprehensively reviewed to optimize agar properties for specific applications. The physicochemical, mechanical, barrier, thermal, antioxidant, and antimicrobial properties of agar-based films are critically examined in relation to their fabrication. The integration of natural extracts, essential oils, metal nanoparticles, and microbial-derived antimicrobial compounds into agar-based films is discussed for extending the shelf life of different food systems. Moreover, the incorporation of natural colorants, namely anthocyanins, shikonin, alizarin, and curcumin, is reviewed in terms of their potential as spoilage indicators and the effect of the agar-based film matrix on the resulting color-indicating behavior. Finally, the sustainability, food contact safety, regulatory considerations, and environmental assessment of agar-based films as potential alternatives to petroleum-based packaging are discussed, with an emphasis on the need for life-cycle assessment and validation under realistic conditions.