Plant extracts for starch-based functional films: Categories, film design, applications, and challenges-A review

Starch-based films are promising renewable and biodegradable materials for food packaging. Plant extracts can convert starch matrices into functional films with antimicrobial, antioxidant, UV-barrier, or freshness-indicating properties. This review organizes recent progress by extract category, film design, food applications, and translation challenges. Essential oils and volatile compounds provide strong antimicrobial effects but require control of volatility, odor, thermal loss, and release. Non-volatile phenolic and flavonoid-rich extracts improve antioxidant performance and light barrier properties, although their interactions with starch can alter color, transparency, and mechanics. Natural pigments such as anthocyanins, betalains, and curcumin enable intelligent freshness monitoring when protected by modified starch, encapsulation, Pickering emulsions, or nanocomposites. The review emphasizes matrix-extract interactions, protection of labile bioactives, release regulation, real-food validation, safety, sensory quality, and scalable processing as priorities for practical starch-based functional films.