Advances in plant-extract-based smart packaging: a review of natural solutions for freshness detection

Abstract This review investigates the potential of plant-extract-based smart packaging as a sustainable approach for food freshness monitoring. A systematic literature review of studies published between 2015 and 2025 was conducted using the Scopus database. An initial search yielded 820 records, which were narrowed to 370 journal articles through keyword refinement and further screened to 103 relevant studies based on predefined inclusion and exclusion criteria. Anthocyanins were identified as the most frequently investigated natural indicators, followed by polyphenols, flavonoids, betacyanins, curcumin, and essential oils. The reviewed studies demonstrated successful applications in monitoring the freshness of meat, seafood, dairy products, and fermented foods through pH-sensitive, colourimetric, and volatile-compound-responsive mechanisms. Anthocyanin-based systems accounted for most of the reported freshness indicators due to their pronounced pH-responsive colour changes. Despite promising laboratory-scale performance, challenges related to indicator stability, environmental sensitivity, standardisation, and industrial scalability remain significant barriers to commercialisation. The review highlights current technological advances, identifies research gaps, and discusses future opportunities for integrating natural bio-indicators into sustainable and intelligent food packaging systems that support food safety and circular economy objectives.