Porous starch embedded with anthocyanins-CMC coating as bifunctional packaging with seafood freshness monitoring properties

In line with the growing demand for more sustainable and efficient materials for food packaging, new bifunctional pH-responsive composites were developed with the dual purpose of packaging and indicating seafood spoilage. Within this study, a fully bio-based composite based on porous starch (PS) was prepared via microwave irradiation ( 1 g/cm3) followed by functionalization via dip-coating with an active solution of anthocyanins-carboxymethyl cellulose (CMC). Here, the edible anthocyanins (Ath) endowed excellent antioxidant and pH-sensing properties to the resulting bifunctional composite (PS-ACMC), covering a pH range of 6-11.5, making it compelling for developing smart food-packaging materials. Moreover, results indicated that the coating scarcely altered the excellent mechanical properties developed by the PS sample, which were comparable with the commercial expanded polystyrene foams. Concurrently, to enhance the competitive properties of the starch component, bifunctional PS-CMC systems were devised crosslinking starch with citric acid. The obtained citrate-starch specimens exhibited a superior porous structure with lower density ( 0.61 g/cm3), antioxidant properties, and about 40% less solubility in water compared to the neat starch sample. Remarkably, this functionalization hindered the colour-switching properties when the active coating was added, likely due to a strong fixation of the CMC with the natural dye. However, PS-ACMC composites exhibited a rapid and effective colour response, transitioning from violet to greenish-blue, facilitating visual and real-time assessment of the freshness when using shrimp as test specimens. The results reported underscored the high potential of such bifunctional biocomposites in obtaining sustainable and smart freshness-monitoring packaging for seafood.