Functional characteristics improvement by structural modification of hydroxypropyl methylcellulose modified polyvinyl alcohol films incorporating roselle anthocyanins for shrimp freshness monitoring

A novel indicator film incorporating roselle anthocyanin extracts (RAE) was prepared to monitor shrimp freshness. Hydroxypropyl methylcellulose (HPMC) modified polyvinyl alcohol (PVA) was applied as film-forming substrates to obtain better functions. Structural characterization results suggested compositions were well dispersed and confirmed the structural modification. The addition of HPMC would improve film functions through generation of new interactions. The films with a ratio (HPMC-to-PVA) of 3:1 exhibited stronger tensile strength (91.88 ± 0.13 MPa), hydrophobic (moisture content of 10.44 ± 0.65%, water contact angle of 56.40 ± 3.11°), barrier properties and larger color variations in response to pH changes, demonstrating positive influences of physical functions on indication properties. Thus, a relationship among structural, physical and indication functions was proposed. Furthermore, the films were applied for shrimp freshness real-time monitoring. The film color changed from rose-red to light green at 4 d, corresponding to the onset of spoilage, and then turned into yellow at 8 d, when the shrimp was severely spoilage. The strong correlation between total color difference and chemical spoilage indexes (P < .05) was observed. Therefore, the incorporation of HPMC could improve film functional characteristics by structural modification of new interaction formation, and the PVA/HPMC/RAE films could be applied as intelligent packaging for real-time shrimp freshness monitoring.