Immobilization of roselle anthocyanins into polyvinyl alcohol/ hydroxypropyl methylcellulose film matrix: Study on the interaction behavior and mechanism for better shrimp freshness monitoring

The roselle anthocyanin extracts (RAE) were immobilized into polyvinyl alcohol (PVA)/hydroxypropyl methylcellulose (HPMC) film matrix, their interaction behavior and mechanism was fully understood for better shrimp freshness monitoring. Structural characterizations revealed RAE was firmly immobilized PVA/HPMC matrix by hydrogen bonds. With increasing RAE contents, dramatic increases of film thickness (from 15.90 +/- 0.14 to 23.20 +/- 3.35 mu m), tensile strength (from 45.66 +/- 1.07 to 56.98 +/- 0.24 MPa), light barrier and active properties (increased by 83.18% for antioxidant and 146.91%, 59.18% for antibacterial activity against E. coli and S. aureus) were observed, while hydrophobic properties decreased significantly. Owing to great ammonia-sensitive ability, the PVA/HPMC/RAE (PHR) films were applied on shrimp freshness qualitative monitoring and greater visible color variations were identified with increasing RAE contents. Furthermore, mathematical models were established for quantitative monitoring. In conclusion, with the increasing RAE contents, the tighter interaction between RAE and PVA/HPMC matrix contributed to the better functional properties and freshness monitoring effects of PHR films.

Automated summary

After immobilizing roselle anthocyanin extracts into a PVA/HPMC film matrix, the film showed increased thickness, tensile strength, light barrier, and active properties, as well as decreased hydrophobic properties. Due to its ammonia-sensitive ability, the film was used for shrimp freshness monitoring, with visible color changes varying with the amount of anthocyanin extracts. Mathematical models were established for quantitative monitoring.