3D printed curcumin-based composite film for monitoring fish freshness

Curcumin/oregano oil Pickering emulsion (COPE) stabilized by pumpkin seed protein/pectin complex was prepared. COPE has excellent stability in 50 d storage period. Using COPE/ potato starch (PS)/polyvinyl alcohol (PVA) based gel as ink, pH-sensitive indicator film was developed by 3D printing technology. The morphology, mechanical strength, water resistance, oxidation resistance and bacteriostasis of different COPE/PS/PVA films were discussed. The nozzle size had a significant impact on the thickness of 3D printed PS/PVA membranes, with the average thickness of the membranes produced using 0.26 and 0.41 mm nozzles being about 0.12 and 0.18 mm, respectively. COPE can obviously improve the antioxidant and antibacterial performance of PS/PVA membranes. The membrane containing 5%, 7% and 10% COPE had a scavenging rate of ABTS free radicals of over 90% and an inhibitory rate of over 10% on S. aureus and E. coli. The prepared 3D printed two-color label realized the color change process of 4D printing under the stimulation of moisture and TVBN during storage of grass carp. In a word, 3D printing has great potential in online production of food indication labels with different shapes, sizes and functional characteristics, and is suitable for the manufacture of smart food packaging.