A visual bi-layer sensor based on Agar/TiO2/butterfly bean flower anthocyanin/κ-carrageenan with photostability for monitoring Penaeus chinensis freshness

 Int. J. Biol. Macromol. 235, 123706 (2023)

Visual indicator bi-layer films were manufactured incorporating κ-carrageenan, butterfly pea flower anthocyanin, varying Nano‑titanium dioxide (TiO2) content and agar for Penaeus chinensis (Chinese white shrimp) freshness detection. The κ-carrageenan-anthocyanin (CA) layer served as indicator, while the TiO2-agar (TA) layer functioned as the protective layer to improve the photostability of film. The bi-layer structure was characterized by scanning electron microscopy (SEM). The TA2-CA film had the best tensile strength with a value of 17.8 MPa and the lowest water vapor permeability (WVP) value of bi-layer films was 2.98 × 10−7 g.m−1.h−1.pa−1. The bi-layer film protected anthocyanin against exudation when immersed in aqueous solution of varying pH. The TiO2 particles filled the pores of the protective layer, increasing the opacity from 1.61 up to 4.49 significantly improving the photostability with a consequent slight color change under illumination of UV/visible light. Under UV irradiation, the TA2-CA film had no significant color change with a ΔE value of 4.23. Finally, the TA2-CA films showed an obvious color change from blue to yellow green in the early stages of Penaeus chinensis putrefaction (≤48 h) then the color change and Penaeus chinensis freshness were well correlated (R2 = 0.8739).

Novel hydrophobic colorimetric films based on ethylcellulose/castor oil/anthocyanins for pork freshness monitoring

 LWT, 164, 2022, 113631

A novel hydrophobic colorimetric film was developed using ethyl cellulose (EC), castor oil (CO) and purple potato anthocyanin (AN) for pork freshness monitoring. The films with CO concentrations of 0% (control), 0.25%, 0.5%, 1% and 2% were developed and expressed as F0, F0.25, F0.5, F1 and F2. Scanning electron microscopy (SEM) images showed that the five films had dense surface and porous internal structures. The F0.5 film exhibited the highest tensile strength (TS) value, optimal color stability, ability to prevent the leaching of AN. The limit of detection (LOD) value of the F0.5 film to ammonia gas was 1.04 μM. The color of F0.5 film turned from red to green along with the spoilage of pork. As a result, the film was expected to be a good colorimetric indicator of pork freshness for intelligent packaging.

Development of nanofiber indicator with high sensitivity for pork preservation and freshness monitoring

 Food Chem. 381, 132224 (2022)

A visual Polyvinylidene Fluoride (PVDF) fibrous film incorporated with Roselle anthocyanin (RS) and Cinnamon essential oil (CEO) (PRC film) was designed via electrospinning technology for pork preservation and freshness monitoring. The PRC film presented well structural integrity and stability in buffer solutions without leaking out RS. And PCR film had well hydrophobic and high permeability with water contact angle (WCA) of 109.52° and water vapor permeability (WVP) of 2.63 × 10−7 g m−1h−1Pa−1. Importantly, PRC film exhibited good antibacterial activity with the inhibition diameter at 29.0 mm and 27.1 mm which against Escherichia coli and staphylococcus aureus, respectively. Finally, the PRC film was employed as a colorimetric sensor for monitoring pork freshness. It presented visible color changes from pink to blue and effectively prolonged the pork shelf-life by 2 days at 4 °C. These results indicate a great potential in intelligent and active packaging.