A Colorimetric Nanofiber Film Based on Ethyl Cellulose/Gelatin/Purple Sweet Potato Anthocyanins for Monitoring Pork Freshness

In this study, colorimetric indicator nanofiber films based on ethyl cellulose (EC)/gelatin (G) incorporating purple sweet potato anthocyanins (PSPAs) were designed via electrospinning technology for monitoring and maintaining the freshness of pork. The film presented good structural integrity and stability in a humid environment with water vapor permeability (WVP) of 6.07 ± 0.14 × 10-11 g·m-1s-1Pa-1 and water contact angle (WCA) of 81.62 ± 1.43°. When PSPAs were added into the nanofiber films, the antioxidant capacity was significantly improved (p < 0.05) with a DPPH radical scavenging rate of 68.61 ± 1.80%. The nanofiber films showed distinguishable color changes as pH changes and was highly sensitive to volatile ammonia than that of casting films. In the application test, the film color changed from light pink (fresh stage) to light brown (secondary freshness stage) and then to brownish green (spoilage stage), indicating that the nanofiber films can be used to detect the real-time freshness of pork during storage. Meanwhile, it could prolong the shelf life of pork by inhibiting the oxidation degree. Hence, these results suggested that the EC/G/PSPA film has promising future for monitoring freshness and extending shelf life of pork.

Development of real-time intelligent films from red pitaya peel and its application in monitoring the freshness of pork

BACKGROUND

Red pitaya peel (RPP) is a good source of polysaccharides, which can be used in the production of biodegradable material. Betacyanins in it possess antioxidant and pH-sensitive properties. However, RPP is commonly discarded during fruit processing. This study aimed to develop real-time intelligent film using RPP to evaluate pork freshness.

RESULTS

Real-time intelligent films were developed with film-forming substrates (FFS) composed of 60-100% (w/w) RPP and 0-4% (v/w) glycerol in pH 4.3 ~ 8.0. Rheology tests revealed that the FFS exhibited shear-thinning behavior. Fourier-transform infrared (FTIR) analysis showed that molecules in the RPP interacted with glycerol and formed hydrogen bonds. It showed that the film developed with FFS of 80% RPP and 2% (v/w) glycerol had strong molecular interaction, dense structure, and optimal tensile strength and elongation at break. Film with pH adjusted to 7.0 had greater sensitivity to ammonia than film that was prepared at an original pH of 4.3, so this film was used to monitor freshness of pork. A visible change in the color of the film was observed during the spoiling process of pork, which correlated with the accumulated total volatile base nitrogen.

CONCLUSION

Based on its sensitivity to ammonia, the film made of 80% (w/w) RPP and 2% (v/w) glycerol at pH 7.0 was recommended for use in monitoring the freshness of protein-rich food. Our findings are of great significance for ensuring meat quality and safety and for reducing food waste. © 2022 Society of Chemical Industry.