Smart labels based on polyvinyl alcohol incorporated with chitosan nanoparticles loaded with grape extract: Functionality, stability and food application.

Anthocyanins (ACNs) are natural compounds with potential applications due to their colorimetric response to pH. Due to their sensitivity to various environmental factors, nanoencapsulation with biopolymers is a successful strategy for stabilizing ACNs. In this work ACNs were extracted from grape skins and encapsulated into chitosan (CS) nanoparticles by ionic gelation using sodium tripolyphosphate (TPP) as a cross-linking agent. CS nanoparticles loaded with ACNs had particle sizes between 291 and 324 nm and polydispersity index around 0.3. The encapsulation efficiency of ACNs was approximately 60 %; and encapsulated anthocyanins (ACN-NPs) exhibited color change properties under different pH conditions. pH-sensitive labels based on polyvinyl alcohol (PVA) were prepared by the casting method. The effect of incorporating ACN-NPs on the physical, structural, and pH-sensitive properties of PVA labels was evaluated, and its application as shrimp freshness indicator was studied. The nanoencapsulation protected ACNs against heat and light treatments, preserving the original purple color. When applying the label, visible changes from red to blue until reaching yellow were observed with the change in the quality of the shrimp at the refrigeration temperature. The results suggest that PVA labels containing ACNs encapsulated in C-NPs can be used as smart packaging labels in the food industry.

A novel colorimetric indicator film based on chitosan, polyvinyl alcohol and anthocyanins from jambolan (Syzygium cumini) fruit for monitoring shrimp freshness.

This study aims to develop and characterize colorimetric indicator films based on chitosan, polyvinyl alcohol and anthocyanins from jambolan fruit (Syzygium cumini) prepared by casting method. The effect of anthocyanin extract on thickness, microstructure, moisture content, solubility in water, hydrophobicity, chemical structure, color and opacity of films was analyzed. In addition, anthocyanins photodegradation in films as well its application to monitoring shrimp freshness was studied. Significant effect (p < 0.05) of anthocyanin extract from jambolan fruit on the thickness and optical properties of the films was observed. Anthocyanin extract from jambolan fruit was efficiently incorporated and dispersed into film. The films containing anthocyanins showed visible changes from red color to blue color when used to monitor shrimp freshness at several temperatures (between -20 °C and 20 °C). This research reports for the first time information regarding the valorization and application of anthocyanins from jambolan fruit as an alternative for food packaging sector.