Sodium Alginate-Based Green Packaging Films Functionalized by Guava Leaf Extracts and Their Bioactivities

Abstract

The aim of this work was to develop green and bioactive films with sodium alginate incorporating guava leaf extracts. Seven formulations were performed with a different sodium alginate: Guava leaf water extract (WE)/ethanolic extract (EE) proportions (100:0, 90:10, 85:15, 80:20), and glycerol were used as a plasticizer. The HPLC-PDA analysis showed the main phenolic compounds in WE were gallic acid, ellagic acid, quercetin-3-O-β-D-xylopyranoside, avicularin and quercetin. The main polyphenols in EE were rutin, isoquercitrin, quercetin-3-O-β-D-xylopyranoside, avicularin, quercitrin, quercetin and kaempferol. Guava leaf extracts could greatly enhance the antioxidant activity, antibacterial activity, tensile strength and water solubility of the sodium alginate film as well as the water barrier property, while inducing a decrease in the moisture content and elongation at the break. The FTIR and SEM analyses indicated that intermolecular hydrogen bonding between the guava leaf extract and sodium alginate resulted in a more compact structure in the composite films. These results indicated that sodium alginate-guava leaf extract films might be developed into antiradical and antimicrobial food packaging materials.

Investigation of Ultrasonic Treatment on Physicochemical, Structural and Morphological Properties of Sodium Alginate/AgNPs/Apple Polyphenol Films and Its Preservation Effect on Strawberry

“…SA/guava leaf extract composite film was prepared by Luo et al Due to the hydrogen interaction between SA and guava leaf extract, the structure of the composite film was more compact, which improved the TS of the composite film. However, the excessive ratio of extract may lead to uneven dispersion in the mixture, resulting in the decrease in TS [ 37 ].…”

“…Luo et al also suggested that the strong interfacial interaction between phenolic compounds and sodium alginate may improve the moisture resistance. However, the high content of phenolic compounds may accumulate in the polymer matrix to produce voids, resulting in a higher WVP value [ 37 ]. Compared with the SA/guava leaf extract composite film (0.55–0.75 × 10 −11 g/m·s·Pa), the WVP value of the film had no significant difference, and the water vapor barrier of the two films was better [ 37 ].…”

“…The change of the peak position and peak intensity is caused by the hydrogen bond between polyphenols and SA. The stronger intermolecular interaction can improve the physical properties of the films [ 37 ]. As a result of the addition of AgNPs, the absorption peak of 3254 cm −1 shifts to 3267 cm −1 , which is similar to that of Sharma et al Additionally, it shows that the absorption peak of -OH moves to the long wavelength due to the formation of the bond between SA and AgNPs [ 36 ].…”

“…Luo et al showed that the guava leaf extract had an antibacterial effect on E. coli and S. aureus , and the higher the concentration, the more obvious the antibacterial effect. Additionally, they suggest that different types of polyphenols have different effects on bacteria, and that polyphenol mixtures are usually much more active than any single polyphenol alone [ 37 ]. This may be due to the different sensitivity of microorganisms to different polyphenols.…”

“…The difference is that Sharma et al proposed that AgNPs have a higher antibacterial effect on Gram-positive bacteria. This is related to the positive and negative charges on the surface of AgNPs, and the negative charge has a stronger antibacterial effect on Gram-positive bacteria [ 37 ].…”