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

Abstract

An antibacterial and anti-oxidation composite film was prepared by a casting method using sodium alginate (SA) and apple polyphenols (APPs) as the base material and glycerol as the plasticizer. Silver nanoparticles (AgNPs) were deposited by ultrasonic-assisted electrospray method. The degree of influence of the addition ratio of SA and AgNPs and different ultrasonic time on the mechanical properties, barrier properties, optical properties, and hydrophilicity of the composite film was explored. The composite films were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results showed that the SA: AgNPs ratio of 7:3 and the ultrasonic time for 30 min have the best comprehensive performance, and SA/AgNPs/APP films showed the lowest water vapor permeability value of 0.75 × 10−11 g/m·s·Pa. The composite film has good strength and softness, with tensile strength (TS) and elongation at break (E) at 23.94 MPa and 29.18%, respectively. SEM images showed that the surface of the composite film was smooth and the AgNPs’ distribution was uniform. The composite film showed broad antibacterial activity, and the antibacterial activity of Escherichia coli (92.01%) was higher than that of Staphylococcus aureus (91.26%). However, due to the addition of APP, its antioxidant activity can reach 98.39%, which has a synergistic effect on antibacterial activity. For strawberry as a model, the results showed that this composite film can prolong the shelf life of strawberries for about 8 days at 4 °C, effectively maintaining their storage quality. Compared with the commonly used PE(Polyethylene film) film on the market, it has a greater fresh-keeping effect and can be used as an active food packaging material.

Antibacterial Biodegradable Films Based on Alginate with Silver Nanoparticles and Lemongrass Essential Oil–Innovative Packaging for Cheese

“…The simple alginate film presented an average value for WVP when compared similar reports [30,83]. The higher value can be explained by the glycerol addition, whic The oxidation process of alginate matrix starts after 200 • C, when multiple exothermic effects, with low intensity, can be observed on DSC curve (inset of Figure 8).…”

“…Therefore, it is important to determine the values for WVP (Table 4). The simple alginate film presented an average value for WVP when compared to similar reports [30,83]. The higher value can be explained by the glycerol addition, which generates hydrogen bonds with alginate and therefore increases the inter-chains distance, allowing moisture to penetrate easier [84].…”

“…Mechanical properties are enhanced by adding plasticizers, glycerol being the most common choice due to its superior compatibility with the polymeric matrix [27,28]. Antibacterial activity can be bestowed to the alginate by adding various nanoparticles such as ZnO [29], Ag [30], CuO [31], natural extracts [32][33][34], or other substances of pharmaceutical interest [35][36][37].…”

Biodegradable Alginate Films with ZnO Nanoparticles and Citronella Essential Oil—A Novel Antimicrobial Structure

“…The obtained values for WVP determination are presented in Table 5 . The WVP value for the alginate control (A) film is average when compared with literature [ 92 , 94 ] due to addition of glycerol, as this will form hydrogen bonds with the base polymer, which further increase the chain–chain distance [ 95 ]. Nevertheless, important decreases in WVP are observed for all samples when compared with alginate control film.…”

Application of Furcellaran Nanocomposite Film as Packaging of Cheese

“…This was probably due to the presence of AgNPs, as they are highly toxic to a wide range of microorganisms [ 13 ]. Other authors have also shown an extension of the shelf life of other food products through the use of films with AgNPs such as: mini kiwi [ 7 ], red grapes [ 45 ], and strawberries [ 46 , 47 ].…”