Antimicrobial packaging efficiency of ZnO-SiO₂ nanocomposites infused into PVA/CS film for enhancing the shelf life of food products

Abstract

In the current work, antimicrobial bionanocomposite films were fabricated based on chitosan (CS), poly (vinyl alcohol) (PVA) and nanocomposites comprised of silicon dioxide nanoparticles doped with zinc oxide nanoparticles (ZnO-SiO₂). The ZnO-SiO₂ nanocomposite was prepared and incorporated into a PVA/CS blend at different ratios (0.50, 1.0, 3.0 and 5.0 %) to generate the PVA/CS/ZnO-SiO₂ bionanocomposites. The prepared ZnO-SiO₂ nanocomposites as well as the PVA/CS/ZnO-SiO₂ bionanocomposite films were evaluated using SEM, FT-IR, XRD and determination of the final contact angle. Furthermore, the mechanical properties, gas permeability (GTR) and water vapor transmission rate (WVTR) of the prepared PVA/CS/ZnO-SiO₂ bionanocomposite films were evaluated. The fabricated bionanocomposite films displayed superior antibacterial activity against Gram-positive bacteria (staphylococcus aureus, S33R) as well as Gram-negative bacteria (Escherichia coli, IRAQ 3). Correspondingly, the prepared PVA/CS/ZnO-SiO₂ bionanocomposites were used for bread packaging. The obtained result revealed the greatly improved visual appearance of the bread that was packaged in the PVA/CS/ZnO-SiO₂ bionanocomposite film. Moreover, the totality of these various observations and testing methods led to an increase in the shelf life and reduced the amounts of food-borne pathogens in the packaged bread. This PVA/CS/ZnO-SiO₂ bionanocomposite film is an antimicrobial packaging material that may reduce the current negative environmental footprint of packaging materials.

Introduction

The demand for fresh, clean, minimally processed foods has been steadily increasing. Nonetheless, expelling compound additives and added substances from food items altogether diminishes their shelf life. To address this, active antimicrobial packaging systems that contain materials inside or on the packaging that effectively restrain nourishment waste microorganisms can be utilized to lengthen the time of realistic usability of food items (Sullivan et al., 2018). Food contamination can happen during collecting, preparing, and conveyance (Al-Tayyar, Youssef, & Al-hindi, 2020).

Packaging is a compelling method for shielding food items from outside contaminants and can prevent substance, physical, and natural changes (disintegration) during storage or arrangement of items. Traditional packaging materials do not effectively control responses inside the items. Boundaries to oxygen, dampness, and light offer great assurance for the most delicate items (Khaneghah, Hashemi, & Limbo, 2018). As of late, biodegradable and biobased packaging materials have gotten many considerations because of the sanitation and ecological issues brought about by utilizing petrochemical-based plastics (Bi et al., 2019; Youssef, El-Naggar, Fouda, & Youssef, 2019). Edible and bionanocomposite films, which are generally created from polysaccharides, proteins, lipids and different biopolymers, speak to the most encouraging options in contrast to manufactured polymers as packaging materials, accordingly adding to the drive to diminish the utilization of these sorts of plastics (El-Sayed, El-Sayed, Ibrahim, & Youssef, 2020; Gutiérrez & Alvarez, 2018; Youssef & El- Sayed, 2018).

Chitosan is a characteristic polysaccharide acquired from the shells of shellfish by the deacetylation of chitin removed from shells (Braz et al., 2018). Chitosan has natural antimicrobial activity because of its highly charged amino groups, which respond to oppositely charged microbial cell layers. This connection brings about a surge of proteins and other intracellular parts from the microbial cells (Moustafa, Youssef, Darwish, & Abou-Kandil, 2019). Chitosan is a nonlethal biopolymer that has antibacterial activity, which makes it a decent choice for packaging (Sharaf et al., 2019; Youssef, El-Naggar et al., 2019). The utilization of chitosan has been shown to broaden the time span of the usability of new leafy foods (Casariego et al., 2008; Shiekh, Malik, Al-Thabaiti, & Shiekh, 2013), meats (Higueras, López-Carballo, Hernández-Muñoz, Catalá, & Gavara, 2014; Ouattara, Simard, Piette, Bégin, & Holley, 2000; Ye, Neetoo, & Chen, 2008) fish (Caner & Cansiz, 2006) and egg items (Azadbakht, Maghsoudlou, Khomiri, & Kashiri, 2018). Even outside of the freezer, chitosan kept food fresh (No, Meyers, Prinyawiwatkul, & Xu, 2007; Shiekh et al., 2013), and it also decomposed without further contamination in dirt. Even so, the downsides of CS are its acidity and poor flexibility (Abd El-Aziz et al., 2019; Chiellini, Corti, & Solaro, 1999). Chitosan is regularly mixed with other nondangerous and biodegradable polymers, such as PVA, to improve its mechanical properties (Bonilla, Fortunati, Atarés, Chiralt, & Kenny, 2014; Zhai et al., 2017).

PVA has numerous valuable properties for use in food packaging films, for example, high hydrophilicity, great compound stability and superb film shaping properties (Limpan, Prodpran, Benjakul, & Prasarpran, 2012; Youssef, 2013; Yu, Li, Chu, & Zhang, 2018). Polyvinyl alcohol (PVA) offers a wide range of positive attributes, including its high structural capacity, that it is a water-dissolvable polymer, its strong compound properties, its great biodegradability, and its ease of use (Youssef, Assem et al., 2019a). PVA has noteworthy physical attributes because of its hydroxyl groups, which empower the formation of hydrogen bonds (Cano et al., 2015). Organic polymers can undoubtedly become debased by polyvinyl alcohol. In the past century, PVA has been used in a broad range of applications for various enterprises; for example, PVA has been used in the areas of medication and nourishment for creating items, for example, food packaging materials, fine strings, saps and veneers (Domene-López, Guillén, Martin-Gullon, García-Quesada, & Montalbán, 2018; Gaaz et al., 2015). In food contact applications, the utilization of polyvinyl alcohol (PVA) has been broken down by EFSA (2005). In this manner, it very well may be presumed that PVA can be utilized as a covering material for various foods without raising any health concerns (Youssef, Assem et al., 2019b).

Silicon is a metalloid that is the most inexhaustible strong component on Earth; it is broadly found as silica (SiO₂) and silicate. Silicon dioxide nanoparticles (SiO₂-NPs) are fused into plastics for expanding their mechanical quality and warm dependability (Garcia, Shin, & Kim, 2018; Hasan, Zhou, Mahfuz, & Jeelani, 2006). In light of their small molecule size, enormous surface area and the reactivity of their surface hydroxyl groups, SiO₂-NPs are stable particles that have been broadly utilized in plastics and elastics and in other materials (Wu, Chen, Shao, & Lu, 2002; Durme, Mele, Loos, & Prez, 2005; Yiwu, Liu, & Wei, 2010). Silicon oxides are viewed as progressively suitable bearers due to their permeable structures and optimal adsorption properties. SiO₂-NPs have the upside of having amazingly high surface movement, which empowers them to assimilate different particles and atoms (Bahador et al., 2016; Matsunami & Hosono, 1993).

Among the metal oxides, zinc oxide (ZnO) is one of the most broadly utilized materials in different fields because of its noteworthy antimicrobial and photocatalytic properties (Vasilache, Popa, Filote, Cretu, & Benta, 2011). Zinc oxide nanoparticles (ZnO-NPs) are great semiconductors with great biocompatibility, substance steadiness, and biocidal exercises both in vitro and in vivo, and they are inexpensive. ZnO-NPs have a band hole of 3.37 eV at room temperature and an enormous free-energizing restricting vitality of 60 meV. Additionally, they have antimicrobial properties against food borne pathogens and microscopic organisms. Furthermore, ZnO-NPs are typically perceived as approved by the FDA for its proposed use under recommended limited properties (Abdeen, Farargy, & Negm, 2018; Li & Li, 2010; Mallakpour & Behranvand, 2016; Rojas et al., 2019; Zhang, Ding, Povey, & York, 2008).

ZnO-NPs have been used in various food-packaging coatings to keep up nourishment hues, to prevent food deterioration, and to improve packaging material properties, including mechanical quality, hindrance properties and stability (Noah, El Semary, Youssef, & El- Safty, 2017; Shi et al., 2014; Sirelkhatim et al., 2015). Three particular types of activity have been reported in the literature: (I) the generation of reactive oxygen species (ROS) due to the semiconductive properties of ZnO-NPs (Applerot et al., 2009; Lipovsky, Nitzan, Gedanken, & Lubart, 2011; Sawai et al., 1998). (ii) the destabilization of microbial films upon direct contact of ZnO particles with foam dividers (Brayner et al., 2006; Jiang, Mashayekhi, & Xing, 2009; Zhang et al., 2008) and (iii) the natural antimicrobial properties of Zn²⁺ particles discharged by ZnO in watery media (Brunner et al., 2006; Fang, Yu, Li, Somasundaran, & Chandran, 2010; Li, Zhu, & Lin, 2011; Pasquet et al., 2014). The antibacterial action of ZnO-NPs results from the interruption of the bacterial cell membrane by Zn²⁺ particles, and furthermore it is accepted that in the presence of dampness, ZnO-NPs caused oxidative damage to the bacterial cell membranes through the production of dynamic H₂O₂ species on its surface (Noah et al., 2017; Saral, Indumathi, & Rajarajeswari, 2019).

In the present work, ZnO-SiO₂ nanocomposite displays effective antibacterial properties that can used to enhance the mechanical and barrier properties of PVA/CS/ZnO-SiO₂ bionanocomposite films. PVA/CS/ZnO-SiO₂ bionanocomposites were successfully fabricated as novel antibacterial films containing different ratios of ZnO-SiO₂ nanocomposite. Furthermore, this study describes a promising method to enhance packaging material currently used in the food industry. Moreover, there is enormous potential for this method in other food preservation applications.