Elsevier

Applied Surface Science

Volume 510, 30 April 2020, 145418
Applied Surface Science

Full Length Article
Enhanced antibacterial performance of gelatin/chitosan film containing capsaicin loaded MOFs for food packaging

https://doi.org/10.1016/j.apsusc.2020.145418Get rights and content

Highlights

  • A novel capsaicin-loaded gelatin/chitosan film was developed for food packaging.

  • Hollow FeIII-HMOF-5 was employed as nanocarriers for loading capsaicin.

  • Hydrophilicity of Cap-FeIII-HMOF-5 improved the compatibility in the matrix.

  • The composite films showed great antibacterial performance on real apple cubes.

Abstract

The high demand for food safety and quality has stimulated the investigation of antibacterial packaging films based on natural biomaterials. Capsaicin, an effective extract of red chili, is thought to be a favorable antibacterial candidate in food packaging. Herein, FeIII doped hollow metal-organic frameworks (FeIII-HMOF-5) were prepared as promising nanocarriers for capsaicin and incorporated into gelatin/chitosan matrix to fabricate antibacterial packaging films. FeIII-HMOF-5 regulated the hydrophobicity of capsaicin and effectively solved the phase separation problem. The addition of capsaicin loaded FeIII-HMOF-5 into gelatin/chitosan film significantly improved the tensile strength, water vapor permeability and UV barrier properties. Moreover, Cap-FeIII-HMOF-5 endowed efficient antimicrobial activity against E. coli to gelatin/chitosan films by practical application on fresh apple cubes. The strategy proposed here provides an effective way to develop promising antibacterial biomaterials for food packaging.

Introduction

Nowadays, the food-borne bacteria have been found in a wide range of food products [1], which can be the human pathogens that cause the food-borne diseases throughout the world [2]. In this regard, the research on antimicrobial food packaging film has attracted great attention in recent years [3]. Antimicrobial food packaging film can act as effective physical barriers against bacteria invasion and prolong the food shelf life [4]. Tremendous efforts have been devoted for the development of antimicrobial food packaging films based on natural biomaterials such as gelatin [5], cellulose [6], sodium alginate [7], pullulan [8] and chitosan [9]. Specifically, combining antimicrobial agents with natural biomaterials is regarded as a promising way to fabricate antimicrobial food packaging films. Compared with the nano-antibacterial agents prepared by different inorganic materials, natural extract is considered to be safe and friendly to human and environment. Capsaicin, the extract of red pepper, is a common food coloring and flavoring agents [10], which has many advantages such as analgesic and anti-inflammatory. More importantly, capsaicin has strong anti-microbial effects against gram-negative bacteria, gram-positive bacteria and fungi [11], which makes it great potential in food preservation [12]. In our previous study [13], capsaicin has been incorporated in the pullulan/sodium alginate composite film, showing strong antibacterial performance against E. coli. However, pure capsaicin is hydrophobic and easy to separate out in the hydrophilic composite system, which limited its application in food packaging. Thus, it is highly desirable to develop novel strategies for regulating the physicochemical properties of capsaicin.

Metal-organic frameworks (MOFs) generally consist of metal ions and organic ligands [14]. MOFs have gained tremendous attention due to its huge specific surface area and controllable pore structure, making it an ideal material in different research field, such as energy storage [15], catalysis [16], chemical separation [17] and sensors [18]. In the meantime, MOFs can also be applied in biological field by choosing the nontoxic ligands and metal ions [19]. Because of the above advantages, researchers have developed numerous methods for coupling biomolecules to MOFs for a series of applications including protein separation [20], drug delivery [21], tissue engineering [22] and biocatalysis [23]. Previous results have demonstrated that the interaction between MOFs and biomolecules can effectively affect the physicochemical properties of biomolecules, which lead to improved performances of biomolecules [24]. However, to the best of our knowledge, the capsaicin loaded MOFs has not been reported.

Herein, for the first time, Cap-FeIII-HMOF-5 was prepared as the capsaicin carrier by absorbing capsaicin into FeIII-HMOF-5. Its hydrophilicity made it well dispersed in gelatin/chitosan composite film as the antibacterial agent for food packaging. Cap-FeIII-HMOF-5/gel/chi composite films were successfully prepared with the addition of Cap-FeIII-HMOF-5 as shown in Fig. 1, displaying good antibacterial activities against E. coli. The practical application for food wrap was also studied. This study provides a novel strategy for antibacterial food packaging films.

Section snippets

Materials and methods

Gelatin, chitosan with a degree of deacetylation ranging from 75% to 85%, glycerin (food grade), capsaicin (C17H7NO3, 97 wt%), glacial acetic acid (CH3COOH), Iron(III) acetylacetonate (Fe(acac)3), triethylamine (TEA), zinc nitrate hexahydrate (Zn(NO3)2·6H2O), 1,4-Dicarboxybenzene (H2BDC), polyvinylpyrrolidone (PVP, Mw of 300,000) and N, N-dimethylformamide (DMF) were purchased from Aladdin Reagent (China). Dichloromethane (CH2Cl2) was purchased from Xiqiao Science Co. Ltd (China).

Characterizations of FeIII-HMOF-5

The morphology of prepared FeIII-HMOF-5 was characterized by TEM (Fig. 2). FeIII-HMOF-5 showed a regular octahedral structure with cavity (Fig. 2a and b). Their average diameter was ~206 nm with shell thickness of 20 nm (Fig. 2c). After adsorbing capsaicin for 12 h, Cap-FeIII-HMOF-5 (Fig. 2d and e) displayed the blurry and black area inside the cavity with a slight increasing diameter of ~215 nm (Fig. 2f), which was caused by the adsorption of capsaicin in FeIII-HMOF-5. Meanwhile, the TEM

Conclusion

Herein, Cap-FeIII-HMOF-5 incorporated composite films were prepared with FeIII-HMOF-5 as the nano-carriers to load capsaicin. The hydrophilicity of FeIII-HMOF-5 effectively improved the compatibility of capsaicin inside the gelatin/chitosan matrix. The addition of Cap-FeIII-HMOF-5 significantly enhanced the mechanical properties, water vapor permeability and UV block properties. Moreover, Cap-FeIII-HMOF-5 endowed efficient antimicrobial activity against E. coli to Gel/Chi composite films by

CRediT authorship contribution statement

Jiayi Zhao: Conceptualization, Methodology, Investigation, Writing - original draft. Feng Wei: Conceptualization, Visualization, Formal analysis, Writing - original draft. Weili Xu: Formal analysis, Validation, Data curation. Xiaojun Han: Resources, Writing - review & editing, Supervision, Project administration.

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgements

This work was supported by the National Natural Science Foundation of China (Grant No. 21773050), the Natural Science Foundation of Heilongjiang Province for Distinguished Young Scholars (JC2018003), the Harbin Distinguished Young Scholars Fund (No. 2017RAYXJ024), and State Key Laboratory of Urban Water Resource and Environment (Harbin Institute of Technology) (No. 2017DX05).

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