Metal–organic frameworks for active food packaging. A review

Engineered Science, 2020

Background: Food product safety, especially at the consumer level, is a major concern around the world. Maintaining product safety from processing to acceptable consumption level is very necessary to avoid the negative effect on human health. The addition of functional material such as Metal-organic frameworks (MOFs) into food packaging material creates a path to ensure product safety. Scope and approach: The role of food packaging can be improvised with the help of other unique technology incorporation such as MOFs, with a group of functional materials possessing unique chemical and physical properties, significantly promising towards food safety due to its high surface area and porous structure. The current review deals with the application of MOF in food packaging, its different synthesis methods, toxicity, future perspectives, and potential purpose in food packaging. Key findings and conclusion: MOFs act as active agents, especially in active food packaging, by improving shelflife, quality, and maintaining the safety of packed foods. Incorporation of MOFs into packaging material in different forms supervised the progress in the field of food packaging to ensure product safety with the perspective of implementing novel solutions in the food supply chain. Antimicrobial properties, active molecule removal, and dishonestly labeled food products are some of the challenges faced in traditional food packaging; thus, the emergence of new materials such as MOFs can be a remedy to overcome these challenges. Properties such as good biocompatibility and non-reacting behavior with the host have made MOFs be an integral part of food packaging.

Chemical communications (Cambridge, England), 2015

In this work we demonstrate that allyl isothiocyanate (AITC), a common food flavoring agent and food preservative, can be effectively captured by and released in a controlled manner from a microporous metal-organic framework (MOF). The extent of AITC-MOF interactions is quantitatively measured by orbital overlap population calculations. Controlled release experiments show that loaded AITC can be released by applying higher relative humidity. Further analysis reveals that the underlying mechanism of the controlled release is associated with the transformation of the MOF from a porous to a nonporous structure at high humidity. This study represents the first example of making use of MOF porosity in food preservation.

Molecules

Food samples such as milk, beverages, meat and chicken products, fish, etc. are complex and demanding matrices. Various novel materials such as molecular imprinted polymers (MIPs), carbon-based nanomaterials carbon nanotubes, graphene oxide and metal-organic frameworks (MOFs) have been recently introduced in sample preparation to improve clean up as well as to achieve better recoveries, all complying with green analytical chemistry demands. Metal-organic frameworks are hybrid organic inorganic materials, which have been used for gas storage, separation, catalysis and drug delivery. The last few years MOFs have been used for sample preparation of pharmaceutical, environmental samples and food matrices. Due to their high surface area MOFs can be used as adsorbents for the development of sample preparation techniques of food matrices prior to their analysis with chromatographic and spectrometric techniques with great performance characteristics.

A B S T R A C T Metal organic frameworks (MOFs) are synthetic porous materials consisting of metal ions or ion clusters bound to organic molecules to create a crystalline structure with a very high internal surface area. MOF molecules have been found to have potential utility in the selective adsorptive binding and release of gaseous fuel and other chemicals. We explored the ability of selected MOFs to bind ethylene and the ethylene action inhibitor, 1-methylcyclopropene (1-MCP) with the intent of evaluating their usefulness in regulating ethylene responses for perishable produce. We screened several MOF compounds and selected two (Basolite C300 and Basolite A520) for in-depth characterization based on their superior capacity for binding ethylene. Basolite C300 is a copper-based MOF with a trimesic acid linker group and Basolite A520 is an aluminum-based MOF with a fumaric acid linker group. Binding efficacy was compared to zeolite Z13X, which was also found to bind ethylene. The copper-based Basolite C300 was more effective at binding and retaining ethylene than the other compounds tested. When ethylene-charged sorbents were moved to dry air, they released little ethylene. However, in the presence of free water, Basolite C300 desorbed a majority of its bound ethylene. Adsorption and desorption behavior differed for other alkenes. Basolite C300 had the highest affinity for 1-MCP, but did not release bound 1-MCP in the presence of humidified air. In contrast, the compound 1-butene, often used as a surrogate to quantify 1-MCP, was bound tightly by the MOF and quickly released in the presence of humidified air. We tested the potential for in-package release of bioactive compounds from a MOF. In a proof-of-concept experiment, we found that ethylene-loaded Basolite C300 released ethylene rapidly into packages of banana fruit and induced ripening; MOF without ethylene loading did not induce ripening. The data suggest that MOFs have the potential to sorb, store, and release gaseous compounds that impact plant physiology and may have some utility as a delivery system for volatile plant growth regulators.

Foods, 2022

Food contains a variety of poisonous and harmful substances that have an impact on human health. Therefore, food safety is a worldwide public concern. Food detection approaches must ensure the safety of food at every step of the food supply chain by monitoring and evaluating all hazards from every single step of food production. Therefore, early detection and determination of trace-level contaminants in food are one of the most crucial measures for ensuring food safety and safeguarding consumers’ health. In recent years, various methods have been introduced for food safety analysis, including classical methods and biomolecules-based sensing methods. However, most of these methods are laboratory-dependent, time-consuming, costly, and require well-trained technicians. To overcome such problems, developing rapid, simple, accurate, low-cost, and portable food sensing techniques is essential. Metal-organic frameworks (MOFs), a type of porous materials that present high porosity, abundant...

Journal of Crystal Growth, 2016

Gamma cyclodextrin (CD) metal organic frameworks (CDMOFs) were synthesized by coordinating γ-CDs with potassium hydroxide (KOH), referred hereafter as CDMOF-a, and potassium benzoate (C 7 H 5 KO 2), denoted as CDMOF-b. The obtained CDMOF structures were characterized using nitrogen sorption isotherm, thermo-gravimetric analysis (TGA), X-ray diffraction (XRD), and scanning electron microscopy (SEM). High surface areas were achieved by the γ-CD based MOF structures where the Langmuir specific surface areas (SSA) of CDMOF-a and CDMOF-b were determined as 1,376 m 2 .g-1 and 607 m 2 .g-1 ; respectively. The dehydrated CDMOF structures demonstrated good thermal stability up to 250 o C as observed by the TGA studies. XRD results for CDMOF-a and CDMOF-b reveal a body centered-cubic (BCC) and trigonal crystal system; respectively. Due to its accessible porous structure and high surface area, acetaldehyde was successfully encapsulated in CDMOF-b. During the release kinetic studies, we observed peak release of 53 μg of acetaldehyde per g of CDMOF-b, which was 100 times greater than previously reported encapsulation in β-CD. However, aldol condensation reaction occurred during encapsulation of acetaldehyde into CDMOF-a. This research work demonstrates the potential to encapsulate volatile organic compounds in CDMOFb, and their associated release for applications including food, pharmaceuticals and packaging.

Angewandte Chemie International Edition, 2010

Metal-organic frameworks (MOFs) represent an extensive class of porous crystals in which organic struts link metalcontaining clusters. The success in controlling the functionality and structure of MOFs has led to numerous applications, [2] most notably gas adsorption, storage of clean gas fuels, [4] catalysis, [5] separations, [6] and drug delivery. [7] However, the vast majority of MOFs described to date are composed of organic struts derived from non-renewable petrochemical feedstocks and transition metals. The challenge in preparing MOFs from natural products lies in the inherent asymmetry of the building units, which are not amenable to crystallization in the form of highly porous frameworks. Herein, we report a strategy to overcome this problem using g-cyclodextrin (g-CD), a symmetrical cyclic oligosaccharide that is mass-produced enzymatically from starch and comprised of eight asymmetric a-1,4-linked dglucopyranosyl residues. These g-CD building units are then linked by potassium ions, in aqueous media at ambient temperature and pressure, to form a body-centered cubic structure, termed CD-MOF-1, which has the empirical formula [(C 48 H 80 O 40 )(KOH) 2 ] n . CD-MOFs can be prepared entirely from edible ingredients: combining food-grade g-CD with salt substitute (KCl) or potassium benzoate (food additive E212) in bottled water and Everclear grain spirit (EtOH) yields porous frameworks which constitute edible MOFs.

Polymers

Bio-nanocomposites-based packaging materials have gained significance due to their prospective application in rising areas of packaged food. This research aims to fabricate biodegradable packaging films based upon polyvinyl alcohol (PVA) and starch integrated with metal-organic frameworks (MOFs) or organic additives. MOFs offer unique features in terms of surface area, mechanical strength, and chemical stability, which make them favourable for supporting materials used in fabricating polymer-based packaging materials. zeolitic imidazolate frameworks (ZIFs) are one of the potential candidates for this application due to their highly conductive network with a large surface area and high porosity. Present research illustrates a model system based on ZIF-67 (C8H10N4Co) bearing 2–10 wt.% loading in a matrix of PVA/starch blend with or without pyrolysis to probe the function of intermolecular interaction in molecular packing, tensile properties, and glass transition process. ZIF-67 nanopa...

Angewandte Chemie, 2010

Metal-organic frameworks (MOFs) represent an extensive class of porous crystals in which organic struts link metalcontaining clusters. The success in controlling the functionality and structure of MOFs has led to numerous applications, [2] most notably gas adsorption, storage of clean gas fuels, [4] catalysis, [5] separations, [6] and drug delivery. [7] However, the vast majority of MOFs described to date are composed of organic struts derived from non-renewable petrochemical feedstocks and transition metals. The challenge in preparing MOFs from natural products lies in the inherent asymmetry of the building units, which are not amenable to crystallization in the form of highly porous frameworks. Herein, we report a strategy to overcome this problem using g-cyclodextrin (g-CD), a symmetrical cyclic oligosaccharide that is mass-produced enzymatically from starch and comprised of eight asymmetric a-1,4-linked dglucopyranosyl residues. These g-CD building units are then linked by potassium ions, in aqueous media at ambient temperature and pressure, to form a body-centered cubic structure, termed CD-MOF-1, which has the empirical formula [(C 48 H 80 O 40 )(KOH) 2 ] n . CD-MOFs can be prepared entirely from edible ingredients: combining food-grade g-CD with salt substitute (KCl) or potassium benzoate (food additive E212) in bottled water and Everclear grain spirit (EtOH) yields porous frameworks which constitute edible MOFs.

Food Packaging and Shelf Life

There is a strong need to reduce food waste while maintaining the quality of packaged food. Thus, we have prepared a new fully organic and metal-free antimicrobial polymer, with the aim of increasing both the shelf life and safety of packaged meat. This antimicrobial polymer is based on widely available commercial acrylic monomers with covalently linked vanillin motifs, which are naturally occurring essential oils with antimicrobial characteristics. The film-shaped antibacterial polymeric material shows antibacterial activity for Escherichia coli, Staphylococcus aureus, and Listeria monocytogenes with an R parameter of up to 3.18, 3.37 and 2.00 and inhibition % of up to 99.95%, 99.96%, and 99.02%, respectively. To show the potential of these materials, we conducted a proof of concept experiment in which the antimicrobial polymer film was used as an absorbent food pad. The results show that the use of the antimicrobial polymer film can increase the shelf life of a packaged meat product by 50%. Since the antimicrobial activity is based on a covalently anchored group, there is no antimicrobial agent diffusion, and the antimicrobial activity persists beyond the first use because it is easily washable and reusable for at least 10 cycles.