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Characterization of Agar-CMC/Ag-MMT nanocomposite and evaluation of antibacterial and mechanical properties for packaging applications
⁎Corresponding author at: Inorganic Materials and Catalysis Division, Bhavnagar, Gujarat, India. hcbajaj@csmcri.res.in (Hari C. Bajaj)
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Received: ,
Accepted: ,
This article was originally published by Elsevier and was migrated to Scientific Scholar after the change of Publisher.
Peer review under responsibility of King Saud University.
Abstract
The effect of silver modified montmorillonite (Ag-MMT) on the physical, mechanical and antimicrobial properties of agar-carboxymethyl cellulose (agar-CMC) bionanocomposites film, prepared by a solution intercalation method were investigated. The nanocomposite of agar and carboxymethyl cellulose (CMC) with Ag-MMT (based on Indigenous clay) has a promise in designing eco-friendly antibacterial packaging. The films were tested for transmittance, tensile and X-ray diffraction patterns which indicated that Ag-MMT the most compatible with Agar-CMC matrix. The Agar-CMC/Ag-MMT bio-nanocomposite films exhibited a great antibacterial activity against both Gram-positive (Bacillus subtilis) and Gram-negative (Escherichia coli) bacteria. Overall, it is seen that the Agar-CMC/Ag-MMT bionanocomposite films could be used as packaging material for food preservation by controlling foodborne pathogens and spoilage bacteria.
Keywords
Bionanocomposite
Packaging films
Antimicrobial activity
Montmorillonite
1 Introduction
Biodegradable and renewable polymers reinforced with nanostructures have been used to produce novel, efficient and eco-friendly materials with adequate thermo-mechanical properties as alternatives to replace conventional materials (Dufresne and Castaño, 2017). One of the most challenging subjects of research in the food packaging sector is to develop environment-friendly materials with additional function such as antimicrobial activity to fulfil the sustainable development and to secure the food safety and to extend the shelf-life of food, (Armentano et al., 2013) as well as solving environmental problems, consequence of slow degradation of synthetic polymers. The growing interest of researchers in the study of bionanocomposites is given by the differentiating functional properties that they confer. As one of the most promising technologies to achieve such goals is bionanocomposites and/or functionalized material with antimicrobial activity, these have emerged due to their excellent and unique properties, environment-friendliness, and functionality (Armentano et al., 2013; Scarfato et al., 2015; Tunç et al., 2016). Biopolymers of polysaccharides and proteins have been widely investigated due to their advantages of eco-friendliness and biodegradability (Castaño et al., 2017; Kumar et al., 2010). Montmorillonite, saponite, and hectorite are the three most commonly used clays in the synthesis of polymer nanocomposites; these clays belong to smectites family (Hong and Rhim, 2008). In addition, organically modified clay minerals have been used to develop antimicrobial packaging materials (Incoronato et al., 2010; Rhim et al., 2009; Yoksan and Chirachanchai, 2010). A variety of antimicrobial agents such as natural or synthetic antimicrobial agents (nisin, carvacrol, allyl isothiocyanate, antibiotics, propionic, benzoic, sorbic acids), enzymes (lysozyme), nanometals (silver, copper), metal oxides (TiO2, ZnO, MgO). Among the inorganic antimicrobial materials, silver nanoparticles (AgNPs) have attracted considerable attention for packaging applications with their unique chemical and physical properties including antibacterial activity and high thermal stability as well as low toxicity (Carja et al., 2009; Girase et al., 2011; Kim et al., 2007). AgNPs are prepared by various routes consisting of complex synthesis or reduction procedures such as UV irradiation, laser ablation, sonochemical and photochemical reduction, and reduction by biological systems such as bacteria, fungi, yeasts, and plant extracts (Carja et al., 2009). However, AgNPs have a tendency to agglomerate when AgNPs are used alone, which causes deterioration of their chemical activities and decreases their antimicrobial properties (Malachová et al., 2009). To overcome this problem, preparation of silver/clay mineral nanocomposites, in which AgNPs are supported within interlamellar spaces of clay mineral or on its external surfaces, has been suggested by several researchers (Malachová et al., 2009; Azeredo et al., 2009; Jafarzadeh et al., 2016). Montmorillonite (MMT) as-layered clay mineral has intercalation, swelling, and ion exchange properties; its interlayer space has been used for the synthesis of silver/clay mineral nanocomposite materials. In addition, the silver/clay mineral nanocomposites are known to have long-term antimicrobial effect (Malachová et al., 2009; Azeredo et al., 2009). Bionanocomposites have gained more importance by the packaging industry, due to the ease of availability, processing, and low costs compared to other nanocellulose, carbon nanotubes (Darder et al., 2003). Although most biodegradable polymers possess excellent properties that are comparable with those of petroleum-based plastics, certain poor properties such as brittleness and high permeability limit their applications. The research on biopolymers has recently been focused on modifying and improving their mechanical and gas barrier properties. The addition of small amounts of nanoparticles to biopolymers improves their mechanical, thermal, and barrier properties, which can expand the use of the polymers to various applications, especially food packaging (Wang and Rhim, 2015). Recently, nanocomposite technology, compositing biopolymer with layered silicate and clay materials such as montmorillonite (MMT), has been tested to improve biopolymer film properties (Rhim, 2013). Among the renewable source-based biodegradable plastic packaging materials, agar is one of the most interesting materials because it is thermoplastic, biodegradable, and biocompatible and has high mechanical strength with moderate water resistance (Rhim, 2012; Wu et al., 2009). Due to these advantageous properties, agar has been tested as an alternative source for petroleum plastic packaging materials (Rhim, 2013; Letendre et al., 2002). most of the agaropectin is removed during processing; hence, commercial agars are mainly composed of the agarose fraction. Most applications for agar are based on its gelling ability and the fact that it is more stable to low pH and high temperature conditions compared to other gelling systems (Rhim et al., 2013). However, brittleness and other properties, such as low thermal stability, medium gas barrier properties, and low solvent resistance (for example, against water) of the pure polymer, are often insufficient for food packaging applications (Patel et al., 2007a).
Carboxymethylcellulose (CMC), a derivative of cellulose, presents low-cost, renewable, hydrophilic, biodegradable, non-toxic and good film-forming properties. Scant literature explores the antimicrobial activity of silver modified Montmorillonite and its nanocomposites with agar-carboxymethyl cellulose, however; no comprehensive report has studied the effect of Ag-MMT on mechanical and antimicrobial properties of agar and carboxymethyl cellulose nanocomposites film formed for food packaging. Based on these arguments, the aim of this study was three folds: (1) to prepare bionanocomposite films with Agar and Carboxymethyl Cellulose (CMC) and Ag-MMT (based on Indigenous clay), (2) to evaluate the influence of the incorporation of Ag-MMT on the physical and antimicrobial properties of the bionanocomposite films, (3) to determine the thermal and mechanical properties of films as alternative of biodegradable materials for food packaging.
2 Experimental
2.1 Materials
Clay, agar, sodium salt of carboxymethyl cellulose and glycerol were employed as raw materials in the preparation of bionanocomposite films. The clay, used as a solid support for AgNPs, was an Indian Montmorillonite (MMT) extracted from the bentonite rock from Kutch in Gujarat (INDIA). It was obtained by purifying Indian clay as reported (Patel et al., 2007b), has a cation exchange capacity (CEC) of 92 meq/100 g. Bacteriological grade Agar-Agar and carboxymethylcellulose sodium salt were obtained from RFCL India. Silver nitrate (AgNO3) purchased from Qualigens fine chemicals, (Mumbai, India). Glycerol was purchased from S D Fine Chem. Ltd. (Mumbai, India).
The tea extract was prepared by boiling 2 g of tea powder (Red label from Tata, India Ltd. 99%) in 100 ml of water and filtered through cellulose acetate filter paper. Crude tea extract contains water-soluble phenolics present in tea grains. Especially catechins are the main phenolics, enabling silver ions to reduce and thereby produce silver nanoparticles (Sökmen et al., 2017). Phenolic profiles and catechin contents of studied samples were already reported previously (Gönül et al., 2016).
2.2 Methods
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Preparation of silver nanoparticles in MMT layers:
Silver modified clay was prepared by simple ion exchange method. The cation exchange was performed by saturation of MMT with silver ions. Ag-MMT was prepared by dispersing 1 g of MMT in 100 ml of 10 mM AgNO3 solution for 24 h. MMT dispersions were centrifuged and dried at 105 °C exchanged silver MMT was reduced by dispersing it in 100 ml of tea extract at room temperature. Then after centrifuge washed with distilled water and dried at 70 °C.
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Preparation of Agar-CMC/Ag-MMT bionanocomposite films:
Agar and CMC based bionanocomposite films were prepared using a solvent casting method proposed by Rhim et al. (Rhim, 2012) Film solutions were prepared by dissolving 3 g of agar and 1 g of CMC in 100 ml of distilled water with 2 g of glycerol as a plasticizer and mixing vigorously for 30 min at 95 °C using a magnetic stirrer. The film solution was casted evenly onto a leveled glass plate (24 cm × 30 cm), dried for 24 h at room temperature and the resultant film was peeled from the casting surface. In addition, agar nanocomposite films with various clay contents, 3, 5, 8 and 10% (part clay per 100 part agar-CMC), were prepared using a solution intercalation method, (Rhim, 2013) and summarized in Table 1. First, precisely weighed clay (Ag-MMT) was dispersed in distilled water and stirred using a magnetic stirrer for 24 h to reach complete swelling of the clay. The fully hydrated Ag-MMT clay dispersion was homogenized by sonication for 10 min using a High-Intensity Ultrasonic Processor (Model B9500E-DTH, VWA, USA). Three grams of agar and 1 g of CMC were then dissolved into the Ag-MMT clay dispersion and heated for 30 min at 95 °C with vigorous mixing using a magnetic stirrer, 2 g glycerol was added after the 10-minute mixture was casted onto the glass plates. Fig. 1 shows a scheme for the preparation of bionanocomposite.
| Sample code | Ag-MMT (%) |
Amount of CMC (g) |
Amount of Agar (g) |
|---|---|---|---|
| AC | 0.0 | 1.0 | 3.0 |
| AC/Ag-MMT 2 | 2.0 | 1.0 | 3.0 |
| AC/Ag-MMT 4 | 4.0 | 1.0 | 3.0 |
| AC/Ag-MMT 6 | 6.0 | 1.0 | 3.0 |
| AC/Ag-MMT 8 | 8.0 | 1.0 | 3.0 |
*AC = Agar-CMC composite.
2.3 Characterization of Agar-CMC/Ag-MMT bionanocomposite films
2.3.1 X-ray diffraction analysis
The intercalation of the polymer in nanoclay layers was confirmed using X-ray diffraction (XRD) analysis carried out with a powder diffractometer (Miniflex-II desktop X-ray diffractometer, Japan) using PW3123/00 curved Cu-filtered Cu-Kα radiation with slow scan of 0.3°/s in a 2θ range of 2–70° The structural properties of Agar-CMC/Ag-MMT films were determined using X-PERT-PRO Panalytical diffractometer at room temperature with a scan rate of 1° min−1. The X-ray source was CuKα (λ = 1.5406 nm) with a generator voltage of 40 kV and 30 mA of current. The basal spacing of MMT in the nanocomposite films was calculated by Bragg's law (nλ = 2dsinθ). Fourier transforms infrared (FTIR) spectroscopy was carried out to characterize the functional groups of the nanomaterials. FTIR spectroscopy was performed with Perkin Elmer (Spectrum GX Spectrophotometer, USA) equipped with a diamond attenuated total reflectance (ATR) in the range of 4000–500 cm−1 at 4 cm−1 of resolution. The background and sample spectra were scanned 64 times in transmittance mode. Data were analyzed with spectral OPUS 7.0 software.
Thermogravimetric analysis was carried out using NETZSCH, TGA, Germany over a temperature range of 50–800 °C at 10 °C/min heating rate in the air flow of 40 ml/min. Scanning electron microscopy (SEM) analysis of the films was observed by SEM (JEOL-JEM 7100F, Tokyo, Japan). Transmission Electron Microscope (TEM) analysis of the films was observed by TEM (JEOL-JEM 2100, Tokyo, Japan).
2.3.2 Microbiological assays
The antibacterial activities of the Agar-CMC/Ag-MMT nanocomposite were investigated by disc method, using the standard procedure described elsewhere. Nutrient agar medium was prepared by mixing peptone (5.0 g), beef extract (3.0 g), and sodium chloride (NaCl) (5.0 g) in 1000 ml distilled water and the pH was adjusted to 7.0. Finally, agar (15.0 g) was added to the solution. The agar medium was sterilized in an autoclave at a pressure of 6.8 kg (15 lbs) for 30 min. This medium was transferred into sterilized Petri dishes in a laminar airflow chamber (Microfilt Laminar Flow Ultra Clean Air Unit, Mumbai India). After solidification of the media, bacteria (Bacillus subtilis and Escherichia coli) (50 ml) culture was spread on the solid surface of the media. Over the inoculated Petri dish, one drop of gel solutions (20 mg/10 ml distilled water) was added using a 10 ml tip and the plates were incubated for 48 h at 37 °C.
2.3.3 Tensile properties
Tensile properties were measured on the universal testing machine (UTM Zwick/Roell, SN825825KN, USA), Sensitivity 2mv/v at a crosshead speed of 50 mm min−1. Tensile tests of bionanocomposite films were evaluated. Tensile modulus, tensile strength and percent of elongation at break were calculated from the stress-strain curves. At least seven individual measurements were carried out for each film formulation.
3 Results and discussion
3.1 Characterization of raw materials
3.1.1 The chemical composition of purified Indian bentonite clay
The chemical composition of MMT (purified Indian bentonite clay) is SiO2, 57.5; Al2O3, 17.4; Fe2O3, 9.2; CaO, 1.5; MgO, 2.9; Na2O, 0.9; K2O, 0.8, and loss on ignition, 8.7% w/w. On the basis of the chemical composition of the clay, we have calculated ionic formula of Indian MMT as (Si3.87Al0.13) (Al1.24Mg0.29Fe0.47) O10 (OH)2 X, X → Na0.11, K0.08. From the ionic formula, it is clearly shown that the Indian MMT contains both Na-MMT and Ca-MMT. The detailed study on the compositional, structural, and property differences for Indian MMT is described by Patel et al. (2007b).
3.2 Morphological characterization
Scanning electron microscopy (SEM) was used to investigate the surface morphology of clay and silver nanoparticles. The SEM pictures of MMT and Ag-MMT are shown in Fig. 2a and b, respectively. The images indicate a clear rough surface with clay particles morphology when compared to silver-loaded bentonite (Fig. 2a), whereas Ag-MMT exhibited nanoparticles distributed throughout the MMT layers. To confirm the presence of silver nanoparticles, the elemental composition of MMT and Ag-MMT was studied by energy dispersive of X-ray (SEM-EDX). EDX analysis confirmed that the Ag-MMT contains 2.73 wt. % Ag, 19.71 wt. % silicon, 22.7 wt. % carbon, 7 wt. % nitrogen, 44.33 wt. % oxygen, 0.23 wt. % sodium, and 5.6 wt. % Al, 3.79 wt. % iron (Table 2).
| Element | Ag-MMT wt. % |
|---|---|
| C | 22.37 |
| O | 44.30 |
| Na | 0.23 |
| Mg | 1.22 |
| Al | 5.64 |
| Si | 19.71 |
| Fe | 3.79 |
| Ag | 2.73 |
| Total | 100 |
The presence and the size of such small Ag particles on MMT were also confirmed by TEM (Fig. 3). The average particle size of silver nanoparticles is 50–60 nm.
3.3 Stability of the Ag-MMT
The stability of the Ag-MMT was studied in water in different pH zeta measurements. Solutions of pH 7 and pH 9 were used to study the aggregation kinetics of the NPs synthesized on MMT layers for a reasonable time period of 5 days (120 h) at room temperature (∼25 °C). The particle size and ζ potential values of the Ag-MMT did not vary much indicating the stability of particle in water (Fig. 4a and b). It was also seen, that there was no significant change in the Particle size and ζ potential values of the particles when dispersed in the 7 and 9 pH solutions. (Balachandran et al., 2013; Rashid et al., 2013)
3.4 Characterization of bionanocomposite
3.4.1 X-ray diffraction analysis
The X-ray diffraction is a suitable technique to know the formation of the silver nanoparticles in the MMT layers. Fig. 5a shows the XRD pattern of MMT and silver nanoparticles-loaded MMT. The diffraction peaks are consistent with the standard patterns of crystal silver (JCPDS file No. 04-0783). The diffraction peaks at 2θ 37.92°, 44.13°, 51.72° 64.29°, and 76.84° and these peaks indexed to the reflections of (1 1 1), (2 0 0), (2 2 0), (3 1 1) planes, indicate face center cubic silver (FCC-AgNPs). The d-spacing values of MMT and Ag-MMT are 1.45 nm and 2.30 nm respectively which indicate the intercalation of silver nanoparticles in MMT layers. Fig. 5b shows the XRD patterns of Agar-CMC/Ag-MMT nanocomposites (0, 3, 5, and 8% w/w). The d-spacing value for agar-CMC/3% Ag-MMT and agar-CMC/8% Ag-MMT are 1.5 nm and 3.5 nm respectively, which indicate the intercalation and partial exfoliation of Agar-CMC in Ag-MMT layers.
3.4.2 Fourier transforms infrared (FTIR) spectroscopy
The FTIR spectra of the purified bentonite clay and Ag-MMT are shown in the Fig. 6. The bands between 3420 cm−1 and 3620 cm−1 are indicative of hydroxyl —OH, hydrogen bond and absorbed H2O of montmorillonite. The broadband centered near 3400 cm−1 is due to —OH stretching mode of interlayer water. 1640 cm−1 and 1036 cm−1 is for N—H bending. FTIR of the clay samples before Ag modification showed the typical absorption bands of aluminosilicates. Peaks at 3620 and 3698 cm−1 are due to OH band stretch for AlOH, MgOH, and SiOH. The shoulders and broadness of the OH bands are mainly because of contributions of several structural OH groups occurring in MMT. The wideband between 3000 and 3500 cm−1 is composed of three different bands: H2O—H2O—H bonds that absorbs around 3398 cm−1; a band at 3200 cm−1 ascribed to an overtone of the H2O bending vibration; and an absorption below 3200 cm−1 due to the presence of small and strongly polarizing cations, such as Al3+, since H2O molecules coordinated to them form stronger H bonds to H2O in outer spheres of coordination. The bands observed at 1625 and 1697 cm−1 are related to H2O bending mode, the presence of two bands indicate differences in coordination water within the structure and the hydration shell. For the treated clays, no changes are observed for structural hydroxyls (3625 cm−1). The overlaid absorption peaks in the region of 1640 cm−1 is attributed to OH-bending mode of water (adsorbed water). IR peaks at 915, 875, and 836 cm−1 are attributed to AlAlOH, AlFeOH, and AlMgOH bending vibration respectively. The band at 1035 cm−1 is attributed to Si—O stretching (in plane) vibration for layered silicates.
3.5 Thermal analysis
3.5.1 Thermal stability of agar-CMC/AgNPs nanocomposite films
Thermo-gravimetric analysis (TGA) and first order derivatives (DTG) of weight loss of Agar-CMC and Agar-CMC/Ag-MMT nanocomposites are depicted in Fig. 6, it shows that the main weight loss occurs between 150 and 400 °C due to the decomposition of Agar-CMC matrix. With the incorporation of glycerol into the agar-CMC matrix, there is a small change in the degradation temperature (in terms of 50% weight loss) from 203 to 345 °C. Here, glycerol acts as a plasticizer, which is previously confirmed by mechanical property measurement. Incorporation of plasticizer into the polymer matrix reduces the interactions between polymer chains and thus reduces the thermal stability. This kind of phenomenon was previously observed in the case of glycerol plasticized chitosan film. Again with the loading of Ag-MMT to Agar-CMC, the matrix increases the thermal stability of Agar-CMC/Ag-MMT film from 203.1 to 212.7, 225.0, 229.2 and 245.6 °C with the loading of 2, 4, 6 and 8 wt. % Ag-MMT, respectively. From the results, it can be concluded that the Ag-MMT loading leads to the increase of the thermal stability of Agar-CMC matrix because the alumina and silicate layers of Ag-MMT act as a heat insulator and prevent to defuse the volatile material (water and substances of low molecular weight), as well as the diffusion of oxygen in the polymer matrix, delaying the initial decomposition process of these of polymer matrix.
3.6 Antimicrobial activity
Nowadays, nanocomposites have been actively investigated for antibacterial applications. Silver nanoparticles are eco-friendly and nontoxic antibacterial material; however, its main disadvantage is poor binding characteristic and stability, which restricted their application. Polymer-stabilized nanoparticles and nanoparticles-embedded nanocomposite are outstanding approaches for their preparations. Hence, antibacterial abilities of silver nanoparticles loaded montmorillonite and Agar-CMC nanocomposite was studied. The efficiency of antibacterial activity was evaluated by calculating their ability to inhibit the bacterial growth of B. subtilis (as Gram-positive bacteria) and E. coli (as Gram-negative bacteria) growth over agar culture dishes. After 48 h of incubation at 37 °C, there was the inactivation of the bacterial zones and no bacterial colonies were observed for Agar-CMC/MMT nanocomposite and Agar-CMC/Ag-MMT nanocomposite shown a promising result as shown in the Petri dishes (Fig. 7). These results are quite expected and seemed to be followed according to the Ag-MMT amount in the nanocomposite matrixes. It was evident from the inhibition zones were observed higher for 3 wt. % Ag-MMT nanocomposites than 1 wt. % Ag-MMT nanocomposite. Hence, the Agar-CMC/Ag-MMT nanocomposite developed from this study can be considered as good antibacterial agents, effective in killing the bacteria (see Fig. 8).
3.7 Mechanical properties
The mechanical properties of the bionanocomposite films are usually measured by means of tensile strength (TS), elongation at break (EB), and elastic modulus (E). The mechanical properties, TS, EB, and E, indicating strength, flexibility, and toughness of a film, respectively, can be used as indicators of the film’s ability to maintain film integrity and to withstand environmental stress during packaging application. Mechanical properties of agar-CMC and agar-CMC/Ag-MMT bionanocomposite films are shown in Table 3.
| Film | Elastic modulus (MPa) |
Tensile strain (MPa) |
Elongation at break (%) |
|---|---|---|---|
| AC | 29.45 ± 1.9 | 6.71 ± 2.2 | 26.44 ± 1.6 |
| AC/Ag-MMT 2 | 11.38 ± 1.5 | 3.85 ± 2.2 | 47.23 ± 3.2 |
| AC/Ag-MMT 3 | 35.51 ± 1.2 | 10.25 ± 2.0 | 33.34 ± 2.5 |
| AC/Ag-MMT 5 | 55.34 ± 2.0 | 13.30 ± 2.9 | 30.53 ± 2.1 |
| AC/Ag-MMT 8 | 26.32 ± 1.6 | 6.88 ± 1.8 | 50.07 ± 1.9 |
The mechanical properties of agar film were greatly influenced by blending with the Ag-MMT. It is observed a decrease of 40 and 57% of elastic modulus and tensile strength, respectively when incorporation 2 wt. % of MMT. This is attributed to the lack of adherence between the matrix and the reinforcement or to poor distribution of the nanoparticles in the matrix by agglomeration. The incorporation of 3 and 5 wt. % MMT increased 20 and 89% the module elastic and 45 and 50% the tensile strength. The increase in mechanical properties is related to good homogeneity and interaction between nanoparticles and matrix, which allow the transfer of efforts of the matrix to the nanoparticles.
Elongation at break increased significantly after Ag-MMT incorporation in the samples, except in AC/Ag-MMT 5. The increase of EB is related to the formation of polymer networks ductile. The mechanical behavior of bionanocomposites films is comparable to the commodity plastic films and still high enough to be used for food packaging applications (Kanmani and Rhim, 2014). The mechanical properties of the films are closely related to the distribution and density of the intra-and intermolecular interactions between the polymer chains in the film matrix (Chambi and Grosso, 2006).
The bionanocomposites are thermally and mechanically stable with time but the antimicrobial properties of bionanocomposites is not steady with long time period. The stability of silver nanoparticles is a big issue which materilas researcher are facing. We have prepared silver nanoparticles in a layer of montmorillonite which is stable than silver nanoparticles alone but not 100% stable. With the help of MMT one can increase the stability of silver nanoparticles. The stability of silver nanoparticles is decreased with time but with proper storage condition of the materials we can increase stability time period of materials up to one or two years (Pinto et al., 2010; Velgosova et al., 2017).
4 Conclusion
Bionanocomposite (Agar-CMC/Ag-MMT) film was developed using carbohydrates such as agar and Carboxymethylcellulose, and fillers such as silver modified montmorillonite. Agar-CMC/Ag-MMT films exhibited improved mechanical and thermal as well as strong antimicrobial activity against both Gram-positive and Gram-negative food-borne pathogenic bacteria. Developed bionanocomposite films have a high potential to be used as eco-friendly antimicrobial packaging materials to improve the shelf-life of packaged food. The outstanding results demonstrated excellent antibacterial properties of Agar-CMC/Ag-MMT bionanocomposites. The mechanical and thermal properties of Agar-CMC based bionanocomposite films exhibited a change depending on the MMT concentration. The better mechanical and thermal properties were observed with incorporation of 5 wt. % or 8 wt. % Ag-MMT into the film matrix. In all Agar-CMC/Ag-MMT nanocomposite films, the degree of total color difference increased with increasing clay concentration.
Acknowledgements
This work was supported by council of scientific and industrial research (CSIR – India) funded project SPEC (CSC-0135).
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