starch based edible nanocomposite films for intelligent food ...biodegradable packaging in food...

The 11th International Chemical Engineering Congress & Exhibition (IChEC 2020) Fouman, Iran, 15-17 April, 2020

Starch based edible nanocomposite films for intelligent food packaging

N. Shahgholian-Ghahfarrokhi, S. M. Mohammadi Sadati, J. Mohammadi-Rovshandeh*, M. Shahrousvand

Caspian Faculty of Engineering, College of Engineering, University of Tehran, Guilan, Rezvanshar, Iran, P.O. Box 43841‑119

[email protected]

Abstract Biodegradable packaging in food materials is a green technology based novel approach to replace the synthetic and conventional packaging systems. pH-sensitive starch based films were developed by incorporating different amounts of zinc oxide nanoparticles and curcumin. Prepared films had suitable mechanical properties. However, starch-ZnO nanocomposite films exhibited higher moisture content and non-transparency than starch film. Among all films tested, nanocomposites film containing 0.1, 0.25, 0.5 and 1 wt% of ZnO on starch basis exhibited the best performance in antioxidant and antibacterial activities. Scanning electron microscopy showed nanoparticles was uniformly distributed in starch films. Also, color variations were observed in starch based nanocomposites films containing of curcumin by changing pH. Results suggested starch-ZnO- curcumin films could be used as promising antioxidant and visible pH-sensing food packing materials.

Keywords: Starch, Nanocomposite, pH-sensitive, Curcumin, Food packing.

Introduction Polymeric packaging applications have the largest market for the plastic industry and have grown rapidly over the past few decades resulting in critical environmental concerns because of resistance of the synthetic polymers to degradation [1, 2]. Thus, studies are focused on developing specific packages for foods by raw and renewable materials. Natural based polymers could be an alternative to synthetic packaging materials because of low price, biodegradability, biocompatibility, and nontoxicity properties [2-7]. Among natural polymers, starch has been considered by many scientists for its low cost, abundance, biodegradability and biocompatibility. Starch is extracted from plants such as corn, wheat and potatoes that contains amylose, amylopectin. Starches have disadvantages such as semi-crystalline, hydrophilic structure, water vapour permeability and poor mechanical properties. To solve this problem, materials such as plasticizer are used to convert thermoplastic starch (TPS). The most commonly used plasticizers are water and glycerol that eliminates the hydrogen bond between starch molecules and placed the plasticizer molecules between the starch chains [8- 10]. The use of nanoparticles and the production of bionanocomposites is one of the ways to improve films production properties [11-14]. Nanotechnology can increase the resistance of water vapour penetration, antimicrobial properties, UV radiation protection and as well as reduces the properties of hydrophilic food


packaging.Zinc oxide nanoparticles have been used as the most widely used nanoparticles for controlling microbes and bacteria, which has filler and photocatalyst properties and absorbs UV light. In recent years, food packaging technology is growing to maintain food quality. Intelligent packaging is a modern innovative system, and with the use of indicators, it is able to perform intelligent tasks such as identifying, sensing and producing information. Changing pH is one of the indicators for determining the quality of food products and with the deterioration of the food material, changes in pH are observed [15-17]. In addition to preventing food oxidation, various antioxidants can be used. There are several different antioxidants to prevent food oxidation that contain various plant extracts such as curcumin extract, which eliminates free radicals [18, 19]. In the acid and neutral pH range, the solution is yellow and pH in alkaline solution is red. It can be used as an antioxidant, antimicrobial and anticancer properties [19, 20]. In this work, we are prepared biodegradable nanocomposite films based on starch/zinc oxide (ZnO) nanoparticles containing curcumin to improve the duration and quality of food (solid or liquid) in food packaging to enhance the antioxidant and antimicrobial properties of the film of packaging. These films will contain a color detector which under different conditions of pH, will change the color of the films. Experimental Materials and preparetion of starch based films Starch was purchased from China and glycerol was prepared from Procter & Gamble Ltd (Tianjin, China). ZnO nanoparticles were purchased from US Nano Company. Distilled water was used in all experiments. In order to preparation starch films with different percentages of glycerol (15%, 20%, 25%, 30%, 35%) by casting method, 5 g of starch, 40 g of water, 40 g of ethanol and different percentages of glycerol were mixed together. The mixture was stirred at ambient temperature for 40 minutes using a magnetic stirrer. Then, the mixture was under heated at 90 °C in a hot water bath on a magnetic stirrer for 40 minutes to form gelatinized. Mixtures were moulding into a Petri dish and incubated in the oven at 50 °C for 24 h. After obtaining the optimum amount of glycerol, different percentages of zinc oxide nanoparticles (0.1%, 0.25%, 0.5%, 1%, 2%) were added to the mixture. Also, after obtaining the optimum amount of zinc oxide nanoparticles, curcumin 0.5% wt. were added to the mixture. At this stage, the optimum amount of curcumin was obtained. Characterization Thermogravimetric data were recorded using a PerkinElmer STA 6000 thermal analyzer. The samples were heated from room temperature to 600 °C at a heating rate of 10 °C/min. The films were coated with gold without any other modification and morphology of the surface failure studied by SEM (AIS 2100, Seron Technology, Korea) in the magnification of 26 kV. Tensile properties were evaluated by an Instron tensile testing apparatus (5566-Applied Science Co., Ithaca, NY) for evaluation of mechanical properties. Results and discussion Starch films with different amounts of glycerol were prepared as described in the preceding section. Fig. 1 shows the samples image after being scratched in the oven. It is clear that Starch-30Gly is in good condition. Also SEM images are shown in Fig. 2. The mode of fracture at the surface reflects the physical behavior of the samples. As it is known, with increasing glycerol content, the fracture surface of CS films is wrinkled which refers to the softening effect of glycerol.


The roughness of the fracture surface increases when plasticizer is present. These results are consistent with the results of the tensile test. Fig. 3 shows Tensile results of starch films with different glycerol content.

Fig. 1. Picture of Starch films with different glycerol content after drying in the oven.

Fig. 2. SEM fracture surface images of Starch films with different glycerol content. The tensile strength decreased remarkably from 34 to 10 MPa by adding the glycerol contents, which could be due to effective plasticizing. This is while tensile strain increased with the increase of glycerol content. Also, the Young's modulus was decreased by increasing the percentage of the Gly. Since the sample containing 30% wt. glycerol has good toughness, this sample was selected as optimum the nanoparticles of ZnO were added to it. Fig. 3B shows the SEM image of the ZnO nanoparticles.

Fig. 3. Image of Starch/glycerol films with different ZnO content after drying in the oven

As is known, the nanoparticles have a rod structure with an average diameter of 30 nm. As the amount of nanoparticles in the starch film increases, the stress concentration points increase during drying (Fig. 3C). So that samples Starch-30Gly-1ZnO and Starch-30Gly-2ZnO are fragmented. The results of the tensile test confirm that the addition of nanoparticles reduces the strength of nanocomposite films. On the other hand, the addition of nanoparticles increases the elongation at break which can be due to the chains swirling around the nanoparticles.

Fig. 4. (A) Tensile strength test results of samples with different ZnO content; (B) TGA results of

Starch/glyserol films with different ZnO content.


Fig. 5. pH- sensitivity of Starch/glycerol/ZnO films with curcumin content.

The samples of Starch-30Gly-0.1ZnO, Starch-30Gly-0.25ZnO, and Starch-30Gly-0.5ZnO were chosen as samples that had 0.5 % wt. of curcumin. Fig. 5 shows pH- sensitivity of Starch/glycerol/ZnO/Curcumin films. As is evident, the films are yellow and brown in acidic and alkaline environments, respectively. Conclusions Films containing different amounts of glycerol were well prepared and optimized. As content of ZnO nanoparticles increased, the tensile strength and elongation at break of nanocomposite films increased and decreased, respectively. The curcumin-containing nanocomposites exhibited a ph-sensitive behavior. These films can be used in smart food packaging. References [1] Muscat, D., Adhikari, B., Adhikari, R., & Chaudhary, D. S. "Comparative study of film forming behaviour of low and high amylose starches using glycerol and xylitol as plasticizers." Journal of Food Engineering 109.2, 189-201 (2012).

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starch based edible nanocomposite films for intelligent food ...biodegradable packaging in food...

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