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  3. Investigating the physical properties of silver polylactic acid nanocomposite film and its effect on the growth kinetics of Escherichia coli bacteria

Investigating the physical properties of silver polylactic acid nanocomposite film and its effect on the growth kinetics of Escherichia coli bacteria

Number of pages: 71 File Format: word File Code: 32474
Year: Not Specified University Degree: Master's degree Category: Food and Packaging Industries
Tags/Keywords: Antimicrobial activity - Escherichia coli - Food poisoning - Nano composite film - Physical properties - Polylactic acid - Silver nanoparticles - Titanium dioxide
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  • Summary of Investigating the physical properties of silver polylactic acid nanocomposite film and its effect on the growth kinetics of Escherichia coli bacteria

    Dissertation for Master's Degree in Food Science and Engineering

    Food Microbiology Orientation

    Abstract:

    Today, the increase in environmental pollution and the decrease in oil resources have led to the development and replacement of biodegradable packaging instead of packages derived from petroleum sources. Also, in this regard, the use of antimicrobial compounds such as silver nanoparticles improves the efficiency of these packages to a great extent. This research work was conducted in order to produce and investigate the properties of polylactic acid film and polylactic acid/silver nanocomposite containing 0.5, 1 and 2% silver nanoparticles using solvent casting method. The antimicrobial effect of these films on the growth parameters of Escherichia coli gram-negative bacteria was investigated by the dynamic-Flask test method using Gompertz and Logistic models, the results of which showed a 4.3% increase in the duration of the lag phase, a 30.9% decrease in the growth rate of Escherichia coli bacteria, and a 32.6% decrease in the final population of this bacterium. In this research, it was observed that with the increase in the percentage of silver nanoparticles, the antimicrobial activity of this nanocomposite increased. In infrared spectroscopy (FTIR), it was observed that a new peak was observed in the range of 3620 cm-1 of composites containing silver nanoparticles at all levels (0.5, 1 and 2% of silver nanoparticles), which was attributed to the chemical interaction between silver nanoparticles and polylactic acid. Also, in examining the XRD diagrams, the observation of Ag(111), Ag(200), Ag(220) and Ag(311) peaks indicates the presence of crystalline silver nanoparticles.

    Key words: Escherichia coli, polylactic acid, titanium dioxide, antimicrobial activity, silver nanoparticles, nanocomposite.

     

     

     

     

    Introduction

    Diseases caused by food poisoning have become an important threat to Human health is a factor for the emergence of the packaging industry. Since plastics make up a major part of the packaging industry, the packaging industry can be considered dependent on petroleum products. Hence, the ever-increasing population growth, pollution caused by packaging materials from petroleum derivatives and problems caused by different methods of disposing of these pollutions, including burning, burying and recycling them, have caused more attention to biopolymers and bio-packaging. Biodegradable packaging films and coatings are suitable alternatives to synthetic films in the packaging industry due to their environmental friendliness and low dependence on non-renewable resources, which have attracted the attention of many researchers. Biodegradable packaging prevents food products from reducing their quality by protecting the product against mechanical, physical and chemical damage. Also, as a carrier of antimicrobial substances in the form of antimicrobial packaging, they can prevent microbial activities and increase the shelf life of food products.

    The use of nano reinforcers in the production of packaging materials and the preparation of biodegradable nanocomposites is considered one of the most important advances in polymer science in food packaging. Among the most widely used nano compounds used in antimicrobial packaging are silver nanoparticles, nano zinc oxide, nano titanium dioxide and nano clay. Silver nanoparticles with strong antimicrobial properties increase the shelf life of food. Also, silver, as an enhancer of the physicochemical properties of biopolymers, can be one of the nanomaterials used in the production of active nanocomposite packaging (Babazadeh and Almasi, 2013).

    In this research, the production of polylactic acid bionanocomposite containing silver nanoparticles has been discussed, as well as the investigation of antimicrobial properties and some studies conducted in this field.

    1-1- Packaging

    With the change of people's lifestyle from a nomadic lifestyle to staying in a safe area, the need for food storage containers arose. By the 1800s, there had been very little improvement in packaging materials, with natural resources such as melons, husks, leaves, and baskets woven from grass and reeds being used to store food. Later, containers such as pottery and glass were introduced to store food. The first found evidence of the origin of pottery and glass dates back to 7000 BC. Also, the industrialization of the process that was implemented by the Egyptians was not seen until about 1500 BC (Kent and Berger[1], 2002).

    Many factors cause the loss of food value, the most important of which are microbial spoilage and the loss of some important properties such as vitamins and minerals. pointed out Since humans need to consume food throughout the year in order to meet their nutritional needs and continue their lives, and the simplest way to protect food is packaging, in this sense, food packaging is of particular importance. Packaging is used as a barrier to prevent product breakage and loss of moisture, oxygen, carbon dioxide, other gases, as well as flavors and aromas. It can also be a barrier against the penetration of light to protect the nutrients and color in a product.

    Packaging is a composite military that has the function of protection and the role of communication or information culture and is used to maintain the quality of food, minimize food waste and reduce the use of preservatives in food.

    1-2- Synthetic polymer

    Environmental pollution caused by the introduction of synthetic polymers, plastics and non-degradable packaging materials into nature is one of the biggest dangers that threaten human life. Preservation and maintenance of the product is the main task of packaging, but on the other hand, it includes a large share of everyday waste, and by burning and burying them, they cause more environmental pollution. Due to their special composition, these materials are rarely decomposed in nature and have a long shelf life, which causes many environmental problems. In general, there are two main methods to solve this problem, which are recycling and production of biodegradable plastics. Despite the problems and heavy costs of recycling operations, the production of biodegradable packaging seems to be a more reasonable solution.

    1-3- Biodegradable polymer

    The great effort to develop the shelf life and increase the quality of food while reducing packaging waste has strengthened the discovery of bio-based and renewable packaging materials. Due to their degradability, the use of these materials can ultimately solve the waste problems.

    In the last decade, biocompatible and biodegradable polymers have received a lot of attention from the point of view of ecology. Polymers that are completely converted into natural products such as water, carbon dioxide and biomass (bacteria and fungi) or enzymes after the decomposition process with the help of microorganisms are called "biodegradable" (Lasperilla et al. [2], 2011; Gennadios [3], 2002). The constituent units are self-degraded and therefore do not remain in the environment.

    The most important biodegradable polymers are fatty polymers such as poly-3-hydroxybutyrate, poly-4-caprolactone, polyglycolic acid and polylactic acid (PLA) (Lasperilla et al., 2011). 

    1-3-1- Polylactic acid (PLA) [4]

    Polylactic acid is a chiral polymer with low molecular weight and containing asymmetric carbon atoms with a spiral structure. Also, the fatty composition is flexible against heat, which is easily biodegradable through enzymatic and hydrolytic ways. This compound was discovered in 1932 by Carothers (DuPont) by heating under vacuum lactic acid (Lasperilla et al., 2011).

  • Contents & References of Investigating the physical properties of silver polylactic acid nanocomposite film and its effect on the growth kinetics of Escherichia coli bacteria

    List:

    Abstract 1

    Chapter One: Introduction

    Introduction. 3

    1-1- Packaging. 4

    1-2- synthetic polymer. 4

    1-3- Biodegradable polymer 5

    1-3-1- Polylactic acid (PLA) 5

    1-4- Nano technology. 6

    1-4-1- Nano. 6

    1-5- composite, nanocomposite, bionanocomposite. 6

    1-6- Silver 7

    1-7- Research objectives. 7

    1-8- research assumptions. 8

    Chapter Two: An overview of the conducted research

    2-1- Packaging. 10

    2-1-1- Definition of packaging. 11

    2-1-2- Purpose of packaging. 11

    2-1-3- characteristics of packaging raw materials. 12

    2-2- Active packaging. 12

    2-2-1- types of active packaging systems. 13

    2-2-1-1- Oxygen absorbent packaging. 13

    2-1-2-2- Carbon dioxide emitting packaging. 13

    2-2-1-3- moisture absorbent packaging. 14

    2-2-1-4- Ethanol diffuser packaging. 14

    2-2-1-5- flavor diffuser/absorber packaging. 14

    2-2-1-6- antioxidant packaging. 14

    2-2-1-7- Antimicrobial packaging. 15

    2-3- Antimicrobial packaging. 15

    2-3-1- Properties of antimicrobial composition. 16

    2-4- Packaging film and cover. 17

    2-4-1- Use of film and packaging covers. 17

    2-4-2- Composition of film and packaging covers. 17

    2-5- synthetic polymers. 18

    2-6- Biodegradable polymers 18

    2-6-1- Classification of biodegradable polymers 20

    2-6-2- Advantages of biodegradable polymers 21

    2-6-3- Polylactic acid. 22

    2-6-3-1- properties of polylactic acid. 23

    2-6-3-2-limitation of polylactic acid. 25

    2-7- Nano technology. 25

    2-7-1- Nano. 25

    2-7-2- Application of nano technology in food packaging industry. 26

    2-8- Composite, nano-composite and bio-nano-composite. 27

    2-9-silver 28

    2-9-1- Mechanism of action of silver against bacteria. 29

    2-10- Escherichia coli. 31

    2-10-1- Escherichia coli pathogenicity. 31

    2-10-2- Escherichia coli infections. 32

    2-11- Production and preparation of the film. 33

    2-12- Film making processes. 34

    2-13- An overview of the conducted research 35

    Chapter three: materials and methods

    3-1- Chemicals. 47

    3-2- Preparation method of polylactic acid/silver nanocomposite 47

    3-2-1- Preparation of polylactic acid/silver nanocomposite using nanosilver colloid 48

    3-2-2- Preparation of polylactic acid/silver nanocomposite using nanosilver powder 49

    3-3- Tests. 50

    3-3-1- Investigating the antimicrobial activity of polylactic acid/silver nanocomposite film 50

    3-3-1-1- Bacteria used and its activation method. 50

    3-3-1-2- Investigation of antimicrobial activity. 50

    3-3-2-Fourier transform infrared spectroscopy (FTIR) 52

    3-3-3- X-ray diffraction test (XRD) 52

    3-4-Statistical analysis. 54

    Chapter Four: Results and Discussion

    4-1- Antimicrobial Activity Analysis of Polylactic Acid/Silver Nanocomposite Film 56

    4-2- Infrared Spectroscopy (FTIR) 60

    4-3- X-Ray Diffraction (XRD) Test Analysis 61

    4-3-1- X-ray diffraction test of silver nanoparticles 61

    4-3-2- X-ray diffraction test of titanium dioxide nanoparticles. 63

    Chapter Five: Conclusion

    5-1- Discussion and conclusion. 66

    5-2- Suggestions. 68

    Resources. 69

    English abstract.

    Source:

     

     

     

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    Afraz and. 2013. Investigating the impact of packaging containing silver nanoparticles on the microbial characteristics and shelf life of vegetable salad compared to polyethylene packaging. Master's thesis. Islamic Azad University, Damghan Branch.

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    Dadashi S, Ebrahimzadeh Mousavi M, Imam Juma Z, Urmia A. 2013. Films based on poly(lactic acid) biopolymer: effect of clay and cellulose nanoparticles on physical, mechanical and structural properties.

    Ramzani R, Karbasi A. 2012. The effect of different packaging and light conditions on the stability of refined sunflower oil. Journal of Agricultural Sciences and Techniques and Natural Resources. Volume six, number two. Pages 148-139.

    Zarei A, Rajabpour A. 2013. Increasing the life span and durability of the packaged product and ensuring the quality of the product, by taking advantage of the antibacterial properties of silver/chitosan nano biocomposites. The second national food security seminar. 26 to 27 October 2011.

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    Fathi M., Mohebi M. 2009. Increasing food security using nanotechnology. Nano Technology Monthly. Number 4. Serial 153. Fraser W, Westhoff D. 2016. Food microbiology. Mortazavi A, Kashaninejad M, Ziaulhaq H. Fifth edition. Publications of Ferdowsi University of Mashhad.

    Qanbarzadeh B, Najafabadi A, Almasi H. 2018. Food-active films for food packaging. Journal of Food Science and Industry. Fall 1390, Volume 8, Number 31, Pages 135-123. Levinson and. 2013. A review of basic and medical bacteriology. Mirzaei M, Bohar Pirayeh S, Mansouri S, Bamri Z. First edition. Borujerd Azad University Publications.

    Liaghati L, Azizi M, Jokar M. 2013. Application of nanocomposites in packaging and food industries. Nano Technology Monthly. 11th year Pages 14-18.

    Mortazavi A. 2017. Application of nano in food packaging industry (second volume). First edition. Publications of Ferdowsi University of Mashhad.

    Musabahi G, Habibi M. 2018. Use of active packaging for meat and meat products. Packaging magazine. seventh year No. 69. 34-40.

    Mehdipour Z., Sedaghat N. 2013. Application of biodegradable packaging in food. The first national snack conference. The first national conference on snacks.

    Mirkhavar Z, Khosravi Darani K, Haqqani H, Yeganeh M. 2013. The role of silver nanocomposite as a preservative in food packaging.  The second specialized conference on advanced polymers in food packaging. Mirnazimi Ziabari H. 1381. Principles of food packaging. The fourth edition of Aizh Publications. Tehran.

    Walipour Motlaq N, Mousaviyan H, Mortazavi A. 2017. The effect of packages containing silver nanoparticles on the quality and shelf life of barberry compared to regular polyethylene packages. 18th National Congress of Food Sciences and Industries. 24 to 25 Mehr 1387.

     

     

     

     

    English sources:

     

    Abbas Ali N., Tariq Mohammed Noori F. 2014. Crystallinity, Mechanical, and Antimicrobial properties of Polylactic acid/ microcrystalline cellulose/ Silver Nanocomposites.

    Abbaszadegan A., Ghahramani Y., Gholami A., Hemmateenejad B., Dorostkar S., Nabavizadeh M., Sharghi H. 2015. The Effect of Charge at the Surface of Silver Nanoparticles on Antimicrobial Activity against Gram-Positive and Gram-Negative Bacteria: A Preliminary Study. Journal of Nanomaterials Volume( 2015), Article ID 720654, 8 pages.

    Alves V., Costa N., Hilliou L

Investigating the physical properties of silver polylactic acid nanocomposite film and its effect on the growth kinetics of Escherichia coli bacteria
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