physical, mechanical and oxygen barrier properties of antimicrobial active packaging based on ldpe film incorporated with sorbic acid.
Based on plastic, such as low density polyethylene, due to its physical properties, outstanding strength and barrier properties, it has received much attention in packaging technology to protect food from microbial contaminants [j]2].
Generally speaking, plastic packaging has several advantages in food packaging, such as light weight, low cost, significant strength, good oil resistance and chemical resistance compared with other packaging materials, excellent gas and water vapor barrier properties for heat sealing, stable heat, easy to reuse and recycle .
However, this traditional packaging is only used for mechanical support and protection of food from external contaminants, and due to the key safety when in contact with food, it is considered passive protection, so as to maintain inertia as much as possible14].
Therefore, in the past decade, new food technology polymer packaging has been developed to overcome this problem.
In terms of safety, industrial food production has shifted to fresh and chemical foods with the highest quality and extended shelf life --life.
In addition, the trend of market globalization has led to a longer distribution of the lifestyle of food and consumers, which is also the driving force for the development and improvement of packaging to expand the functions of traditional packaging.
In fact, polymer packaging is now transforming foam protection into an active role in improving food quality.
In recent years, the polymer packaging film combined with antibacterial drugs has achieved remarkable development in improving the preservation of packaged foods.
These films have the potential to improve the microbial stability of food by acting on the surface of food [1,12].
The modification of the polymer structure of plastic materials can be achieved by traditional chemical methods or by ionising radiation from radioactive sources or highly accelerated electrons.
Among them, radiation grafting is considered a versatile and clean method due to its large penetration rate in the polymer matrix, quickly and evenly forming active sites for triggering grafting throughout the matrix, this is useful for developing new materials with unique properties. Radiation-
Inducing grafting in its simplest form involves heterogeneous systems, the substrate is a film, fiber, or even a powder, and the monomer to be grafted onto the substrate can be a liquid, steam, or solution.
Polymers are often irradiated to change chemical and physical properties and are particularly interested in achieving specific desired properties.
Under appropriate experimental conditions, modification of polymer properties can be done not only on the surface, but also throughout the internal phase of the polymer .
Grafting of polyethylene with polarized functional groups is a very good way to obtain new materials with special physical properties
Incorporation of polarization functional bases such as Carbonyls (C=O)
Polymer-forming chains provide specific sites for interaction, such as hydrogen-bound and bonded bonds, which improves the compatibility of polymers with other materials .
In addition, the attachment of the bonded bond provides long-life Chemical stability by introducing the chain compared with the physical coated polymer chain 9]. Sorbic acid (2,4-
Considered a GRAS additive used in beverages, processed fruits and vegetables, commonly used as a model additive in the release study [5,6].
In addition, effective enrichment generally does not change the taste or smell of the food and is considered harmless .
Induced grafting of antimicrobial agents on polymer films, x-
It is reported that [there are gamma rays or ultraviolet rays]13,10,4].
However, so far there have been no reports of radiation
Grafting sorbic acid was induced on low density polyethylene film.
Therefore, this study aims to evaluate the properties of the oxygen permeability, tensile strength, breaking elongation, water contact angle and surface morphology of the antibacterial low density polyethylene film grafted with sorbic acid.
Method: material: low density polyethylene film (
About 50pm thickness)
Extrusion by blowing film extrusion.
Sorbic acid is purchased from Sigma-
Received Aldrich andused.
Solvents and chemical reagents are laboratory-level and can be used without further purification. Radiation-
Induction grafting: Pre-
By irradiation grafting, sorbic acid (SA)
In low density polyethylene (LDPE)film.
Put 10 cm x 10 cm sq ft of low density polyethylene film in a zip bag, seal after nitrogen rinse and shine with an electronic accelerator at dry ice temperature, EPS 3000 available at Agensi nuk
The irradiated membrane is directly used for grafting reaction.
Grafting reaction was carried out in anpou, the irradiated samples were placed in anpou and soaked at 60 [for 3 hours with sorbic acid solution of 2%, 5% and 10% SA concentration]degrees]C.
The sample is then taken out of the solution and cleaned by ultrasound in distilled water for 1 hour, then repeatedly cleaned with distilled water until the subsequent weight does not drop.
Representation of the film: using a constant-
Pressure system and soap foam flowmeter.
Conduct penetration test on degrees]
C. The pressure of the feed gas is 5 bar gauge.
Repeat measurements three times per sample.
Calculate pure gas permeability using the equation. (1): P = l/A[DELTA]p dv/dt (1)
Here P is the penetration rate ,[DELTA]
P is the differential pressure across the membrane (Pa)
A is the effective surface area (12. 5 x 10-4[m. sup. 2])
L is the thickness of the film (m)
T is penetration time (s)
V is the volume of gas that runs through the film ([m. sup. 3](STP)).
Measure tensile performance on SHIDMADZU Autograph TensileTest machine model
G according to ASTM D1822L.
The cross speed of 30mm specification length wasset and 1 mm/min was used and tested under 25 [+ or -]3[degrees]C.
Analysis of the change law of graft membrane grafting morphologywas produced by atomic force microscope (ShimadzuSPM-9500J2).
The water contact point on the surface of the sample is measured by a drop method with a static contact angle (
Three times per sample analysis).
Results: Discussion: as shown in Table 3.
1. Oxygen permeability (OP)
Value of control film and sorbic acid film (SA)
Grafting at different concentrations was compared.
The grafting effect of sorbic acid on the tol membrane plays an important role in the improvement of OP.
From the results, the lowest OP was observed at low density polyethylene + 10% SA and 3. 07 x [10. sup. -16][m. sup. 3]m/[m. sup. 2]
SPa which is very different from other movies.
The OP value of 2% and 5% grafted low density polyethylene of SA is 3. 34 x[10. sup. -16]and 3. 21 x [10. sup. -16][m. sup. 3]m/[m. sup. 2]
The SPa has the highest OP value of low density polyethylene + 2%, respectively, which indicates that the film does not comply with good oxygen prevention compared to other films.
With the addition of SA, the OP of the film decreases, which may be due to the limited inter-molecular chain fluidity, and the free volume of the film decreases with the decrease of the OP.
This result shows ofl-g-
SA film used as an antibacterial package can prevent food deterioration.
Thin films with low oxygen permeability are suitable for candy products, baked goods, nuts and other products that are easily oxidized .
Tensile strength (TS)
And breaking elongation (EAB)
Table 3 shows low density polyethylene films grafted with different concentrations of SA. 1.
The addition of SA significantly improved TS and EAB.
The control film shows lower TS (20. 48 MPa)and lower EAB (193. 25%)
Than those grafted movies.
TS also increased from 31 when SA concentration increased from 2% to 10%. 25 MPa to 32. 61 MPa.
On the other hand, the EAB of the antibacterial film increased significantly from 201 compared with the control film. 10% up to 254.
47%, the concentration of SA from2 % increased to 10%.
However, the TS and EAB of the film with SA 2% and 5% are lower than the film with SA 10%, which indicates the excellent TS and EAB performance with 10% sorbic acidexhibit
The improvement of the mechanical properties of the grafting film may be due to the grafting of SA onto the tobackbone of the low density polyethylene film, thus increasing the flexibility of the polymer chain.
Tensile results show that the addition of sorbic acid by radiation grafting can improve the tensile properties of low density polyethyleneg-SAfilm.
Contact angle measurements were carried out to provide information about the contact angle of water on the surface of low density polyethylene and low density polyethyleneg-SA.
As shown in figure 3.
1. Under normal circumstances, all contact points for grafting sorbic acid on low density polyethylene film are above 90 [degrees]
This means that the film has a hydrophobic surface.
Before grafting, the contact angle of the control low density polyethylene film was about 86. 42[degrees]
This means that the surface of the material is hydrophilic.
For grafting membranes, the water contact angle is increased to 105. 25[degrees]
, This indicates that the grafting of sorbic acid resulted in a decrease in the surface moisture of the graft film compared to the original low density polyethylene.
Enhancement of low density polyethyleneg-
The chemical composition and surface morphology of the surface of the material determine the moisture properties of the material, which is related to the roughness of the surface of the material.
These results are well correlated with the AFM micrographic observations, which show the attachment of sdopid acid to the surface of the film. Figure 3.
Two show three-
Size AFM images obtained from the original film sample and the grafted film.
It is clear from this result that the grafted sample appears to have a relatively rough surface topography, which supports the early results in figure 3. 1.
From the pictures of grafting samples with small new spikes, it can be seen that the effect of grafting on the topological structure may show considerable grafting SA compared with the ungrafted low density polyethylene film.
Conclusion: This study shows that sorbic acid (SA)
It has an important influence on the performance of the film. LDPE-g-
The SA film has shown excellent improvement in both tensile strength and fracture elongation, which is the result of increased flexibility of the polymer chain, which affects the morphology of the film, resulting in an increase in surface roughness of the film.
The contact point of the graft film shows a decrease in surface moisture, which means that the film has a hydrophobic surface.
In general, the use of SA as an active substance provides a high potential for the development of antimicrobial active films for food packaging.
Therefore, future research in this field should focus on the application of this antibacterial film in food to evaluate the effectiveness of its antibacterial properties.
Article information article history: revised February 28, 2014 received on May 25, 2014 received on June 6, 2014 received online received on June 20, 2014 author would like to thank the International Atomic Energy Agency (IAEA (IAEA)
A coordinated research programme (CRP)
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Taylor and Francis, organic acids and food preservation. (1,2)
Not Azwin Shukri ,(1)
Zulkafli Ghazali ,(1)
It\'s not AzillahFatimah ,(1)
Pad Uzir wait (1)
Atomic Energy Agency of Malaysia, radiation treatment technology, Bani, 43000, Kajang, Selangor, Malaysia. (2)
University of Malaysia, Center for composite materials, Johor, Johor, Shin Shan, Malaysia, 81310.
Author: Malaysia Atomic Energy Agency, radiation treatment technology, Bangi, 43000, Kajang, Selangor, Malaysia.