Abstract
The incorporation of antimicrobial agents into packaging materials is an effective method to inhibit the microbial population and aimed at specific microorganisms to provide better and safe products. The present study aims at developing an effective antimicrobial film with silver ions as an antimicrobial agent with and without ethylene-vinyl acetate (EVA). In the present work, two different masterbatches (MBs) were prepared. In the first case MB of 90%, linear low-density polyethylene (LLDPE) and 10% silver ions as an antimicrobial agent were prepared. In the second case MB of 80%, LLDPE, 10% silver ion, and 10% EVA were prepared. An antimicrobial film with low-density polyethylene and different percentages of the MB (0–30%) was prepared and tested under Japanese Industrial Standard (JIS Z 2801:2000) for
Keywords
Introduction
The antimicrobial film has emerged as a new concept of active packaging. Incorporation of the antimicrobial agent into polymer film suppresses the activity of microorganisms resulting in the protection of foods against deterioration by the action of microorganisms. The use of antimicrobial packaging is more effective compared to direct adding of antimicrobial agents into foods.
The effect of silver ions against microorganisms is well established because of its low risk for bacterial resistance, effectiveness in very low concentrations, and having no human toxicity. Many polymers have been used for preparing the antimicrobial film for food packaging including low-density polyethylene (LDPE), high-density polyethylene, polypropylene, polystyrene, and so on.
The preparation of polymer film by blown film extrusion is a quick method and suitable for large production. However, many of the antimicrobial agents are highly sensitive to film production processing conditions and loss of antimicrobial agents at an elevated temperature and pressure results in a decline in their performance.
In this study, a convenient method for the production of antimicrobial polymer film has been carried out by the use of masterbatch (MB). Also, the evaporation of antimicrobial agents due to processing conditions has been addressed by incorporating ethylene-vinyl acetate (EVA).
Food products can be contaminated by undesirable microbes. Antimicrobial films prolong the shelf-life and improve the safety or sensory properties of fresh foods. 1
The integration of antimicrobial agents in packaging materials is aimed at killing or inhibiting microorganisms. The use of antimicrobial agents in food packaging can control the microbial population and target specific microorganisms. Antimicrobial agents are an effective tool for controlling the microbial population and targeting specific microorganisms.
2,3
Applications of various antimicrobials substance such as sorbates, nisin, silver zeolite, and various polymers used for food packaging such as polypropylene, high-density polyethylene, polystyrene, and LDPE have been reported.
4,5
Due to the relatively high temperature involved in the manufacturing of antimicrobial film, there is considerable loss of antimicrobial agents during the film blowing process.
6
-8
The use of MB for the incorporation of the antimicrobial agent is an effective method. Some researchers have used EVA/antimicrobial MB for the production of antimicrobial film and reported retention of a greater amount of volatile antimicrobial agent.
9,10
Nisin was found to be effective in suppressing
Materials selection
LLDPE M26500 Reliance grade.
LDPE 24 FS 040 Reliance grade.
EVA N 8038 Polene grade.
Silver ion antimicrobial agent.
Table 1 lists the properties of materials.
Properties of materials.
LLDPE: linear low-density polyethylene; LDPE: low-density polyethylene; EVA: ethylene-vinyl acetate.
MB preparation
In the plastics industry, concentrates of pigments and additives in a polymer matrix are characterized by the term MB. This is usually in the form of pellets. They are used for dust-free precise feeding of pigments and additives into polymers and compounds. They produce a high-quality product, and higher uniform loading of additives is possible. For preparing MBs, two different compositions were prepared. In the first composition for preparing, the antimicrobial MB, silver ion as antimicrobial agent additives is chosen for this research works. In this case, an MB is prepared with 90% LLDPE and 10% silver ion as antimicrobial agent additive. In the second case, EVA is used in antimicrobial MB due to the inherent property of activity against the bacteria and as a coupling agent along with silver ion. In this case, the MB is prepared with 80% LLDPE, 10% EVA, and 10% silver ion antimicrobial agent additive. Tables 2 to 4 show the formulation for antimicrobial polymer film.
Formulation for antimicrobial MB without EVA.
MB: masterbatch; EVA: ethylene-vinyl acetate; LLDPE: linear low-density polyethylene
Formulation for antimicrobial MB with EVA.
MB: masterbatch; EVA: ethylene-vinyl acetate; LLDPE: linear low-density polyethylene.
LDPE film formulation with different concentrations of antimicrobial MB with and without EVA.
LDPE: low-density polyethylene; MB: masterbatch; EVA: ethylene-vinyl acetate.
Film preparation
The production of plastic film is primarily achieved by blown film extrusion. Many important factors are considered for the production of antimicrobial film, such as the method used to incorporate the antimicrobial agent into the polymer or MB, the optimal extrusion conditions to minimize the loss of agents, the extent to which an additive polymer could reduce the evaporation losses of volatile antimicrobial agents, and the extent to which an additive polymer could control the release of the antimicrobial agent into the food product.
The following steps were carried out for film processing. Processing conditions for the film are mentioned in Table 5. LDPE films were cast through an extruder with and without EVA at a different percentage (0–30%) of the MB. All the films are tested under JIS Z 2801:2000. After testing, a comparison is carried out between colony-forming unit (CFU) forms in the antimicrobial MB and EVA-based antimicrobial MB. The MB is prepared with a twin-screw counterrotating screw extruder.
LDPE film processing conditions.
LDPE: low-density polyethylene.
Determination of antibacterial activity using JIS Z 2801:2000
A cell suspension of either
Results and discussion
Figure 1 and Table 6 show variation in the living bacteria cells of

Effect of the silver ion as an antimicrobial agent on

Effect of the silver ion as an antimicrobial agent on
Result for
MB: masterbatch; EVA: ethylene-vinyl acetate; CFU: colony-forming unit.
Result for
MB: masterbatch; EVA: ethylene-vinyl acetate; CFU: colony-forming unit.
Figure 3 and Table 8 show variation in the living bacteria cells of

Effect of the silver ion as an antimicrobial agent on

Effect of the silver ion as an antimicrobial agent on
Result for
MB: masterbatch; EVA: ethylene-vinyl acetate; CFU: colony-forming unit.
Result for
MB: masterbatch; EVA: ethylene-vinyl acetate; CFU: colony-forming unit.
Figure 5 shows variation in living bacteria cells with percentage variation in the MB of the antimicrobial agent for 24 h with and without EVA for

Effect of the silver ion as an antimicrobial agent on

Effect of the silver ion as an antimicrobial agent on
Conclusion
There is a decrease in the living amount of bacteria with an increase in the percentage loading of the MB. With the maximum loading, that is, 30% of the MB, the living amount of
Footnotes
Declaration of conflicting interests
The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.
Funding
The author(s) received no financial support for the research, authorship, and/or publication of this article.
