DEVELOPMENT OF THE NOVEL ACTIVE PACKAGING FILM
PREVENTING MIGRATION OF ANTIMICROBIAL COMPONENT
Rivka Cahana, Vadim Goldsteinb, Binjamin Finkelsteinb, Edward Bormashenkoa
a
The College of Judea and Samaria, The Research Institute, 44837, Ariel, Israel
b
Actipol LTD, 12900, Katzrin, Israel
ABSTRACT. The paper presents new antimicrobial active packaging intended to
improvement of safety and quality of food, as well as to extending its shelf -life. We
tried to develop active packaging material in which migration of the antimicrobial
ingredient would be hindered by special preliminary treatment, performed according
to guest-ligand technology. In this research we investigated the effect of thermoplastic
film
mixed
with
antiseptic
material
(starch
potato,
polyacrylamid
and
mercaptobenzothiazol) on bacterial growth. Thermoplastic film was introduced to
Bacillus cereus culture. The culture was grown at 37ºC in NB broth. We studied the
rate of the culture growth and it was revealed that the antimicrobial film inhibited
growth of the culture up to 50-70% comparatively to the control culture after 3-4
hours of observation.
1. Introduction
Foods are spoiled by a variety of both bacteria and fungi, but only particular
microorganisms typically attack each type of food. This is because the chemical
properties of foods vary widely, and different foods are colonized by the indigenous
spoilage organisms that are best able to utilize the nutrient. In general,
microorganisms grow on food surfaces thereby development of active packaging
where the antibacterial agent is immobilized tightly, will be the answer to consumers’
demand for food without preservatives.
The traditional passive packaging is restricted in protecting food products
because of the way that food is distributed and stored. Furthermore, the extended shelf
-life of manufactured foods and the consumers demand for minimal additions of
preservatives to food products have lead to the innovation of active packaging. Major
active packaging technologies that exist based on use of: oxygen scavengers, moisture
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regulators, ethylene absorbers, taint removal, ethanol and carbon dioxide emitters as
well as antimicrobial systems [1]. The antimicrobial active packaging technology
based on antimicrobial agents that are immobilized with the polymeric structure or
incorporated in plastic resins, before film casting. This technology can be divided into
two types: preservatives that are released slowly from the packaged materials to the
food surface or preservatives that are firmly fixed and do not migrate into the food
products. Both are assumed to control growth of undesirable microorganisms.
Among the common microorganisms that contaminate food and drink
products are E.coli, Staph. aureus, Campylobacter, Salmonella, Clostridium
perfringens and Bacillus cereus. Toxins produced by microorganisms or growth of
microorganisms in the human body after the contaminated food has been eaten cause
food poisoning. There are few chemical antimicrobial agents that are used
commercially to control microbial growth in foods [2-5].
Many of these chemicals, like sodium propionate, have been used for many
years with no indication of human toxicity. Others, like nitrites, ethylene or propylene
oxides, are more controversial antimicrobial control because of evidence that these
agents are harmful to human health. In recent years there are several reports of using
bacteriocins, proteins that possess antimicrobial activity, and are produced by
microorganisms, as food preservatives [4]. Development of different kinds of active
packaging is under intensive progress now [6-7]. One of the key problems of the
active packaging technologies resides in the controlled release of the antimicrobial
agent from the polymer film [8]. However as yet very limited published works are
available in the area.
Polyethylene and its copolymers are much popular materials for food
packaging but they don’t hold molecules of additives for a long time. At the same
time it is well-known fact that polyethylene and its copolymers form clathrates
(complex compounds) with organic compounds containing active functional groups.
We proposed to treat antimicrobial additive according to guest-ligand technology (in
our case antimicrobial additive is a guest), and to form clathrates dispersed uniformly
in polymer matrix will provide controlled release of active additive in time. Our paper
presents very preliminary results of the testing of antimicrobial activity of
polyethylene copolymer films containing antimicrobial clathrates.
In the USA, Japan and Australia, active packagings already exist. However, in
Europe, due to strict legislative, active packaging systems have been restricted so far.
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2. Experimental
2.1 Obtaining of antimicrobial film
Copolymer ethylene-vinyl acetate (EVA) was used a matrix material.
Chemical structure of EVA is presented below:
-[CH2-CH2-CH-CH2-CH2-CH2]-n
O
C
O
CH3
EVA copolymer is distinguished by its high clarity, puncture-resistance,
impact strength and low heat-seal temperature. These properties make EVA a superior
resin for many high performance flexible packaging applications [9]. We used EVA
copolymer with melting index 2.5 g/10 min, suitable for blown film extrusion.
The process of film preparation is presented in Fig. 1. 1 wt.% per cent of
preliminary treated antimicrobial additives were mixed with polyethylene wax PW300 under temperature 100 ºC, then mixture was cooled and pelletized granules of the
mix were introduced into single-screw extruder Econ-Film, manufactured by
“Plastengineering Knauff LTD”, equipped by blown film die, and film stretching
unit. Parameters of the extruder: diameter of the screw: 30 mm, L/D = 26.
Temperature regime of extrusion: T1=120 ºC, T2=125 ºC, T3=140 ºC, T4=155 ºC, N =
55 rpm.
2.2. Measurement of antimicrobial activity.
An overnight Bacillus cereus culture in nutrient agar pH 7 (Difco. USA) was
transferred into fresh nutrient broth medium (final volume, 30 ml), pH 6.5. The
cultures were grown with or without EVA film mixed with the antimicrobial agent, at
37°C with aeration. Optical density was determined at intervals of 30 min, at 660 nm
with Jenway 6300 spectrophtometer.
3. Results and discussion
The main problem, which we tried to solve could be formulated in such a
way is it possible to keep antimicrobial properties of the film and to prevent migration
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of the antimicrobial agent simultaneously? Does antimicrobial agent keep its activity
after formation of the clathtate complex?
In our study we introduced the antimicrobial agent (Mercaptobenzothiazol,
Polyacrylamidand starch potato) into EVA film. Bacillus cereus culture have been
grown on N.B with or with out EVA film mixed with antimicrobial agent, and it was
shown that under 3-4 hours of observation, bacterial growth in the culture, grown in
the presence of the film has been reduced to about 50-70% comparatively to the those
of untreated culture.
References
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their physical properties and antimicrobial activity, Journal of Plastic Film
and Sheeting, 13, (1997), pp. 287-298.
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compounds into biodegradable packaging films, Journal of Food Protection,
61, (1998), pp. 303-307.
4. Ming X., Weber G.H., Ayres J.W., Dandine W.E., Bacteriocins applied to
food packaging materials to inhibit Listeria monocytogenes on meats, Journal
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preliminary treatment
of the antimicrobial
additive with a ligand
introduction
of
treated additive
polyethylene wax
the
and
extruded
blend
extruder
antimicrobial
film
drawing unit
blown film
die
Fig. 1
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