ADVANCED BIO-FRIENDLY POLYMERS
Food packaging and use of stabilizers
Györgyi Szarka
Packaging materials
• Paper
• Metal
• Plastic:
-PP
-PET
-PS
-PVC
-Polyesthers
-PE
box
foil
light,
transparent,
unbreakable,
minimal use of material,
good gas and aroma closing,
valuable raw material
http://www.foodpackagingforum.org/Food-Packaging-Health/Food-Packaging-Materials
C. Silvetre et. al. Prog. Polym. Sci., 36, 2011, 1766.
Polymer additives
FUNCTIONAL
•
•
•
•
•
•
•
Plasticizer
Lubricant
Antistatic
Filler
Foaming / Crosslinking
Colorant
Flame retardant
PROTECTING
•
•
•
Heat stabilizer
Light stabilizer
Antioxidant
TYPICAL STABILIZERS
Primary stabilizers/ antioxidants:
Hindered phenols, aromatic amines
Secondary stabilizers / peroxide
decomposers:
Organic thioesters, phosphites and metalthiocarbamates
Chelating agent/metal deactivator:
Organic phosphites and hydrazides
Problem related to food packaging
•
•
•
Migration of additives
Chemical changes during processing
Health problem due to synthetic
stabilizers
FOOD
FOOD
FOOD
Strategies to avoid migration
•
Macromolecular stabilizer
grafting by chemical decomposition of 1,2,2,6,6-pentamethyl-4piperidyl-acrylate (PMPA)
•
Connect the stabilizer to the polymer (grafting / copolymerization )
1. time antioxidant used in
copolymerization with olefin
under Ziegler-type conditions
M. L. Binet, S. Commereuc, P. Lajoie, J. Lacosta, J. Photochem. Photobiol. A: Chem., 137, 71, (2000)
T.L. Pattorn, J. T. Horeczy, D. E. Brown (to Esso Research and Engineering Co.) U. S. 3,477,991 (1969)
T. Iwata, J. Sasaki (to Mitsui Petrochemical Co., Ltd), Canadian 876,769 (1971)
Changes during processing
•
Manufacturer should guarantee not only the safe use of the additive but
the product(s) of them after processing
There are some health concern in relation to BHT, the quinone form causes
lung cancer in mice. Human health problem has not been proved yet.
Natural materials in packaging
Environmental and health problem due to synthetic stabilzers
•Natural antioxidant: lignin, carotin, quercetin
•Radical scavenger: vitamin E
carotin
vitamin E
quercetin
BIODEGRADABLE POLYMERS:
• PHA, PHB, PLA
(Ecoflex, Ecovio)
1. Brocca, D.; Arvin, E, Mosbaek, H: Water Res., 36, 3675-3680, 2002
2. Pataki P., Imra B., Földes E., Pukánszky B., Műanyag és Gumi, 2012, 1
1935/2004/EC regulation
•
This Regulation covers all materials and articles that are intended to
come into contact with food: all types of packaging, bottles (plastic and
glass), cutlery, and even adhesives and inks for printing labels.
•
They must under no circumstances transfer substances to the food with
which they are in contact in quantities likely to:
– endanger human health;
– bring about an unacceptable change in the composition of the food; or
– bring about a deterioration in the organoleptic characteristics thereof.
•
Active materials and articles: intended to come into contact with food:
materials and articles that are intended to extend the shelf-life or to maintain
or improve the condition of packaged food. They are designed to
deliberately incorporate components that would release or absorb
substances into or from the packaged food or the environment surrounding
the food.
•
Intelligent materials and articles intended to come into contact with food:
materials and articles which monitor the condition of packaged food or the
environment surrounding the food.
Active and intelligent material
•
Oxygen absorbents: ascorbic acid, metal-sulfides, glucose oxidase,
catalase enzyme, amorphous polyamide
•
Oxygen exclusion: ethylene/vinyl alcohol closing coating
with Fe-compound
Water vapour absorbents: molecular sieve, silica, CaO, Al coating
Moisture controller: salts
Antimicrobial packaging: sorbic acid, Ag
•
•
•
Summary
• The use of plastics is rapidly expanding in food
packaging industry
• The new products are more sophisticated and fit
better to the improved claims with special
polymers and active additives
• These materials should improve not only the
physical, chemical but the health safety
properties of the package (EU) due to
- reducing migration
- and full controll of all the used
materials and evolved products during
processing
Macrostabilizer strategy
Compatibilizer
Hyperbranched
polymer
Stabilizers
Acknowledgement
HUSK /1101/1.2.1/0209
Hungarian Academy of Sciences
Research Centre for Natural Sciences
Institute of Materials and Environmental Chemistry
Department of Polymer Chemistry
Packaging
•
•
Barrier protection - A barrier from oxygen, water vapor, dust, etc., is often required.
Permeation is a critical factor in design. Some packages contain desiccants or
Oxygen absorbers to help extend shelf life. Modified atmospheres or controlled
atmospheres are also maintained in some food packages. Keeping the contents
clean, fresh, and safe for the intended shelf life is a primary function..
Convenience - Packages can have features which add convenience in distribution,
handling, stacking, display, sale, opening, reclosing, use, and reuse.
Macromolecular stabilizers
 Advantages
– Very low migration to the surface
– Long and predictable effect
– Properties (eg. solubility, miscibility) can be
easily modified by molecular weight and
functionality
Disadvantages
– Further functionalization reactions, which
are often expensive and time consuming
INTERPACK 2011
Other additives
• Antiaging additives:
BHT has been cleared by the FDA
MULTIFUNCTIONAL HYPERBRANCHED
POLYMERS
Dendrimers:repetitively branched molecules start-up of one well defined central core
 low viscosity
 high chain-end funcionality
 developing of generations can be made by only
expensive, difficult and time consuming methods
and reactions
Hyperbranced polymers:
 no special main chain
 statistical distribution of branch points
The branched polymers have all the
beneficial properties of dendrimers.
Synthesis: different one-step reactions
 Polycondenzation of ABn-type
monomers
 Sequential grafting
 INIMER POLYMERIZATION
 Self-grafting of polymers
HYPERBRANCHED
POLYGLYCEROL
Properties
 Synthesis: cationic or anionic Ring Opening Polymerization of glycidol
OH
OH
O
OH
O
Core
OH
OH
base
slow monomer
addition
O
O
Core
O
O
OH
O
O
HO




OH
HO
OH
Well defined product (Mn, PD, number of OH-groups)
Good solubility in water
OH-groups can be functionalized easily
Biocompatible
─ does not induce an immune response
─ oligomers are FDA approved for food and pharmaceutical additives
THE TARGET STABILIZER
OH
OH
O
OH
O
O
O
O
O
O
OH
O
O
OH
O
OH
O
OH
O
O
O
O
O
OH
OH
OH
OH
O
OH
OH
O
O
O
O
O
O
OH
O
O
OH
STABILIZER
COMPATIBILIZER
•
Effect
of
antioxidant
Stabilization of chain-breaking antioxidants
• Stabilization by preventive (secondary) antioxidants
phosphites, organic sulfides
Effect of heat stabilizer
The processing temperature is about 180-200
°C.
• ROOH + Mn+
(n-1)+
• ROOH +M M
/M
n+
• 2ROOH
(n-1)+
ROO. + M(n-1)+ + H+
RO. + Mn+ +OHROO. + RO. + H2O
Much more efficient inhibition is achieved by
using metal deactivators, together with the
antioxidants.
Effect
of
light
stabilizer
Small amounts of impurities or chromophores can be sufficient to
induce photooxidaiove degradation even in the absence of
appreciable UV absorption by a polymer.
Types:
• UV absorbers: absorption of harmful UV radiation and it dissipation
that does not form heat. Need a thickness.
Hxdroperoxybenzophenones and hydroxyphenyl benzotriazoles.
• Quenchers of excited states: light stabilizers able to take over
energy absorbed by the chromophores present in the plastic and to
dispose of it efficiently to prevent degradation.
• Hydroperoxide decomposers: metal complexes of sulfurcontainig compounds such as dialkyldithiocarbamates,
dialkyldithiophosphates and thiobisphenolates.
• Free radical scavengers: n-butylamine-nickel-2,’2-thio-bi-(4-tert.octylphenolate) nickel-bis(3,5-di-tert.-butyl-4-hydroxybenzolphosphonic acid monobutylester). Hindered amine typelight
stabilizers: bis(2,2,6,6-tetramethyl-4-piperidyl) sebacate.
Food packaging and use of stabilizers
Györgyi Szarka, Béla Iván
Department of Polymer Chemistry
Institute of Materials and Environmental Chemistry
Research Centre for Natural Sciences, Hungarian Academy of Sciences