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Food Pathogens and Consumer Practices 75-13
system is suppressed by other medical conditions. These plastic bag under cold water. Since cold water
groups represent 20% of the American population (23). thawing requires about 30 minutes per pound
All food safety guidelines related to hand washing, of frozen meat, it should not be used for very
cooking meat,seafood,poultry and eggs properly,avoiding large items (10 hours would be needed to thaw
cross-contamination and keeping foods at safe temperatures a 20lb. turkey by this method). The risk of bac-
are important for control of food illnesses of all people, terial contamination could be high if the water
including those in high-risk groups. In addition to following is not changed regularly during thawing (53).
the guidelines listed above, additional precautions are If meat is microwave-defrosted, it must be
suggested for the high-risk groups. Pregnant women should cooked promptly after thawing because some
be encouraged to avoid ready-to-eat foods known to be areas of the food become warm during
sources of L. monocytogenes,avoid contact with cat feces, microwaving. Raw meat can be thawed at room
and cook or reheat foods well before eating. Elderly and temperature for short periods of time as long as
immune compromised persons should avoid raw or under- it is refrigerated or cooked while it is still cold
cooked seafood,raw sprouts,foods that contain raw eggs, and contains ice crystals. Cooking from the
and food known to be sources of L. monocytogenes. For frozen state requires food to be cooked about
young children, use of pasteurized milk and fruit juices, 1½ times longer than for thawed products of
avoiding raw sprouts, and washing fruits and vegetables the same size and shape.
before eating are important food safety behaviors (23). (cid:1) Ground meats. Ground meat must be handled
with special care because bacteria on the sur-
face are spread throughout the meat during
VI. FOODS THAT CONSUMERS SHOULD grinding. Ground meats should always be
cooked to 160°F, and verified with a ther-
HANDLE WITH EXTRA CARE
mometer inserted sideways into meat that has
While all foods should be handled by following the basic been lifted out of the pan on a spatula. Turning
rules (practice good personal hygiene, cook foods ade- ground meat patties frequently assures even
quately,avoid cross-contamination,and keep foods at safe distribution (54).
temperatures), some foods require extra care or special (cid:1) Hot dogs and lunch meats. These products are
handling. perishable and should be kept in the refrigera-
tor. Hot dogs should be cooked before eating
(cid:1) Eggs and foods containing eggs. Fresh eggs and luncheon meats should be heated to steam-
must be handled carefully, for even eggs with ing if they are to be eaten by a person at high
clean, uncracked shells may contain risk for listeriosis.
Salmonella bacteria. Eggs should be purchased (cid:1) Stuffed meat or poultry. When stuffing meats
only from a refrigerated case and checked for and poultry, stuffing should be not be tightly
cleanliness and intact shells. Eggs should be packed, to allow heat to penetrate throughout
refrigerated promptly in their original carton quickly, and these items should be stuffed just
and not in the rack that may be on the refriger- before cooking. Stuffing needs to reach a tem-
ator door,because the temperature on the door perature of at least 165°F as verified with a
fluctuates widely. Eggs and dishes containing thermometer. Whole,stuffed poultry should not
eggs need to be cooked thoroughly, with both be cooked in a microwave oven because the
the yolk and white cooked to firmness or to stuffing may not get hot enough to kill harmful
160°F. Dishes containing eggs should be bacteria.
cooked to 160°F as verified by thermometer. (cid:1) Using a microwave oven to cook meat,poul-
Dishes with raw or lightly cooked eggs require try,or fish. Cooking in a microwave oven can
the use of pasteurized eggs or a modified recipe leave cold spots that present a food safety prob-
(available from the American Egg Board lem. Using meat that is the same temperature
http://aeb.org). Cooked eggs and egg dishes throughout aids in even cooking; if defrosted in
should be reheated or refrigerated within 2–3 the microwave,a rest period of 20 to 30 minutes
hours of their preparation, including hard- between defrosting and cooking allows the tem-
cooked eggs used for Easter egg hunts. perature to equalize. Covering the meat item,
(cid:1) Thawing meat/fish/poultry. Recommended cooking at medium power (50%), and rotating
thawing of frozen meat,poultry and fish includes food frequently all aid in more even cooking
thawing in the refrigerator (generally requires and the elimination of cold spots. A food
24 hours for each five pounds of product) or thermometer should be used to ensure food is
submerging the frozen package in a watertight cooked to the proper temperature. Letting food
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75-14 Handbook of Food Science, Technology, and Engineering, Volume 2
stand covered for 5–10 minutes after cooking overripe tomatoes or tomatoes from frost-killed
also equalizes internal temperatures. vines should not be used for canning since they
(cid:1) Fresh produce. The U.S. Food and Drug lose acidity as they mature or if they are frozen.
Administration (FDA) has offered specific con- Many Cooperative Extension offices have
sumer advice about the purchase and handling information and bulletins, and some conduct
of fresh produce: buy produce that is not classes, with specific directions and scientific
bruised or damaged; fresh cut produce should time and temperature recommendations for
be refrigerated or surrounded by ice at the home canning and other food preservation
store; perishable produce should be promptly methods. Research based information for home
refrigerated; wash produce just before eating canning, the USDA Complete Guide to Home
using cool tap water and reasonable agitation, Canning, is available online at the National
and removing bruised or damaged areas (pre- Center for Home Food Preservation (57).
washed packaged vegetables labeled “Ready
To Eat”do not need to be washed at home; firm
produce such as melons and cucumbers should VII. MOTIVATING CONSUMERS TO
be scrubbed with a clean produce brush) (55).
ADOPT SAFE FOOD HANDLING
Some outbreaks of E. coliO157:H7 have been
PROCEDURES
caused by apple cider; homemade apple cider
should be heated to at least 160°F. Many consumers are aware that they can reduce their risks
(cid:1) Honey. Infants are susceptible to a very rare of foodborne illness by their own actions regarding hand
form of botulism that is caused by ingesting washing,adequate cooking,avoiding cross-contamination,
Clostridium botulinum bacteria. An infection refrigeration of foods and avoiding risky foods and water.
results when these bacteria grow in the infant’s However, they may not have sufficient motivation and
intestinal tract. (In contrast, botulism in adults knowledge plus the proper equipment to successfully
is caused by eating food contaminated with the implement all of the recommended behaviors. Some
toxin that the bacteria produce.) Babies with examples of barriers to adopting recommended behaviors
infant botulism are constipated and have diffi- and ways to reduce the barriers follow:
culty holding up their heads and sucking.
Because honey can contain C. botulinum, the (cid:1) Strong motivation is required to modify habit-
U.S. Centers for Disease Control and ual behaviors. Change may occur when people
Prevention state that children who are less than participate in programs that make them aware
a year old should not be exposed to honey (56). of their actions when they wash their hands or
(This includes foods made with honey such as when preparing food in a way that results in
honey graham crackers, muffins and jellies.) cross contamination.
Pasteurized honey is not a solution,because the (cid:1) Knowledge regarding how to implement recom-
heat treatment that produces the desired crys- mended behaviors may be lacking. To reduce
tallization is too mild to kill the spores. While this barrier, food safety education should be
only 5 percent of the nation’s infant botulism more common, including in school curricula,
cases have been traced to honey, protecting and emphasized in television cooking shows.
children from honey before their first birthdays (cid:1) Current recommendations may be different
is one step that parents and caregivers can from what the person learned previously. For
actively take. example,the current recommendation is to cook
(cid:1) Home canned foods. Low-acid foods (meat, ground beef to 160°F. Previously, consumers
fish,poultry,and vegetables) must be canned in were advised to cook ground beef until it
a pressure canner. Boiling-water canners, appeared to be cooked and had no traces of
ovens,steamers without pressure and open ket- pink. Extensive education about the new recom-
tles do not get the food hot enough to kill the mendation is necessary to replace the previous
spores of Clostridium botulinum, so it is not behavior.
safe to can vegetables,fish,meat or poultry — (cid:1) Equipment needed to implement the recom-
or mixtures containing these foods — by any mended behavior may not be readily available.
method other than using a pressure canner. For example, if a consumer decides to cook
Tomatoes with added acid in the form of lemon ground beef patties to 160°, they will need an
juice or citric acid, pickled vegetables, and instant-read thermometer, preferably one that
fruits can be canned safely in a boiling water has recommended endpoint internal tempera-
canner because they are more acidic. However, tures printed on the sheath. Fortunately, these
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Food Pathogens and Consumer Practices 75-15
types of thermometers are now much more 15. JL Smith. Long-term consequences of foodborne toxo-
commonly available to consumers. plasmosis: effects on the unborn, the immunocompro-
mised, the elderly and immunocompetent. J Food
Educational efforts are needed to increase food handlers’ Protect 60(12):1595–1611,1997.
16. CS DeWaal, K Barlow, L Alderton, and MF Jacobson.
knowledge of correct procedures and motivation to per-
Outbreak Alert! Center for Science in the Public
form recommended behaviors. Equipment should be
Interest,October,2001,http://www.cspinet.org/reports/
designed to reduce opportunities to make food handling
index.html.
mistakes. Improvement in behaviors is likely to result in
17. JM Jay. Modern Food Microbiology. 6th ed.
reduction in incidence of foodborne illnesses.
Gaithersburg, MD: Aspen Publishers, Inc., 2000, pp.
461–465,474–476,479,513–514,552–555.
18. SF Altekruse, NJ Stern, PI Fields and DL Swerdlow.
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9. U.S. Food & Drug Administration, Center for Food Bowers, RJ Blodgett and A DePaola. Vibrio vulnificus
Safety & Applied Nutrition, Foodborne Pathogenic and Vibrio parahaemolyticusin U.S. retail shell oysters:
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Excess mortality associated with antimicrobial drug- sumer food-handling behaviors for food safety education.
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8(5):490–495,2002. 31. American Society for Microbiology. Don’t get caught
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336:1111–1115,1990. 33. DR Patrick,G Findon,and TE Miller. Residual moisture
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34. Food Safety and Inspection Service, United States 47. Food Safety and Inspection Service, United States
Department of Agriculture, Consumer Education and Department of Agriculture, Consumer Education and
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Department of Agriculture. PR/HACCP rule evaluation DR Buege,WP Henning,JB Morgan,TP Ringkob,GR
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September 3,2002,http://www.fsis.usda.gov/oa/research/ home storage of fresh beef retail cuts. Dairy Food
HACCPimpacts.htm. Environ Sanit 22(10):740–744,2002.
36. Food Safety and Inspection Service, United States 49. G Brown, DS Gianato, BD Hunley, SA Layne, SR
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Morales, WD Schlosser and R Whiting. Salmonella n_040403.asp.
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risk/index.htm. 52. V Hillers and M Aegerter. You can prevent foodborne
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Disinfecting Solutions for Healthy Child Care. Undated industry. SafeFood News 7(3), 2003. http://www.
fact sheet. colostate.edu/Orgs/safefood/NEWSLTR/v7n3s02.html.
41. JD Eifert and GC Sanglay. Chemistry of chlorine sani- 54. M-S Rhee, S-Y Lee, VN Hillers, SM McCurdy, and
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22(7):534–538,2002. ods for reduction of Escherichia coliO157:H7 in ground
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hold sanitizers for reducing levels of Escherichia colion 55. Food and Drug Administration, FDA Talk Paper. FDA
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43. TL Parnell and LJ Harris. Reducing Salmonella on 2000. http://www.cfsan.fda.gov/(cid:1)lrd/tpproduc.html.
apples with wash practices commonly used by con- 56. Centers for Disease Control & Prevention, Division of
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FDA issues import alert on cantaloupes from Mexico, botulism_g.htm.
October 28, 2002, http://www.fda.gov/bbs/topics/ 57. National Center for Home Food Preservation, USDA
ANSWERS/2002/ANS01167.html. Complete Guide to Home Canning, September 1994.
45. JY Ikawa and JS Rossen. Reducing bacteria in house- http://www.uga.edu/nchfp/publications/publications_us
hold sponges. J Environ Health 61(4):18–22,1999. da.html.
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76 Migratory Chemicals from Food
Containers and Preparation Utensils
Yvonne V.Yuan
School of Nutrition, Ryerson University
CONTENTS
I. Introduction........................................................................................................................................................76-1
II. Migration Theory................................................................................................................................................76-2
III. Migration of Packaging Materials ....................................................................................................................76-3
IV. Concerns with Migration of Packaging Materials ............................................................................................76-4
V. Sources of Food Packaging Migrant Chemicals................................................................................................76-4
A. Polymers ....................................................................................................................................................76-4
B. Vinyl Derivatives ........................................................................................................................................76-5
C. Polyolefins ..................................................................................................................................................76-7
D. Polyesters....................................................................................................................................................76-7
E. Other Packaging Materials ........................................................................................................................76-8
VI. Additives Used in Polymer Formulations ........................................................................................................76-8
A. Functionality in Polymers ..........................................................................................................................76-8
B. Plasticizers ................................................................................................................................................76-11
VII. Factors Which Influence the Migration Kinetics of Plasticizers ....................................................................76-11
VIII. Migration of Plasticizer from Polymer Films..................................................................................................76-11
IX. Metabolism of Plasticizers ..............................................................................................................................76-12
X. Toxicity of Plasticizers:Phthalates ..................................................................................................................76-13
XI. Effects of Ionizing Radiation on Packaging Materials....................................................................................76-14
XII. Alternative Food Packaging Materials ............................................................................................................76-15
XIII. Conclusion........................................................................................................................................................76-16
References....................................................................................................................................................................76-16
I. INTRODUCTION phenomenon occurs due to the potential for contact and
migration or transfer of polymer components from con-
Plastics have revolutionized the packaging and transporta- tainers or packaging films into foods during processing,
tion of foods,allowing foods to be packaged in light weight packaging and storage. Plastics (e.g. polyethylene,
materials while offering excellent physical protection polypropylene,polystyrene etc.) are also extremely preva-
against mechanical damage,water vapour transmission and lent as food service utensils and containers both inside and
light oxidation. Approximately 70 to 80% of food and outside the home (3,4). Polymer additives can fall into two
ingredients are packaged in polymeric materials (1). functional categories:those that modify the physical prop-
However, the use of plastic organic polymers containing erties of polymers, namely catalysts, plasticizers, lubri-
functional additives such as plasticizing agents, antioxi- cants and colouring agents etc. and those that have a
dants, U.V. light and heat stabilizers or lubricants in the stabilizing or protective effect on polymer degradation
manufacture,packaging and serving of common foodstuffs (antiaging additives), such as antioxidants, U.V. light and
such as meat, cheese, margarine, bacon, vegetables heat protection agents (5, 6). Plasticizers are synthetic
and beverages may result in these polymer constituents organic additives characterized by low molecular weight
potentially becoming indirect food additives (1, 2). This with low melting points or low volatility with high boiling
76-1
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76-2 Handbook of Food Science, Technology, and Engineering, Volume 2
points and high miscibility with the parent polymeric polystyrene (PS,T (cid:2)80–100°C),polyethylene terephtha-
g
matrix (e.g. phthalic acid esters (PAEs)). They are used to late (PET, T (cid:2)67–81°C) and polytetrafluoroethylene
g
improve the plasticity (e.g. flow, workability and flexibil- (PTFE,T (cid:2)115–125°C) are able to quickly establish a new
g
ity) of polymers such as the vinyl derivatives (e.g. equilibrium when a diffusant chemical is absorbed and
polyvinyl chloride (PVC), polyvinyl acetate (PVA), transported through the rubbery matrix of the polymer (25).
polyvinyl alcohol (PVAL)) and the polyolefins (e.g. poly- Conversely, glassy polymers at T(cid:3)T , which comprise
g
ethylene (PE),polypropylene (PP)). In this way,plastic for- the various forms of the olefins PE (T (cid:2)(cid:4)30 (cid:5)15°C) and
g
mulations can contain up to 60% of plasticizer materials to PP (T (cid:2)(cid:4)17 (cid:5) 5°C) are unable to rapidly establish a
g
transform an otherwise rigid polymer into a plastic with homogeneous environment upon absorption of a diffusant.
improved physical and mechanical properties such as flex- In rubbery polymers, diffusion of chemicals obey
ibility,durability,and impact resistance (1,2,7). However, Fick’s Laws of Diffusionand can be explained on the basis
due to the relatively low molecular weight of residual poly- of the adhesion theory, which refers to the physical
meric monomers and certain additives (i.e. plasticizers and interaction of two materials.
antioxidants), the migration to and absorption of these
Fick’s First Law of Diffusion
compounds by both solid and liquid foods is known to
occur (8–10). This may result in off-odours or -flavours ∂C
being imparted to the packaged food (11, 12) resulting in J(cid:2)(cid:4)D(cid:6)∂XA
the loss of product and sales. As well, the toxicology of
these substances has been the subject of intense investiga- where
tion in animal models (13–17) and human subjects J (cid:2)flux (i.e. moles/sec cm2)
(18–21). These issues gain relevance due to the prevalence D(cid:2)diffusion coefficient (i.e. cm2/sec)
of microwavable convenience foods which are heated in C (cid:2)concentration of substance A (i.e. moles/cm3)
the packaging containers,as well as the increasing interest X(cid:2)distance (i.e. cm)
in irradiating packaged foods for increased microbiological
Fick’s Second Law of Diffusion
safety against foodborne illnesses (22–24). Gamma-irradi-
ation of packaged foods is known to result in alterations ∂C ∂2C
(cid:6) (cid:2)D(cid:6) 0(cid:3)x(cid:3)l
such as crosslinking and scission of polymeric materials ∂t ∂2x
and component additives which may be,in turn,adsorbed
where
by the packaged food contained therein. This chapter will
C (cid:2)concentration of substance (liquid or plasticizer)
discuss these issues as well as examining potential alterna-
D(cid:2)diffusivity in the membrane
tives to the traditional polymeric packaging materials dis-
x (cid:2)space coordinate
cussed in the recent literature.
l (cid:2)length of the geometric shape in question
t (cid:2)time
II. MIGRATION THEORY
Fick’s first lawof diffusiondescribes steady-state diffusion
The investigation and mathematical modelling of the diffu- wherein mass transfer from a region of high concentration
sion,migration and sorption of materials from food packag- to a region of low concentration occurs and eventually
ingmaterials into foods or in contrast,from foods into the approaches equilibrium (26,27). Whereas,unsteady-state
packaging polymer itself, have been the subject of several diffusion is described by Fick’s second law of diffusion
recent reviews and reference book compilations (2,5,6,25, wherein for a constant diffusivity,the rate of change in the
26).Generally,the movement of molecules within a pack- concentration of the substance of interest with time is pro-
aging system reflects the motion of mass or energy from one portional to the rate at which the concentration gradient
location to another. Mass transport by diffusion will be changes with distance in a given diffusion direction.
influenced by the behaviour of the polymer itself (i.e. glassy In glassy polymers, on the other hand, diffusion of
versus rubbery state) as well as the solubility of the diffusant compounds is more complex,in that diffusion can be:
chemical in the polymeric matrix and the partition coeffi-
cient of the diffusing chemical between the two contact a. Class I or Fickian,where the rate of diffusion is
media (25). Polymers are classified as either rubbery or much less than the relaxation of the diffusant-
glassy depending on whether the temperature of the poly- polymer system; or
mer is above or below the glass transition temperature (T ) b. Class II, where the rate of diffusion is very
g
for that polymer,respectively. Above the T,polymer chains rapid compared to the relaxation processes of
g
will be able to move more freely in space versus below the the polymer system; or
T , where chain mobility will cease and the polymer c. Anomalous diffusion, where the rates of diffu-
g
becomes glassy and hard. Rubbery polymers at T(cid:1)T , sion and relaxation of the polymer system are
g
which include polyvinylchloride (PVC, T (cid:2)80–100°C), comparable to each other (25).
g
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Migratory Chemicals from Food Containers and Preparation Utensils 76-3
This non-ideal behaviour can be linked to swelling or III. MIGRATION OF PACKAGING
shrinkage of the food in question,or the packaging poly-
MATERIALS
mer. Food components,particularly water,may influence
the swelling and plasticity/mobility of the polymer chains Of primary concern to polymer and food scientists as well as
leading to non-ideal diffusion (27). the consumer are the migration and sorption processes which
There are two mechanisms by which adhesion plays may impact on the organoleptic quality,nutrition and safety
an important role in the migration of packaging material of packaged foods. Migration of plastic packaging con-
components. The first is through the adhesion and loss of stituents may result in the introduction of undesirable and/or
food constituents (i.e. volatiles) to the packaging material, unsafe substances into the food, thus rendering the food
resulting in a reduction of food sensory qualities and thus, unsuitable for consumption. Similarly, sorption processes
acceptability. The second is through the adhesion of the may result in nutrient or flavour and odour loss from the
packaging material to the foodstuff,which may introduce packaged food into the packaging material,giving rise to a
toxicants, unwanted flavours or odour-active substances, poor quality product. Thus, sorption phenomena involve
again resulting in the potential loss of food quality as well packaged foods wherein concern for product organoleptic
as safety (5,28). The adhesion phenomena can be explained qualities and nutrient retention are the primary focus.
according to the conditions listed in Table 76.1 (5,28,29). Packaging materials can adsorb flavour components from
The term migration typically refers to the movement of food systems rendering the food product unacceptable over
chemical compounds from the packaging material into time (i.e. during the distribution and delivery process) due to
the food or beverage contained therein. This migration “flavour scalping”as in the case of terpenoids in juices (32).
activity would then include the movement of gases, low In addition,the use of heat treatment or other adhesive phe-
molecular weight compounds and water vapour from the nomena will contribute to weight loss or reduced volume and
package into the food (5). This phenomenon is distinct altered nutrient retention in packaged foods (33).
from sorption, which involves the movement and uptake Migration of packaging materials into food is a function
of food constituents, such as flavour and odour compo- of the chemical composition and concentration of the pack-
nents,into packaging materials (28). These processes are agingmaterials and the solubility of the migrating chemi-
dynamic and can occur simultaneously by diffusion (30). cal in the polymer,or its partition coefficient between the
At steady state,the flux can be described as a function of polymer and the contact surface of the food. The fat content
the concentration difference of the migrating chemical and more specifically,the fat-releasing properties of con-
across the distance of diffusion when referring to Fick’s tact foods can greatly influence migration of low molecu-
first law of diffusionabove (31). In general,migration and lar weight compounds (34). For example,migration of the
sorption are similar processes which can ultimately affect plasticizer stearyl 3-(3,5-di-tert-butyl-4 hydroxyphenyl)
food quality. Both phenomena are influenced by the propionate into mayonnaise (an oil-in-water emulsion with
chemical and physical properties of the substrate and the moderate fat-releasing properties) resulted in a mean con-
receivingmedium. centration of 69µg/dm2 compared to 792µg/dm2 into a
TABLE 76.1
General Tenets to Adhesion Theory Involving Migration of Food Packaging Materials1
Type of Adhesion Interaction Molecular Interaction Description of Interaction
Mechanical interlocking Macro- and microscale Rugosity of surface increases
locking of film components.
Wetting Liquid dispersion and Electrodynamic intermolecular forces
surface tension create dispersive and attractive forces
at surfaces.
Electrostatic Ionized substrates form Double layer is positively charged while
electrical double layer outer interface is negatively charged.
Adhesive forces act by attraction through
electrical double layer in films.
Chemical Covalent bonding between Contact time and processing dependent.
surfaces and polymer
components
Diffusion Polymer and additive Contact time,temperature,molecular
migration weight,polymer type,viscosity and
concentration dependent.
1References:5,28,29.
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76-4 Handbook of Food Science, Technology, and Engineering, Volume 2
testfat (34). Migration efficiency will also be affected by consisting of PET contaminated with toluene and
the storage or thermal processing temperature used (i.e. chlorobenzene sandwiched between two virgin PET layers
heating the food inside the packaging material, e.g. demonstrated significant migration of the contaminants into
microwavecooking),as well as the amount of time during water,3% acetic acid and iso-octane. Migration of contam-
which the food is in contact with the package material (3). inants into 3% acetic acid (50°C over 10–131 days) from
Thus,the migration of chemicals from packaging materials the contaminated PET into 3% acetic acid ranged from 4.1
into foodscan be mathematically modelled and predicted to 33.3µg/dm2 and(cid:3)0.1–20.7µg/dm2 without and with
(4, 35, 36). Any toxicological hazard associated with the barrier layers respectively for toluene and (cid:3)0.1–17.0
migration of food packaging materials into foods would µg/dm2 and(cid:3)0.1–12.3µg/dm2 without and with barrier
therefore be a function of the amount of migratory mate- layers for chlorobenzene (36). Thus,the effects of diffusion
rial originating from the polymer which enters the food of core layer contaminants in plastic films must be consid-
and the intrinsic toxicity of this material or its metabolites ered when using coextruded recycled materials.
(16,17,37).
It is important to recognize that the conditions involved
IV. CONCERNS WITH MIGRATION OF
with the use of plastic packaging of foods will not be
PACKAGING MATERIALS
isothermal throughout the life of the polymer. Moreover,
food systems are,by their nature,very complex with aque- The classes of packaging material migrants that fall into the
ous and hydrophobic components often co-existing in one category of food safety concerns include the amine precur-
food matrix. In order to study the extent of the migration of sors and nitrosamines (44),plasticizers (1,45) and polymer
polymer components into foods, laboratories use estab- monomers such as vinyl chloride and styrene (17, 20).
lished food simulants (i.e. distilled water, 3% NaCl, 3% Amine precursors and nitrosamine formation have been
NaHCO3, 3% acetic acid, 3% lactic acid, 20% sucrose, reported from the interaction of the rubber netting used to
15–50% ethanol and olive oil or iso-octane) as model package nitrite containing cured meats and from other
systems to estimate migration of chemicals into foodstuffs foods contained in paperboard containers (5,44,46). The
(31, 34–36). Frequently, elevated temperatures are used to focus of the following discussion will concentrate on the
simulate accelerated storage conditions and the worst-case polyolefin and vinyl derivative packaging materials and
scenario. Standard test conditions accepted by additives. The most commonly used plasticizers to improve
regulatory bodies in the United States (US Food, the working properties of PVC,for example,are the esters
Drug and Cosmetic Act enforced by the Food and Drug of dibasic or tribasic organic acids known as phthalates
Administration (FDA)), Canada (Division 23 of the Food which comprise as much as 60% of the market (47).
and Drugs Act and Regulations), United Kingdom Phthalic acid esters are the subject of concern due to
(Ministry of Fisheries and Foods (MAFF)), and European the structural similarity of these compounds to the known
Union (EU Scientific Committee for Toxicity, Ecotoxicity teratogen thalidomide (phthalidomide) (48). Indeed,di(2-
and the Environment (CSTEE)) include 10 days at 40°C, ethylhexyl) phthalate (DEHP) has been demonstrated to
2hr at 70°C and 1hr at 100°C (10,34,38,39). These data, have fetotoxic,embryolethal and teratogenic effects in rats
used in conjunction with toxicological testing,have resulted at a dose of 1g/kg/day (14). Finally,vinyl chloride polymers
in the establishment of regulatory allowances for food pack- (polyvinylchloride; PVC) are widely used in many types of
aging components migrating into foodstuffs set at a dietary packaging materials and have also been shown to migrate
concentration of 0.5µg/kg in the US by the FDA (36, 40, into foods (8, 48). PVC contains allylic chlorine atoms,
41) and maximum total migration limits to be set at 10 which can be released from the polymer upon exposure to
mg/dm2, or less than 60mg/kg food by the EU (7, 42). light or heat treatment of the packaged food. The primary
Packaging design and construction which incorporate the concern with PVC and the monomer vinyl chloride used
concept of functional barriers (i.e. laminate films) to limit in the manufacture of this plastic, is due to animal and
the migration of noncarcinogenic chemical components to human epidemiological data from workers exposed to
food to a level less than the threshold of 0.5µg/kg are vinyl chloride indicating that exposure to vinyl chloride is
regarded acceptable in the US (36). Functional barriers rep- strongly linked to hepatic carcinoma (17,19,20,49).
resent a concept whereby the specific package design and
construction limit the migration of packaging materials into
V. SOURCES OF FOOD PACKAGING
food in amounts regarded below this threshold level (36,
43). This is especially pertinent given the trend to use recy- MIGRANT CHEMICALS
cled materials in packaging. Quite often, a contaminated
A. POLYMERS
material will be co-extruded with virgin materials acting as
a functional barrier against taint migration from the inner Numerous polymers are used in food packaging to store
layer of recycled polymer material (36). Tripartite poly- and protect food from deterioration due to chemical or
ethylene terephthalate (PET) films made from core material physical damage due to radiant or heat energy, while at
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Migratory Chemicals from Food Containers and Preparation Utensils 76-5
TABLE 76.2
Common Polymers and Migration Chemicals in Food Packaging Materials1
Polymer Example of Use Migration Chemicals
Polyethylene (PE) Dairy product and other food Acetaldehyde,allyl alcohol,acrolein.
containers,water pipes,food
wrap films
Polyvinylchloride Beverage and water bottles, Allylic chlorine,vinyl chloride
(PVC) food wrap films,water pipes monomer,plasticizers and
stabilizers.
Polypropylene (PP) Bread packaging,bottles, Isopropyl alcohol,methyl alcohol,
frozen foods,microwavable formaldehyde,antioxidants and
foods stabilizers.
Polystyrene (PS) Microwave meals,cookie bags Styrene monomers,dimers,trimers,
and syrup containers polystyrene.
Polyethylene Beverage and water bottles, Acetaldehyde,cyclic oligomers,
Terephthalate (PET) box liners,boil-in-bag pouches, ethylene glycol.
microwave food trays
Paper and paperboard Milk and juice cartons Polychlorinated biphenyls (PCBs),
alkyl and aryl aldehydes.
Melamine-Formaldehyde Tableware Melamine and formaldehyde residues.
Vulcanized rubber Rubber nettings for packaged Polycyclic aromatic hydrocarbons
meats,food industry equipment (PAHs) including benzo[a]pyrene,
nitrosamines,alkanes,alkenes,
acids,antioxidants,plasticizers and
sterols.
1References:1,2,4,5,8,11,12,35,46,50.
the same time enabling the consumer to view and evaluate TABLE 76.3
the product. Examples of common polymers used in food Monomers and Degradation Products from Food
packaging materials and migratory components of con-
Packaging Polymers
cern are presented in Table 76.2 and chemical formulae of
Compound Name Chemical Structure
plastic resin monomers and polymers provided in Tables
Ethylene CH2 CH2
76.3 and 76.4,respectively.
Propylene H C CHCH
2 3
B. VINYL DERIVATIVES Ethyl acetate CH3COOCH2CH3
Polyvinyl chloride (PVC) is second only to PE in world- Vinyl acetate CH3COOCH CH2
wide production, estimated at approximately 22(cid:7)106 Vinyl chloride CH CHCl
2
metric tons (2). PVC film is manufactured by the low
Vinylidene chloride CH CHCl
2
pressure free radical polymerization of vinyl chloride
(Table 76.3) at temperatures ranging from 50–160°C (50).
PVC film is a versatile thin cling film ((cid:3)25µm or 1mil Styrene CH CH2
thick) which is transparent and has high oxygen perme-
ability but is naturally brittle and therefore requires plas- CH3 CH3
cis-1,4-isoprene (rubber) C C
ticizing agents,such as the phthalic acid esters (Table 76.5),
to be incorporated into the polymer (50). Plasticizer con- CH3 H
tent of PVC polymers can vary from 3.0 to as high as 80%
(1). A copolymer of vinyl chloride and vinylidene chloride
(Table 76.3), more commonly known by its trade name, monomer (VCM) is a residue of PVC film manufacture
Saran™, is a high quality cling-film wrap used commer- which is removed following the polymerization reaction.
cially and in the home. As plasticizers are not polymerized However, VC has received considerable attention due to
directly into the polymer matrix, and have high mobility its link to angiosarcoma of the liver (ASL) (17, 19, 20).
associated with a low molecular weight, migration from An Italian study indicated that significant quantities of VC
the PVC polymer into the food product can occur. (13 to 83ppt) could be detected in PVC-bottled drinking
Migration is influenced by the fat content, pH and the water (8). Moreover, the concentration of VC in bottled
alcohol content of the foodstuff (48). Vinyl chloride water was observed to increase linearly with storage time
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76-6 Handbook of Food Science, Technology, and Engineering, Volume 2
TABLE 76.4
Common Food Packaging Polymer Materials
Compound Class Name Abbreviation Chemical Structure
Polyolefins Polyethylene PE (CH2 CH2)n
(CH CH )
2n
Polypropylene PP
CH
3
Vinyl derivatives Polyvinylchloride PVC (CH2CHCl)n
Polyvinylidene chloride PVDC (CH2CCl2)n
Polyvinylalcohol PVAL (CH CHOH)
2 n
(CH CHOCCH )
2 3n
Polyvinylacetate PVA
O
Polystyrene PS (CH CH )
2 n
O
O
O
Polyesters Polyethylene terephthalate PET R
O
n
R = OH, Mylar™
R = OCH , Terylene
3
Polyfluorocarbons Polytetrafluoroethylene PTFE Teflon™ (CF2 CF2)n
O O
R NH
Polyamides Polyamide PA
n
R=(CH ) , i.e. Polyamide 6
2n
CH
3
CH CH CH C CH CH CH
2 2 2 2 2 2
Ionomers Poly(ethylene-co- Surlyn™
methacrylic acid) C O n
O−
Na+
CH CH
2 2
Rubber Poly (cis-1,4-isoprene) C C
CH H
3 n
(approx. rate 1ng/l/day),resulting in the recommendation health effects from VC is from occupational exposure
that storage dates be placed on the labels of PVC-bottled in manufacturing plants (18,19). Workers exposed to VC
water (8). While migration of VC into vinegar (9.4mg/L), from manufacturing plants have been reported to suffer
cooking oil (14.8mg/kg), butter and margarine (approx. from primary nonangiosarcoma liver tumours as well as
50µg/kg) have been reported (48), the greatest risk of ASL (18,19,49). Workplace exposure to VC has also been
