Jung Han. Innovations in Food Packaging

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Innovations in Food Packaging

only deny the petition if a fair evaluation of all data before the FDA fails to establish

that the proposed use of the food additive, under the conditions of use specified in the

regulation, will be safe, or if those data show that the proposed use of the additive would

promote deception of the consumer, or otherwise result in adulteration or misbranding

of food. There is also a provision that the petition must be denied if the additive has

been found to induce cancer when ingested by man or animal.

Food contact substance notifications

Since 1958, the food additive petition process had been the major process by which

food additive approvals were granted for both direct and indirect food additives.

However, in 1997 Congress further amended the FFCDA to include a notification

process for the approval of food-contact substances. A food-contact substance means

"any substance that is intended for use as a component of materials used in manufac-

turing, packing, packaging, transporting, or holding food if such use is not intended to

have any technical effect on the food" (FFDCA Section 409(h)). Under the notifica-

tion process, a manufacturer may notify the FDA of its intent to market a new food-

contact substance at least 120 days prior to introducing it, or delivering it for

introduction, into interstate commerce. The notification must provide the basis for the

determination by the manufacturer that the intended use of the food contact substance

is safe under the general safety standard for all food additives. Thus, the food contact

substance notification will contain essentially the same information relating to the

identity, conditions of use, technical effect, manufacture, and safety, as a food additive

petition contains.

There are, however, several important differences between the food additive peti-

tion process and the food contact notification process. First, the food contact notifica-

tion becomes effective 120 days after the date of its receipt by the FDA, unless the

FDA objects to the notification. If the FDA objects, the objection must be based on a

determination that the data and information before the secretary do not establish that

the proposed use of the food contact substance would be safe. If the FDA does not

object, the food contact substance notification becomes effective, and from that time

the notified material may be introduced, or delivered for introduction, into interstate

commerce. Consequently, the FDA does not promulgate a food additive regulation as

required for a petition. Instead, the notification serves to describe the specifications

and conditions under which it may be safely used. Second, unlike food additive reg-

ulations, which are generic and apply equally to all manufacturers, an effective food-

contact notification is effective only for the manufacturer or supplier identified in the

notification. Third, while the petition process results in a food additive regulation

printed in the Code of Federal Regulations (CFR), the notification process results

in a listing on the FDA's website. A chronological list of effective food contact

substance notifications may be found on the CFSAN website. The listings of effec-

tive notifications are often linked to conditions of use described in food additive

regulations.

Food and

Drug

Administratio

Special considerations for antimicrobial

food additives

The general provisions applicable to all indirect food additives state, in part, "that the

quantity of any food additive that may be added to food,

a result of its use

articles

in that contact food, shall not exceed that which results from the use of the substance in

an amount not more than reasonably required to accomplish the intended technical

effect in the food contact article." As stated previously, the FDA requests

data

relating to

the technical effect of a proposed new food additive in both food additive petitions and

food contact substance notifications. These technical-effect

data

are not used to set per-

formance standards for additive technical effects, nor to compare the effectiveness of

one additive to another; rather they are used to ensure that the amount of the additive

migrating to food is at the lowest possible level reasonably required to accomplish the

intended technical effect. Because the FDA's authority to deny a food additive petition

is limited to safety issues, and issues that may lead to deception of the consumer, adul-

teration of food or misbranding, the FDA views technical effect

data

only from these

perspectives. Consequently, there are no distinctions in the approval processes between

components of traditional or passive packaging materials (like polymeric plasticizers

and stabilizers) and the "active" components of active or intelligent packaging materi-

als. Importantly, no distinction needs to be made to arrive at a safety determination.

Although our current food additive approval processes readily accommodate food

additive petitions and food contact substance notifications for components of active

and intelligent packaging, certain types of packaging materials, whether they are

active or passive, deserve additional consideration. Importantly, as stated above, the

food contact substance notification process is intended only for the approval of mate-

rials that exert no technical effect on the food. Consequently, substances that are

employed in active packaging materials and that have no intended technical effect on

the food, such as freshness indicators, may be approved through the notification

process. However, approvals for substances that exert a technical effect on the food,

even though they may be incorporated in or delivered from the package, would be

processed through the food additive petition program.

particular, packaging materials that contain antimicrobial additives may fimction in

either a passive or an active manner. If the antimicrobial additive is functioning

a mate-

rial preservative in the package, then its fimction is passive, and there is no effect on the

food in the package. Such a substance is a candidate for approval through the food

contact substance notification process. However, if the antimicrobial additive is intended

to be slowly delivered to the packaged food by migration, or any other type of time-

release mechanism, then the intended technical effect is on the food, and a food additive

approval would generally be sought through the food additive petition process. Marketing

claims such as "improved shelf life" generally indicate a technical effect on the food.

There are other ways that antimicrobial food additives, whether passive or active,

are treated differently from other food additives

the approval process. While many

food additive products improve the quality, appearance or flavor of foods, antimicro-

bial food additive products, often called preservatives, have the potential to improve

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Innovations in Food Packaging

the safety of food. Since food safety is of paramount importance, the FDA has devel-

oped an expedited petition review process for antimicrobial food additives to ensure

that safe antimicrobial food additives may enter the marketplace as quickly as possi-

ble. Also, when an antimicrobial additive is intended to have a technical effect on the

food, whether it is added directly to the food or delivered to the food from an active

package, that antimicrobial is a food preservative and is subject to the food labeling

requirements for all food preservatives under section 403(k) of the FFDCA.

Antimicrobials, like all biocides, are generally intended to exhibit toxic effects, and

are therefore expected to be more toxic than other food additives. For this reason, the

FDA has established lower exposure thresholds for requesting additional toxicologi-

cal data. For example, whereas the use of a polymeric stabilizer resulting in an expo-

sure just above 50 parts per billion may require two additional subchronic studies to

establish that the use is safe, an exposure in excess of 10 parts per billion to an anti-

microbial additive may require the same additional studies.

Because the technical effect of any antimicrobial is to control the growth of micro-

organisms, the technical effect data in food additive petitions, or food contact notifi-

cations, for antimicrobial additives are reviewed by the FDA's microbiological review

scientists. Whether the antimicrobial effect is on the food or in the package, as in the

case of a material's preservative, the microbiological review focuses on whether the

petitioner (or notifier) has demonstrated that the intended technical effect is achieved,

and whether it is achieved using the minimum amount of the additive reasonably

required. Whenever the antimicrobial technical effect is intended to be in or on the

food, some additional safety-related questions arise. The first relates to the spectrum

of organisms against which the additive may be effective. In particular, the petitioner

should address the potential for the proposed use of the antimicrobial additive to

establish conditions that may control the growth of spoilage organisms, while allow-

ing for the opportunistic growth of pathogens. Second, if the antimicrobial additive is

an oxidizing agent, the petitioner should address the extent of oxidative degradation

of the nutrients in the food being preserved.

Finally, antimicrobial additives that are intended to control micro-organisms in or

on a food packaging material may also be subject to registration under the Federal

Insecticide, Fungicide and Rodenticide Act (FIFRA, Title

US Code 136 et seq.) by

the US Environmental Protection Agency (EPA) as pesticides. Antimicrobials that are

intended to have a technical effect on processed foods, whether they are added

directly to the foods or delivered from an active package, are not subject to FIFRA

registration. Such substances are food preservatives by law, and not pesticides.

Other active or intelligent packaging materials

Many food packages are designed to contain diffusion barriers or oxygen scavengers,

either to prevent gases from either entering the package or becoming a component of

food, or to prevent gases from leaving the package. Other polymeric additives are

intended to scavenge minor chemical constituents of the package material itself to

Food and Drug Administration

481

prevent them from migrating to food and affecting its flavor or aroma. Such uses of

polymeric additives may or may not be "active packaging," depending on the definition

of active packaging to which one subscribes. Because the FDA's premarket review,

under section 409 of the FFDCA, focuses upon safety as it relates to the migration and

exposure to the package components, there is no need to distinguish between active and

passive packaging materials. Therefore, the FDA has not attempted to define the term.

Importantly, diffusion barriers and scavengers have no direct technical effect on the

food, and are therefore food-contact substances that are subject to the notification

approval process. Although the use of diffusion barriers and oxygen scavengers has the

potential to create a modified atmosphere

within

the package that could promote the

growth of anaerobic pathogens, the production of safe food is assured by good manu-

facturing practice regulations found mainly in 21 CFR Parts 110-129. The criteria and

definitions in these parts are used, in part, to determine whether food is adulterated, or

whether it has been prepared under conditions that would make it unfit for consumption.

Other types of functional food packaging include indicator and tamper-resistant

packaging. Indicator packaging may be used to indicate the state of freshness of the

packaged food. Tamper-resistant packaging generally indicates whether the package has

been opened prior to purchase. Again, the FDA's premarket safety review focuses on the

safety of the chemicals that may be expected to migration from the package to the food.

Whether such packages are called "active" or "intelligent" does not impact the FDA's

safety review. The FDA encourages innovation in these types of applications, but

reminds developers that such materials are subject to the food additive approval process

if the components of the package are reasonably expected to become components of

food, or otherwise to affect the characteristics of food as a result of their intended use.

Conclusions

In summary, food additives are deemed to be unsafe until the FDA writes a regulation,

allows a food contact substance notification to become effective, or writes an exemp-

tion. Regulations, effective notifications, and exemptions all stipulate an identity,

specifications, and conditions of safe use for that food additive. Food contact sub-

stances and indirect food additives have no intended technical effect on food.

Although food additive regulations are generic and apply to anyone, and notifications

apply only to the manufacturer named in the effective notification, neither approval is

a specific product approval. Importantly, because the FDA's premarket safety review

focuses on the safety of the chemicals that may be expected to migrate from the pack-

age to the food and not on the relative effectiveness of the additives, it is irrelevant

whether packaging materials are seen to be active, passive, or intelligent. Although

the safe use of chemicals in the production of food-contact materials is assured by

compliance with the food additive provisions in section 409 of the FFDCA, the pro-

duction of safe food is assured by compliance with the provisions

section 402 of the

FFDCA

and,

more specifically, the good manufacturing practice regulations

Parts

1 10-1 29 of Title

1 of the Code of Federal Regulations.

Introduction

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Non-thermal food processing

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Plastic packaging materials

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Packaging for non-thermal food processing

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Futureresearch 494

References

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Introduction

Pulsed electric fields (PEF), high-pressure processing (HPP), irradiation, and pulsed

light have been developed as non-thermal food preservation methods to satisfy con-

sumers, who like fresh foods. These non-thermal food preservation methods process

foods at temperatures below those used for thermal pasteurization, and inactivate both

spoilage and pathogenic micro-organisms without significant loss of flavor, color, taste,

nutrients, and functionality of the foods.

The success of extending the shelf life of an initially high-quality food greatly

depends on the packaging. Proper packaging materials and methods need to be selected

to maintain the initial high quality of non-thermally processed food flavors, colors, and

nutrients.

Plastic packaging materials have been widely used as moldings, thermoforms, films,

label stocks, closures, and coatings (Brown, 1992). The selection of plastic packaging

materials depends on the packaging requirements of mechanical, thermal, barrier, and

optical properties, as well as the targeted shelf-life length and the cost (Brown, 1992).

The exposure to different processing conditions may alter physical andlor chemical

properties of the plastic packaging materials, and this alteration can influence the

quality of the packaged food products (Ozen and Floros, 2001).

HPP

and irradiation

may require the processing of foods inside packages. The interaction between pack-

aging materials and these processing methods is important, and should be addressed.

Innovations in Food Packaging

ISBN:

0-12-3

1632-5

2005 Elsevier Ltd

All

rights of reproduction

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form reserved

Packaging for non-thermal food processing

483

Current research in food packaging involves the development of active packaging.

Active packaging contributes to the preservation of food products by providing

antioxidant andlor antimicrobial properties. Such packaging materials interact directly

with the food and the environment, to extend shelf life and improve food quality

(Hotchkiss, 1995). This chapter presents an overview of the non-thermal food preser-

vation methods of PEF, HPP, irradiation, and pulsed light, a summary of packaging

materials used for non-thermal food preservation methods, and a direction for future

research in food packaging for non-thermal foods.

Non-thermal

food

processing

The mechanisms and critical factors of non-thermal food processing methods such as

pulsed electric fields (PEF), high-pressure processing (HPP), irradiation, and pulsed

light are summarized in Table 27.1.

PEF

treatment uses high-intensity electric field generated between two electrodes.

large flux of electrical current flows through the food product when a high-intensity

electric field is generated. A non-thermal treatment is obtained by the use of a very

short treatment time in pulses (i.e. microseconds).

Various types of PEF treatment chambers, which house electrodes and deliver PEF

to foods, have been used (Zhang

al., 1995).

uniform distribution of electric field

strength in the PEF treatment chamber is desirable to ensure that each microbial cell

within a population receives the same PEF treatment, and thus to develop mathemat-

ical kinetic models for the prediction of microbial inactivation and quality control

(Fiala

al., 2001). The high-voltage pulse generator converts low voltage into high

voltage and provides the high voltage to PEF systems (Qin

al., 1995a). The square,

exponential decay, and oscillatory waveforms are generally used for PEF treatments

(Barbosa-Canovas

al., 1999).

Structural damage of cell membranes, which leads to ion leakage and metabolite

losses, has been used to explain the microbial inactivation by PEF (Kinosita and

Tsong, 1977; Benz and Zimmermann, 1980). Chang and Reese (1990) introduced the

effects of PEF on microbial cells. Primary effects include structural fatigue due to

induced membrane potential and mechanical stress. Secondary effects include mate-

rial flow after the loss of the integrity of cellular membranes caused by the electric

field, local heating, and membrane stress. Tertiary effects include cell swelling or

shrinking, and disruption due to the unbalanced osmotic pressure between the cytosol

and the external medium.

The cell membrane is regarded as an insulator due to its electrical conductivity,

which is six to eight times weaker than that of the cytoplasm (Barbosa-Canovas

al.,

1999). Electrical charges are accumulated in cell membranes when microbial cells are

exposed to electric fields. The accumulation of negative and positive charges in cell

484

Innovations in Food

Packaging

Process Conditions

Mechanism

for

microbial

Critical

faaors

inactivation

'ulsed electric fields PEF treatment occurs inside PEF

Membrane structural or Electric field strength, PEF

PEF) treatment chambers, which

functional damage. PEF treatment time, pulse width,

houses electrodes and deliver PEF temporarily increases the trans-

pulse shape, treatment

(at 20-80 kV/cm for <1 s) to foods. membrane potential of cells temperature, electric

The square, exponential decay, and

by accumulating compounds conductivity, density, viscosity,

oscillatory waveforms are generally of opposite changes in pH, water activity, microbial

used membrane surroundings. characteristics

Continuous increase in trans-

membrane potential can cause

pore formation. Electroporation

in protein channels and lipid

domains results in osmotic

swelling of the cell and

membrane weakening until the

cell bursts.

iigh-pressure

HPP refers to the exposure of foods Deprotonation of charged

Pressure range, temperature,

~rocessing (HPP) within vessels to high pressures groups and disruptions of pH, protein structure, solvent

(300-700 MPa) for a short time salt bridges and hydrophobic composition, water activity,

(few seconds-several minutes) at bonds. Changes in cell

composition of foods,

<O°C->lOO°C) morphology involve the collapse microbial characteristics

of intercellular gas vacuoles,

anomalous cell elongation,

and cessation of movement

of micro-organisms.

rradiation Food irradiation involves exposing Damaging genetic materials Molecular weight of organic

prepackaged or bulk foods to (DNA). This damage prevents compounds, composition of

y-ray, X-ray, or electrons. The multiplication and terminates foods, efficiency of repair

radioisotope used in most commercial most cell functions

y-irradiation facilities is 60~o. The

mean energy of 60~o y-irradiation is

1.25 MeV. Electrons and X-ray are

restricted to 10 and 5 MeV,

mechanisms for DNA of micro-

organisms

respectively

Used light

Pulsed light is composed of about The antimicrobial effects of Efficiency of penetration of the

25% ultraviolet, 45% visible, and 30%

ultraviolet wavelengths are pulsed light (transmissivity),

infrared radiation. Energy density

primarily mediated through geometry of foods, the power

ranges about 0.01 to 50~/cm'. absorption by highly conjugated wavelength, arrangement of

Duration range: 1 ps-0.1 s. Flash: carbon-to-carbon double-bond light sources

1-20 flashesls system in proteins and nucleic

acids. DNA mutations are

induced by DNA absorption of

ultraviolet light

Packaging for non-thermal food processing

485

membranes forms the transmembrane potential.

high transmembrane potential

gives rise to pressure on the cell membranes. This increase in pressure decreases the

thickness of cell membranes, and ultimately causes pore formation (Zimmermann,

1986). The critical transmembrane potential (i.e. that which causes pore formation)

varies depending on the pulse duration time, number of pulses, and PEF treatment

temperatures (Barbosa-Canovas et al., 1999). Electroporation in protein channels and

lipid domains by PEF results in osmotic swelling of the cell and membrane weaken-

ing until the cell bursts (Tsong, 1991).

Harrison et al. (1997) reported that transmission electron microscopy

(TEM)

micro-

graphs of PEF treated Saccharomyces cerevisiae in apple juice exhibited disruption of

organelles and lack of ribosomes. They proposed that the damaged organelles and

lack of ribosomes afier PEF treatment are an alternative inactivation mechanism to

the electroporation theory.

The extent of microbial inactivation depends on the electric field strength, PEF

treatment time, pulse width and shape, treatment temperature, electric conductivity,

density, viscosity, pH, water activity, and microbial characteristics.

The potential for commercialization of PEF technology has drawn attention to the

food industry.

commercial-scale PEF system with flow rates of 50&2000Vh has

been constructed, and has processed orange and tomato juice successfully (Min et al.,

2003a, 2003b).

HPP

HPP, foods are exposed to high pressures (300-700 MPa) for a short period, typi-

cally ranging from a few seconds to several minutes. Foods are pressurized by direct

and indirect methods using a pressure-transmitting medium such as water (Farr, 1990;

Mertens and Deplace, 1993). HPP at 100-1000MPa inactivates micro-organisms and

enzymes (Knorr, 1995).

HPP damages microbial cell membranes (Farr, 1990). Changes in cell morphology

involve the collapse of intercellular gas vacuoles, cell elongation, and cessation of

movement in micro-organisms (Barbosa-Canovas and Rodriguez, 2002). High pressure

causes deprotonation of charged groups and disruption of salt bridges and hydro-

phobic bonds, resulting in conformational changes and denaturation of proteins (Barbos-

Canovas et al., 1998). The effect of HPP in the reduction of microbial populations has

been reviewed in detail by Smelt (1998).

The factors determining the efficiency of microbial inactivation by HPP include the

type and number of micro-organisms, the magnitude and duration of HPP treatment,

and the temperature, pH, and composition of the suspension media or foods (Hoover

et al., 1989; Barbosa-Canovas et al., 1998). Generally, bacteria are more resistant to

HPP than are yeasts and molds. Spores of bacteria are extremely resistant to HPP

(Nakayama et al., 1996). The inactivation of microbial spores by HPP is strongly

influenced by temperature (Barbosa-Canovas et al., 1998).

Enzymes are inactivated by HPP as a result of the conformational changes at

enzyme active sites. Recovery

activity after decompression depends on the degree

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Innovations in Food Packaging

of distortion of the molecule. The chances of the recovery decrease with an increase

in pressure beyond

3000

atrn (Jaenicke,

1981).

DNA molecules are more stable at high pressures compared to proteins. However,

DNA transcription and replication are disrupted by high pressures due to the inactiva-

tion of enzymes by HPP (Landau,

1967).

Irradiation

More than

countries permit the use of irradiation for over

types of foods (Ozen

and Floros,

2001).

Food irradiation involves exposing prepackaged or bulk foods to

y-rays, X-rays or electrons.

Radiation inactivates micro-organisms by damaging genetic materials (Grecz

al.,

1983).

This damage prevents multiplication, and terminates most cell functions. A

photon of energy or an electron randomly strikes the genetic material of the cell, and

causes a lesion in the DNA. The lesion breaks strands of DNA. Large numbers of

single-strand lesions may result in the death of microbial cells (Dickson,

2001).

Radiation also directly and indirectly damages other components of microbial cells,

such as membranes, enzymes, and plasmids (Dickson,

2001).

The sensitivity of a micro-organism to irradiation is related to the efficiency of its

DNA repair mechanisms. Micro-organisms that have a more efficient DNA repair

mechanism are more resistant to irradiation (Dickson,

2001).

Other factors determin-

ing the efficiency of microbial inactivation by irradiation include the molecular

weight of organic compounds, and the composition of foods (Barbosa-Canovas

al.,

1998).

The inactivation of gram-positive bacteria that have significance to the public

health significance by irradiation has been discussed in detail by Dickson

(2001).

Vitamins A,

and

are

known

to be sensitive to irradiation. Carbohydrates,

lipids, and proteins will not be noticeably degraded by irradiation, but minor compo-

nents may be disproportionately depleted by free radicals formed during irradiation

(Bloomfield,

1993).

Irradiation can be used for frozen foods, and is the only preservation method avail-

able for the inactivation of pathogenic micro-organisms in frozen foods (Barbosa-

Canovas

al.,

1998).

Pulsed

light

Pulsed light is a rapid, intense, and magnified flash of light or electrical energy (Dm,

1996).

Pulsed light is applicable in inactivating micro-organisms on the surfaces of

foods, of packaging materials and of processing equipment (Barbosa-Canovas

al.,

1998).

The spectrum of light used for sterilization includes wavelengths in the ultravio-

let to those in the near infrared region. Pulsed light consists of about

25%

ultraviolet,

45%

visible, and

30%

infrared light

(Dunn,

1996).

The energy density of one pulse of

light ranges from

0.01

~/cm' (Dunn

al.,

1991).

The pulse width is in the range

ps to

0.1

s, and the flashes are typically applied at a rate of

1-20

flashes per

second (Barbosa-Canovas

al.,

1998).

Packaging for non-thermal food processing

487

Pulsed light is effective when it can penetrate food surfaces or packaging materials

(Dunn, 1996). Pulsed light inactivates a wide range of micro-organisms, including

bacterial and hngal spores. Dunn (1996) showed inactivation of micro-organisms in

fresh juices by pulsed light without impairment of the sensory quality. Food applications

of pulsed-light treatments have been reviewed in detail by Hoover (1997).

The antimicrobial effects of ultraviolet light are primarily due to its absorption

by highly conjugated double-bond systems in proteins and nucleic acids of micro-

organisms. Comparison of the antimicrobial effects obtained using pulsed light with

those obtained using non-pulsed or continuous ultraviolet light indicated that pulsed light

inactivated more micro-organisms than did continuous ultraviolet light (Barbosa-

Canovas

al., 1998).

The effectiveness of pulsed light on the shelf-life extension of fresh fruits and veg-

etables is limited due to their irregular surfaces. The microbial inactivation by pulsed

light depends on the efficiency of the penetrating pulsed light (transmissivity), the

geometry of the foods, the power wavelength, and the arrangement of the light sources

(Dunn, 1996).

Plastic packaging materials

Food packaging is one of the major fields for the application of plastic materials

(Baner and Piringer, 1999). Plastic packaging materials have been developed for the

packaging of fresh quality products (Yam and Lee, 1995).

The shelf life of foods packaged in plastics depends on the permeation of gas and

water vapor through the packages. This is because a significant amount of food dete-

rioration results from oxidation and changes in the water content (Varsanyi, 1986).

Factors affecting the permeability include the chemical structure, crystallinity and

molecular weight of polymers, the degree of polymerization, the molecular orienta-

tion, the presence of double bonds, the film thickness, the polarity, the additives

(including plasticizers), the permeate size, and the density, temperature and pressure

(Pascat, 1986).

Polyolehs, styrenics, polyesters, and vinyls are the principal families of thermo-

plastics in food packaging (Brown, 1992). Polyolefins include polyethylene (PE) and

polypropylene (PP). Polystyrene (PS) is a type of styrenic. Polyethylene terephthalate

(PET) and polycarbonates (PC) are examples of polyesters.

Various materials with specific functionality are available. Amorphous polyamides

(MA) have recently appeared in food packages as gas-barrier materials. The barrier

property of AmPA is intermediate between the high barrier ethylene vinyl alcohol

(EVOH) and polyvinylidene chloride (PVDC), and the lower barrier PE. The barrier

property increases with increasing relative humidity

@H).

AmPAs have oxygen

permeabilities around 2 cc-miY100 in2 day atm (800 cc p,m/m2 day atm) when the

low. The oxygen permeability decreases to about 1 cc rn11100 in2 day atm at 80%

(Brown, 1992). Brown (1 992) presented a polycondensation product of adipic acid and

metaxylylene diamine,

MXD6,

which is not sensitive to moisture compared