Jung Han. Innovations in Food Packaging

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458

Innovations in Food Packaging

Active packaging

Although some active packaging technologies have been commercialized for more

than

years, commercial applications in the United States to date have been rela-

tively disappointing. Today, active packaging technologies are largely developmental

and subject to both incremental and breakthrough change, with only about

4000-4500

million packages (less than

of all packages) using an active packaging technology

in the United States in

2003.

Developments appear to project a

20%

compound annual

growth rate for the

2004-2009

period.

As indicated above, active packaging refers to packaging materials that sense envi-

ronmental change and respond by changing their properties, on their own, to better

retain product safety, quality, shelf life, and functionality, beyond the protection of the

base package structure against the varying distribution environments. Intelligent pack-

aging refers to structures that sense and signal a variation of the conditions of the

package or the contained product, but do not change the properties of the package.

Active packaging encompasses about ten broadly defined functions, each applying

a different technology. Within most of the technologies there are multiple methods to

obtain the desired result. Active packaging functions and technologies include:

Moisture control

Waterlpurge or fluid squeeze or drip from the product

Water vapor in equilibrium with the water within the product

Relative humidity control

2. Oxygen-permeable films to obviate respiratory anaerobiosis

Oxygen scavengerslabsorbers

Ferrous iron

Ascorbates

Nylon MXD6

Unsaturated ethylenics such as butadiene

Benzoacrylates

Antioxidants

Oxygen generators

Carbon dioxide controllers

Removers

Generators

Odor controllers

Flavor enhancement

8. Ethylene removal

Antimicrobials

10.

Microwave susceptors

usually controlled by a user rather than by sensing a

product, and thus not included in this chapter.

Depending on the technology, active packaging can sense changes in the internal

package, in external temperatures, or time; or can sense changes in the gaseous, physical,

Commercial uses of active food packaging and modified atmosphere packaging systems

459

chemical, or biological environments. The package material andlor the active pack-

aging device responds to these changes by altering its properties to effect the change.

As shown in Table 25.1, three active packaging technologies appear to account for

almost all of the active packaging unit usage

oxygen scavengers, in several forms

(50%); desiccants, also in several forms (34%); and purge absorbers (14%). By 2006,

these three technologies will decline slightly relative to others, accounting for about

95% of the active packaging units used. Oxygen scavengers, the largest active pack-

aging technology in terms of volume, will have the lowest average annual growth rate

at about 12%. Relative humidity controllers will have the highest growth rate of more

than 58%, albeit from a very small base of only 10 million packages in 2003.

More than 50 end-use product applications for active packaging have been identi-

fied to create Tables 25.1 and 25.2. Although most end-use applications have focused

on only one active packaging technology, several applications

including bakery

products, processed meat, poultry, and military rations

currently apply more than

one active packaging technology.

Oxygen scavenging packaging

Active packaging has enjoyed good growth over the past ten years, to 350W500 million

units in 2003. Once regarded as a failure in the United States, the oxygen scavenger mar-

ket grew 15-fold during the 1990s and currently appears to be on an exponential growth

curve. Recognition and appreciation by food packaging technologists of the ability of

oxygen scavengers to better retain the quality of packaged products has led to a multipli-

cation of the application of basic inorganic scavenger-containing sachets (e.g. ferrous

salts) and the incorporation of organic oxygen scavengers such as nylon MXD6 and ben-

zoacrylates directly into package materials.

The concept of incorporating oxygen scavengers directly into plastic materials has

challenged polymer and packaging technologists for more than 20 years. Early problems

included regulatory concerns over the involved compounds and obvious secondary

Table

25.1

dve

packaging applications,

2003

(units)

Application Million units (2003)

Annual

growth

2003-2006

of units 2003

Moisture controllen*

Purge absorbers

controllers

Desiccants

Oxygen scavengers

Controlled gas permeability

Ethylene absorbers

Antimicrobials

Odor controllers

Total

Excludes pulp pads.

Source: PackagingJBrody, Inc.

460

Innovations in Food Packaging

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Commercial uses of active food packaging and modified atmosphere packaging systems

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Innovations in

Food

Packaging

lable

ZS.5

Oxygen-absorbing

technologies,

zUU3

(unlts)

Technology Million units

Projected

annual

growth

rate

(2003) 2003-2006

Oxygen absorber in bottle 840 13%

Capllinerllidding 612 15%

Oxygen absorber

film

105

54%

Sachet 283

Total 1840 12%

Source: PackagingJBrody, Inc.

effects. Previous package structures were able to approach actually mimicking the

zero oxygen permeation of sealed glass. When coupled with the later introduction of

oxygen scavenger-containing oxygen-barrier closures, the resulting bottles and jars

demonstrated no measurable oxygen movement. Such outcomes were heralded as

major breakthroughs to the packaging of highly oxygen-sensitive products such as

beer and fruit beverages in lightweight, non-breakable, semi-rigid plastic structures.

A multi-billion-package market represents a highly inviting investment opportunity

for polymer manufacturers, package converters, and others. Currently, depending on

how oxygen scavenging is defined, more than half a dozen competitive systems are

offered, with more certain to come.

Ferrous iron oxygen scavengers in in-package sachets are oRen dismissed as archaic,

but retain a leadership position in a wider variety of packaged products. More reliable

adherence to package interiors and fabrication in flat label form has helped to grow

their position. Ferrous iron-based oxygen-scavenger sachets have proved to be func-

tional, reliable and effective. Despite its dark color, ferrous iron is a preferred oxygen

scavenger for incorporation into plastics, which suggests a continuing future.

As costs for oxygen scavengers decline, and when the hurdles have in large part been

overcome, the use of oxygen controllers such as scavengers should increase for pack-

aging oxidation-sensitive foods. Adverse biochemical oxidation reactions and aerobic

microbiological spoilage growth can be retarded in a host of foods, including fruit bev-

erages, tomato products, home meal replacements, shredded cheese, and processed

meats, whose distribution life is now limited. Gradually, the use of passive oxygen bar-

riers will be enhanced by active oxygen scavengers to enhance quality retention.

Table

25.3

shows the four major oxygen-absorbing technologies, and Table

25.4

lists the major end product users of oxygen-absorbing technologies in the

US.

High gas-permeability package

structures

Probably the best example of classical active packaging is Landec's lntellipacB. This

material senses temperature increases

and,

unlike passive packaging, markedly increases

its gas permeability as a result. In modified atmosphere packaging (MAP), increases

in temperature lead to increases in product respiration rate, which can consume the

oxygen and lead to anaerobic conditions that in turn can produce off-flavors. The high

Commercial uses of active food packaging and modified atmosphere packaging systems

463

Table

25.4

oxygen scavengers, 2003 (units)

Product

Beer

Juice

Ketchup

Beef jerky

Case-ready meats

Pasta

Processed meats

Military rations

Gluten-free bread

Prepared foods

Cheese

Total

Source: PackaginglBrody, Inc.

Million units (2003)

gas permeability packaging concept might possibly be applicable to low-acid wet

food products vulnerable to pathogenic anaerobic microbial growth, e.g. home meal

replacements, thus obviating this deterrent to category growth.

High

relative

humidity

control

The control of in-package moisture is practically a very usehl commercial technique,

because:

Moisture control, although long ago dismissed as a casual or matter-of-fact

method, is probably the leading active packaging technology, and will remain so

Moisture control is being coupled to other active packaging technologies, such as

oxygen scavengers and antimicrobials, to produce synergistic active packaging.

Always a source of spoilage and a poor, messy appearance, purge or liquid drip from

fresh and minimally processed foods has been linked to the adverse effects of relative

humidity in closed-package environments. Control of purge by gel-forming poly-

meric absorbers has been demonstrated in commercial testing for the purpose of

measurable enhancement of quality retention. Among the consequences is that these

active packaging technologies are moving from independent pulp pads or "diapers"

the tray base to functional incorporation into plastic package tray and pouch struc-

tures; further technology development will concentrate on hiding the purge and con-

trolling internal package relative humidity.

By mixing moisture-activated antimicrobials into the gel-forming polymers, the

preservation benefits of the active packaging may be multiplied. Beyond the dual

effect, moisture-activated oxygen scavengers may become a third material to function

in synergy

to provide controlled relative humidity, oxygen, and microbial growth

within the package. Food products such as fresh poultry can be envisioned to benefit

from this potential enhancement of hurdle technologies.

464

Innovations in Food Packaging

Low relative humidity control

At the other end of the moisture spectrum of humidity controlling technology are

dry

products sensitive to even minute quantities of environmental moisture. While effec-

tive water vapor barriers are used for the packaging system, their functionality is

exponentially increased by the presence of desiccant sachets and/or cartridges. Such

devices are limited by capacity, proximity, and lack of persistence.

Probably one of the most significant active packaging technologies is the concept

of developing high surface-area channels on interior package surfaces on which des-

iccants are spread to capture moisture. This structure is so powerful that it can con-

tinue to remove water vapor even after the package has been opened and exposed to

air, thereby providing low humidity conditions after reclosure.

Still in its infancy, the notion of exponentially increasing the internal package sur-

face area and coupling this with active packaging technology

in this instance, des-

iccants

represents a strong argument for the growth of active packaging. Although

confined today to desiccants, it is possible that this could be extrapolated to combine

moisture-triggered oxygen scavengers

with

antimicrobials to form an extraordinary

food preservation hurdle technology. As food scientists and technologists evolve from

process to packaging technologies to enhance quality retention, hurdle or combina-

tion technologies such as active packaging on internal surfaces will emerge as effec-

tive tools to achieve this objective.

Antimicrobials

Headlined and apparently used widely in Japan, in-package antimicrobials have not

been applied in the United States for a variety of reasons, including:

Regulatory concerns

The fear of adverse secondary effects

A lack of evidence on the efficacy

The fact that too many are contact functional only, limiting their potential

Cost.

Experience in Japan an4 to some degree, in Europe has not translated to the United

States. Too many antimicrobials, such as silver salts and ~icroban~, function only

in contact with micro-organisms present on smooth food surfaces. Antimicrobials

that are claimed to function at a distance, such as chlorine dioxide or ethanol, have

been limited by secondary effects and a narrow spectrum of activity. There is a great

deal of excitement regarding the concept of building microbiostatic andlor micro-

biocidal agents into package materials to extend microbiological shelf life. To

date, food packagers have been hesitant with proceeding to commercialization.

Controlling visible fungal growth on fresh hit or cheese would be a desired result for

those organizations that become the early adopters and lead the category into active

packaging.

Commercial uses of active food packaging and modified atmosphere packaging systems

465

Odor controllers

Odor control derived from active packaging has been the subject of considerable

philosophical debate. If the odor of a packaged product is enhanced by a desirable

aroma, the consumer may be deceived into the perception that the product is better

than it is. When food and food-packaging scientists and technologists employ the

flavor add-back in instant coffee or juice concentrate, there have been no questions

about "synthetically enhanced" flavor. However, when the source of the aroma is the

package material, questions may arise. The opposite end of the odor control spectrum

is the overt removal of confinement or even minor spoilage odors. Some argue that

minute sulfurous or arnine odors are trivial and indigent to many protein foods, and

are therefore harmless; thus their removal should be a benefit since some consumers

might reject the product for no good reason. Lipid oxidation odors, such as aldehydes

or ketones at low levels, are generally inconsequential, and their removal should be

equally beneficial for consumers. On the other hand, some experts argue that food

spoilage odors

including sulfide and lipid oxidation odors

are overt signals to con-

sumers of an incipient hazard, and should not be artificially suppressed. Since the

driving forces for odor-control systems have been from both users and technology

suppliers, the question will not be answered until consumers are educated on the

issues and make their own decisions.

Conclusions on active packaging

Active packaging is very much

its infancy, with both suppliers and potential users

needing and wanting to spark a broad front of new applications. However, too many

elements must be comprehended and remain to be refined. The result so far has been

slow and uneven growth in the segments.

Active packaging today is largely supplier-driven. Furthermore, many of the tech-

nologies originated and are being nurtured in offshore locations, while North American

organizations puzzle over the benefit versus cost. Unlike Europe, where independent

central laboratories such as the Carnpden

Chorleywood Food Research Association

Group

(UK)

or TNO (The Netherlands) evaluate active packaging technologies, no

such agencies exist in the United States or Canada, and North American-based organ-

izations such as universities have barely touched on active packaging technology.

The short-term potential for any single active packaging technology capturing

more than a handful of niche applications today is small. Several large petrochemical

companies, such BP Chemical and Chevron Phillips, are drivers in unsaturated hydro-

carbon oxygen-scavenger technology.

long-time pioneer in oxygen scavengers,

Mitsubishi Gas Chemical (Japan) still leads in ferrous iron sachets, with Multisorb

Technologies (of Buffalo, NY) close behind. The Japanese company is also the sup-

plier of the oxygen-scavenging nylon

MXD6.

Multisorb Technologies, whose sole

business is active packaging, is by far the leader in desiccant sachets. A large specialty

chemical company, Ciba, is also

this market.

The package material converters that are active in active packaging include Cryovac

Sealed

Air,

and Cadillac, in flexible packaging; Continental PET Technologies, Amcor,

466

Innovations in Food Packaging

Pechiney, and Crown Cork

Seal, for bottles; and Silgan, for plastic cans. The numbers

are too few for flexible packaging and cans, but there is the opportunity for strong

competition in bottles if a market should emerge.

Mainstream moisture-absorbing pads are not regarded as active packaging. The

new super-absorbent gels fall into the definition of active packaging and belong to

entrepreneurial firms such as Maxwell-Chase, which are still seeking their market

segments. Desiccant sachets/cartridges are produced by Multisorb Technologies,

~m-~hemie, and United Desiccants, which are all relatively modest sized compa-

nies. The progenitor of the in-package desiccant is CSP Technologies (Capitol

Specialty Plastics Technologies), which is a relatively small company whose core

competency is in injection molding of small vials for M&M@ milk chocolate candies

and for pharmaceuticals.

Odor controllers have been pushed by two different operations; DuPont, and

Cellresin Technologies (a development company).

Most of the proposed in-package antimicrobials come from relatively small entre-

preneurial development companies, such as AgION, Japan's Certex, and Bernard

Technologies, plus a small operation in the textile giant Milliken.

The variety of organizations involved in active packaging might be classified as

heterogeneous. The active packaging technology market is dominated by start-up sup-

pliers and developers, with a sprinkling of specialty operations in large chemical com-

panies, apparently targeting the potentially lucrative plastic beer bottle market. There

are too few converters actively studying. Although the history dates back more than a

decade, few (if any) organizations have entered and subsequently dropped out of the

development projects of active packaging technologies. The array of technologies

continues to attract a range of participants.

Modified atmosphere packaging

Although modified atmosphere and vacuum-packaged foods are not highly visible in

food marketing, they constitute a substantial and growing proportion of

food sup-

plies, mostly in distribution packaging. Vacuum packaging, modified atmosphere pack-

aging

(MAP)

and controlled atmosphere packaging

(CAP)

are all regarded by most

observers as part of the same technology.

History

CAP

and

MAP

For decades, food and food-packaging technologists have been taught the principles

of microbial growth and retardation, including reducing temperature to inhibit micro-

bial activity rates and applying heat to destroy micro-organisms. Micro-organisms

slow down their respiratory and growth rates when oxygen is reduced and the respiratory

gases such as carbon dioxide are increased. Aerobic respiration is the basis for the

degradation of plant materials after removal from the growing plant. Plant-product

respiration is slowed by increasing carbon dioxide and reducing oxygen and ethylene.

Commercial uses of active food packaging and modified atmosphere packaging systems

467

In the early years of the twentieth century, fresh meat shipped from the Antipodes

to England was sometimes chilled by solid carbon dioxide. Mutton, beef, and lamb in

the shipment were noted to have shelf lives longer than carcass meat held under wet

ice only, and this phenomenon was later attributed to the disruption of the gaseous

atmosphere. During the 1930s, fresh apples and pears were placed in enclosed ware-

houses. The natural respiratory reaction of the fruit reduced the oxygen and increased

the carbon dioxide within the storage areas sufficiently to slow the respiration rate

markedly. The stored apples or pears could be consumed six months after the original

harvest

an extension of about double the normal chilled storage shelf life. The use

of natural respiratory-controlled storage for apples and pears was expanded rapidly

during the 1950s in both New York and the Pacific Northwest.

Tectrol

During the 1950s and 1960s in the US, Whirlpool Corporation's food technologists

developed methods to control the atmospheres surrounding meat, fruit, and vegetable

products. The concept was adapted to the bulk and industrial distribution of fresh fruit

and meat products. The name Tectrol (Total Environmental ConTROL) was applied

to total control of warehouses. By the mid- to late-1960s, hundreds of apple and pear

warehouses throughout the United States and Europe were equipped with Tectrol sys-

tems to extend the shelf life of the fruits.

Transfresh

The Tectrol concept was spun off to the produce grower, Bruce Church, in California, and

reorganized under the name Transfresh. The Tectrol/Transfresh concept has since been

expanded to transport containers in order partially to control the internal gas content

surrounding the contents. The Tectrol/Transfresh system is now used to deliver bulk

and consumer-size packages of fresh-cut vegetables to

HRI

and retail outlets, and pallet

loads of strawberries to subdistributors.

1990, the process was refined into complete

control of shipboard container loads.

Mer spin-off from Transfresh is Fresh Express,

the largest producer and packager of retail and foodservice fresh-cut vegetables.

Cryovac

During the 1960s, barrier shrink-film vacuum packaging that was used to protect

frozen turkeys in distribution was applied to fresh red meat by the Cryovac organiza-

tion, which also gave its name to the process. Under reduced oxygen, the growth of

micro-organisms responsible for meat spoilage are retarded. Simultaneously, how-

ever, the original purple myoglobin color of fresh red meat is retained. During the

mid-1960s, Cryovac and Iowa Beef Packers (now IBP, Tyson) joined in the concept of

slaughtering cattle at a central location

and,

rather than shipping in hanging carcass

form, breaking the meat into primal and sub-primal cuts. These products were subse-

quently vacuum-skin packed into high gas-barrier multiple-layer plastic film bags.

The reduced oxygen in the vacuum pack retarded microbial growth and oxidation of

fat. Furthermore, the bag did not permit the passage of water vapor, and so weight loss

due to evaporation was significantly reduced. These filled bags were then packed in