Yam, Kit L. (ed.). The Wiley encyclopedia of packaging technology

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PdM—Predictive Maintenance

PdM, one of the most popular terms in the maintenance

ﬁeld, covers a wide range of practices, all of which try to

refute the old adage, ‘‘If it ain’t broke, don’t ﬁx it.’’ PdM

practitioners follow a credo more like, ‘‘Don’t wait for it to

actually break before you ﬁx it—ﬁgure out when it is going

to break and make sure you don’t have to ﬁx it in the

middle of production.’’

From http://www.plant-maintenance.com/terminolo-

gy.shtml, predictive maintenance can be said to be an

equipment maintenance strategy based on measuring the

condition of equipment in order to assess its present

condition, predict its remaining useful life, and determine

an expected failure time in the future and then taking

ongoing appropriate action to avoid the failure and its

consequences. The condition of equipment could be mon-

itored using condition monitoring, statistical process con-

trol techniques, by monitoring equipment performance, or

through the use of the human senses. The terms condi-

tion-based maintenance, on-condition maintenance, and

predictive maintenance could be used interchangeably.

As the name implies, predictive maintenance antici-

pates equipment outages rather than reacting to them.

Beneﬁts include fuller useful life for equipment and lower

backup inventory. It goes beyond preventive maintenance,

which at least strives to shift plant downtime to noncri-

tical periods. Initial cost of predictive monitoring systems

tends to be high, but much less than forced reactive

maintenance due to just one serious outage of a manufac-

turing line. In an era of intensive competition, where asset

usage and plant operating efﬁciency must be maximized,

it is predictive maintenance that should be a tool along

with reliability centered maintenance.

Diagnostic equipment is central to the PdM methodol-

ogy, and therefore it is no surprise that there are thou-

sands of products that enable users to anticipate machine

failure. Software—like CMMS, ERP, and EAM packages—

is a big part of this.

PM—Preventive Maintenance

In his 1998 book, Developing Performance Indicators for

Managing Maintenance (Industrial Press), Terry Wire-

man has this to say about PM:

The preventive maintenance program is the key to any

successful asset management process. The preventive main-

tenance program reduces the amount of reactive maintenance

to a level low enough that the other initiatives in the asset

management process can be effective. However, most compa-

nies in the United States have problems keeping their PM

programs focused. In fact, surveys have shown that only 20

percent of the companies in the United States feel their PM

programs are effective.

Historically; PM was introduced in the United States in

the 1950s and then adopted into the Japanese philosophy

of TPM (see below). PM is sometimes seen as an outmoded

concept today, having been supplanted by more recently

honed philosophies like RCM, TPM, and PdM, but its

general foundation of what TPM guru Seiichi Nakajima

calls ‘‘time-based maintenance featuring periodic inspec-

tion, servicing and overhaul’’ is still the basis for many

maintenance initiatives today. Regarding overhauling

equipment, it is now being more recognized by industry

to overhaul equipment based on predictive analysis and

inspection and overhaul as needed, not on a ﬁxed cyclical

time parameter.

QCP—Quick Change Process

Quick change process (Figure 1) can be deﬁned as all those

tasks that must be done quickly with accuracy and preci-

sion when changing from one product to another or one

Quick Change

Process

(QCP)

First Time Right & Quick

for Production Processes

People

Protocols (PP)

Change Part

Protocols (TP)

Machine

Protocols (MP)

Safety/STI/SOP

Cleanliness/Order

Decontamination

Storage/Transfer/Staging

Skill Level & Training

Vendor Support

Wear/Maintenance

Concept/Design/Specs

Decontamination

Clean Up

Vendor Support

Identify & Document

Safety & Ergonomics

Decontamination

Clean Up

Transfers & Storage

Input

Protocols (IP)

Supplier Support

Cleanliness/Order

Decontamination

Design/Specs/Tolerances

Transfers & Storage

Continuous Improvement

Company Policy/Management

Design/Specs

Wear/Maintenance

Safety & Ergonomics

Laws

Certifications

Standards

(Regional,

National,

International)

Quick Change Process

Loading/Housekeeping

Figure 1. An overview of the quick change process.

888 PACKAGING LINE PERFORMANCE

SKU to another. To accomplish this requires the proper

execution of associated tasks that are related to a given

SKU. The main tasks are made up of:

1. Ofﬂine preparatory, documentation, and ready

events.

2. Purge-out activities.

3. Change-out activities or changeover.

4. Run-up or start-up.

The interrelationship of all these tasks and their subtasks

involved in the change process can be very complex. A

review of this complexity will be done, along with discus-

sion of why changing the packaging process to be quick

change is a coordinated holistic effort.

Today the change-out process has to be taken seriously

and integrated into company policy in order to:

. Develop a just-in-time or on-demand production

philosophy.

. Increase their margins and proﬁts.

. Run a large variety of different products on the same

line.

. Demonstrate control to regulatory groups.

. Maintain and increase market share.

Quick change process is fundamentally a signiﬁcantly

modiﬁed version of single minute exchange of die (SMED)

philosophy and techniques expanded and targeted to

production facilities especially related to packaging, blow

molding, and converting industries. SMED uses philoso-

phical concepts and industrial engineering techniques to

facilitate the quick exchange of die sets in stamping

operations, as found in the automotive industry.

RCM—Reliability-Centered Maintenance

There is a whole sub-industry in the maintenance ﬁeld

centered on RCM and its offspring, RCM2. Reliability can

be deﬁned as ‘‘the process of managing the interval

between failures. If availability is a measure of the equip-

ment uptime or conversely the duration of downtime,

reliability can be thought of as a measure of the frequency

of downtime.

RCM thinking and practice began in the commercial

airline industry—a ﬁeld where ‘‘downtime’’ has some

pretty unfortunate connotations—in the 1960s. In the

following decades, two engineers, Stanley Nowlan and

Howard Heap of United Airlines, published a study on

the subject that established it as a standard maintenance

practice.

There is likely nobody who has done as much to spread

the cause of RCM and RCM2 as John Moubray, who,

through his Aladon consulting ﬁrm (www.aladon.co.uk),

has worked with plants worldwide on reliability-based

initiatives. He deﬁnes RCM2 as ‘‘a process used to decide

what must be done to ensure that any physical asset,

system or process continues to do whatever its users want

it to do.’’

SCM—Supply Chain Management; or ISCM—Integrated

Supply Chain Management

Always a tough one to deﬁne—there are several competing

theories as to where the industrial chain of raw goods,

manufacturing, and distribution actually starts and ends.

Practitioners have, within the last few years, taken to

referring to ‘‘integrated supply chain management’’

(ISCM) just to further confuse the issue, but basically

they are the same.

ISCM is a process-oriented, integrated approach to procuring,

producing, and delivering products and services to customers.

ISCM has a broad scope that includes sub-suppliers, suppliers,

internal operations, trade customers, retail customers, and

end users. ISCM covers the management of material, informa-

tion, and funds ﬂow:

You can ﬁnd an excellent overview of the subject in the

‘‘Supply Chain Management Review’’ online magazine site

at: http://www.manufacturing.net.

Six Sigma

It is a systematic quality program that strives to limit

defects to three standard deviations on either side of the

mean or a total of six sigma. Sigma is just a term for one

standard deviation about the mean of a signiﬁcant popu-

lation of measurements of a process variable. One of the

major focuses of Six Sigma is to reduce process variation.

In most companies, quality loss will be by far the smallest

of the OEE losses. A Six Sigma or equivalent program may

be necessary to maintain focus on quality improvements.

SPC—Statistical Process Control and SQC Statistical Quality

Control

Statistical process control (SPC) and statistical quality

control (SQC) methodology is one of the most important

analytical developments available to manufacturing in

this century. SPC has come to be known as an online

tool providing close-up views of what’s happening to a

process at the moment. SQC provides ofﬂine tools to

support analysis and decision-making to help determine

if a process is stable and predictable from shift to shift, day

in and day out, and from supplier to supplier. When SPC

and SQC tools work together, users see the current and

long-term picture about processing performance. SPC

provides online tools that permit a close-up view of what’s

currently happening to a process. SQC provides ofﬂine

tools to support analysis and decision-making about pro-

cess stability over time.

Before SPC, products were inspected after they were

completed and defective products were discarded or re-

worked. The idea behind continuous improvement is to

focus on designing, building, and controlling a process that

makes the product correctly the ﬁrst time at the point of

manufacture.

How to Improve Using SPC and SQC

Key to improving a process is removing as much variation

as possible. When products and services are delivered

PACKAGING LINE PERFORMANCE 889

with minimal variation, customer requirements and

expectations are met. Manufacturers applying SPC and

SQC techniques rely on a variety of methods, charts,

and graphs to measure, record, and analyze processes to

reduce variations. In general, processes achieving the

most beneﬁt from SPC and SQC are products with:

1. Highly repetitive manufacturing processes.

2. High-volume production and low margins.

3. Narrow tolerances.

To make SPC and SQC work, key parameters indicating

product variations are measured and recorded. For exam-

ple, key parameters for a roll of cloth could include

shrinkage, color, strength, and ﬂaws per yard (meter).

SQC methods are used to analyze recorded data and

establish which variations are a natural part of the

process and which unusual variations are caused by

external factors, such as variations in raw materials.

SPC and SQC Tools

Control charts are a fundamental tool of SPC and

SQC and provide visual representation of how a process

varies over time or from unit to unit. Control limits

statistically separate natural variations from unusual

variations. Points falling outside the control limits are

considered out-of-control and indicate an unusual source

of variation.

Performance improvements of personal computer hard-

ware and software permit real-time data collection, num-

ber crunching, and graphing. Providing SPC information

in real-time allows operators to make adjustments or to

schedule maintenance on an as-needed basis. SPC and

SQC are an effective part of continuously improving a

manufacturing process. When measurements are accu-

rately collected and analyzed, improvements are identi-

ﬁed and implemented, and controls established to ensure

improvements are permanent and the process is well on

its way to meeting quality requirements.

Process capability Cp or Cpk is a process that is used

within the SPC environment. It is a process that is a

unique combination of tools, materials, and methods, and

people engaged are producing a measurable output; for

example a manufacturing line for machine parts. All

processes have inherent statistical variability that can

be evaluated by statistical methods. The process capability

is a measurable property of a process. It is usually

reported in terms of the inherent variability of a process

and its output.

Two parts of process capability are: (1) Measure the

variability of a process and (2) compare that variability

with a proposed speciﬁcation or product tolerance.

Process capability compares the output of an in-control

process to the speciﬁcation limits by using capability

indices. The comparison is made by forming the ratio of

the spread between the process speciﬁcations (the speciﬁ-

cation ‘‘width’’) to the spread of the process values, as

measured by 6 process standard deviation units (the

process ‘‘width’’).

The process capability index uses both the process

variability and the process speciﬁcations to determine

whether the process is ‘‘capable.’’

We are often required to compare the output of a stable

process with the process speciﬁcations and make a state-

ment about how well the process meets speciﬁcation. To do

this, we compare the natural variability of a stable process

with the process speciﬁcation limits.

capable process is one where almost all the measure-

ments fall inside the speciﬁcation limits. This can be

represented pictorially by the plot below:

LSL USL

Actual process spread

Allowable

rocess s

read

There are several statistics that can be used to measure

the capability of a process: C

, C

, and C

Most capability indices estimates are valid only if the

sample size used is ‘‘large enough.’’ Large enough is

generally thought to be about 50 independent data values.

The Cp, Cpk, and Cpm statistics assume that the popula-

tion of data values is normally distributed. This is dis-

played by the graph above in which there is a two-sided

speciﬁcation,



X and s are the mean and standard devia-

tion, respectively, of the normal data and USL, LSL, and T

are the upper and lower speciﬁcation limits and the target

value, respectively. References are

http://www.itl.nist.gov/div898/handbook/pmc/section1/

pmc16.htm or

http://www.isixsigma.com/st/process_capability/ or

Pyzdek, T, Quality Engineering Handbook, 2003, ISBN

0824746147

Bothe, D. R., Measuring Process Capability, 2001, ISBN

0070066523

Godfrey, A. B., Juran’s Quality Handbook, 1999, ISBN

007034003

ASTM E2281, Standard Practice for Process and Mea-

surement Capability Indices

890 PACKAGING LINE PERFORMANCE

TPM—Total Productive Maintenance

In the trendsetting 1982 book TPM Tenkai (which was

translated into English as TPM Development Program:

Implementing Total Productive Maintenance and pub-

lished in 1989 by Productivity Press), editor Seiichi

Nakajinia writes that in the years during and immedi-

ately following World War II, Japanese industrial man-

agers sought to compete in the world marketplace by

improving on the quality of their products. Building on

the American PM model, the Japanese developed the ﬁeld

of TPM in the 1970s—most notably in the Toyota auto-

motive plants, as a way of furthering reﬁning their main-

tenance practice. The overall aim of TPM is ‘‘a double

goal—zero breakdowns and zero defects.’’

Nakajinia says that TPM was deﬁned in 1971 by the

Japan Institute of Plant Engineers with these 5 goals in

mind:

1. Maximize equipment effectiveness (in improving

overall efﬁciency).

2. Develop a system of productive maintenance for the

life of the equipment.

3. Involve all departments that plan, design, use, or

maintain equipment in implementing TPM (engi-

neering and design, production, and maintenance).

4. Actively involve all employees from top manage-

ment to shop ﬂoor workers (Top down approach).

5. Promote TPM through motivation management:

autonomous small-group activities.

For overviews of TPM, go to NASA’s site at www.larc.

nasa.gov/ or search for TPM.

Other Performance-Enhancing Methodologies

ABC/M Activity-Based Costing/Management

BPI Business Process Improvement

BPR Business Process Reengineering

CI Continuous Improvement

EAM Enterprise Asset Management

ERP Enterprise Resource Planning

JIT Just-in-Time (manufacturing)

LCC Life Cycle Costing

LEAN Lean production or manufacturing

MES Manufacturing Execution System

MP Maintenance Prevention

MPI Maintenance Performance Indicators

MRP Material Requirements Planning (MPR-I

and MPR-II)

MSDS Material Safety Data Sheet

MTBF Mean Time Between Failure

MTTR Mean Time to Repair (MTOF—Mean Time

of Failure)

RCAF Root Cause Analysis of Failure

RCD Reliability-Centered Design

SMED Single Minute Exchange of Dies

TCO Total Cost of Ownership

TMM Total Maintenance Management

TQM Total Quality Management

ZD Zero Downtime

BIBLIOGRAPHY

1. P. J. Zepf, P. Eng., CPP, How to Implement Performance

Measurements into a Production Process, Zarpac Inc., Oak-

ville, Ontario, Canada, 2002, http://www.zarpac.com.

2. T. J. Zepf, The Art of Work, Tanis Media, Oakville, Ontario,

Canada, 2006, www.amazon.com or http://www.tanismedia.

net.

3. A. B. Godfrey, Juran’s Quality Handbook, 5th edition,

McGraw-Hill, New York, 1999.

4. T. Pyzdek, Quality Engineering Handbook, 2003.

5. D. R. Bothe, Measuring Process Capability, ISBN

0070066523, 2001.

6. W. Kaydos, Operational Performance Measurement, Increas-

ing Total Productivity, CRC Press LLC, Boca Raton, FL, 1998.

7. E. E. Lewis, Introduction to Reliability Engineering, 2nd

edition, John Wiley & Sons, New York, 1996.

8. J. M. Moubray, Reliability-Centered Maintenance, 2nd edi-

tion, Industrial Press, New York, 1997.

9. J. D. Oleson, Pathways to Agility, Mass Customization in

Action, John Wiley & Sons, New York, 1998.

10. D. A. Shafer, Successful Assembly Automation, A Develop-

ment and Implementation Guide, Society of Manufacturing

Engineers, Detroit, MI, 1999.

11. W. Soroka, Fundamentals of Packaging Technology, 3rd edi-

tion, Institute of Packaging Professionals (IoPP), Naperville,

IL, 2002.

12. T. Wireman, Developing Performance Indicators for Mana-

ging Maintenance, Industrial Press, New York, 1998.

13. O. Kwon, New methodology for Measuring equipment perfor-

mance and managerial effect in TPM. PhD. Thesis, Depart-

ment of Industrial Systems and Information Engineering,

Graduate School, Korea University.

PACKAGING OF FOOD

GORDON L. ROBERTSON

Food



Packaging



Environment,

Brisbane, Australia

INTRODUCTION

Role of Food Packaging

Food packaging is essential and pervasive: It is essential

because without packaging the safety and quality of food

would be compromised, and it is pervasive because almost

all food is packaged in some way. Food packaging performs

a number of disparate tasks (1). It protects the food from

contamination and spoilage; it makes it easier to transport

and store foods; and it provides uniform measuring of

contents. By allowing brands to be created and standar-

dized, it makes advertising meaningful and makes large-

scale distribution and mass merchandising possible. Food

packages with dispensing caps, sprays, reclosable open-

ings, and other features make products more usable and

convenient.

PACKAGING OF FOOD 891

Functions and Attributes of Food Packaging

Four primary and interconnected functions of packaging

have been identiﬁed: containment, protection, conveni-

ence, and communication (1).

Containment. This function of packaging is so obvious

as to be overlooked by many, but it is the most basic

function of packaging. Food products must be contained

before they can be moved from one place to another. The

containment function of packaging makes a huge contri-

bution to preventing losses from the myriad of foods that

are moved from one place to another on numerous occa-

sions each day.

Protection. This is often regarded as the primary func-

tion of the package: to protect its contents from outside

environmental effects, be they water, water vapor, gases,

odors, microorganisms, dust, shocks, vibrations, compres-

sive forces, and so on, and to protect the environment from

the product.

For the majority of food products, the protection af-

forded by the package is an essential part of the preserva-

tion process. For example, aseptically packaged milk in

paperboard laminate cartons only remains aseptic for as

long as the package provides protection; vacuum-pack-

aged meat will not achieve its desired shelf life if the

package permits oxygen to enter. In general, once the

integrity of the package is breached, the product is no

longer preserved.

Freedom from harmful microbial contaminants at the

time of consumption can also be inﬂuenced by the pack-

age. Firstly, if the packaging material does not provide a

suitable barrier around the food, microorganisms can

contaminate the food and make it unsafe. Microbial con-

tamination can also arise if the packaging material per-

mits the transfer of, for example, moisture or oxygen from

the atmosphere into the package. In this situation, micro-

organisms present in the food but presenting no risk

because of the initial absence of moisture or oxygen may

then be able to grow and present a risk to the consumer.

Packaging also protects or conserves much of the

energy expended during the production and processing

of the product. For example, to produce, transport, sell,

and store 1 kg of bread requires 15.8 MJ (megajoules) of

energy. This energy is required in the form of transport

fuel, heat, power, and refrigeration in farming and milling

the wheat, baking and retailing the bread, and distribut-

ing both the raw materials and the ﬁnished product. To

produce the polyethylene bag to package a 1 kg loaf of

bread requires 1.4 MJ of energy. This means that each unit

of energy in the packaging protects 11 units of energy in

the product. While eliminating the packaging might save

1.4 MJ of energy, it would also lead to spoilage of the bread

and a consequent waste of 15.8 MJ of energy (1).

Convenience. Modern industrialized societies have

brought about tremendous changes in lifestyles, and the

packaging industry has had to respond to those changes

that have created a demand for greater convenience in

household products: foods that are pre-prepared and can

be cooked or reheated in a very short time, preferably

without removing them from the package; condiments

that can be applied simply by pump-action packages;

dispensers for sauces or dressings which minimize mess;

reclosable openings on drink bottles to permit consump-

tion on the go, and so on. Thus packaging plays an

important role in allowing products to be used

conveniently.

Two other aspects of convenience are important in

package design. One of these can best be described as

the apportionment function of packaging. In this context,

the package functions by reducing the output from indus-

trial production to a manageable, desirable ‘‘consumer’’

size. An associated aspect is the shape (relative propor-

tions) of the primary package in relation to convenience in

use by consumers (e.g., easy to hold, open, and pour as

appropriate) and efﬁciency in building into secondary and

tertiary packages. Packaging plays a very important role

in permitting primary packages to be unitized into sec-

ondary packages (e.g., placed inside a corrugated case)

and then for these secondary packages to be unitized into

a tertiary package (e.g., a stretch-wrapped pallet). As a

consequence of this unitizing function, materials handling

is optimized since only a minimal number of discrete

packages or loads need to be handled.

Communication. There is an old saying that ‘‘a package

must protect what it sells and sell what it protects’’; that

is, the package functions as a ‘‘silent salesman.’’ The

modern methods of consumer marketing would fail were

it not for the messages communicated by the package

through distinctive branding and labeling, enabling

supermarkets to function on a self-service basis. Consu-

mers make purchasing decisions using the numerous

clues provided by the graphics and the distinctive shapes

of the packaging. Other communication functions of the

package include (a) a UPC (Universal Product Code) that

can be read accurately and rapidly using modern scanning

equipment at retail checkouts and (b) nutritional informa-

tion on the outside of food packages which has become

mandatory in many countries.

Attributes. There are also several attributes of packa-

ging that are important (2). One (related to the conve-

nience function) is that it should be efﬁcient from a

production or commercial viewpoint—that is, in ﬁlling,

closing, handling, transportation, and storage. Another is

that the package should have, throughout its life cycle

from raw material extraction to ﬁnal disposal after use,

minimal environmental impacts. A third attribute is that

the package should not impart to the food any undesirable

contaminants. Although this last attribute may seem self-

evident,

there has been

a long history of so-called food

contact substances migrating from the packaging material

into the food (3). For many years the solder used in three-

piece metal cans resulted in lead migrating into some

foods; the switch to welded side seams eliminated this

source of lead. Plasticizers have also migrated into foods—

for example, phthalates (4), as well as monomers [e.g.

styrene monomer (5)], catalysts [e.g., antimony from

PET bottles (6)], and photoinitiators from printing inks

892 PACKAGING OF FOOD

[e.g., ITX (7)]. Not surprisingly, food packaging materials

are highly regulated to ensure consumer safety.

DETERIORATIVE REACTIONS IN FOODS

Foods are frequently classiﬁed on the basis of their

stability as nonperishable, semiperishable, and perish-

able. An example of the ﬁrst classiﬁcation is sugar;

provided that it is kept dry, at ambient temperature and

free from contamination, it should have a very long shelf

life. However, few foods are truly nonperishable, and an

important factor inﬂuencing their perishability is the

packaging.

For example, hermetically sealed and heat processed

(e.g., canned) foods are generally regarded as nonperish-

able. However, they may become perishable under certain

circumstances—for example, if the can seams are faulty,

or if there is excessive corrosion resulting in internal gas

formation and eventual bursting of the can. Foods with

low moisture content, such as dried fruits and vegetables

and baked goods, are classiﬁed as semiperishable. Frozen

foods, though basically perishable, may be classiﬁed as

semiperishable, provided that they are properly stored at

freezer temperatures. The majority of foods (e.g., ﬂesh

foods (such as meat and ﬁsh), milk, eggs, and most fruits

and vegetables) are classiﬁed as perishable unless they

have been processed in some way. Often, the only form of

processing that such foods receive is to be packaged and

kept under controlled temperature conditions.

Deteriorative reactions occur in foods during proces-

sing and storage, and they combine to affect food quality.

These reactions can be biochemical (typically enzymic),

chemical, physical (typically as a result of moisture gain or

loss), and biological (both microbiological and macrobiolo-

gical due to insect pests and rodents). Knowledge of the

kinds of changes that inﬂuence food quality is an impor-

tant ﬁrst step in developing food packaging that will

minimize undesirable changes in quality and maximize

the development and maintenance of desirable properties.

Once the nature of the reactions is understood, knowledge

of the factors that control the rates of these reactions is

necessary in order to fully control the changes occurring in

foods during storage—that is, while packaged. The nature

of the deteriorative reactions in foods, along with the

factors that control the rates of these reactions, has been

reviewed in detail elsewhere (1).

The rates of deteriorative reactions of particular foods

are inﬂuenced by two factors: the nature of the foods and

their surroundings. These factors are referred to as in-

trinsic and extrinsic parameters. Intrinsic parameters are

an inherent part of the food and include water activity

), pH, redox (oxidation–reduction) potential (E

), oxy-

gen content, and product formulation including the pre-

sence of any preservatives or antioxidants. The a

of a

particular food can affect the rates of deteriorative reac-

tions in different ways; for example, the rate of none-

nzymic browning peaks at around 0.65 a

while the rate of

autoxidation of lipids decreases as a

rises from zero to 0.3

and then increases with further rises in a

. The destruc-

tion or inhibition of enzymes and microorganisms is

necessary for shelf-stable, high moisture content

B0.85–1.0) foods, and this can be achieved through

the selection of suitable packaging materials and the

manipulation of extrinsic factors.

Extrinsic factors that control the rates of deteriorative

reactions include temperature, relative humidity (RH),

gas atmosphere, and light; packaging can inﬂuence the

impact of these factors on the rates of deteriorative reac-

tions to varying degrees, depending on the speciﬁc packa-

ging material.

The RH of the ambient environment is important and

can inﬂuence the a

of the food unless the package

provides a moisture barrier. Many ﬂexible plastic packa-

ging materials provide good moisture barriers but none

are completely impermeable, thus limiting the shelf life of

low-a

foods. The presence and concentration of gases in

the environment have a considerable inﬂuence on the

growth of microorganisms, and modifying the atmosphere

inside the package is widely used. Increased concentra-

tions of gases such as CO

are used to retard microbial

growth and thus extend the shelf life of foods. Further-

more, vacuum packaging (i.e., removal of air (and thus

) from a package prior to sealing) can also have a

beneﬁcial effect by preventing the growth of aerobic micro-

organisms.

The deterioration of packaged foods depends largely on

transfers that may occur between the internal environ-

ment inside the package and the external environment

that is exposed to the hazards of storage and distribution.

For example, there may be transfer of water vapor from a

humid atmosphere into a dried product, or transfer of an

undesirable odor from the external atmosphere into a high

fat product, or development of oxidative rancidity if the

package is not an effective O

barrier. As well, ﬂavor

compounds can be absorbed by some types of plastic

packaging materials, a phenomenon referred to as scalp-

ing (8).

INDICES OF FAILURE

In designing suitable packaging for foods, it is important

to clearly deﬁne the indices of failure (IOF) of the food—

that is, the quality attributes that will indicate that the

food is no longer acceptable to the consumer. These might

be development of rancid ﬂavors in cereals due to oxida-

tion; loss of red color (bloom) in chilled beef due to

depletion of oxygen; reduction in carbonation in bottled

soda due to permeation of CO

through the bottle wall;

caking of instant coffee due to moisture ingress; develop-

ment of microbial taint in chilled poultry; moisture loss in

green vegetables, resulting in wilting; and loss of vacuum

in canned berry fruits due to hydrogen gas production

with consequent bulging of the can ends.

Once the IOFs for a particular food have been deﬁned,

the next step is to attempt to quantify the magnitude of

the particular degradation—for example, how much

moisture or O

can react with the food before it becomes

unacceptable. The ﬁnal step is to ascertain which (if any)

of the IOFs might be inﬂuenced by the packaging material

since packaging cannot prevent all deteriorative reactions

PACKAGING OF FOOD 893

in foods. If, for example, the IOF of a snack food was loss of

crispness, then the packaging material could inﬂuence

this, depending on the extent to which it permitted the

ingress of moisture. Different plastic ﬁlms, for example,

have different WVTRs; thus the shelf life obtained will

vary, depending on the particular plastic selected. Similar

considerations apply to foods where the IOF is oxidation.

However, it is not just the packaging material per se that

can inﬂuence shelf life; the method of ﬁlling the product

into the package is also important. For example, with

roasted and ground coffee, vacuum ﬁlling into metal cans

will remove 95% or more of the O

from the can compared

with inert gas ﬂush packing in plastic foil laminate

pouches which will remove or displace 80–90% of the O

in the package. The residual O

in the package at the time

of ﬁlling will have a major inﬂuence on shelf life regard-

less of the O

barrier properties of the package itself.

Data on the WVTR and OTR of various plastics are

widely available. However, such data are often determined

on ﬂat samples of ﬁlm rather than actual packages where

creasing and sealing can adversely affect barrier proper-

ties. The dimensions of the package for a given weight of

food can have a large inﬂuence on shelf life. While a

spherical shape will minimize the surface area of the

package (and thus the quantity of moisture or O

that

will permeate into the package), it is not a practical shape

for commercial use; in practice, most packages tend to be

rectangular or cylindrical. Extremely thin packages have

a much greater surface area:volume ratio and thus re-

quire a plastic with better barrier properties to get the

same shelf life than if the same product were packaged in

a thicker format. For the same product packaged in

different sized packages using the same plastic material,

the smallest package will have the shortest shelf life

because the package surface area:volume ratio increases

with decrease in package size.

PACKAGING OF MAJOR FOOD GROUPS

Space does not permit a detailed description of the IOFs

and typical packaging materials used for the wide variety

of foods available to consumers today; such detail can be

found elsewhere (1). Instead the major food groups and

their packaging will be brieﬂy considered.

Flesh Foods

Flesh foods such as meats, poultry, and seafood are subject

to rapid microbial spoilage due to their high pH and a

Oxidation of fat is also a problem, especially with pork and

poultry; another problem is oxidation of pigments in red

meats.

Beef. The importance of color as a marketing attribute

of red meat is well established, especially for self-service

retailing. Consumers, used to seeing bright red meat

prepared for sale, associate this color with good eating

quality, although there is little correlation between the

two. This association of the color of red meat (both in

the chilled and frozen form) with freshness has been the

dominant factor underlying retail meat marketing. The

loss of this bright red color, known as loss of ‘‘bloom’’ in the

industry, is affected by many factors, although the con-

sumer will usually relate the color loss to bacterial growth.

Because of the importance of meat color, various methods

of transportation, distribution, and packaging have

evolved which optimize the maintenance of a desirable

meat color.

The color of fresh meat depends chieﬂy on the relative

amounts of the three pigment derivatives of myoglobin

present at the surface: myoglobin (Mb), also referred to as

deoxymyoglobin; oxymyoglobin (O

Mb); and metmyoglo-

bin (MetMb). Mb is purple in color and predominates in

the absence of oxygen; O

Mb is bright red in color and

results when Mb is oxygenated or exposed to oxygen,

producing the familiar ‘‘bloom’’ of fresh meat. MetMb is

brown in color and exists when the oxygen concentration

is between 0.5% and 1%, or when meat is exposed to air for

extended periods of time. The color of meat as perceived by

the consumer is primarily determined by factors such as

the concentration and chemical form of the myoglobin, the

morphology of the muscle structure, and the ability of the

muscle to absorb or scatter incident light. To preserve red

meat, the objective is to retard spoilage, permit some

enzymic activity to improve tenderness, retard weight

loss, and ensure an O

Mb or bright red color at the

consumer level.

In distribution, most red meat is packaged under

vacuum in high O

and water vapor barrier ﬂexible

packaging materials to retard deterioration. Vacuum

packaging achieves its preservative effect by maintaining

the product in an O

-deﬁcient environment (nominally

less than 500 ppm). Any residual O

is rapidly consumed

by meat and muscle pigments, and CO

is produced as the

end product of tissue and microbial respiration. At the

retail level, highly oxygen-permeable ﬂexible packaging

permits restoration of the bright red O

Mb color while

retarding the passage of water vapor.

Vacuum packaging has the inherent disadvantage that

both package and meat are subjected to mechanical strain.

Mechanical pressure on the meat may increase drip loss;

and if bone is present and not adequately covered with a

suitable material, the pack may be ruptured. As an

alternative to vacuum packaging, attempts have been

made to store meat under various gaseous atmospheres,

a process referred to as modiﬁed atmosphere packaging or

MAP. The strain on the packaging material can be alle-

viated by introducing another gas or mixture of gases after

evacuation and before sealing. The intention has generally

been to preserve the fresh meat color (O

Mb) and prevent

anaerobic spoilage by using high concentrations of O

(50–

100%) along with 15–50% CO

to restrict the growth of

Pseudomonas and related bacteria; EVOH is commonly

used as the barrier layer in coextruded ﬁlms.

Poultry. Raw poultry meat is a perishable commodity of

relatively high pH (5.6 for breast muscle and up to 6.4 for

leg muscle) which readily supports the growth of micro-

organisms when stored under chill or ambient conditions.

The shelf life of such meat depends on the combined

effects of certain intrinsic and extrinsic factors, including

894 PACKAGING OF FOOD

the numbers and types of psychrotrophic spoilage organ-

isms present initially, the storage temperature, muscle pH

and type (red or white), as well as the kind of packaging

material used and the gaseous environment of the

product.

The vacuum packaging of poultry carcasses, cuts, and

other manufactured products can extend shelf life, pro-

vided that the product is held under chill conditions.

Vacuum packaging of poultry meat leads to the develop-

ment of mainly lactic acid bacteria, sometimes accompa-

nied by cold-tolerant coliforms. Although vacuum

packaging may be used to encourage the development of

an atmosphere around the product which delays microbial

spoilage, other systems in use involve addition of at least

20% CO

, to either individually packaged items or bulk

packs of varying size in an O

-impermeable plastic ﬁlm.

Seafood. Flesh foods such as ﬁsh and shellﬁsh are

highly perishable due to their high a

, relatively high

pH, and the presence of autolytic enzymes which cause the

rapid development of undesirable odors and ﬂavors.

The effects of MAP on seafood are similar to those

described above for meat and poultry. Vacuum and MAP

(including ﬂushing with N

and CO

), which suppress the

normal spoilage bacteria that cause off-odors and ﬂavors,

extend the shelf life of seafood.

Most studies of MAP of seafood indicate a shelf-life

extension from a few days up to a week or more compared

with air storage, depending on species and temperature.

Differences in spoilage microﬂora and pH are mainly

responsible for the observed differences in shelf life,

provided that similar gas:product ratios are used.

Although some claims have been made of a shelf life of

up to 3–4 weeks for the refrigerated storage of MAP ﬁsh,

this is generally considered to be unrealistic. Target shelf

lives of these products are typically in the range of 10–14

days, but may reach 18–20 days if the temperature is

controlled very closely just above freezing point.

High-temperature abuse (21–271C) for periods of 12–

24 h is a major concern since MAP ﬁsh generally do not

become overtly spoiled under these conditions yet may be

toxic, whereas ﬁsh held at the same temperatures under

similar aerobic conditions start to become putrid before

toxin production occurs. If MAP ﬁsh are held at tempera-

tures greater than 101C, strong spoilage signals may not

develop in advance of C. botulinum toxin production.

The use of active packaging technologies such as O

scavengers and CO

emitters does not improve microbial

safety above that obtained by traditional MAP, and it gives

little or no additional shelf life to fresh seafood products

compared to MAP and vacuum packaging (9).

Horticultural Products

Fruits and vegetables are perishable products with active

metabolism during the postharvest period. Their shelf life

can be extended by, in simple terms, retarding the phy-

siological, pathological, and physical deteriorative pro-

cesses (generally referred to as postharvest handling).

Fruits may be divided into climacteric and nonclimacteric

types. Climacteric fruits are those in which ripening is

associated with a distinct increase in respiration and

ethylene production, with low temperatures greatly redu-

cing the magnitude of the climacteric. Typical climacteric

fruits include apples, pears, peaches, nectarines, bananas,

mangoes, plums, tomatoes, and avocados. Ethylene is a

natural plant hormone and plays a central role in the

initiation of ripening; it is physiologically active in trace

amounts (less than 0.1 ppm).

Aerobic respiration involves the oxidation of starch,

sugars, and organic acids to simpler molecules (CO

and

O) with the concurrent production of energy (ATP and

heat). If hexose sugar is used as the substrate, the overall

equation can be written as follows:

þ 6O

! 6CO

þ 6H

O þenergy

This equation suggests that if the CO

in the atmosphere

were increased (or the O

decreased), the respiration rate

would decrease and the storage life would be extended.

Such is the case, and the application of this approach is

the basis of MAP. The availability of absorbers of O

,CO

, and water provide additional tools for the packaging

technologist to use to maintain a desired atmosphere

within a package. Fresh fruits and vegetables vary greatly

in their relative tolerance to low O

concentrations and

elevated CO

concentrations. Reduction of the O

concen-

tration to less than 10% provides a tool for controlling the

respiration rate and slowing down senescence, although

an adequate O

concentration must be available to main-

tain aerobic respiration.

Minimally processed fruits and vegetables (MPFVs) are

products that have the attributes of convenience and

fresh-like quality, with their forms varying widely depend-

ing on the nature of the unprocessed commodity and how

it is normally consumed. They are sometimes referred to

as ‘‘fresh-cut’’ produce. Polymeric ﬁlms are the most

common materials used for the packaging of horticultural

products including MPFVs; such ﬁlms require a high

permeability to gases to avoid the development of injur-

ious atmospheres inside the package. This can typically

be achieved by microperforation of the ﬁlm to give holes

with diameters ranging from 40 to 200 mm. In addition to

enabling the creation of MA conditions, polymeric

ﬁlms provide other beneﬁts including maintenance of high

RH and reduction of water loss. In packages where it is not

intended to create a MA, the main concern is to avoid

anoxic conditions and condensation of water vapor inside

the package. This is most easily achieved either by

incomplete sealing or by perforation of the plastic

packaging.

Dairy Products

Dairy products are derived from milk, which is usually not

sterile. Pasteurization is a low-heat process to destroy

disease microorganisms but not all microorganisms that

could cause spoilage. Pasteurized dairy products must be

maintained under refrigeration.

Milk is processed into a variety of products, all having

different and varying packaging requirements. The sim-

plest product is pasteurized milk where, after a mild heat

PACKAGING OF FOOD 895

treatment, the milk is ﬁlled into a variety of packaging

media and distributed. Nonreturnable packages such as

blow-molded HDPE bottles or LDPE-coated paperboard

gabletop packages are most often used for packaging and

distributing milk under refrigeration; the shelf life of such

a product varies from 2 to 10 days. UHT milk is subjected

to a more complex process and is aseptically packaged; the

packaging is sophisticated (typically a paperboard lami-

nate foil carton) and its shelf life can be up to 8 months at

ambient temperatures. Cream is typically processed and

packaged in a way similar to that of ﬂuid milk and has a

similar shelf life. Fermented dairy products, although

being subjected to more complex processing operations,

are also typically packaged in a manner analogous to that

of ﬂuid milk.

The other dairy products (butter, cheese, and powders)

are quite different in nature when compared to ﬂuid milk,

and their packaging requirements are therefore also quite

different. Butter is very susceptible to light-induced ﬂa-

vors, which results in off-ﬂavors. Since butter is generally

exposed to ﬂuorescent light during storage in retail dis-

play cabinets, the packaging material has a marked effect

on the amount of light transmitted and the related

intensity of the oxidized ﬂavor. Butter packaged in various

types of conventional parchment papers develops objec-

tionable levels of oxidized off-ﬂavor after a few hours

exposure in a supermarket display cabinet, while alumi-

num foil laminates are satisfactory even after 48 days of

continuous exposure.

Cheese is the generic name for a group of fermented

milk-based food products produced in at least 500 vari-

eties throughout the world. With the exception of some

soft cheeses, most cheese varieties are not ready for

consumption at the end of manufacture but undergo a

period of ripening (also referred to as curing or matura-

tion) which varies from about 4 weeks to more than 2

years. The duration of ripening is generally inversely

related to the moisture content of the cheese, although

many varieties may be consumed at any of several stages

of maturity depending on the ﬂavor preferences of con-

sumers (1).

The two key parameters contributing to the stability of

cheeses are pH and a

. However, neither of these para-

meters is low enough to ensure complete stabilization of

the product, with the result that cheeses as a class

lie between perishable foods on the one side and inter-

mediate moisture foods on the other. While the packaging

will have no inﬂuence on the pH of the cheese, the a

the surface (and ultimately the interior) of the cheese will

be affected by the water vapor permeability of the packa-

ging material. Two other key factors that must be con-

sidered in the packaging of cheese are the effect of light

and O

. Light initiates the oxidation of fats, even at

temperatures found in refrigerated display cabinets, giv-

ing rise to off-ﬂavors. In addition, the ingress of molecular

through the packaging ﬁlm is undesirable because it

will contribute to the oxidation of fats and the growth of

undesirable microorganisms. Thus packaging ﬁlms for

cheese must be sufﬁciently impermeable to O

to prevent

fat oxidation and mold growth. The introduction of pure

into the package often produces the appearance of

vacuum packaging after a certain period of storage as a

result of absorption of CO

by the cheese as well as some

loss by diffusion through the packaging material.

Cereals, Bakery Products, Snack Foods, and Candy

Cereals. Cereals are the fruits of cultivated grasses,

with the principal cereal crops being wheat, barley, oats,

rye, rice, maize, sorghum, and the millets. The presence of

water and air renders grains susceptible to biochemical

deterioration; grains are also subject to infestation from

insects and rodents. It is essential that grain be dried to a

moisture content corresponding to 0.70 a

or less prior to

packaging and storage. Consumer packages for grain

commonly consist of heat-sealed pouches made from

LDPE ﬁlm; these provide a satisfactory moisture barrier

and result in the required shelf lives for the grains.

Breakfast cereals contain most of the whole grain in

cooked or toasted form plus ﬂavorings, vitamins, and

minerals. There are ﬁve modes of deterioration to be

considered when selecting suitable packaging materials

for breakfast cereals. They are moisture gain resulting in

loss of crispness; lipid oxidation resulting in rancidity and

off-ﬂavors; loss of vitamins; breakage resulting in an

aesthetically undesirable product; and loss of aroma

from ﬂavored products. The shelf life of breakfast cereals

depends to a large extent on the content and quality of the

oil contained in them. Breakfast cereals are packaged in

glassine, waxed glassine, or, mostly, polyoleﬁn coextru-

sions in the form of pouches or bags within paperboard

cartons. Sugared cereals are often packaged in aluminum-

foil laminations to retard water vapor transmission.

Bakery Products. A wide variety of bakery products can

be found on supermarket shelves, including breads, un-

sweetened rolls and buns, doughnuts, sweet and savory

pies, pizza, quiche, cakes, pastries, biscuits, crackers, and

cookies. It is useful to classify bakery products on the basis

of their a

and pH since these parameters are a good

indication of the spoilage problems likely to be encoun-

tered. Microbial growth—in particular, mold growth—is

the major factor limiting the shelf life of bakery products;

chemical preservatives are used by the bakery industry to

prevent or retard microbiological spoilage. Staling is the

common description of the decreasing consumer accep-

tance of bakery products as they age, caused by changes in

crumb other than those resulting from the action of

spoilage organisms; it is the major mode of deterioration.

The objective in packaging bread is to maintain the

bread in a fresh condition by preventing too rapid drying

out without providing too good a moisture barrier, which

would promote mold growth on a soggy crust. Vacuum

packaging is not a suitable technology to extend the mold-

free shelf life of most soft bakery products since the

product is crushed under a vacuum. However, it has

been used to prevent mold problems in ﬂat breads and

pizza crusts. An alternative to vacuum packaging is to

modify the atmosphere inside the package. A range of gas

mixtures has been used to extend the shelf life of bakery

products, from 100% CO

to 50% CO

and 50% N

896 PACKAGING OF FOOD

Extensions of 3 weeks to 3 months at room temperature

are achievable using appropriate mixtures of CO

and N

Hard baked goods such as cookies and crackers gen-

erally have moisture contents within the range 1–5%, a

values of about 0.1, and often a high fat content. Loss of

crispness and development of rancidity are the two major

IOFs. The typical material used for the packaging of

cookies and crackers is OPP, either as plain or pearlized

OPP ﬁlm. If a superior O

barrier is required, acrylic-

coated OPP is used, and sometimes one side is coated with

PVC/PVdC copolymer rather than acrylic. Soft cookies are

packaged in low WVTR laminations containing aluminum

foil or metallized plastic ﬁlm.

Snack Foods. Snacks foods comprise a very wide range

of products including potato and corn chips, pretzels,

popcorn, extruder puffed and baked/fried products, and

rice-based snacks. Fried snack foods can consist of many

different ingredients; but common to them all is fat, which

is used as a processing agent to dehydrate the product or

puff it and develop characteristic ﬂavors. There are two

major IOFs of fried snack foods: development of fat

rancidity and loss of crispness. Thus a satisfactory pack-

age for fried snack foods would need to provide a good

barrier to O

, light and moisture.

Fried snacks foods are typically packaged in multilayer

structures, although spiral-wound, paperboard cans lined

with aluminum foil or a barrier polymer and sealed under

vacuum with an LDPE/foil end are used for some specialty

products that also require mechanical protection. The

major mode of deterioration for extruded and puffed

snacks is loss of crispness; for example, the critical a

for puffed corn curl is 0.36. Many extruded and puffed

snack foods are packaged in material identical to that for

fried snack foods. However, since the major mode of

deterioration is loss of crispness, a package that provides

a good barrier to water vapor is the primary requirement.

Candy. The three basic types of candies are chocolate

and hard and soft sugar. Chocolate is a suspension of

ﬁnely ground roasted cocoa beans or cocoa mass and sugar

particles in cocoa butter (the lipid fraction of the cocoa

mass). Chocolates may be either solid, solid with inclu-

sions such as nuts, or molded with centers. The chocolate

acts as a water vapor barrier that helps protect the

inclusions and ﬁllings such as nuts, crisped rice, or liquid

cherry, which are susceptible to water gain or loss. Oxida-

tive and lipolytic rancidity are ﬂavor defects, with the

former coming from oxidation of unsaturated fats and the

latter coming from enzymic hydrolysis of short-and med-

ium-chain triglycerides. Cocoa butter contains tocopher-

ols, which act as antioxidants and therefore confer a

natural protection against oxidation during storage. Being

high in fat, chocolate is very likely to absorb any foreign

odors from the surrounding atmosphere. Thus suitable

packaging materials must provide a good barrier to light,

, water vapor, and foreign odors. The most common

material used to package blocks of chocolate is a laminate

consisting of aluminum foil and LDPE, making it possible

to heat seal the package; chocolate products are also

packaged in pearlized OPP.

Hard candies consist almost entirely of sugar with

added ﬂavors and are heated under vacuum to reduce

the moisture content to about 1%. They are extremely

hygroscopic, hard, and fragile. Soft candies include jellies,

marshmallows, and other crystallized products; they con-

tain a matrix of water that can be lost as a consequence of

evaporation, and so these products must be protected

against water loss. An important difference in the mode

of deterioration between the various candies is that crys-

tallized products tend to dry out under normal storage

conditions, while uncrystallized products tend to pick up

moisture from the atmosphere. Sugar candies are sealed

in packaging with a low WVTR such as cast polypropy-

lene; individual twist wraps are also common for many

candies.

Beverages

Beverages may be still or carbonated, alcoholic or non-

alcoholic. The major categories are water, juices, carbo-

nated soft drinks, and beer.

Water. The major deteriorative reaction in bottled

water is microbial growth. To avoid this, the water is

usually treated prior to bottling with chlorine or ozone.

Glass bottles were long considered the container of choice

for sparkling waters and carbonated soft drinks; but in

recent years, PET bottles have gained an increasing share

of this sector. The majority of still waters are now pack-

aged in plastic containers, with ﬁve principal resin alter-

natives: PET, PVC, PP, HDPE, and PC.

Juices. The quality of a juice depends essentially on the

species and maturity of the fresh fruit, the main factors

inﬂuencing the quality being the sugar:acid ratio, the

aroma volatiles, the phenolic components, and the ascor-

bic acid content. The four key deteriorative reactions in

juices are microbiological spoilage, nonenzymic browning,

oxidation resulting in loss or degradation of ﬂavor compo-

nents and nutrients (essentially ascorbic acid), and ab-

sorption of ﬂavor compounds by the package. The rate of

browning and nutrient degradation is largely a function of

storage temperature.

For many years, juices were packed in metal cans using

the hot-ﬁll/hold/cool process to ensure that the juice was

commercially sterile. The use of glass bottles is also wide-

spread, with glass being the preferred packaging medium

for high-quality juices. However, over recent years an

increasing proportion of juices has been packaged asepti-

cally, generally into laminates of plastic ﬁlm/aluminum

foil/paperboard. These products are then held at ambient

temperatures and the shelf life and nutrient composition

are greatly inﬂuenced by the barrier properties of the

carton, the interactions of the juice with the carton, and

the storage environment. The end of shelf life is related to

the extent of nonenzymic browning and the sorption of key

aroma and ﬂavor compounds by the plastic in contact with

the juice, with the latter process being referred to as

‘‘scalping.’’

Flexible packaging is also used for juices; a variety of

laminate constructions are available, the most common

PACKAGING OF FOOD 897