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

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of in-mold labeled PET and PP bottles are made by

injection-stretch blow molding.

The greatest percentage of labels for EB-IML is still

produced by integrated converters on large gravure

presses, but polyoleﬁn ﬁlm is now the preferred substrate

over 60-lb, coated two-side (C2S) paper litho stock. Film

in-mold labels (FIML) are now used in the majority of

EB-IML applications, and this trend is expected to con-

tinue for the foreseeable future.

Both paper and ﬁlm labels for EB-IML require a heat-

activated sealant layer on the backside. This sealant layer

can be an ethylene–vinyl acetate heat seal coating applied

on-press by the converter or a coextruded layer produced

during the ﬁlm manufacturing process by an independent

substrate supplier. Regardless of the production method,

the proper choice of adhesive is critical to the successful

functioning of the label during the blow molding opera-

tion. Label defects such as blisters can result if the

adhesive does not activate completely during blow mold-

ing. Once the labels are printed, they are die cut into

stacks of individual labels by any one of several different

methods including ﬂat bed, rotary, or ‘‘high-die.’’

Gravure printed in-mold labels can have up to 10 colors

and offer the highest quality graphics. Advances in print

quality now make it feasible to successfully print in-mold

labels by other methods such as sheet-fed offset, web

offset, and a variety of narrow-web combination presses.

These narrow-web presses can combine ﬂexo, uv-ﬂexo,

rotary letterpress, and hot-foil stamping to create the

type of highly unusual effects desired for labeling of

personal care products. Narrow-web or sheet-offset prin-

ters use paper or ﬁlm label stock that has been precoated

with the heat-activated adhesive by another converter or

an independent substrate supplier. Labels printed on

narrow-web equipment can be rotary die cut inline or

ofﬂine; those printed by sheet-fed offset presses are gen-

erally high-die cut.

The most successful ﬁlm in-mold labels for EB-IML are

polyoleﬁn-based materials supplied in both white opaque

and clear versions. Many of these are coextrusions of

modiﬁed HDPE that incorporates a sealable layer and

thus do not require application of a liquid adhesive

during the converting process. Film in-mold labels offer

many advantages over paper IML. These include im-

proved moisture and product resistance, fewer label

defects, easier recycling, and the ability to create a

‘‘no label’’ look. A ﬁlm in-mold labeled container also has

little or no label panel bulge typical of a paper IML

application. However, ﬁlm labels still cost at least 50%

more than paper labels and are more difﬁcult to print

and handle because of static and other problems unique

to thin, unsupported plastic substrates. Other disadvan-

tages of the EB-IML process are higher tooling and setup

costs, cycle time penalty for label placement and bottle

cool-down, and the need to remove paper labels for

recycling.

Film in-mold labels have captured a large share of

the market and are now used extensively on laundry-

product, household-cleaner, premium orange-juice, and

motor-oil containers. They have replaced pressure-

sensitive and heat-transfer labels in a number of health

and beauty aid applications where the ‘‘no label’’ look is

desired.

INJECTION IN-MOLD LABELING

Injection in-mold labeling (IM-IML) of open top contain-

ers, which has long predominated over EB-IML of bottles

in Europe and Asia, is now showing signiﬁcant growth in

North America. The largest market for these containers is

for dairy products such as butter, margarine, ice cream,

and yogurt. Buckets for paint and cups for soft drinks are

also rapidly growing markets. Injection molded in-mold

labeled containers can be almost any shape and size from

the smallest rectangular tub holding 100 g to large 10-L

buckets.

Injection molding of plastic containers differs signiﬁ-

cantly from blow molding in several ways. Instead of a hot,

taffy-like parison inﬂated by high pressure air into the

conﬁnes of a hollow blow mold, the plastic used in injection

molding is a viscose liquid injected under high tempera-

ture and pressure through ports or ‘‘gates’’ into the closed

mold. The open space in the closed injection mold will

become the container as deﬁned by the male and female

halves of the closed mold. The liquid plastic completely

ﬁlls this space, forming the shape of the container. Once

the plastic has solidiﬁed, the mold opens and the container

is ejected.

Another difference is the labels used for IM-IML. Un-

like EB-IML labels, IM-IML labels do not require a heat

activated adhesive on the back side. These labels are

thinner and are made of the same material as the con-

tainer. The liquid plastic, injected at high temperature

and pressure, fuses to the back of the label without the

need for an adhesive. The most common container and

label material is polypropylene. Injection molds are man-

ufactured to very tight tolerances and so must the labels

used for IM-IML. Die cutting precision required for IM-

IML is about three times that of EB-IML.

As in EB-IML, the IM-IML process requires magazines

to hold the labels, robotics to pick the labels from the

magazine, and molds designed to accommodate the labels.

The most common method of holding the label in the mold

before the mold closes is electrostatic attraction. The label

is given an electrostatic charge after it is picked up from

the magazine by the robot.

If the label is for a rectangular container, an assisting

device pushes it into the mold cavity. The charge on the

label causes it to transfer to the inner surface of the mold.

The mold closes and the molten plastic is injected into the

mold, either through the male half (inside gating) or from

the female side through a hole in the bottom of the label

(outside gating). The plastic completely ﬁlls the space

between

the back of

the label clinging to the mold cavity

wall and the male half of the mold. A single label in the

shape of a Maltese cross can cover the bottom and all four

sides of a rectangular container in one operation. The

‘‘wings’’ of the label are carefully die cut to meet on the

corners of the container (Figure 2).

Cylindrical containers are in-mold labeled in much the

same way except that the charged label wraps around the

358 DECORATING: IN-MOLD LABELING

core before the core is inserted into the mold cavity. Once

inside the mold cavity, the static charge causes the label to

transfer from the core to the inside surface of the mold.

The injected molten plastic ﬁlls the space between the

back of the label and the core.

THERMOFORM IN-MOLD LABELING

Labels similar in appearance to those used in IM-IML are

given an electrostatic charge and inserted into the open

mold cavity. These labels can be ﬁlm or paper and have a

heat-activated adhesive on the back side very much like

those used in EB-IML. Once the labels are positioned in

the mold cavity, plastic ﬁlm or sheet is positioned over the

open mold and heated to the point where it just begins to

lose its structural integrity. A ram that matches the

interior of the container forces the hot plastic ﬁlm down

into the mold cavity. The heat from the plastic ﬁlm and the

pressure from the ram activates the adhesive on the back

of the label. The ﬁnished, labeled container is then ejected

from the mold. T-IML containers can be polypropylene,

polystyrene, or other suitable plastics.

Thermoforming machine manufacturers are working to

improve both the quality of T-IML containers and the

efﬁciency of the process to better compete against IM-IML.

IML has evolved from the simple blow-molded and

injection-molded containers produced in the early days

of the process into the sophisticated, even elegant pro-

ducts found in retail markets around the world. Further

reﬁnements in materials and processes can be expected to

provide better containers at lower costs in the years

ahead.

BIBLIOGRAPHY

General Reference

R. B. Schultz, The ABC’s of IML: A Basic Course, seminar guide

presented by RBS Technologies, Inc., March 2007.

DIAGNOSTIC SENSORS IN PACKAGING AND

IN SHELF-LIFE STUDIES

J. J .F. VAN VEEN and

W. D.

VAN DONGEN

TNO Quality of Life, Advanced

Food Analysis Group, Zeist,

The Netherlands

INTRODUCTION

Active and intelligent packaging may provide several

beneﬁts to the quality and safety of packed food. The

active systems focus on the extension of the shelf life by

keeping its quality for a longer period.

The intelligent systems monitor the quality of the food

product or the storage conditions of the packed food. In the

EU, ‘‘intelligent’’ packaging is deﬁned as ‘‘packaging that

monitors the internal and/or external conditions of a

product through its life cycle.’’ However, a more suitable

name would be diagnostic systems because their main

function is to monitor the quality or the storage conditions

of the food. A real intelligent system would be a package

that takes an appropriate action after a deviation from the

desired situation is measured. The value of a measured

parameter will in that case act as a trigger for an active

packaging system.

Degradation of food products may cause off-ﬂavors or

loss of nutritional value resulting in inferior product

quality and consumer rejection. The mechanism of degra-

dation and the reaction products highly depend on the type

of product. Degradation of nutrients, ﬂavour, and additives

is mainly determined by light, pH, oxygen (oxidation),

moisture, and other product matrix components.

Optimization of the composition and packaging of

food products with respect to shelf life and sensory

quality can be done with classical techniques such as high-

performance liquid chromatography (LC) and gas chro-

matography (GC) and microbial testing.

However, noninvasive sensors provide an attractive

alternative, because no sampling is required and the

same package can be monitored in time under various

conditions. This is in contrast to classical techniques

where each measurement requires its own sample. In

addition, if monitoring of each food package is required,

these cheap noninvasive sensors are the only possible

solution.

Apart from degradation, monitoring of contaminants

such as pathogens or pesticides, in terms of quality control

of food products, is also a useful application of noninvasive

sensors in this ﬁeld (1).

A useful classiﬁcation of noninvasive sensors in packa-

ging that can be used for diagnostic purposes and for shelf-

life studies is:

. Time–temperature indicators (TTIs), monitoring the

conditions during storage and transportation of the

food products

. Leak indicators in modiﬁed atmospheric packaging

(MAPs) monitoring the integrity of the food package

Figure 2. ‘‘Wings’’ of a container label.

DIAGNOSTIC SENSORS IN PACKAGING AND IN SHELF-LIFE STUDIES 359

. Freshness or spoilage indicators monitoring the ac-

tual condition of the packed food product.

. Microbiological growth indicators monitoring the in-

crease of the microbiological cell number or cfu.

All of these indicators, except for TTIs, are positioned

inside the package and consequently they have to be

considered as food contact materials (FCM).

In the United States, Japan, and Australia, smart

packaging is already being successfully applied to extend

the shelf-life food quality and safety. In Europe, the

application of smart packaging systems is limited. The

main reason for this is that until 2004, the legislative

position of such food contact materials was uncertain.

One could raise the question, Who is waiting for these

diagnostic sensors? Are they consumer-oriented or are

they a desire of the retail or is it purely B2B (business-

to-business)? Or is it purely meant for R&D purposes? The

latter is certainly true as can be seen in the examples

given in the following paragraphs. In our vision it is also

clear that at this moment, B2B applications, like quality

control in the food chain, will be the main application.

Because these diagnostic sensors in food packaging

are at the moment not meant for checking the quality of

the food product by the consumer, a visual detection of the

sensor response is not strictly required. Therefore, the

readout of the sensor could also be realized in an instru-

mental way, detecting features that cannot be observed by

the human eye. This could be an optical scanner detecting

optical changes in the sensor, such as ﬂuorescence or

absorption changes in the infrared region or the change

in certain electrical properties.

Enabling technologies for discovery of markers and for

(future) developments of diagnostic sensors in food packa-

ging are advanced, comprehensive analysis for the dis-

covery of food degradation markers, the integration with

RFIDs (electronic version of noninvasive sensors), and the

implementation of nanotechnology in new, innovative

sensor concepts.

TIME–TEMPERATURE INDICATORS (TTIs)

These indicators or sensors are meant for those food

products that easily deteriorates at higher temperature.

The basic idea behind it is that they monitor the history of

the temperatures at which the food product has been

exposed. In fact they display an irreversible change,

typically a color change, caused by both the time and the

temperature.

In that way they should safeguard whether or not the

food product has been exposed to high temperatures

somewhere in the food chain, typically the cold chain.

The ‘‘run-out’’ time of the sensor has to be correlated to the

shelf life of each food product or groups of food products

because the parameter time–temperature is only an in-

direct measure of the quality of the food product.

A major advantage of TTIs is that they can be attached

to the outside of the package and as a consequence no food

approvals are required here because they are not food

contact materials.

Principles used for this type of sensors are enzymatic

reactions, polymerization reactions, and even microbiolo-

gical responses. These irreversible reactions are, in gen-

eral, coupled to a colorimetric change that accumulates in

time and that can be detected visually (Figure 1). A

number of companies are active in this ﬁeld, such as

Vitsab, Lifelines, Timestrip, and Cryolog.

Because these sensors behave in an accumulative way,

the reagents have to be stored in separate chambers and

the reaction has to be started or in other words the TTI

has to be activated. This is typically done by means of a

mechanical action.

Nowadays the introduction of RFID has raised the

question, Can these electronic devices be used for mon-

itoring the temperature history as well? Indeed, this is

possible with so-called active RFIDs (RFID with internal

power supply in the label) that are coupled to a tempera-

ture sensor. In contrast to the visual TTIs, they can tell us

not only if the food product has been exposed to a high

temperature, but also when this has happened because

these devices log the temperature in time (at the moment

with only a limited time resolution). A major drawback of

these electronic devices, in particular active RFIDs, is that

their cost price is still far too high to be applied in single

food packaging.

LEAK INDICATORS

Nowadays, many packaging concepts are based on mod-

iﬁed atmosphere packaging (MAP) that apply modiﬁed

concentrations of oxygen, nitrogen, or carbon dioxide.

Usually, low oxygen (O

) or high carbon dioxide (CO

)

atmospheres are used to increase the shelf life of the food

product of oxygen-sensitive products such as beer, meat,

or pre-baked products. This clearly leads to a need for O

or CO

indicators that can be applied as noninvasive

sensors inside the package.

These sensors could also be used for indicating micro-

bial growth in the case of nonpermeable packaging

0.00

0.20

0.40

0.60

0.80

1.00

0 5 10 15 20

Absorption

°C

colour

threshold

temperature

Figure 1. Schematic graph of the principle of operation of a TTI;

color change from green (safe) to yellow (unsafe).

360 DIAGNOSTIC SENSORS IN PACKAGING AND IN SHELF-LIFE STUDIES

material (e.g., glass). However, in ﬂexible packaging the

consumption or production of these metabolic gases will

always be in competition with the ingress or losses

through these materials.

Therefore the main application of O

or CO

indicators

in packaging will be as leakage indicators to safeguard the

integrity of the package (seal defects, pinholes) or to verify

the efﬁciency of oxygen or carbon dioxide scavangers. The

main application at the moment would be in B2B applica-

tions, in quality control at ﬁlling lines, and in R&D

applications.

In the latter they could be used for gas permeation

measurements, testing of packaging materials, or testing

of packaging concepts (for instance, beer in plastic bot-

tles). This could also be used in shelf-life studies or in

studies measuring the rates of fat oxidation or of oxygen

consumption by microorganisms.

TNO developed a noninvasive optical technique (2) that

is based on the quenching of ﬂuorescence of a dye

embedded in a gas-permeable hydrophobic polymer by

oxygen (Figure 2). This quenching also results in a change

in the ﬂuorescence lifetime of the dye. This effect can be

recorded by an optical reader, also taking care of the

illumination by means of a blue light-emitting diode.

The oxygen concentrations can be measured in

liquids (e.g., dissolved oxygen) or in gas. Today this

technique is being marketed as the Oxysenset techni-

que, enabling the detection of oxygen concentrations

from ambient (21%) down to 0.01 mg/L in liquids or

0.02% by volume in gas. The sensor is independent of

pH (2–12), is almost free of interference by other matrix

components and the measurements itself does not con-

sume oxygen.

Other noninvasive oxygen sensors, including those

based on color or ﬂuorescent intensity changes, have

been described in literature. Commercially available sys-

tems for oxygen detection are currently provided by GSR/

NCSR, Ocean Optics, PreSense, and Oxysense.

Noninvasive CO

indicators for food packaging, based

on similar optical principles, are being developed at

this moment in various research institutes. These are

mainly sensors that make use of the permeation of carbon

dioxide into a polymer with impregnated pH-sensitive

dyes. These indicators can be color-based for visual detec-

tion or ﬂuorescence based for instrumental detection

(Figure 3).

DISCOVERY OF FOOD DEGRADATION MARKERS

For the development of smart packaging, which is able to

monitor compounds correlating with freshness, quality, or

safety, it is essential to have speciﬁc markers. A lack of

speciﬁcity means that, for example, color changes indicat-

ing contamination can occur in products free from any

signiﬁcant deterioration. Therefore exact correlations ap-

pear necessary between target metabolites (indicators),

product type, and (organoleptic) quality and safety. To ﬁnd

the appropriate marker, advanced analytical approaches

in combination with food packaging research techniques

allow obtaining insight in the key processes of food

degradation. The combination of analytical techniques

and food packaging research techniques such as gas

permeability and optical oxygen measurements allow the

selection of appropriate markers to avoid food degradation

processes like lipid oxidation and growth of aerobic

microorganisms.

To study more complex research issues such as off-

ﬂavor research, optimization and control of products, and

aging or alteration of food during storage such as oxida-

tion in complex food stuffs, more advanced analytical

methods can be applied. The idea is to perform a compara-

tive nonbiased determination of nearly all components in

a broad range of polarity and molecular weight in a

sample. This is in contrast to target analytical techniques

as mentioned above, which aims at measuring a limited

With Oxygen

Fluorescence decay

without Oxygen

Time

fluorescence

Light pulse

Figure 2. Sample with oxydot and

reader pen (left), ﬂuorescence decay

curve (right).

2000

4000

6000

8000

400 450 500 550 600 650

Int

0% CO

0.05% CO

0.1% CO

0.2% CO

0.5% CO

1% CO

3% CO

Figure 3. Spectra of the ﬂuorescent intensity (green light) of a

noninvasive carbon dioxide sensor excited by a blue polymer LED.

DIAGNOSTIC SENSORS IN PACKAGING AND IN SHELF-LIFE STUDIES 361

number of known parameters and/or compounds. Such

comprehensive techniques are based on GC or LC coupled

to mass spectrometry (MS). Next, data preprocessing tools

and multivariate data analysis (MVA) are applied to ﬁnd

the relevant correlations between the analytical data with

certain properties of interest (e.g., food degradation).

FRESHNESS OR SPOILAGE INDICATORS

Freshness indicators would be more ideal as, for instance,

TTIs or leak indicators, because they also take into

account the starting quality of the product as well as all

‘‘supply chain’’ mistakes. Real freshness indicators will

indicate the actual freshness of the product instead of

indirect measures of the freshness.

The freshness of a food product may express itself in

certain metabolic products, gaseous or dissolved in the

product. A freshness indicator that indicates if the product

is not suitable for consumption anymore is referred to as a

spoilage indicators. However, it is preferred if in an earlier

stage an indication of the decrease of freshness is ob-

tained. In that case we speak about a freshness indicator.

Nearly all of the freshness or spoilage indicators are still

in a development stage at universities, research institutes,

or innovative companies. In general, it can be stated that

gaseous metabolic products are less complicated to detect

than dissolved metabolic products.

Issues that also play an important role here are micro-

biological quality and sensory quality.

XAMPLES OF SPECIFIC PARAMETERS THAT CAN BE USED FOR

FRESHNESS OR SPOILAGE INDICATORS

Speciﬁc Parameter/Marker

Volatile amines

Ethanol, ethylene

Acetaldehyde

Hexanal, butyric acid

ATP

Toxins

Food Product

Fish

Poultry

Vegatables, fruit

Yogurt, fruit

Salads (oils, fats)

Meat, ﬁsh

Meat (salads)

An important safety issue—in particular, in the case of

(raw) meat products—is the monitoring of toxins or the

pathogenic microorganisms such as Salmonella or Cam-

pylobacter that produce these toxins. Some attempts have

been made to accomplish this, like the immunochemical

detection principle for toxins by Toxin Alert.

The key challenge for toxin indicators is that patho-

genic microorganisms generally exist in or on a food

product at very low concentrations which can already be

dangerous for humans. In addition, they are not homo-

geneously distributed throughout the whole food. Conse-

quently, an indicator or sensor for toxins has to be

extremely sensitive and needs to have a contact area

with the food as large as possible. For all of these reasons,

it is not likely that toxin indicators will become available

in the near future.

Other, more realistic examples are, for instance, indi-

cators for H

S, volatile amines, ethanol, ethylene, or

volatile carbonic acids.

A useful freshness indicator for poultry has been

developed by VTT in Finland based on the color change

of myoglobin from brown to green in the presence of the

marker H

Ethylene is a useful indicator for the ripeness of most

fruits. Colorimetric indicators for this parameter are under

development by several institutes (e.g., RipeSenset).

Another good example is the freshness indicator of

fresh-packed ﬁsh products (Figure 4). This indicator can

be speciﬁcally based on the amount of trimethyl amine

(TMA) formed by the bacterial reduction of trimethyl

amine N-oxide (TMAO) or, less speciﬁcally, on the total

volatile base concentration (sum of basic reduced nitrogen

gases, including ammonia). These indicators have to be

validated for speciﬁc type of ﬁsh products (e.g., fatty or

nonfatty ﬁshes) and they have to be sensitive enough to

predict the shelf life on a reliable basis. The latter implies

that they have to be able to monitor TMA or TVB (total

volatile base) on a ppm level. TNO has developed such a

sensor based on a visual detectable color change from

green to blue of a few ppm of either ammonia or trimethyl

amine.

Another indicator from TNO being in the same cate-

gory as the volatile base indicator is the one based on the

sum of volatile carbonic acids, as a measure of rancidity

for fatty products such as salads, that change color from

purple to blue.

A special kind of freshness indicator is a so-called

microbial growth indicator, because this will display the

freshness of the product by means of the number of

microorganisms present in the food product in stead of

speciﬁc (chemical) parameters formed in the product or in

the headspace of the packaging. Such an indicator has to

be nonspeciﬁc with respect to the type of microorganism,

and it could be useful for monitoring the overall freshness

of meat products.

Such a nonspeciﬁc sensor is under development at TNO

(3). This development started for sterile products in

closed, aseptic containers (for instance, in case of tissue

engineering or clinical food) where the indicator only tells

whether or not the product is (still) sterile (see Figure 5).

In most food applications, however, sterility is not an issue

and the indicator has to display the growth instead of the

presence of microorganisms.

This particular indicator or sensor is based on the

assumption that microorganisms will produce certain

extracellular enzymes, such as proteases and amylases,

which can be detected by means of a color change or by

means of a chance in ﬂuorescent properties of the indica-

tor. Because the applied principle is cumulative, the

indicator will not only be able to detect low levels of initial

growth, but will also hold its value after the logarithmic

growth phase of the microorganisms.

In the graph in Figure 6, it can be seen that the sensor,

more or less independent of type of microorganism,

will only depend on its growth rate and on its cap-

ability to produce external enzymes like, in this case,

proteases.

362 DIAGNOSTIC SENSORS IN PACKAGING AND IN SHELF-LIFE STUDIES

LEGISLATION

The EU is the only region in the world which has legisla-

tion speciﬁc for smart packaging substances. However,

delays in drawing up the legislation have hampered the

introduction of smart packaging (especially for releasing

systems) in Western Europe food markets. A European

Commission funded project [FAIR-project CT-98-4170 (4)]

known by the acronym ACTIPAK came up with recom-

mendations that were taken up in the drafting of amend-

ments to the EU Framework Directive for food contact

materials 89/109/EEC (5). This resulted in the adoption of

a new framework Regulation (1935/2004) (6) in which

provisions are made to allow the use of smart packaging

systems. The new Regulation applies to smart packaging,

containing deliberately added substances, provided that

the packaging can be shown to enhance the safety, quality,

or shelf life of the packaged foods or provides information

on the conditions of the packaged food. A major provision

is that the composition of food may be changed by the use

of active packaging, provided that the ﬁnal food complies

with relevant rules on food and food additives. However,

such changes should never result into the masking of

spoilage or misleading the consumer. The Regulation

(1935/2004 is valid in all EU Member States without a

need for implementation in national laws) announces

additional rules laid down in a speciﬁc measure. At the

moment a speciﬁc regulation [EMB/973 Rev. 6B (7)] for

smart packaging is being drafted and discussed with the

Member States. The ﬁnal regulation most likely will not

differ signiﬁcantly from the document now available.

However, the extent of the authorization procedure is still

open for discussion. It is clear that any authorization will

only be related to the substance(s) that cause the smart

function. Inert parts of a smart packaging (i.e., a sachet,

box, foil) will remain the responsibility of the manufac-

turer. The inert part should comply with the rules for food

contact materials valid at EU or national level [e.g.,

Directive 2002/72/EC (8)].

In addition, some of the systems are subject to regula-

tions on food additives, labeling, environment/waste, food

hygiene, and general safety. The EU system requires the

opinion of the European Food Safety Authority (EFSA)

before it can be inserted in any regulation. Therefore, the

smart components need to be evaluated by the EFSA for

its safety in food contact applications. EFSA guidelines

are under preparation but may be adapted to the ﬁnal

speciﬁc regulation for smart packaging. The following

issues will (most likely) be part of the guidelines:

. Toxicological evaluation of the smart components,

taking into account the potential level of migration

into the food.

. Demonstration of efﬁcacy of smart materials is under

discussion. Because this is not a safety issue, in many

cases, the need for a demonstration of efﬁcacy may be

reduced or completely withdrawn. In those cases it is

a up to the user to ensure that the smart packaging is

efﬁcious. However, the requirement in the Frame-

work regulation that the consumer should not be

misled may be a reason to check the efﬁcacy even in

the absence of a health risk

Storage time on ice (days)

Panel score

mg N /100 g

Freshness score mg N-TMA / 100 g

mg N-TVB / 100 g

Blank

25 ppm NH

Figure 4. Freshness indicator for freshness of ﬁsh products based on total volatile base detection.

Figure 5. Photograph of a noninvasive sensor for sterile pro-

ducts with optical readout.

DIAGNOSTIC SENSORS IN PACKAGING AND IN SHELF-LIFE STUDIES 363

. Migration data regarding the smart component. Con-

ventional migration methods may not be applicable,

and dedicated migration methods may be required to

demonstrate that migration of smart components

does not endanger human health.

. Advise to the Commission for insert of the smart

component in a list of authorized components.

Based on the outcome of that evaluation, the Commission

(DG SANCO) will grant a petitioner, authorization for the

submitted smart systems, which will be entered in the

Regulation. The general requirements for food contact

materials (1935/2004/EC (6)) also apply to smart packa-

ging systems and, consequently, they shall not endanger

human health. Labeling should comply with the food

additive Directive89/107/EEC (9).

TRENDS

Presently, diagnostic sensors are mainly applied in the

business-to-business (B2B) market in the form of TTI

indicators to monitor the storage conditions of tempera-

ture-sensitive products. However, TTI is only an indirect

measure of food quality and is not likely to replace the

‘‘best-before’’ dates.

The main drivers in packed food for the near future will

be food safety and quality of fresh products. This implies

that there will be a need for freshness, microbial growth,

and toxin indicators. In this respect, it will be essential

that the indicators provide a clear, unambiguous indica-

tion of product quality, safety, and shelf life. Probably all

new diagnostic sensors will ﬁrst be used in B2B applica-

tions with a some form of added value. It could be used as

a quality indicator or shelf-life indicator, removed before

presenting the products to the consumer, or invisible to

the consumer. If the retail can guarantee that no patho-

gens are present in meat, this will give added value to the

product. It would, for instance, allow the retailer to sell

higher-value raw meat products. Or by improved selection

and order picking directed by the shelf-life indicator,

replacing the principle of ‘‘ﬁrst-in ﬁrst-out’’ by picking on

remaining shelf life, the shelf life could be increased. An

additional shelf-life day is absolutely a very interesting

business driver for fresh products.

Nanotechnology will be more and more applied in the

development of new freshness and toxin indicators, en-

abling more sophisticated and more selective sensor

principles.

Also the combination with electronic devices, such as

RFID and polymeric electronics, will expand the possibi-

lities of diagnostic and intelligent packaging in future. A

major demand for these devices will be the breakdown of

cost price.

Currently, the market for diagnostic packaging is small

compared to the more mature market of active packaging.

However, we believe that the overall trend for diagnostic

packaging will be a growth scenario.

BIBLIOGRAPHY

1. S. Gunasekaran., ed., Nondestructive Food Evaluation, Marcel

Dekker Inc, NewYork–Basel, 2001.

2. A. Draaijer, Optical Sensor for Measuring Oxygen, WO 01/

63264, August 30, 2001.

3. J. J. F. van Veen; Method for the Non-invasive Detection of

Micro-organisms in Closed Containers, WO 04/024945.

4. FAIR-Project PL 98-4170. ‘‘Actipak’’: Evaluating Safety, Effec-

tiveness, Economic–Environmental Impact and Consumer

Acceptance of Active and Intelligent Packaging, Duration

1998–2001. Final report: 2003.

5. Council Directive 89/109/EEC of 21 December 1988 on the

approximation of the laws of the Member States relating to

materials and articles intended to come into contact with

foodstuffs, Ofﬁcial Journal, L040, 11/02/1989, 0038–0044.

6. Regulation (EC) No. 1935/2004 of the European Parliament

and the Council of 27 October 2004 on materials and articles

intended to come into contact with food and repealing Direc-

tives 80/590/EEC and 89/129/EEC, Ofﬁcial Journal of the

European Union L338, 13-11-2004, 4–17.

7. Working Document on a Draft Regulation on active and

intelligent materials and articles intended to come into contact

with foodstuffs. Version updated to 16 June 2006; EMB/973

Rev. 6B.

−50

150

250

350

450

550

0246810

Accumulative protease activity at rt (a.u.)

E.Coli

L.B.Plantarum

A.Niger

Figure 6. Proof-of-principle with a ﬂuorescent indicator (left) for different microorganisms. Quantiﬁcation of a color indicator (right) for

various protease.

364 DIAGNOSTIC SENSORS IN PACKAGING AND IN SHELF-LIFE STUDIES

8. Corrigendum to Commission Directive 2002/72/EC of 6 August

2002 relating to plastic materials and articles intended to come

into contact with foodstuffs (Ofﬁcial Journal L220, 15/8/2002,

0018–0058), Ofﬁcial Journal L0392, 13/02/2003, 01–42.

9. Council Directive of 21 December 1988 on the approximation of

the laws of the Member States concerning food additives

authorised for use in foodstuffs intended for human consump-

tion (89/107/EEC), Ofﬁcial Journal L040, 11/02/1989, 0027–

0033.

DISTRIBUTION HAZARD MEASUREMENT

DENNIS E. YOUNG, CPP

School of Packaging, Michigan

State University, East Lansing,

Michigan

To be successful in the marketplace, products must be

available to consumers. Most manufacturers produce pro-

ducts in one or several central locations, gaining the

efﬁciency of larger scale operations. Markets and consu-

mers, however, are far less concentrated and are located in

widely separated areas, even thousands of miles away

from the point of manufacture. This characteristic of most

producers and consumers generates the need for physical

distribution, which represents a key part of the supply

chain system of any manufacturer. As global markets open

and distribution channels grow in length and complexity,

logistics takes on increasing importance.

Physical distribution in its simplest form combines

three related logistic activities. Transportation moves

products from point to point using a plethora of modes

and equipment. Warehousing buffers the uncertainties of

production and demand and helps ensure availability to

satisfy demand. Handling connects the elements of the

system, which include production to warehouse, ware-

house to truck, truck to retail, and so on. Each element

includes hazards to the safe passage of products and

packages. In each case, the hazards are characteristic of

the operations performed within that distribution ele-

ment. All these activities also occur in an atmosphere

that may change the results of the activities. Temperature

and moisture, for example, can affect the characteristics of

packaging materials, which compromises their protective

ability.

Transportation requires vehicles, and vehicles produce

vibration as a consequence of their motion. The disconti-

nuities of transit media, such as road roughness, rail

irregularities, water waves and air currents, are among

the original sources of vibration. The vehicle reacts to

these irregularities, amplifying some types and reducing

other types. Vehicle suspension and structure play a role

in vibration modiﬁcation. The result is a complex mix of

vibration frequencies and intensities, which change in

response to immediate conditions. Figure 1 shows an

example of actual vehicle vibration, demonstrating the

change of vibration intensity over time. These transit

vibrations may produce fatigue, abrasions, crumbling,

separation, and other types of damage in products and

packages.

Warehouses gain efﬁciency by the careful use of space.

This usually involves stacking one product and package

on another to ﬁll the available storage cube of the building.

Unit loads of products may be stacked several items high

in ﬂoor loading warehouses. Even with storage that uses

Drop Height Distribution

All significant drops on all packages

6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36

Drop Height (in.)

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

Frequency

Cumulative %

Figure 1. Example drop height distribution data.

DISTRIBUTION HAZARD MEASUREMENT 365

racks to contain packages and unit loads, stacking often

occurs, albeit with lower heights. The loads imposed on

packages by the warehousing system can exist for weeks

or even months. These warehouse loads may produce

collapse, denting, buckling, bending, and other types of

damage in products and packages.

Handling operations include the manual movement

and placement of packaged products in sorting, transfer-

ring, and vehicle loading and unloading. Persons are often

assisted by mechanical tools in this handling, including

lift trucks, dollies, conveyors, and similar devices. Some

handling operations are fully automated and use robotics

or purpose-built devices to lift and place packages. Vehi-

cles are also handled, and vehicle impacts such as railcar

switching and truck docking may be hazardous. Inherent

in handling is the possibility of accidental or purposeful

drops, including severe mishandling. The shocks experi-

enced by the product and package when dropped in

handling may produce breakage, shatter, bending, mis-

alignment, chipping, and other types of damage in pro-

ducts and packages.

Along with packaging material performance and pro-

duct fragility, knowledge of the hazards of distribution is

critical to successful protective packaging development.

Data on package drops, vehicle vibration, compressive

loads, and atmospheric conditions are central to determin-

ing the target performance of packages. If the general

probability of occurrence of these hazards is known, then

intelligent decisions on level of protection are possible.

Small, battery-powered instruments capable of accu-

rate measurements and recording of transit hazards are

available from several manufacturers. Instruments that

can measure shock, drop, impact, and vibration usually

employ accelerometers, or acceleration transducers. Like-

wise, instruments for detecting compressive loads would

use some version of a load cell or weighing transducer.

Temperature and humidity measurement requires appro-

priate sensors. In all cases, power from batteries and

signal conditioning matched to the sensors are needed.

Data are converted from the continuous or analog form

into small, discrete steps by internal electronics. This

analog-to-digital conversion (ADC) allows the data to be

stored and understood by digital devices, including com-

puters. Once detected, hazard data are stored in compu-

ter-compatible memory within the instrument, which is

available for eventual transfer to a personal computer for

analysis.

The process of measuring the hazards of distribution

requires careful planning. The following steps are

recommended:

. Observation

. Measurement

. Analysis

. Speciﬁcation

. Validation

The ﬁrst step to a quantitative understanding of supply

change distribution hazards is qualitative. Obser-

vation of the distribution system details the elements of

distribution, such as handling, transit, and warehousing,

and it assists in understanding how these pieces ﬁt

together into a system. Attention should be paid to

possible sources of handling drops or impacts. A block

diagram of how a package travels from manufacture to

consumption is a useful tool to develop. With these ob-

servations, targets for the measurement step may be

selected. A certain handling operation, or a transportation

mode or route, or an entire trip or system, may be selected.

Independent variables, such as position in the vehicle or

weight of package may be targeted at this stage. Much

may be learned from observation alone. Although largely

qualitative, the information gained is valuable to establish

the order of events and the speciﬁc characteristics of

equipment (vehicles, conveyors, etc.) and process (unload-

ing, sorting, loading, etc.).

The measurement step concentrates on qualitative

data collection. The location of the measurement system

and transducers is critical at this point. Measurement

needs to be taken at a point where eventual tests will be

controlled. For example, if the goal is a vibration test, then

the test system will be taking the place of the vehicle bed,

as this is the point of input to packages transported in the

vehicle. The test system will be programmed to simulate

the motion of this vehicle. Accordingly, the measurement

system must monitor the vehicle bed. Measurements

taken of the response vibration, inside the packaging,

will be interesting for package performance characteriza-

tion but are not speciﬁcally useful for the development of

test speciﬁcations.

Drop height data are collected by an instrument inside

of the package that experiences the drop. Data on com-

pressive load would also be taken by inside-package

instruments. Shock and impact data-collection points

depend on how the eventual test will be controlled.

Temperature and humidity data may be taken at any

point but with due consideration of the mitigating effects

of the package.

All data types should be time stamped and date

stamped when collected if possible. This allows the user

to evaluate the location of each data event, which includes

the truck terminal, warehouse, road or rail section, ﬂight

number

, or loading

dock. Small parcel tracking and vehi-

cle global positioning system (GPS) information are tools

to help interprete the data collected.

The analysis step focuses on converting raw data to

information. Data from an electronic recorder are orga-

nized and stored by events as individual readings or

packets of time. Slowly changing data, such as tempera-

ture, atmospheric pressure, or relative humidity, may be

sampled by individual readings. Dynamic data, i.e., shock

and vibration, need to be captured in time packets so that

the rapidly changing nature of the original event may be

observed. Drop heights may be estimated by the instru-

ment software, and vibration data may be sorted for

frequency content.

Data analysis should begin with a careful consideration

of the goal of the measurement program. Temperature and

relative humidity data help to deﬁne the exposure to

extreme levels, the time of exposure, and how exposure

changes over time and with the distribution situation.

366 DISTRIBUTION HAZARD MEASUREMENT

These data can be used to develop laboratory tests or to

assess the degree of hazard to product or package.

If the goal is the development of a random vibration

test, then spectral analysis is the typical form. If data

taken by a recorder inside a package are to be used to set

up a drop test speciﬁcation, then data analysis should

include the number of drops, orientation of drops, and

drop-height distribution. A useful form of data analysis for

drop-height distribution is a drop-height histogram with

cumulative percentages. Figure 1 shows an example from

handling drop data collected in shipments by a parcel

delivery mode (1). Similar results have been obtained in

less-than-truckload (LTL) domestic shipments (2) and in

many other studies.

Figure 2 shows a summary analysis of truck vibration

in a truck distribution environment, in this example, a

large semitrailer on intercity roads in China (3). In all

these examples, the information should serve as illustra-

tions of analysis form and content, not as deﬁnitions of

these shipment conditions.

One key advantage of laboratory testing is the ability to

compress time in the evaluation of package performance.

A shipment that might take several days of elapsed time

can be simulated in the laboratory in a matter of hours.

The speciﬁc technique for time compression depends on

the test being performed.

Time compression for drops is clear. The time between

drops in actual shipment may range from minutes to days.

In the laboratory simulation, drops are conducted with

minimal waiting time, so the elapsed time is compressed.

The time compression for top-load compression tests to

simulate the effects of long term storage in a short test

time is being developed by some users.

Time compression for vibration is more complex. In

general, increased test amplitude intensity (G level) may

be traded for reduced time. There are undoubtedly prac-

tical limits to such compression. A shipment of 20 h transit

time probably cannot be effectively simulated in 10 min.

Random vibration test durations of one to X6 h may prove

successful in replicating ﬁeld damage. Shorter or longer

vibration test durations may be required to achieve de-

sired results. The default vibration time of 3 h used by

ASTM D4169 is suggested as an initial target Interna-

tional Safe Transit Association (ISTA) links test time and

transportation distance using a similar relationship. The

ISTA process relates test time to transportation distance.

For example, a palletized load would be tested in one axis

for time = miles traveled/5 , with a maximum time of

240 min (5). There are several approaches to vibration

time compression. Among these is the following general-

ized approach. Within limits, the trip time may be

compressed to laboratory time using the following rela-

tionship, which was adopted from test equivalence for-

mula (6):

¼ L



where

= level of lab test vibration (overall G

rms

)

= time duration of lab test

= level of ﬁeld measurement (overall G

rms

)

= time duration of ﬁeld measurement

a = exponent, typically 0.3–0.5

Test speciﬁcations should also include consideration of

the diversity of distribution environment hazard levels. For

example, a series of drop heights should be constructed to

Vertical: overall=0.20 G

Longitudinal: overall=0.08

Lateral: overall=0.07 G

China project

1.0000000

0.1000000

Power spectral density (PSD) (G

rms

/Hz)

0.0100000

0.0010000

0.0001000

0.0000100

0.0000010

0.0000001

0.1 1.0 10.0

Frequency (Hz)

100.0 1000.0

Data sort

rms

>=0.04

Timer partition

Data by

DYA Inc.

Figure 2. Example random vibration spectrum date.

DISTRIBUTION HAZARD MEASUREMENT 367