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principle of identifying the CCP (critical control point).

Documentation and veriﬁcation are integral to hazard

analysis and establishing CCP. Flowing from this basic

concept, HACCP is simply a methodical and systematic

application of the appropriate science and technology to

plan, control, and document the safe production of foods.

HACCP covers three types of potential food safety

hazards that could lead to a health risk—biological,

physical, and chemical—whether they are naturally oc-

curring in the food, contributed by the environment, or

generated by something in the manufacturing process.

Chemical hazards will be of primary interest to packagers,

although, of course, chemicals are used at numerous

points in the food production chain (see Table 1). While

these types of chemicals do not usually represent health

hazards when used properly, some of them are capable of

causing illness or even death when used improperly.

Another potential hazard of interest to packagers is a

physical hazard such as glass shards associated with the

use of glass bottles as packaging.

PRINCIPLES OF HACCP

NACMCF (8) recommends that the HACCP system should

be built upon a solid foundation of prerequisite programs

(e.g., Good Manufacturing Practices, Sanitation Standard

Operating Procedures, supplier approval program). In

preparation for developing an HACCP plan, NACMCF

recommends that ﬁve preliminary tasks be accomplished

to facilitate the application of HACCP principles to a

speciﬁc product and process. These preliminary tasks

are: (a) assemble the HACCP team, (b) describe the food

and its method of distribution, (c) identify the intended

use and consumers of the food, (d) develop a ﬂow diagram

that describes the process, and (e) verify the ﬂow diagram.

According to the NACMCF 1997 document (8), HACCP

is a systematic approach to food safety consisting of seven

priciples:

Principle 1: Conduct a Hazard Analysis

W ith information from the preliminary tasks, the HACCP

team conducts a hazard analysis to (a) determine signiﬁcant

food safety hazards associated with the product and (b)

identify appropriate control mesaures for those signiﬁcant

hazards. The hazard analysis consists of two stages: hazard

identiﬁcation and hazard evaluation. In the hazard identi-

ﬁcation stage, the HACCP team prepares a list of potential

biological, chemical, and physical hazards that may be

introduced, enhanced, or controlled at each of the steps in

the ﬂow diagram, including potential hazards associated

with ingredients and packaging materials. The HACCP

team then conducts a hazard evaluation, based on the

severity of the potential hazard and its likelihood of occur -

rence, to determine which of the potential hazards are

signiﬁcant and must be addressed in the HACCP plan. In

other words, the hazard anlysis identiﬁes the steps in the

process where hazards of potential signiﬁcance can occur

and thus warrants control in the HACCP plan. Table 2

enumerates examples of packaging questions that may be

considered during the hazard analysis.

For inclusion in the list of signiﬁcant hazards and thus

the HACCP plan, a hazard must be of such a nature that

its prevention, elimination, or reduction to an acceptable

level is essential to the production of a safe food (8, 14).

Potential hazards that are of a low severity and/or not

likely to occur (i.e., low risk potential hazards) would not

require further consideration when developing the

HACCP plan. Low-risk hazards, however, should not be

dismissed as insigniﬁcant to the operation and may need

to be addressed by other means, for example, by the total

quality management (TQM) team.

The HACCP team must then consider what control

measures, if any, exist that can be applied for control of

each signiﬁcant hazard. If a signiﬁcant hazard is identiﬁed

in the hazard analysis but no control measure exists in the

process, the HACCP team must modify the process and

product so that a control measure can be applied. Control

measures are physical, chemical, or other factors that can

be used to control an identiﬁed signiﬁcant health hazard.

More than one control measure may be required to control a

speciﬁc hazard. More than one hazard may be controlled by

a speciﬁed control measure. Potential chemical hazards

Table 1. Examples of Chemicals Used in Food Production

and Processing

Point of Use Types of Chemicals

Growing crops Pesticides, herbicides, defoliants

Raising livestock Growth hormones, antibiotics

Production Food additives, processing aids

Plant maintenance Lubricants, paints

Plant sanitation Cleaners, sanitizing agents, pesticides

Packaging Adhesives resins, surfactants,

defoaming agents, slimicides, polymers

Table 2. Examples of Packaging-Related Questions to Be Considered in a Hazard Analysis

Does the method of packaging affect the multiplication of microbial pathogens and/or the formation of toxins?

Is the package clearly labeled ‘‘Keep refrigerated for safety’’ if this is needed for safety?

Does the package include instructions for the safe handling and preparation of the food by the end user (e.g., validated cooking

instruction)?

Is the packaging material resistant to damage, thereby preventing the entrance of microbial contamination?

Are tamper-evident packaging features used?

Is each package and case legibly and accurately coded?

Does each package contain the proper label?

Could the packaging materials contribute any potential physical hazard (e.g., glass) to the product during processing?

Could the packaging materials contribute any chemical compound to the product that may make the product unsafe to consume?

568 HAZARD ANALYSIS AND CRITICAL CONTROL POINTS

applicable to packaging that the HACCP team may consider

during the analysis include the inks, indirect additives, and

prohibited substances in packaged ingredients and packa-

ging materials if the intended use is food packaging. The

points of control may be, for example, prior to receipt, and

the control measures may be compliance with speciﬁcations ,

letters of guarantee, vendor certiﬁcation, and/or approved

uses listed in the Code of Federal Regulations. In a food

plant producing canned salmon, a signiﬁcant biological

hazard is a pathogen such as Clostridium botulinum in

the salmon. Retorting (a point of control) using the appro-

priate scheduled process is a control measure that can be

used to eliminate the pathogen hazard. In the packaging

step (a point of control), proper double seaming will prevent

recontamination of the product with potential pathogens

from the processing plant environment, as well as during

distribution, storage, and retail and in the consumer’s

home. The control measure is forming a proper double

seam to prevent leakage and recontamination.

Principle 2: Determine the Critical Control Points (CCPs)

A critical control point is deﬁned as a step in the process at

which control can be applied and is essential to prevent or

eliminate a food safety hazard or reduce it to an accpetable

level. The HACCP team determines CCPs based on the

outcomes of the hazard analysis. An ideal CCP has the

following characteristics: (a) critical limits that are sup-

ported by scientiﬁc data from research and the technical

literature; (b) critical limits that are speciﬁc, quantiﬁable

or otherwise measurable, and provide the basis for a yes/

no decision on acceptability of product; (c) technology for

controlling the process at a CCP that is readily available

and at reasonable cost; (d) adequate monitoring (prefer-

ably continuous) and automatic adjustment of the opera-

tion to maintain control; and (e) historical point of control.

All signiﬁcant hazards identiﬁed by the HACCP team

during the hazard analysis must be addressed with at

least one CCP.

Examples of CCPs may include cooking, chilling, acid-

iﬁcation, packaging of processed foods, labeling, speciﬁc

sanitation procedures, product formulation control, pre-

vention of cross-contamination, and certain aspects of

employee and environmental hygiene.

Principle 3: Establish Critical Limits

A critical limit is deﬁned as maximum and/or minimum

value to which a biological, chemical, or physical parameter

must be controlled at a CCP to prevent, eliminate, or reduce

to an acceptable level the occurrence of a food safety hazard.

As HACCP evolves, a critical limit can also include the

presence of an attribute that is not necessarily a quantita-

tive value (e.g., products passing through a functioning

metal detector). Each CCP will have one or more control

measures that must be properly controlled to assure pre-

vention, elimination, or reduction of hazards to acceptable

levels. Each control measure has associated critical limits

that serve as boundaries of safety for each CCP. Critical

limits may be set such as temperature, time, physical

dimensions, sealing conditions , humidity, moisture level,

water activity (a

), pH, titratable acidity, salt concentration,

available chlorine, viscosity, presence or concentration of

preservatives, and sometimes attributes such as presence of

an intact screen of appropriate pore sizes and a functioning

metal detector with appropriate sensitivity (14). Critical

limits may be derived from sources such as regulatory

standards and guidelines, literature review, experimental

studies, and experts. The food industry is responsible for

engaging competent authorities to validate that the critical

limits will control the identiﬁed hazard.

Canning operations offer an example of a critical limit

for packaging. The Low Acid Canned Food Regulations

(Title 21, Code of Federal Regulations Part 113) require

that cans should be examined for presence of visual

defects, and cans should be periodically removed from

the line and torn down to verify that can seam measure-

ments are within speciﬁcations (15). If the HACCP team

determines that recontamination of product by pathogens

due to seam defect and leakage is a hazard reasonably

likely to occur after retoring, then a control measure must

be identiﬁed to address the hazard, for example, in the

form of proper seams on cans to protect consumers from

foodborne illness, and a CCP would be established at the

sealing machine. The monitoring activities are the visual

observation and the seam teardown and double-seam

measurements. The seam measurement would be com-

pared to the minimum acceptable dimensions (critical

limits) speciﬁed by the container supplier. Another exam-

ple of a critical limit is the time and temperature for the

retorting of canned salmon. At the retorting CCP, the

process must be designed to eliminate the heat-resistant

spore-forming pathogen, Clostridium botulinum, which is

reasonably expected to be present in the incoming raw

salmon. Technical development of the appropriate critical

limit(s) requires accurate information on the operation of

the retort, heating rate of the product, and heat resistance

of Clostridium botulinum.

A partial hazard analysis for canned salmon is shown

in Table 3, which also illustrates how the ﬁrst three

principles of HACCP may be documented by the team.

Principle 4: Establish Monitoring Procedures

In the monitoring process a planned sequence of observa-

tions or measurements is conducted to assess whether a

CCP is under control and to produce an accurate record for

future use in veriﬁcation. Monitoring serves three main

purposes:

1. Monitoring is essential to food safety management

in that it tracks the operation of the system. If

monitoring indicates that there is a trend toward

loss of control (i.e., exceeding a target level), then

action can be taken to bring the process back into

control before a deviation from a critical limit occurs.

2. Monitoring is used to determine when there is loss of

control and a deviation occurs at a CCP–that is,

exceeding or not meeting the critical limit. When a

deviation to a critical limit occurs, corrective action

must be taken.

3. Monitoring provides written documentation for use

in veriﬁcation of the HACCP plan.

HAZARD ANALYSIS AND CRITICAL CONTROL POINTS 569

Examples of monitoring activities include:

. Visual observations

. Temperature

. Time

. pH

. Moisture level

. Can teardown and seam dimensions

Principle 5: Establish Corrective Actions

The HACCP system for food safety management is de-

signed to identify health hazards and to establish strate-

gies to prevent, eliminate, or reduce their occurrence.

However, ideal circumstances do not always prevail, and

deviations from established processes may occur. Correc-

tive actions are designed to prevent products that may be

hazardous from leaving the process facility. When mon-

itoring indicates that there is a deviation from an estab-

lished critical limit, corrective actions must be taken. The

ﬁrst step is to bring the process and the CCP under control

by determining and correcting the cause of noncompli-

ance. Second, put all product on hold until determination

has been made on the safety of the product to facilitate

appropriate product disposition. A third component is to

prepare records that document the corrective actions

taken. Because of the diversity of possible deviations

in a food process, speciﬁc corrective action procedures

cannot always be developed for every incident. However,

a plan should be developed that addresses the process, the

product, and the recordkeeping components, with proce-

dures developed in advance for those deviation scenarios

that are likely to occur or are expected. The actions taken

must demonstrate that the CCP has been brought under

control. Individuals who have a thorough understanding

of the process, product, and HACCP plan are to be

assigned responsibility for taking corrective actions. The

corrective action plan should be documented in the

HACCP plan.

Principle 6: Establish Veriﬁcation Procedures

Veriﬁcation is deﬁned as those activities, other than mon-

itoring, that determine the validity of the HACCP plan and

that the HACCP system is operating according to the plan.

Monitoring is a distinct activity from veriﬁcation. For

example, veriﬁcation may be calibration of a thermometer

once per day while an example of monitoring is continuous

chart recording of the temperature of the scheduled pro-

cess. The NAS (4) pointed out that the major infusion of

science in a HACCP system centers on proper identiﬁca-

tion of the hazards, critical control points, critical limits,

and instituting proper veriﬁcation procedures. An example

of a veriﬁcation activity is the scientiﬁc or technical

process to ensure that critical limits at CCPs are adequate

and effective. This is sometimes referred to as validation

of the HACCP plan. Veriﬁcation activities should take

place during the development and implementation of the

HACCP plan (14). There are a few aspects involved in the

veriﬁcation process. An important aspect of veriﬁcation is

the initial validation to determine that the HACCP plan is

scientiﬁcally and technically sound and that the HACCP

plan, when properly implemented, will be effective in

controlling food safety hazards. The validation process

ensures that the HACCP plan in the facility is functioning

effectively. Another aspect of veriﬁcation is evaluating

whether the HACCP system is implemented according to

the HACCP plan. This aspect includes ongoing veriﬁcation

of CCPs that involves evaluating that day-to-day compli-

ance of the monitoring and other activities speciﬁed in the

HACCP plan at each CCP as well as a periodic HACCP

system compliance audit. A third aspect of veriﬁcation

consists of periodic validations or reassessments, indepen-

dent of audits or other veriﬁcation procedures, that must

be performed to ensure the accuracy and adequancy of the

Table 3. Partial Hazard Analysis, CCP and Critical Limits for Canned Salmon

Critical Control Point (CCP) Hazard(s) to Be Addressed

in HACCP Plan

Control Measures Critical Limits

Processing—processes

designed to provide

commercial sterility

C. botulinum Retorting Minimum 2501F for 3 min for product

Other critical factors as speciﬁed by

processing authority

Sealing of containers

C. botulinum due to

recontamination

Creating and maintaining

hermetic seal

No visible cutovers, seam sharpness,

false seams, deadheading, product

overlapping the ﬂange, product

leakage, or other visual defects

Cover hook: minimum 0.70 in., body

hook 0.072–0.088 in.; width: maximum

0.125 in.; thickness 0.052–0.058 in.;

tightness minimum 70%

Cooling of containers—applies

to water-cooled cans only

Pathogens due to

recontamination

Chlorination Measurable residual chlorine at

discharge

Note: The partial HACCP plan in this table is for illustrative purposes only and it is not intended to replace the processor’s hazard analysis and HACCP plan

development.

Source for crticial limits at this CCP: FDA’s Fish and Fishery Products Hazards and Controls Guidance, 3rd edition (June 2001), except that the tightness

value (i.e., the percent of the cover hook that is free of wrinkles) is based on an industry guideline.

Some processors may conclude in their hazard analysis that recontamination with C. botulinum due to can defects is a hazard likely to occur in the absence of

control, in light of at least two botulism outbreaks associated with recontaminated canned salmon. In this case, critical limits are established for the CCP at

the sealing step to control the hazard.

570 HAZARD ANALYSIS AND CRITICAL CONTROL POINTS

HACCP plan. A fourth aspect of veriﬁcation deals with the

government’s regulatory responsibility and actions to en-

sure that the HACCP system in the facility is functioning

satisfactorily. FSIS and FDA conduct risk-based inspec-

tions of facilities producing meat and poultry products and

seafood and juice products, respectively, which include

veriﬁcation of the HACCP plan.

Principle 7: Establish Record-Keeping and Documentation

Procedures

Record-keeping provides written conﬁrmation of the ha-

zard analysis, the HACCP plan, and the implementation

of the HACCP plan. HACCP records provide written data

for review, and records must be maintained for the

required period of time. Well-maintained records sub-

stantiate that the HACCP plan is being followed and

that requirements in the HACCP plan are being met

during production; HACCP records help document the

safety of the products being produced.

The approved HACCP plan and associated records

must be on ﬁle at the food establishment. Generally,

HACCP records include the following:

1. Summary of the hazard analysis.

2. The HACCP plan. NACMCF (8) recommends that

HACCP plan records include:

a. A list of the HACCP team and assigned

responsibilities.

b. A description of the product, its distribution,

intended use, and customer.

c. A veriﬁed ﬂow diagram for the manufacturing

process with CCPs indicated.

d. A HACCP plan summary table that contains

information tabulated in Table 4, including the

CCPs, the hazards to be addressed in the HACCP

plan at each CCP, critical limits, monitoring

procedures, corrective action plan, veriﬁcation

procedures, and record-keeping.

3. Supporting documentation.

4. Daily operational records.

HACCP AND PACKAGING

HACCP plan requirements in the manufacture of packa-

ging materials cannot be known until a hazard analysis

has been conducted. Methodical steps of the HACCP

process will prove most helpful in assessing the safety

versus the quality needs of the manufacturing plant. The

supplier may need records for its buyers that such an

assessment has been conducted even if no hazards have

been found during the hazard anlysis. Critical steps in

quality may come under different programs—for example,

ISO. Grocery Manufacturers Association and the National

Fisheries Institute favor interpreting HACCP as a pro-

gram that focuses only on food safety hazards. Thus, in the

case of milk carton manufacture, paperboard stock is

Table 4. HACCP Plan Master Sheet

Critical

Control Point

(CCP)

Hazard to be

Addressed in

HACCP Plan

Critical Limits

for Each

Control

Measure

Monitoring

Corrective

Action

Verification

Activities

Record-

Keeping

ProceduresWhat How Frequency Who

Source: Scott and Stevenson (14).

HAZARD ANALYSIS AND CRITICAL CONTROL POINTS 571

required by the Pasteurized Milk Ordinances (16) to have

no more than 50 bacterial colonies per 8 square inches. By

our interpretation, this would be a quality speciﬁcation

and not a HACCP CCP, if historical data show that these

are spoilage microorganisms rather than pathogens that

are likely to cause illness.

End use of the packaging materials may lead to an

exception to the above rule that HACCP is not needed in

package manufacture. Some examples follow:

. Active packaging is now a very viable area of re-

search, and much of that research has focused on

incorporating into the material types of antimicro-

bials that are efﬁcacious against microorganisms.

If such a compound/product is used in commercial

packaging and is itself an allergen to some popula-

tions, the labeling step may become a CCP, if the

HACCP team concludes in their hazard analysis that

the undeclared allergen is a hazard likely to occur.

In this case, the CCP is the label, the hazard is

the undeclared allergen, and the critical limit is

the proper notation on the label with visual monitor-

ing by the label operator or label scanner for the

correct label each time the labels are loaded. In some

cases, the HACCP team may conclude that the

hazard of an undeclared allergen is not reasonably

likely to occur due to a labeling prerequisite program

in place; in this case, no CCP would be needed.

. Gas combinations in modiﬁed atmosphere packaging

(MAP) may also prove critical in outgrowth of patho-

gens because oxygen concentrations below 2–3%

allow or enhance the growth of anaerobic organisms

such as Clostridium botulinum. Oxygen concentra-

tion would be a CCP in the MAP-packaging of mush-

rooms where growth of Clostridium botulinum is a

hazard reasonably likley to occur, for example. A

special case in fresh seafood packaging is vacuum

packaging. As noted in the Seafood Hazards Guide

(13), packaging material with an oxygen transmis-

sion rate (OTR) of 10,000 cc/m

/24 h has permeability

sufﬁcient to allow aerobic spoilage to occur before

toxin can be produced. Selection of proper gas com-

binations and OTRs are CCPs in the cases of certain

commodities, where growth of anaerobic pathogens

such as Clostridium botulinum is a hazard reason-

ably likely to occur in the absence of control.

SUMMARY

HACCP is a systematic approach to assuring the safety of

food products based on the concept of prevention. The

HACCP program is widely used in the food industry in the

United States as well as worldwide. Although the seven

HACCP principles are well-developed and application

guidelines have been developed and revised based on

experience gained during HACCP implementation in the

last several decades, there is no universal formula for

putting together the speciﬁc details of a HACCP plan. The

plan must be speciﬁc to each facility and be dynamic,

allowing for modiﬁcations to production, substitution of

new ingredients and new materials (including specialized

packaging materials and packaging steps), and develop-

ment of new products. The plan is participatory at all

levels of management, both in formulating and managing

the plan. The strength in an HACCP program is in

providing a risk management framework that a company

can use effectively to organize and manage the safety of

the products which are produced.

BIBLIOGRAPHY

1. D. A. Corlett, Jr., HACCP User’s Manual, Aspen Publishers,

Gaithersburg, MD, 1998.

2. DHEW, Proceedings of the 1971 National Conference on Food

Protection, U.S. Dept. Health, Education, and Welfare, Public

Health Service, Washington, DC, 1971.

3. Pillsbury Company, Food Safety through the Hazard Analysis

Critical Control Point System, Contract No. FDA 72-59, Re-

search and Development Department, The Pillsbury Company,

Minneapolis, MN, 1973.

4. National Academy of Sciences, An Evaluation of the Role of

Microbiological Criteria for Foods and Food Ingredients, Na-

tional Academy Press, Washington, DC, 1985.

5. M. D. Pierson and D. A. Corlett, Jr., eds., HACCP, Principles

and Applications, Van Nostrand Reinhold, New York, 1992.

6. NACMCF (National Advisory Committee on Microbiological

Criteria for Foods), HACCP Principles for Food Production,

USDA, FSIS, Washington, DC, 1989.

7. NACMCF, ‘‘Hazard Analysis and Critical Control Point Sys-

tem,’’ Int. J. Food Microbiol. 16, 1 (1992).

8. NACMCF, ‘‘Hazard Anlaysis and Critical Control Point Prin-

ciples and Application Guidelines,’’ J. Food Prot. 61, 762–775

(1998).

9. Codex, ‘‘Hazard Anlaysis and Critical Control Point (HACCP)

System and Guidelines for Its Application,’’ Annex to the

Recommended International Code of Practice General Princi-

ples of Food Hygiene, FAO/WHO Codex Alimentarius Commis-

sion, Rome, 2003.

10. U.S. Department of Agriculture/Food Safety and Inspection

Service (FSIS), ‘‘Hazard Analysis and Critical Control Point

(HACCP) Systems; Final Rule,’’ 9 CFR Part 417, Federal

11. U.S. Department of Health and Human Services/Food and

Drug Administration (FDA), ‘‘Procedures for the Safe and

Sanitary Processing and Importing of Fish and Fishery

Products; Final Rule,’’ 21 CFR Part 123, Federal Register

60, 65197 (December 18, 1995).

12. U.S. FDA, ‘‘Hazard Analysis and Critical Control Point

(HACCP); Procedures for the Safe and Sanitary Processing

and Importing of Juice; Final Rule,’’ 21 CFR Part 120, Federal

13. U.S. FDA/Center for Food Safety and Applied Nutrition,

Fish & Fisheries Products Hazards & Controls Guidance,

3rd edition (online), Chapter 13, http://www.cfsan.fda.gov/

~comm/haccp4.html, 2001.

14. V. N. Scott and K. E. Stevenson, eds. HACCP: A Systematic

Approach to Food Safety, A Comprehensive Manual, 4th

edition, Food Products Association, Washington, DC, 2006.

15. U.S. FDA, Thermally Processed Low-Acid Foods Packaged in

Hermetically Sealed Containers, Title 21, Code of Federal

Regulations, Part 113, U.S. Government Printing Ofﬁce,

Washington, DC, 1992.

572 HAZARD ANALYSIS AND CRITICAL CONTROL POINTS

16. U.S. FDA/Center for Food Safety and Applied Nutrition,

Grade ‘‘A’’ Pasteurized Milk Ordinance, 2001 Revision, Ap-

pendix J, Part C (online), http://www.cfsan.fda.gov/~ear/

pmo01j-k.html.

HIGH-VOLTAGE LEAK DETECTION (HVLD)

TECHNIQUE FOR HERMETICALLY SEALED

PACKAGES

YOON S. SONG

United States Food and Drug

Administration, Ofﬁce of Food

Safety (OFS), Process

Engineering Branch,

Summit-Argo, Illinois

INTRODUCTION

High-voltage leak detection (HVLD) is one of the emerging

technologies for inspecting package defects and tamper-

ing. HVLD operates by applying a high-voltage potential

to electrically conductive products inside non- or semicon-

ductive package materials. Pinholes are identiﬁed when

electrical discharges are detected between products and

device electrodes. The HVLD system with different fre-

quencies has been successfully validated and used for

years to test the integrity of glass ampoules and vials

in the pharmaceutical industry (1, 2) and recently was

introduced into the food industry within the United

States. It has been demonstrated that this detection

system is a powerful tool to detect pinholes in vacuum

pouches containing frankfurters. Therefore, the applic-

ability of this high-voltage technique to various containers

of different types and compositions is of great interest to

the industry.

PRINCIPLES

The HVLD system is composed of four unique elements:

high-voltage power generator, support electrode, inspec-

tion electrode, and a detector (Figure 1). The power

generator subjects the outside of a test package to a

certain predetermined high voltage (0.1–25 kV). In typical

HVLD systems, a package wall is nearly nonconductive

and thus can be regarded as the dielectricum of a con-

denser. When high voltage is applied to the support

electrode on which a test package is placed, it electriﬁes

product particles inside the package. While high voltages

are applied, the surface of a test package is scanned with

an inspection electrode as shown in Figure 2. In the

presence of a leak, electrons are discharged through the

hole. The detector can then measure current and/or

voltage discharges through the inspection electrode. A

data acquisition system in connection with an oscilloscope

is used to measure voltage or current proﬁles discharged

from a package. When voltage discharges are measured,

(kV) value, a high-voltage applied to the supporting

electrode when voltage discharge measured from the

inspection electrode exceeds the threshold value of 10 V,

Package

Products

Supporting

Electrode

Inspection

Electrode

High-Voltage

Power Supply

−

Data Acquisition

(Oscilloscope)

Discharge Current

Detector

Figure 1. Schematic diagram of HVLD system setup.

(a)

(b)

Figure 2. (a) The front and (b) top views of the Type-JH manual

HVLD unit (see text for explanation of operation).

HIGH-VOLTAGE LEAK DETECTION (HVLD) TECHNIQUE FOR HERMETICALLY SEALED PACKAGES 573

can be used as an indication of the detection. When

discharge current is monitored, the ability of the HVLD

to detect a leak is largely dependent on the gain setting.

With the gain control, a minimum current measured at a

constant high voltage applied can be adjusted and opti-

mized to within a measurable range to accommodate the

most important factors that could inﬂuence the detection

limit during a leak test.

FACTORS OF INFLUENCE

The ability of the HVLD system t o detect leaks can

be dependent upon various factors of product, package,

and defect. Jain and Song (3, 4) conducted a set of

experiments to evaluate the signiﬁcance of various pro-

cessing var iables on detection of pinholes in ﬂexible

pouches using a manual HVLD unit (Model DCC-1-AC,

Jovan Electronics Corp., Japan) (Figure 2). Sever al

critical variables, such as thi ckness (2.5, 4.5, 6.0 mil),

structure (plastic, paper and metallized laminates),

height (0.3, 0.7, 1.1 in . from a top of the support electrode

where a package is placed on), contact surface area (5, 11,

22, 33 in

), and dielectr ic constant (e) (1.63, 1.87, 2.01,

2.34) of pouches, volume (100, 200, 300 mL), electrical

condu ctivity (k) (0.7, 1.5, 8.5, 10.8 mS/cm), and type

(liquid, semisoli d (10% pectin), solid (0.85A

pecti n)) of

model products, an d location (0, 1.9, 3.7 in. from a

package center) and dia meter (10, 20, 30, 40, 50 mm) of

laser-drilled pinholes, were tested.

Effects of the critical variables on detection of 50-mm

pinholes in polypropylene (PP)/Nylon/PP laminated

pouches containing liquid model products are presented

in Figures 3 and 4 (3). In general, the greater the contact

surface area of packages and the higher the electrical

conductivity of products, the voltage required to detect

package defects is lower (po0.05). The statistical analysis

of data revealed that height and dielectric constant of

packages, product volume, and defect location were not

signiﬁcant factors affecting detection by the HVLD unit

within the ranges tested (pW0.05), but HVLD responses

were signiﬁcantly affected by thickness and surface area

of packages and by electrical conductivity of products

(po0.05). Results from a full factorial design experiment

with two levels and four factors (surface area, 5 and

33 in.

; ﬁlm thickness, 2.5 and 4.5 mil; product conductiv-

ity, 1.5 and 10.8 mS/cm; pinhole size, 10 and 50 mm)

indicated that, among the independent variables, surface

area had the most signiﬁcant effect followed by ﬁlm

thickness, pinhole size, and product conductivity

0.45

0.55

0.65

0.75

0.27 0.66 1.08

Package height (in.)

(kV)

0.45

0.55

0.65

0.75

100 200 300

Food volume (ml)

(kV)

0.0

0.5

1.0

1.5

2.0

2.5

5112233

Contact surface area (in

)

(kV)

1.5 mS/cm

10.8 mS/cm

0.45

0.55

0.65

0.75

0.0 1.9 3.7

Distance from a geometrical center (in.)

(kV)

1.5 mS/cm

10.8 mS/cm

1.5 mS/cm

10.8 mS/cm

1.5 mS/cm

10.8 mS/cm

(b)

(a)

(

)

(

)

Figure 3. Effects of (a) package height, (b) package contact surface area, (c) product volume, and (d) defect location on V

values for

PP/nylon/PP laminated pouches (e = 2.01) with 50-mm pinholes, containing 100, 200, and 300 mL of liquid model products (k = 1.5 and

10.8 mS/cm).

574 HIGH-VOLTAGE LEAK DETECTION (HVLD) TECHNIQUE FOR HERMETICALLY SEALED PACKAGES

(po0.01) (4). Strong interactions between those variables

were also observed (po0.01). In particular, two evident

interactions—between ﬁlm surface area and ﬁlm thick-

ness and between product conductivity and ﬁlm thick-

ness—contributed to the factorial model at a signiﬁcant

level. HVLD responses to both paper/PP laminated

pouches and metallized pouches for different processing

variables were comparable with those from plastic lami-

nated pouches containing liquid model products. Similar

results were also reported for semisolid and solid model

products.

Moll et al. (5) validated the HVLD technique for 100%

inspection of low-dens ity polyethyle ne (LDPE) ampoules

by using a fully auto mated online unit (Model 920-004,

Rommelag, G ermany). Factors such as detector geometry,

electrical conductivity of semisolid model products

(7.8–8.5 mS/cm), and wall thickness of ampoules (20–

30 mil) were found to be critical in detecting defective

ampoules with 5- to 200-mm pinholes. They also suggested

that the temperatur e an d relative humidity at the site

of t esting, along with the speed of conveyor belt carry-

ing ampoules, may have an inﬂuence on equipment

sensi tivity.

LIMIT OF DETECTION

It has been reported that for plastic pouches, the HVLD

can detect pinholes as small as 10 mm, even under worst-

scenario conditions, such as 4.5-mil ﬁlm thickness, contact

surface area of 5 in.

, and electrical conductivities of

0.7 and 1.5 mS/cm for semisolid and liquid products,

respectively (3). Limits of detections for liquid, semisolid,

and solid products were 10, 10, and 50 mm, respectively.

For metallized pouches, the HVLD can also detect

pinholes as small as 10 mm, even under worst-scenario

conditions, such as 6.0-mil ﬁlm thickness, contact surface

area of 5 in.

, A

of 0.85 for solid products, and electrical

conductivities of 0.7 and 1.5 mS/cm for semisolid and

liquid products, respectively. The limit of detection was

10 mm for liquid, semisolid, and solid products. The HVLD

technique can also reliably detect 5- to 10-mm pinholes in

LDPE ampoules containing a medium-viscosity hydrogel

with conductivity of 7.8 mS/cm (5).

CONCLUSIONS

The HVLD is an innovative testing system for fully auto-

matic detection of package leaks and tampering. It requires

that products inside a package be in direct contact with

packaging material’s surface where the inspection elec-

trode is applied. The site on the package at which leaks

and/or tampering have occurred can be instantly and

effectively identiﬁed when electrical discharges are de-

tected between a product and device electrodes. Due to

high voltages applied, however, a defective package may be

further damaged, as evidenced by post detection results

where 5- to 10-mm pinholes were widened to 50–60 mm(5).

The HVLD technique is capable of detecting pinholes less

than 10 mm in diameter. Package surface area, thickness

and geometry, headspace, product type, and electrical con-

ductivity are parameters requiring testing to determine the

necessary system conﬁguration. Parameters that do not

appear to be signiﬁcant barriers to the use of HVLD were

height and dielectric constant of package, produce volume,

and location of pinhole. It can be concluded that the HVLD

technique is a promising nondestructive and online method

to detect pinhole defects, which may be applicable to a wide

range of hermetically sealed packages.

BIBLIOGRAPHY

1. P. Rufﬁeux, Pharm. Ind. 47, 976 (1985).

2. H. Barnickel, Pharm. Ind. 48, 388 (1986).

3. B. Jain, and Y. Song, Evaluation of a Non-destructive High

Voltage Technique for the Detection of Pinholes in Flexible

Pouches for Foods, Poster at IFT Annual Meeting, Chicago,

IL, 2007.

4. B. Jain, and Y. Song, Validation of a Non-Destructive High

Voltage Technique for the Detection of Pinhole Defects in F ood

Pouches , Poster at IFT Annual Meeting, New Orleans , LA, 2008.

5. M. Moll, D. L. Doyle, M. Haerer, and D. M., Guazzo, J. Pharm.

Sci. Tech. 52, 215–227 (1998).

PET (ε = 1.87)

BOPA (ε = 1.63)

0.35

0.45

0.55

0.65

1.5 10.8

Electrical conductivity (mS/cm)

1.5 10.8

Electrical conductivity (mS/cm)

(kV)

0.35

0.45

0.55

0.65

(kV)

PET (ε = 1.87)

Nylon (ε = 2.01)

(b)(a)

Figure 4. Effects of dielectric constant (e) and electrical conductivity (k)onV

values for (a) 2.5- and (b) 4.5-mil-thick plastic pouches

(PET = PET/PE; BOPA = BOPA/PE; Nylon = PP/nylon/PP) with 50-mm pinholes, containing 100 mL of liquid model products.

HIGH-VOLTAGE LEAK DETECTION (HVLD) TECHNIQUE FOR HERMETICALLY SEALED PACKAGES 575

HOT-FILL TECHNOLOGY

RAYMOND A. BOURQUE

Ocean Spray Cranberries, Inc.,

Lakeville, Massachusetts

Food processors use a variety of processing, formulation,

and storage methods to assure that food products do not

spoil due to microbiological activity throughout their shelf

life. Products such as cereals, breads, and confectionaries

are formulated with sugars and/or salts to lower water

activity (a

). Water activity below B0.90 will not support

the growth of most food-spoilage bacteria (1). Chemical

preservatives, such as benzoate or sorbate, are added to

many products to inhibit microbiological growth. Many

dairy products, fruit juices, fruits, vegetables, meat, ﬁsh,

and prepared meals are distributed under refrigeration

or frozen conditions. Shelf-stable, low-acid foods—such as

vegetables, meat, and ﬁsh, with a pH Z 4.6—rely on a

thermal process. Thermal processing of low-acid foods is

achieved in a retort at pressures of 10–20 psi (7–14 kg/m

)

and temperatures of 240–2601F (116–1271C) (2,3). Food

products with a pHZ4.6 will support bacteria, yeast, and

mold growth. Commercial sterility is deﬁned as the elim-

ination of all microorganisms that can grow and metabo-

lize in a product. To achieve commercial sterility in foods

with a pHZ4.6, bacteria must be destroyed as well as

yeast and mold. The destruction of many bacteria requires

temperatures in excess of 2121F (1001C). To achieve

temperatures above the boiling point, overpressurization

in a retort process is necessary. The high temperature

achieved not only destroys micro-organisms in the food

but also sterilizes the package. Packages historically used

for retorted low-acid foods include metal cans, glass jars,

and to a lesser extent, retortable pouches.

High-acid foods with a pHo4.6 support the growth of

yeast and mold but, unlike low-acid foods, only a limited

number of bacteria. Yeast, mold, and the types of bacteria

that can metabolize in high-acid foods are more tempera-

ture-sensitive than those that grow in low-acid foods.

Temperatures in the range of 170–2001F (77–901C) are

usually adequate to destroy these microorganisms. Com-

mercial sterility of high-acid food products and the ster-

ilization of the containers in which they are packed is

achieved with temperatures of o2121F (1001C). There-

fore, retorting with overpressure is not required. High-

acid foods are thermally processed in one of three different

ways: hot ﬁlling, postﬁll pasteurization, or pasteurization

with aseptic ﬁlling. This article focuses on hot ﬁlling.

HOT-FILL PROCESSING

Foods such as fruit juices, fruit sauces, jams, jellies,

tomato sauces, ketchups, and barbeque sauces are often

hot-ﬁlled. The hot-ﬁll process consists of heating the food

product to an adequate temperature to destroy the yeast,

mold, and limited types of bacteria that can grow in the

food, and then holding the food at that temperature

for an adequate time to destroy these microorganisms.

The temperatures required range from 170 to 2121F (77–

1001C), and the hold times vary from 30 to 60 s depending

on the food product. The hot product is then ﬁlled directly

into the container or package. The headspace in the

package may then be nitrogen- or steam-ﬂushed to reduce

headspace oxygen. The package is then hermetically

sealed and inverted to sterilize the lid or closure. The

hot product sterilizes the package. To accomplish package

sterilization, the product must be at or above the mini-

mum temperatures [170–2001F (77–931C)] for an adequate

time (usually 1–3 min) (4). Thus, the control points for a

hot-ﬁll process are the minimum ﬁll temperature and the

minimum hold time (see Figure 1). Depending on the heat

sensitivity of the speciﬁc food, the products may or may

not be quickly cooled after the minimum hold time is

achieved. Cooling is usually accomplished in a water-

spray tunnel or immersion bath. Fruit juices and pre-

serves are examples of products that require cooling

directly after hot ﬁlling to protect product color, ﬂavor,

and nutrient content (vitamin C). Barbecue sauce is an

example of a product that is not heat-sensitive and can be

allowed to cool under ambient conditions after being

packed in corrugated shipping containers.

Historically, high-acid products have been packaged

primarily in metal cans and glass jars. However, in the

1980s and 1990s, several rigid and ﬂexible plastic

packages were developed for hot ﬁlling.

TINPLATE CANS

The traditional metal cans used for hot-ﬁlled foods are

made of tinplate. Some are enameled inside to protect the

food from the migration of iron or tin from the can into the

food, which may cause a loss of color or off-taste. Other

tinplate cans are not enameled inside; these are referred

to as plain tinplate cans. The lack of an inside enamel

allows the tin to migrate into the product. The color of

some canned products, such as white grapefruit juice, is

preserved by tin salts. Tinplate cans are also enameled to

protect

the can itself

from the corrosive effects of some

high-acid products. High-acid products, such as tomatoes

and cranberries, can corrode tinplate cans, which results

in perforations and leaking cans. The hot ﬁlling of tinplate

cans consists of hot-water washing the cans to remove

dust or other foreign contamination, hot ﬁlling the cans

with the high-acid food, ﬂushing the headspace with

steam or nitrogen, double-steaming a metal lid onto the

can, inverting the can to sterilize the lid, and conveying

the hot can for an adequate distance to provide the

necessary hold time prior to entering a water-spray cooler.

The cans are cooled to approximately 90–1101F (32–431C).

The maximum cooler exit temperature is speciﬁed accord-

ing to the product’s heat sensitivity. The minimum cooler

exit temperature is established to ensure that the cans are

not too cool to prevent the evaporation of remaining water

beads. If the can is not warm, then rust will occur, staining

the label and distracting from the general appearance of

the can. If the can is too cool, then labeling may be difﬁcult

as the hot melt used in labeling will set up too quickly,

which causes misapplied labels. A vacuum is generated in

576 HOT-FILL TECHNOLOGY

the can as it cools. The vacuum at the exit of the cooler

ranges from approximately 16 to 25 in. of mercury (41–

64 cm Hg) depending on the headspace, product density,

and size of the can. The vacuum is formed by a combina-

tion of the condensation of the steam in the headspace and

the contraction of the product as it cools. The vacuum is

important as it provides integrity to the can by pulling the

ends inward and not allowing them to ﬂex during dis-

tribution. The concavity of the end caused by the vacuum

also provides visual evidence to the consumer that the can

is properly sealed.

LIGHTWEIGHT ALUMINUM CANS

In the 1980s, a new hot-ﬁlling process was developed that

allowed the hot ﬁlling of lightweight aluminum cans. This

technology is now used extensively for hot-ﬁlled fruit

juices and juice drinks in 11

¼ fl ¼ oz cans. Lightweight

aluminum cans could not be hot ﬁlled with traditional

processes because the aluminum cans would panel as a

result of the vacuum created when the product cooled. The

new hot-ﬁll process includes dosing the ﬁlled cans with

liquid nitrogen immediately prior to applying and double-

seaming the can end. The cans consist of a drawn and

ironed aluminum body with an E-Z open aluminum end.

Directly following the dosing of the liquid nitrogen and the

application of the end, the nitrogen vaporizes and creates

internal pressure. In the case of hot fruit juices, this

nitrogen dosing creates an initial pressure of approxi-

mately 45–50 psi (31.6–35.1 kg/m

) prior to cooling and

25–35 psi (17.6–24.6 kg/m

) after cooling. Thus, the

nitrogen overpressure more than compensates for the

vacuum created by the product as it cools, and the ﬁnal

package is overpressured to compensate for its light-

weight construction. The hot-ﬁll nitrogen dosing process

for juice and juice drinks consists of cleaning the cans with

hot water or air, hot ﬁlling with juice, leaving a headspace

of approximately 0.3–0.4 in. (7–10 mm), dosing liquid ni-

trogen, applying the can end, double-seaming the can end

to the can body, and ﬁnally cooling the product to approxi-

mately 90–1101F (32–431C). This hot-ﬁll process allows the

use of lightweight aluminum cans for fruit juice and offers

the potential for hot ﬁlling a variety of other food products.

(See also Cans, aluminum.)

GLASS CONTAINERS

Hot-ﬁlling technology has been used for ma ny years

for, not only tinplate cans, but also for vacuum-packed

glass jars and bottles. The hot-ﬁll process used for glass

packages is very similar to that used for tinplate cans.

One main difference is that glass packages must be

preheated prior to hot ﬁlling to prevent breakage caused

by thermal shock. Th is problem is particularly trouble-

some in the w inter, when glass is either stored in cold

warehouses or ﬁlled dire ctly off delivery trucks. It is

gener ally belie ved that thermal-shoc k br eakage is not a

problem if the glass temperature after preheating is no

more than 751F(241C) less than the hot product. Thus, if

the prod uct ﬁll temperature is 1851F (851C), then the

glass must be preheated to at least 1001F (431C) before

ﬁlling. The preheating process is usually accomplished

Figure 1. A typical hot-ﬁll process for high-acid food or beverage products.

HOT-FILL TECHNOLOGY 577