Caballero B. (ed.) Encyclopaedia of Food Science, Food Technology and Nutrition. Ten-Volume Set

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Further Reading

Carter CM (2001) The Immune System. In: Shaw V and

Lawson M (eds) Clinical Paediatric Dietetics, 2nd edn.,

pp. 193–214. London: Blackwells.

Devlin J, Stanton RJH and David TJ (1989) Calcium intake

and cow’s milk free diets. Archives of Disease in Child-

hood 64: 1183–1193.

Host A, Koletzko B, Dreborg S et al. (1999) Dietary prod-

ucts used in the treatment and prevention of food allergy.

A joint statement of the European Society for Paediatric

Allergology and Clinical Immunology (ESPACI) and

European Society for Paediatric Gastoenterology, Hepa-

tology and Nutrition (ESPGHAN). Archives of Disease

in Childhood 81: 80–84.

Hourihane JO’B (1997) Peanut allergy – current status

and future challenges (review). Clinical Experiments in

Allergy 27: 1240–1246.

Joneja JV (1998) Dietary Management of Food Allergies

and Intolerances. A Comprehensive Guide, 2nd edn.

Vancouver: JA Hall.

Sampson HA (1999) Food allergy part 1. Immunopatho-

genesis and clinical disorders. Journal of Allergy and

Clinical Immunology 103: 717–728.

Sampson HA (1999) Food allergy part 2. Diagnosis and

management. Journal of Allergy and Clinical Immun-

ology 103: 981–989.

Sampson HA, Mendelson L and Rosen JP (1992) Fatal and

near-fatal anaphylactic reactions to food in children and

adolescents. New England Journal of Medicine 327:

380–384.

Sicherer SH (1999) Food allergy: when and how to perform

oral food challenges. Pediatric Allergy and Immunology

10: 226–234.

FOOD LABELING (LABELLING)

Applications

P Berry Ottaway, Berry Ottaway & Associates Ltd,

Hereford, UK

Background

0001 Accurate labeling of food has an important role in the

marketing and distribution of food, both in providing

information to the consumer and in helping to sell the

product. Over the past 150 years, labels have

developed from being on-pack advertisements for

the food to providing information on the compos-

ition, nutritional value, usage instructions, and ap-

propriate storage conditions for the food. The

increase in consumer awareness of food composition,

processing and nutritional content, together with the

need for national and international distribution of

food products has inevitably led to increased legisla-

tion on labeling.

Essential Labeling Requirements

0002 Irrespective of the country, the legislative require-

ments for labeling contain most, if not all, of a

number of essential requirements in common. These

requirements are laid down in the Codex Alim-

entarius General Standard for the Labeling of

Prepackaged Foods (CODEX STAN 1-1985, Rev

1-1991) and are:

0003an appropriate product name and/or description;

0004a list or description of ingredients;

0005a net quantity declaration;

0006usage or preparation instructions where appro-

priate;

0007address of the manufacturer or marketer;

0008batch or lot coding to allow traceability;

0009date marking and storage instructions;

0010country of origin.

As 165 countries were members of Codex Alimentar-

ius (Codex) in 2000, adherence to the essential

requirements for labeling is becoming universal. For

example, in the European Union, the directive on

food labeling (2000/13/EC) is, in general, consistent

with the Codex Standard.

Name of the Food

0011According to Codex, the name of the food must indi-

cate the true nature of the food and should normally

be specific and not generic. Where a name has been

established in a Codex Standard or is prescribed in

national legislation, the prescribed name should be

used. Where a name for the food has not been pre-

scribed, either a common or usual name based on

common usage or an appropriate descriptive term

for the food that is not misleading or confusing to

the consumer can be used. Where a brand name, trade

mark, or ‘fancy’ name is given to the food for

marketing purposes, it must be accompanied by a

specific name, as defined above.

2648 FOOD LABELING (LABELLING)/Applications

0012 The Codex Standard also requires that any add-

itional words and phrases necessary to describe the

food to avoid misleading or confusing the consumer

with regard to the true nature and physical condition

of the food should appear on the label in conjunction

with, or in close proximity to, the name of the food.

This description should include, but is not limited to,

the type of treatment the food has undergone (e.g.,

dried, concentrated, reconstituted, smoked).

List of Ingredients

0013 The Codex Standard requires that a list of ingredients

be declared on the label except in the case of single

ingredient foods. This list should be headed or pre-

ceded by an appropriate title that should consist of, or

include, the word ‘ingredients.’ The list should consist

of all ingredients listed in descending order of weight

(m/m) at the time of manufacture of the food, often

referred to as the ‘mixing bowl’ stage.

0014 Added water should be declared in the list of ingre-

dients, except when it forms part of an ingredient

such as brine, syrup, or broth used in a compound

food and which is declared as such in the list of

ingredients. If the water, or other volatile ingredients,

are evaporated in the course of the manufacture of the

food, there is no need for a declaration.

0015 Codex provides that where a compound ingredient

for which a name has been established in a Codex

Standard or in national legislation constitutes less

than 5% of the food, the ingredients that make up

the compound ingredient, other than food additives

serving a technological function (e.g., antioxidants or

preservatives), need not be declared. A compound

ingredient at higher levels in the food can be declared

as such, provided that its ingredients are listed in

descending order by weight in brackets after the

name.

0016 The Codex requirement for compound ingredients

is not followed in the European Union (EU) where,

since 1979, the directive permits that where a com-

pound ingredient constitutes less than 25% of the

finished product, the subcomponents of that ingredi-

ent do not have to be declared. It is likely that this

exemption will eventually be repealed.

0017 In the USA, there are two options for compounded

ingredients. The first is to list the ingredient by its

established common or usual name with the compon-

ents given in descending order by weight in brackets.

The second is to theoretically break down the com-

pounded ingredient and incorporate each component

in the ingredients list in their weight order.

0018 The declaration of permitted food additives is re-

quired by Codex to include the class of additive in

accordance with the list of additive classes given in

the Standard (Table 1). The equivalent list in the

European Union labeling directive differs from

Codex in that the categories of color retention agent

and foaming agent are not included, but modified

starch(es) is included in the EU list.

0019The increasing awareness and concern over aller-

gens in foods are addressed by Codex, which specifies

that foods or food ingredients known to cause hyper-

sensitivity should always be declared. These foods

and ingredients are given in a list (Table 2). Very

few countries have included this requirement into

their legislation. The Food and Drugs Administration

(FDA) in the USA has not formally defined allergens

but has provided examples of foods that are com-

monly associated with allergic responses. Further to

concerns that certain allergenic foods might have

been inadvertently excluded from specific declar-

ations, the FDA issued a warning letter to manufac-

turers on the topic in 1996, which clearly laid out

the need to label potentially allergenic ingredients.

The letter also acknowledged that potentially aller-

genic substances (e.g., collective labeling for spices,

flavorings, and colorings) may be exempt from

specific declaration under the current regulations.

tbl0001Table 1 Additive classes for labeling (Codex Standard 1–1985

(Rev: 1–1991))

Acidity regulator Flour treatment agent

Acids Flavor enhancer

Anticaking agent Gelling agent

Antifoaming agent Glazing agent

Antioxidant Humectant

Bulking agent Preservative

Color Propellant

Color retention agent Raising agent

Emulsifier Stabilizer

Emulsifying salt Sweetener

Foaming agent Thickener

Firming agent

The following class titles may also be used for food additives

falling into the respective classes:

Flavor(s) and flavoring(s) Modified starch(es)

tbl0002Table 2 Foods and ingredients that are known to cause

hypersensitivity and must always be declared (Codex Standard

1–1985 (Rev: 1–1991))

Cereals containing gluten, i.e., wheat, rye, barley, oats, spelt,

or their hybridized strains and products of these

Crustacea and products of these

Eggs and egg products

Fish and fish products

Peanuts, soybeans, and products of these

Milk and milk products (lactose included)

Tree nuts and nut products

Sulfite in concentrations of 10 mg kg

1

or more

FOOD LABELING (LABELLING)/Applications 2649

EU legislation to require the labeling of a number of

allergens has been proposed, but was still not adopted

by mid-2001.

0020 One aspect of the ingredient list that tends to be

inconsistent is the declaration of processing aids

and the carryover of food additives. Codex defines

a processing aid as a ‘substance or material, not in-

cluding apparatus or utensils, and not consumed as a

food ingredient by itself, intentionally used in the

processing of raw materials, foods or its ingredients,

to fulfill a certain technological purpose during treat-

ment or processing and which may result in the non-

intentional but unavoidable presence of residues or

derivatives in the final product.’

0021 In general, processing aids and additives carried

over into the food at a level less than that required

to achieve a technological function do not have to be

declared. However, if a food additive such as an

antioxidant or preservative is carried over into the

food from an ingredient in an amount sufficient for

it to act in that function in the final food, it must be

declared in the list of ingredients.

Net Contents

0022 All prepackaged food should carry a declaration of

net quantity. Whilst Codex requires that net content

declarations are given in the metric system, this still

does not apply in some countries. For example, the

law in the USA requires the weight to be given in

terms of avoirdupois pounds and ounces, and liquid

in US gallons, quarts, pints, fluid ounces, and subdiv-

isions thereof. The American gallon is not the same

volume as the Imperial gallon originally in use in

the UK and many British Commonwealth countries.

Declarations for net contents should be:

0023 by volume for liquid foods;

0024 by weight for solid foods;

0025 by either weight or volume for semisolid or viscous

foods.

Codex also requires that food packed in a liquid

medium should carry a declaration, in the metric

system, of the drained weight of the food. A liquid

medium refers to the water, syrup, or salt solutions

used, for example, in canned fruits and vegetables.

Depending on the legislation of the country, the net

contents declaration can be based on the ‘average

weight’ system or ‘minimum weight’ system, or in

some cases both.

Instructions for Use

0026 The labels of foods should contain instructions

for use, as applicable, to allow the correct or best

utilization of the food. Where necessary, details of

reconstitution or other ingredients needed to prepare

the food should be given.

Name and Address

0027There is a general requirement that the name and

address of a person or company responsible for the

food should be included on the label. This can be the

name and address of the manufacturer, packer, dis-

tributor, importer, or exporter, and should be the

most appropriate contact. European food labeling

legislation requires that the name and address must

be of a person or company established within the EU.

The name and address are required to allow the

authorities or consumers to contact those responsible

for the food in case of complaint or recall.

Batch or Lot Marking

0028In order to ensure traceability and identification of

the food in terms of production, a batch or lot identi-

fication must be indelibly printed or embossed on

each container. The identification can be in code or

in clear and must identify the producing factory, the

batch (lot) number, and/or the date and time of pro-

duction. In some cases, national legislation dictates

the method by which the batch or lot number must

be declared.

Date Marking

0029Many countries, including those in the EU, require an

easily understood indication of the minimum durabil-

ity or shelf-life of the food. The Codex Standard on

Food Labeling gives the criteria for the date marking

of food in cases where there are no special require-

ments in individual Codex Standards on foods over

commodities.

0030Codex requires that a ‘date of minimum durability’

must be declared. The form in which this date is given

depends on the estimated life of the food and should

consist of the day and the month for products with a

minimum durability of not more than 3 months, and

the month and the year for products with a minimum

durability of more than 3 months. If the month is

December, under Codex requirements, it is sufficient

to indicate the year. For the first case where the day

and month are given, the date should be preceded by

the words ‘Best before ...,’ and where the month and

year is given, by the words ‘Best before end . . . ’ These

statements should be clearly visible on the package or

label. Where it is impractical to print the date in

conjunction with the statement, there should be a

reference to where the date can be found, for

example: ‘Best before end: see bottom of can.’

2650 FOOD LABELING (LABELLING)/Applications

0031 According to Codex, the declaration of the day,

month, and year should be declared in an uncoded

numerical sequence. The month, however, may also

be indicated by letters in those countries where such

use will not confuse the consumer. The use of letters

for the month can be particularly important in the case

of trade between the USA and Europe. In the USA,

when defining the date in numerical terms, it is

common to place the month before the day (i.e., 04/

12 for 12 April), whereas in most European countries,

the day comes before the month.

0032 The Codex Standards exempt a number of foods

and drinks from the date marking requirements

(Table 3). An important declaration that should ac-

company the date of minimum durability on the label

is that giving any special storage conditions required

if the validity of the date (i.e., the shelf-life) is depend-

ent on the conditions under which the product is kept.

Nutrition Labeling

0033 An increasing awareness of healthy eating and the

impact of the diet on heart disease has led to a con-

sumer demand for information relating to the nutri-

tional composition of foods. This demand has led

to many food labels containing information on the

nutrient content, and to ensure consistency in the

manner in which this information is given, most

countries have included detailed requirements for

nutrition labeling in their legislation.

0034 As with the general labeling of food, Codex also

has produced guidelines on nutrition labeling (CAC/

GL 2-1985. Rev 1-1993). According to Codex, the

information supplied in a nutrient declaration should

be for the purpose of providing consumers with a

suitable profile of the nutrients contained in the

food and which are considered to be of nutritional

importance. This information should not lead con-

sumers to believe that there is exact quantitative

knowledge of what individuals should eat in order

to maintain health, but rather to convey an under-

standing of the quantities of the nutrients contained

in the food. Nutrition labeling should not be used to

deliberately imply that a food that carries such label-

ing necessarily has any nutritional advantage over a

similar food that is not so labeled.

0035The Codex guidelines lay down both the nutrients

that should be declared, and the form in which the

information should be given. It lists those declar-

ations that should be mandatory as:

0036the energy value of the food;

0037the amounts of protein, available carbohydrate

(i.e., excluding dietary fiber), and fat;

0038the amount of any other nutrient for which a nutri-

ent claim is made;

0039the amount of any other nutrient considered to be

relevant for maintaining a good nutritional status,

as required by national legislation.

Where a claim is made for the type and/or quantity of

a carbohydrate, the amount of total sugars should be

listed, and the amounts of starch or other forms of

carbohydrate may also be listed. In the context of this

requirement, sugars are defined as mono- and disac-

charides present in the food. Similarly, where a claim

is made for the quantity and/or type of fatty acids, the

amounts of the saturated and polyunsaturated fatty

acids should be declared.

0040If a claim is made for a dietary fiber content, the

amount of dietary fiber should also be declared. The

Codex guidelines define dietary fiber as ‘edible plant

and animal material not hydrolyzed by the endogen-

ous enzymes of the human digestive tract as deter-

mined by the agreed upon method.’ As this definition

may differ in detail from that used in some countries,

national legislation needs to be considered to ensure

that the calculation of dietary fiber is carried out

appropriately.

0041The vitamins and minerals that can be declared,

and the method of their declaration, can vary from

country to country. The Codex guidelines are general

in that they state that, in addition to the information

described above, vitamins and minerals may be listed

but only for those micronutrients for which recom-

mended intakes have been established and/or which

are of national importance in the country concerned.

0042Where vitamins and minerals are declared, only

those present in significant amounts should be listed.

As yet, there is no international agreement on what

constitutes a significant amount of a micronutrient in

a food. Codex states that, as a rule, 5% of the recom-

mended intake of the population concerned, supplied

by a serving as quantified on the label, should be

taken into consideration in deciding what constitutes

tbl0003 Table 3 Products for which an indication of the date of

minimum durability shall not be required

Fresh fruits and vegetables, including potatoes that have not

been peeled, cut or similarly treated

Wines, liqueur wines, sparkling wines, aromatized wines, fruit

wines, and sparkling fruit wines

Beverages containing 10% or more by volume of alcohol

Bakers’ or pastry-cooks’ wares, which, given the nature of their

content, are normally consumed with 24 h of their manufacture

Vinegar

Food-grade salt

Solid sugars

Confectionery products consisting of flavored and/or colored

sugars

Chewing gum

FOOD LABELING (LABELLING)/Applications 2651

a significant amount. European law, however, states

that, as a rule, 15% of the recommended allowance

for the vitamin and mineral supplied by 100 g or

100 ml or per serving, if the package contains only a

single portion, should be taken into consideration in

deciding what constitutes a significant amount.

0043 When the nutrient content of a food is declared, it

is essential that the calculations are in accordance

with national legislation, as there are differences be-

tween countries in the way in which energy and the

quantities of nutrients are to be calculated.

0044 Codex and European nutrition labeling law require

that protein is calculated as the Total Kjeldahl nitro-

gen  6.25. However, in Codex, there is the rider that

this factor is to be used unless a different factor is

given in a Codex Standard or a specific Codex

method of analysis for a food.

0045 The Codex guidelines give the conversion factors to

be used for the calculation of energy (Table 4). These

factors are not consistently used across the world. For

example, European law introduces a further category

of polyols contributing 2.4 kcal/10 kJ g

1

0046 The format for the presentation of nutrition infor-

mation can vary from country to country, although

the 15 EU member states and many non-EU countries

closely follow the Codex guidelines. Codex requires

that the declarations of nutrient content should be

numerical, but additional presentation in other

forms (e.g., pie chart) is not excluded. The energy

statement should be given in kilojoules and kilocal-

ories per 100 g or 100 ml or per package if the pack

only contains a single portion. The energy may also

be given per serving or per portion, provided the

serving size is given on the label, or the number of

portions in the package are given on the label.

0047 The information on the quantities of protein,

carbohydrate, and fat should be given in grams and

in the same manner as the energy statement. The

information on vitamin and mineral content should

be given in the metric system (milligrams or micro-

grams as appropriate) and/or as a percentage of

the nutrient reference value per 100 g or per 100 ml

or per package, if the product only contains a single

portion. The nutrient reference values for nine vita-

mins and five minerals are given in the Codex guide-

lines. The EU nutrition labeling directive 90/496/EEC

gives reference values (as recommended daily allow-

ances) for 12 vitamins and six minerals, and requires

that the micronutrients also be given as a percentage

of these values.

0048In the USA, there is also a requirement for micro-

nutrients to be labeled as a percentage of reference

daily intakes. In both European and US law, the order

in which vitamins and minerals are to be declared is

laid down. However, these requirements differ in

detail. There is also some confusion between the EU

and USA in the way in which the activity of certain

vitamins is calculated. For example, in Europe, the

activity of thiamin (vitamin B

) is measured as

the cation, whereas in the USA, it is often measured

as the salt. US law also has specific labeling require-

ments for micronutrients in products that fall into the

category of a dietary supplement under the Dietary

Supplement and Health Education Act 1994.

Claims

0049The use of claims on food labels is the most contro-

versial aspect of food labeling with a lack of agree-

ment between countries as to what is permitted.

0050In most countries, food law prohibits the making of

claims that a food can prevent, cure, or treat a human

condition or disease. In most cases, this prohibit-

ion has been in the law for decades. More recently,

there has been increasing awareness that certain diets,

and possibly certain foods, may play a significant part

in the reduction of risk of a disease such as heart

disease or cancer.

0051Since the mid-1990s, the interest in functional

foods has increased the debate as to what claims

could be permitted. Claims have been classified into

two categories, both with further subdivisions. These

are:

0052nutrition claims and

0053health claims.

Nutrition Claims

0054A nutrition claim is any representation that states or

implies that a food has particular nutritional proper-

ties. These include, but are not limited to, the energy

value and the contents of protein, carbohydrate, fat,

vitamins, and minerals. It is generally accepted that

the mention of nutrients in an ingredient list or in a

nutritional declaration does not represent a claim.

0055Nutritional claims can be categorized as:

0056Nutrient claims that describe the amount of a

nutrient in a food, such claims can be either for

enhanced levels of a nutrient in a food or for

reduced levels of certain nutrients, such as fat, or

tbl0004 Table 4 Conversion factors that should be used for the

calculation of energy from food

Protein 4 kcal/17 kJ g

1

Carbohydrate 4 kcal/17 kJ g

1

Fat 9 kcal/37 kJ g

1

Organic acid 3 kcal/13 kJ g

1

Alcohol (ethanol) 7 kcal/29 kJ g

1

2652 FOOD LABELING (LABELLING)/Applications

2.0057 Comparative claims that compare the nutritional

components of a food with different versions of

the same food or with similar foods, an example

would be the comparison of a low fat or low

energy food with the normal version, or

0058 Nutrient function claims that relate to the func-

tion of a nutrient in the body, such claims relate to

the biological functions of the nutrient in the body,

for example ‘calcium aids in the development of

strong bones and teeth’ or ‘protein helps build and

repair body tissues.’ A nutrient function claim

should be based on scientific consensus and should

not imply that, by carrying out its function, the

nutrient would prevent, treat, or cure a disease or

adverse condition.

Health Claims

0059 A health claim is any statement or implication in the

labeling or advertising of food that the food is benefi-

cial to health. The area of health claims is controver-

sial, but such claims can be categorized as either:

0060 Claims related to dietary guidelines or healthy

diets where the composition of the food can con-

tribute to the meeting of the guidelines when

consumed as part of the diet; or

0061 Disease risk reduction claims where the claim

relates to the consumption of a food or food

component, which might help reduce the risk of

a specific disease or condition. Although it may

be considered to come under the concept of

‘prevention,’ and thus illegal, a claim that a food

or food component helps in reducing the risk of a

disease is different from the claim that it prevents a

disease. In the USA, a limited number of disease-

risk reduction claims have been permitted by the

Food and Drugs Administration, provided that all

the conditions in the permission are met by the

food. Examples of these claims are those for:

0062 calcium and osteoporosis;

0063 dietary lipids and cancer;

0064 sodium and hypertension;

0065 folate and neural tube defects;

0066 fruit and vegetables and cancer.

0067 Enhanced function claims that concern the specific

beneficial effects of nutrients or other components

of a food on the physiological or psychological

functions of the body. Such claims can also cover

biological activities beyond the established roles of

nutrients in growth, development, and other

normal functions of the body.

There is little international agreement on which

health claims could be permitted, and whilst discus-

sions are taking place within Codex Alimentarius, the

European Commission, and a number of countries,

there is unlikely to be common consent before about

2005.

Warnings

0068Through the 1990s, food-related product liability

issues and litigation increased significantly. This has

led to an increase in warnings on the product labels,

mostly related to ingredients. Whereas a number of

the warnings are voluntary and relate to possible

allergens in the food, some have become statutory.

For example, in the USA, food products containing

saccharin must, by law, include the statement ‘Use of

this Product May be Hazardous to Your Health. This

Product Contains Saccharin Which Has Been Deter-

mined to Cause Cancer in Laboratory Animals.’

In addition, products containing the sweetener

Aspartame must be labeled with the warning

‘Phenylketonurics – Contains Phenylalanine.’ A very

similar requirement is found in European law when

the warning has to be ‘Contains a source of phenyl-

alanine.’

0069In Europe, it is also a legal requirement to include

the warning ‘Excessive consumption may produce

laxative effects,’ where a product contains 10% or

more by weight of added polyols, regardless of the

serving size of the food.

Other Labeling Requirements

0070There are some aspects of food labeling for which

international agreement has not been reached but

have already been introduced into the legislation of

some countries.

0071One such requirement is the quantitative declar-

ation of ingredients (QUID), which became part of

European labeling law in 2000. A QUID declaration

is required when, for example, an ingredient or

category of ingredients appears in the name of a

product (e.g., ham and mushroom pizza or straw-

berry yogurt) or where an ingredient is emphasized

on the label in words, pictures, or graphics. In such

cases, it is required that the percentage of the ingredi-

ent in the food product must appear either after the

name of the food or in the list of ingredients or

category of ingredients in question.

0072From 1997, there has been consumer-driven con-

cern in a number of countries, particularly some in

the EU, about the use of genetically modified organ-

isms (GMOs) or byproducts of GMOs used in foods.

As a consequence, from 1998, EU law required

the labeling of certain GMO sources if genetically

modified protein or deoxyribonucleic acid can be

detected. Rapid developments in the use of genetic

FOOD LABELING (LABELLING)/Applications 2653

modification technology meant that by the end of

2000, the legislation was already becoming outdated,

and more comprehensive labeling of GMO sources

had to be considered. In many countries, there has not

been the same consumer reaction to GMO ingredi-

ents, and their labeling has not been a priority.

Seealso: Food Intolerance:FoodAllergies; Nutrition

Policies in WHO European Member States

Further Reading

Blanchfield JR (2000) Food Labelling. Cambridge, UK:

Woodhead.

Codex Alimentarius Commission (1999) Food Labelling

Complete Texts, revised. Joint FAO/WHO Food Stand-

ards Programme. Rome: FAO.

Food and Drug Administration USA (1997) A Food Label-

ing Guide. FDA Center for Food Safety and Applied

Nutrition http://vm.cfsan.fda.gov/-dms/flg-1.html

FOOD POISONING

Contents

Classification

Tracing Origins and Testing

Statistics

Economic Implications

Classification

D Roberts, Central Public Health Laboratory, London,

This article is reproduced from Encyclopaedia of Food Science,

Introduction

0001 The term food poisoning is used to describe a disturb-

ance of the gastrointestinal tract following the

consumption of contaminated food or water. Some

regulatory or surveillance agencies prefer to use the

terms ‘foodborne disease’ or ‘foodborne infections

and intoxications’, but for simplicity and ease of

understanding by most people the term ‘food

poisoning’ will be used in this article.

0002 A wide range of agents can give rise to food

poisoning and the most common of these are listed

in Table 1. In Europe and North America by far the

most common causes of food poisoning are microor-

ganisms, in particular bacteria and viruses (see Tables

2 and 3). The involvement of other agents, such as

parasites, naturally toxic foods, and chemicals, will

vary according to country, diet of the population, level

of hygiene in food production, and level of food-pro-

cessing technology. For example, in countries where

there is a shortage of food containers there is oppor-

tunity for accidental contamination of food ingredi-

ents when barrels and sacks have been previously used

for different commodities which may be toxic. (See

Parasites: Occurrence and Detection and also individ-

ual agents.)

Symptoms

0003The symptoms of food poisoning may be very diverse

and the combinations which are manifest in a patient,

together with the incubation period, are often indica-

tive of the agent involved, and thus a useful diagnostic

tool. The most common symptoms are nausea, vomit-

ing, and diarrhea with or without fever. In severe

cases and with particular agents there may be more

serious effects, such as septicemia or involvement of

the nervous system.

0004Table 2 summarizes the incubation period, symp-

toms, and duration of illness of the main types of

bacterial food poisoning. Full descriptions of these

illnesses may be found in the relevant articles

elsewhere in this encyclopedia. Refer to individual

microorganisms. This table also includes Listeria

monocytogenes which, although it does not usually

give rise to typical food-poisoning symptoms, can be

transmitted via food.

0005A short incubation period of a few hours with a

vomiting-type syndrome is usually associated with

a toxin or poisonous chemical already present in the

food, either by accidental contamination (as with

some chemicals) or by growth of bacteria such as

Staphylococcus aureus and Bacillus cereus. The

2654 FOOD POISONING/Classification

toxin produced by Clostridium botulinum is a neuro-

toxin and takes longer to act. With agents that pro-

duce an infection within the human gut the

incubation period is usually longer – 24 h or more;

the organisms require this length of time to pass

through the stomach and reach the intestine before

they multiply and produce their effect.

Chemical Food Poisoning

0006 In the UK chemical food poisoning is uncommon and

probably responsible for not more than 1% of all

episodes; however, it may be more common in other

countries. The source of the chemical may be acciden-

tal contamination, leaching out of chemicals from

cooking utensils or pipework (copper, cadmium,

lead), mistaken identification of powders, e.g., those

resembling flour (nicotinic acid, sodium fluoride), or

carry-over from harvested produce previously treated

with fungicides, herbicides, or insecticides. With the

exception of one or two neurotoxins, the main

characteristic of chemical food poisoning is vomiting

within a few minutes to half an hour of ingestion of

the food – a much shorter incubation period than

with bacterial food poisoning, where symptoms

rarely appear in less than 2 h. Recovery is usually

rapid, although with some poisons there may be a

high case-fatality rate. Some foods, of both plant

and animal origin, are poisonous to humans because

they contain certain naturally occurring toxic mater-

ials such as the lectin of the red kidney bean and

tetrodotoxin of puffer fish. Others become toxic

owing to the concentration of chemical poisons pro-

duced by the organisms upon which they feed, e.g.,

shellfish and fish which feed on the marine protozoa

which produce the toxins responsible for paralytic

and diarrheic shellfish poisonings and ciguatera

poisoning. Scombroid fish, which are rich in histi-

dine, become toxic owing to the breakdown of the

histidine to histamine by their own natural microbial

flora during poor storage following harvesting. (See

Contamination of Food; Fish: Spoilage of Seafood;

Histamine; Shellfish: Contamination and Spoilage of

Molluscs and Crustaceans.)

Bacterial Food Poisoning

0007The term ‘bacterial food poisoning’ is usually

restricted to the acute gastroenteritis caused by the

presence of bacteria, usually in large numbers, or the

products of their growth in food. It may be subdiv-

ided into three basic types according to the mode of

action of the bacteria responsible:

0008Infection-type bacterial food poisoning results

from the in vivo multiplication of bacteria con-

sumed with the food, e.g., Salmonella, Vibrio

parahaemolyticus. The dose of organisms required

to initiate infection is usually large (10

or more

per g); this enables sufficient organisms to pass

through the acid region of the stomach and reach

the intestine, where they set up their infection.

However, infections may result from a low dose

of organisms if the food has a protective effect

through the stomach, e.g., if it is high in fat or

has a high buffering capacity. Thus outbreaks of

salmonella infection have resulted from foods such

as chocolate and cheese containing levels of 100

salmonellae or less per gram of food.

0009Toxin-type poisoning results from the ingestion of

food in which a toxin has already been formed as a

result of microbial growth in the food. Examples

of this type include Staphylococcus aureus (enter-

otoxin), B. cereus (emetic toxin) and C. botulinum

(neurotoxin). The organisms need to multiply to

levels exceeding 10

organisms per g in order for

sufficient toxin to be produced to cause illness.

The emetic toxins which act on the vomiting

tbl0001 Table 1 Agents of food poisoning

Examples

Bacteria Salmonella, Staphylococcus aureus,

Clostridium perfringens, C. botulinum,

Bacillus cereus

Viruses Parvovirus; Norwalk agent; small,

round, featureless viruses

Molds Claviceps purpurans (ergotism)

Aspergillus flavus (aflatoxicosis)

Marine protozoa Gonyaulax tamarensis (paralytic

shellfish poisoning)

Gambierdiscus toxicus (ciguatera

poisoning)

Prorocentrum lima and several species

of Dinophysis (diarrheic shellfish

poisoning)

Parasites (helminths,

protozoa, amebae)

Trichinella spiralis, Taenia solium, Giardia

lamblia, Cryptosporidium, Entamoeba

histolytica

Chemicals Heavy metals, e.g., lead, zinc, copper,

cadmium, mercury, arsenic.

Insecticides, herbicides, fungicides,

cleaning agents, disinfectants

Toxic plants Toadstools, hemlock, deadly

nightshade

Raw or undercooked red kidney beans

(Phaseolus vulgaris lectin)

Apricot kernels (glucoside-amygdalin),

green potatoes (solanine)

Toxic food animals Puffer fish (tetrodotoxin), red whelk

poisoning (tetramine)

Scombroid fish, poorly processed

(histamine)

FOOD POISONING/Classification 2655

center produce symptoms fairly rapidly, within a

few hours of consumption of the food, while the

neurotoxin of C. botulinum takes longer to act.

0010 In intermediate-type poisoning the organism

(e.g., C. perfringens) releases an enterotoxin, but

in the bowel; the toxin is not produced readily

in the food. Again, a high dose of organisms is

required in the food to insure that some survive

through the stomach and reach the intestine,

where they sporulate and release the enterotoxin,

which causes fluid production and diarrhea.

Viruses, which cannot multiply in foods because they

require living cells in which to replicate, cause the

infection type of food poisoning. The infectious dose

level may be very small.

Introduction of Microorganisms into

Foods

0011 Table 3 summarizes the principal food sources of

the most common food-poisoning organisms and

L. monocytogenes. Foods of animal origin are the

primary source of many of these microorganisms.

Those found in the live animal can be carried through

to raw meats after slaughter, may persist through

further processing, and may ultimately appear in the

final retail product if insufficient attention is paid to

hygiene and temperature control. Many animals are

mass-reared for food, and a large proportion may

arrive at the slaughterhouse excreting organisms,

such as Salmonella and Campylobacter, in addition

to the pathogens that form part of their normal fecal

flora, such as C. perfringens, Escherichia coli, Yersi-

nia enterocolitica, and L. monocytogenes. Continu-

ous line processing will increase spread from carcass

to carcass. Comminution of meat results in a spread

of organisms throughout the product. (See Meat:

Slaughter.)

0012During laying, eggs may be contaminated on the

shell surface by Salmonella from chicken feces, which

may be transferred to the contents during unhygienic

breaking out. A small proportion may also be infected

while in the hen’s ovary. Milk, when freshly drawn

from a healthy animal using hygienic dairy practices,

should contain very few bacteria. However, various

pathogens may be acquired from the milking animal

herself (fecal contamination or udder infection) or

from the dairy environment and equipment. Some

outbreaks of salmonellosis and campylobacteriosis

tbl0002 Table 2 The main agents of bacterial food poisoning

Organism Incubationperiod (h) Duration Symptoms

Salmonella

(infection)

6–48 (usually 12–36) 1–7 days D, Abp, V, F

Staphylococcus aureus

(toxin in food)

2–6 6–24 h N, V, D, Abp; collapse and

dehydration in severe cases

Clostridium perfringens

(toxin in intestine)

8–22 24–48 h D, Abp, N

C. botulinum

(toxin in food)

12–96 (usually 18–36) Death in 24 h to 8 days or

slow convalescence

over 6–8 months

Lassitude, fatigue, dizziness,

D followed by C;

CNS involvement, disturbance

in vision and speech

Bacillus cereus

(toxin in food)

Vomiting syndrome, 1–6 6–24 h N, V, sometimes D

Diarrheal syndrome, 8–16 18–24 h Abp, D, sometimes N

B. subtilis

(toxin in food)

<1–14 (median 2.5) 1.5–8 h V, D, Abp, N

B. lic heni f ormis

(toxin in food)

2–14 (median 8) 6–24 h D, V, Abp

Escherichia coli

(infection and toxin)

12–72 1–7 days D with blood and mucus in stool

Vibrio parahaemolyticus

(infection)

2–48 (usually 12–18) 2–5 days Profuse D, Abp, V, F, often

dehydration

Yersinia enterocolitica

(infection)

24–36 (3–5 days) 3–5 days Moderate D to chronic enteritis

Streptococcus

(toxin in food? and infection)

3–22 24–48 h Abp, V, D

Campylobacter jejuni

(infection)

3–5 days Days or weeks F, headache, Abp, profuse D with

blood and mucus

Listeria monocytogenes

1–70 days Days to years, high

mortality rate (30%)

Mild, flu-like illness, septicemia,

meningitis, abortion

D, diarrhoea; N, nausea; Abp, abdominal pain; C, constipation; V, vomiting; F, fever; CNS, central nervous system.

A foodborne infection rather than true food poisoning.

2656 FOOD POISONING/Classification

are associated with the consumption of raw milk, and

a range of organisms may be found in the product

(Table 3). This source of infection can be eliminated

by heat treatment of the product. (See Milk: Process-

ing of Liquid Milk.)

0013 Fish and shellfish may become contaminated either

from the water from which they are harvested or from

the environment during further processing. When

fished from water polluted with sewage they may

contain many fecal pathogens (Table 3). Vibrio para-

haemolyticus is a common marine microorganism

and is a frequent contaminant of raw fish and other

seafoods. Shellfish are filter feeders and thus can

concentrate microorganisms (bacteria, viruses, and

protozoa) from the water in which they are breeding.

Consumption of raw shellfish, e.g., oysters, or those

that have been inadequately heat-treated, can lead to

bacterial and viral infections.

0014 Some food-poisoning bacteria are common envir-

onmental organisms; they may be present on the soil,

in river mud, and on vegetation. Thus many raw foods

may be contaminated from this source with organisms

such as C. perfringens, B. cereus, and other Bacillus

spp., and L. monocytogenes. Fruits, vegetables, and

cereals will frequently carry a number of these organ-

isms. Where crops require artificial irrigation and/or

fertilization, particularly if polluted water and animal

or human excreta are used, there is a risk of contamin-

ation with enteric bacterial pathogens.

0015Thus raw foods and ingredients are frequently con-

taminated with a range of pathogenic organisms.

Many of these will be rendered safer by the applica-

tion of some form of heat treatment, but they are

unlikely to be sterile unless a stringent heat process

such as the ‘botulinum cook’, applied to certain

canned foods, is used. Pasteurization temperatures

will eliminate most vegetative cells, but the spores

of Clostridium spp. and Bacillus spp. will survive.

The spores of some of the clostridia are extremely

heat-resistant, and the heat processes applied in the

canning industry are aimed at eliminating the most

heat-resistant spores of the most serious food-

poisoning organism, C. botulinum.(See Heat

Treatment: Chemical and Microbiological Changes;

Pasteurization: Principles.)

0016The food-poisoning toxins produced by bacteria

vary in their ability to withstand a heat treatment.

The toxins of C. botulinum are heat-labile and readily

destroyed by boiling, while some of the enterotoxins

produced by Staphylococcus aureus are very heat-

resistant and will withstand boiling for 30 min. The

emetic toxin of B. cereus is extremely heat-resistant

and remains active after 90 min at 121



0017Further manipulation of a product after heat

treatment will allow entry of a wide range of organ-

isms. Those of particular concern include Y. entero-

colitica and L. monocytogenes both of which can

multiply at refrigeration temperatures – refrigeration

being the common means of short-term preservation

of foods. Thus care must be exercised with respect to

hygiene of production, temperature control during

storage and display, and shelf-life of the product, if

the introduction and growth of these bacteria are to

be prevented.

0018Organisms may also be transferred to food by

the food handler, either directly or by cross-

contamination through the use of hands, surfaces,

utensils, and equipment that have not been ad-

equately cleaned and disinfected between the prepar-

ation of different foods, especially between raw and

cooked foods. It is in relation to S. aureus food

poisoning that the food handler has an important

role as a direct source of contamination. This organ-

ism is commonly carried in the nose and on the skin of

humans, as well as causing skin infections, and can be

readily transferred to foods by handling. Subsequent

tbl0003 Table 3 Principal food sources of the common microorganisms

causing food poisoning

Agent Foodsource

Salmonella Raw meat and poultry, raw milk,

eggs

Staphylococcus aureus Cold meats and desserts (much

handled during preparation);

dairy products, especially if

prepared from raw milk

Clostridium perfringens Raw meat, poultry, dried foods,

herbs, spices, vegetables

C. botulinum Improperly preserved meat,

fish, and vegetables

Bacillus cereus and other

Bacillus spp.

Cereals, dried foods, dairy

products, meat and meat

products, herbs, spices,

vegetables

Escherichia coli Many raw foods, particularly of

animal origin

Vibrio parahaemolyticus Raw and cooked fish, shellfish

and other seafoods

Yersinia enterocolitica Raw meat and poultry, meat

products, milk and milk

products, vegetables

Streptococcus Raw milk, raw meat and poultry,

foods prepared by infected

food handlers

Campylobacter jejuni Raw poultry meat, raw or

inadequately heat-treated

milk, untreated water

Viruses Raw shellfish, cold foods

prepared by infected food

handlers

Listeria monocytogenes

(a widespread

environmental organism)

Meat, poultry, soft cheese and

other dairy products,

vegetables, shellfish

FOOD POISONING/Classification 2657