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

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specialized storage procedures, this means that local

satsuma fruit can be available for up to 8 months of

the year.

Harvesting and Marketing

0047 The growing, harvesting, and marketing of manda-

rins as soft fruit present many problems, which can be

best overcome by specialist growers and carefully

selected growing localities. They are comparatively

higher in all these costs, when compared with other

types of citrus production. Present day mandarin pro-

duction focuses on careful type and cultivar selection

to best suit local climatic conditions and cultural

practices, in order to achieve a successful product

and outcome.

0048 Mandarins are mature and are ready for harvesting

for a much shorter period of time than most other

citrus types. Fruit left on the tree for more than a few

weeks quickly pass the stage of optimum maturity

and marketability, usually becoming insipid (reduced

juice acidity), puffy, soft, and dry.

0049 Early in the season, some cultivars may be in-

ternally mature before the rind color has fully de-

veloped, like Marisol clementine. Most respond to

selective initial harvesting for larger fruit sizes or the

required rind color development. All mandarins re-

quire careful harvesting, transport, and grading for

size in order to reduce rind blemish and damage.

Some cultivars are more difficult to harvest and re-

quire clipping to reduce plugging, where a small piece

of rind is left attached to the stalk that remains on

the tree.

0050 Unlike many other citrus fruits, which may be

available the whole year, mandarins are normally

available as fresh fruit only in late autumn, winter,

and spring. Within this period, a range of modern

cultivars are now available for the main commercial

types (common, clementine, and satsuma) that

permit the production and marketing of fresh fruit

from very early, early, mid (season), late, and very late

maturity periods. See Figure 4 for an example of the

maturity range and sequence for some important cul-

tivars in the Mediterranean region. All selection and

breeding programs have a basic need to develop new

cultivars that fit into a particular maturity period,

when no cultivar is currently available or some

major problem exists with the current cultivar (alter-

nate cropper, poor fruit size, pest- or disease-suscep-

tible).

0051 Apart from the normal marketing periods, all

mandarins are unsuitable for long-term cold storage.

They are more perishable than sweet oranges or

grapefruit and very susceptible to common storage

breakdown problems and chilling injury. In normal

export trade, careful storage is often necessary for

several weeks depending on the shipping distance

between producing countries, such as southern hemi-

sphere producers like Argentina, Southern Africa,

and Australia, exporting to the northern hemisphere’s

major markets in Europe, South-east Asia, Japan, and

North America.

Crop Utilization

0052Mandarins are the second most important citrus

type grown through the world with 17% of total

production in 1998–99, after oranges (with 66%)

but ahead of lemons and limes (11%), and grapefruit

(6%).

0053As with all citrus fruits, mandarins are principally

marketed according to how they are consumed, with

domestic or local fresh fruit and exports totaling 92%

of world production, with only a minor 8% processed

– compared with 34% of oranges processed in 1998–

99 (Figure 5).

0054In the world mandarin fresh export fruit trade in

1997–89, the following regions/countries (as gener-

ally noncitrus-producing) were the major importers –

Mediterranean, Germany, France, UK, the former

USSR, and The Netherlands.

0055As fresh or dessert fruits, mandarins are usually

eaten out of hand, as they are generally easier to

peel and separate into segments (than other citrus

types) and have a distinctive, pleasant flavor. This

is why mandarins are also known and promoted

by a range of other descriptive terms, i.e., easy

peelers, zipper-skin, TV fruit, soft fruit, kid glove

citrus, picnic, or lunch box fruit. In some cultures,

the presentation and eating of citrus, for example

during the Chinese New Year, are considered im-

portant. Fresh mandarin segments are also suitable

for garnishing and decorating salads or topping

desserts.

0056In the home, mandarins can be widely used for

juicing; cooking (as with mandarin bran muffins or

mandarin-glazed spare ribs), sweets (like mandarin

trifle and chocolate coating), marmalade, drying,

glace, or crystallizing.

0057Mandarins are used as commercial processed prod-

ucts, mainly as segments in syrup or natural juice,

with only limited production of juice products

(often because of the limonene bitterness factors)

and rind oil or essence, as often used in aromatherapy.

After the juice has been extracted, there remain resi-

dues that can be a source material from which over

300 valuable byproducts can be produced. Some

specialized types are also candied (the peel), dried,

or used for marmalade and pectin manufacture.

1376 CITRUS FRUITS/Mandarins

VARIETY SEPTEMBER OCTOBER NOVEMBER DECEMBER JANUARY FEBRUARY MARCH APRIL MAY

W1 W2 W3 W4 W1 W2 W3 W4 W1 W2 W3 W4 W1 W2 W3 W4 W1 W2 W3 W4 W1 W2 W3 W4 W1 W2 W3 W4 W1 W2 W3 W4 W1 W2 W3 W4

HASHIMOTO

CLAUSELLINA

OKITSU

LORETINA

MARISOL

ORONULES

ARRUFATINA

OWARI

ESBAL

MAPO

COMUNE

OROVAL

COMUNE SRA 63

TOMATERA

OROGRANDE

FINA

CLEMENULES

AVANA APIRENO

FAIRCHILD

NOVA

NOUR

HERNANDINA

CLEMENTAR

AFOURER

ELLENDALE

AVANA Di CIACULLI

MINNEOLA

ORTANIQUE

FORTUNE

MURCOTT

W represents weeks of the month, 1 is the first week to 4 which is the last week.

Satsuma Clementine Other Mandarins

Source: Adapted from various maturity tables

fig0004 Figure 4 Some typical mandarin maturity periods in the Mediterranean region.

(See Citrus Fruits; Composition and Charac-

terization; Processed and Derived Products of

Oranges.)

0058 Over 400 different constituents have been isolated

from fruit of different citrus species including manda-

rins. The principal components of non-acid fruits

(like lemons and limes) are carbohydrates, which in-

clude mainly sucrose, glucose and fructose. These

constitute about 75% of the total soluble solids

(TSS) in juice. Organic acids, mainly citric and malic

constitute less than 10% of the TSS and free amino

acids, nitrogenous bases and glutathione about 6%.

The remaining components include inorganic ions

(about 3%), vitamins (2.5%), flavonoids and vola-

tiles (1.2%) and lipids (1.2%).

See also: Citrus Fruits: Types on the Market; Composition

and Characterization; Processed and Derived Products of

Oranges

Further Reading

Cottin R (coordinator) (1997) Citrus of the World: A

Citrus Directory. San Giuliano, France: SRA INRA-

CIRAD.

FAO (1999) Citrus Fruit Fresh and Processed, Annual Stat-

istics, Tables 1–10 and 16–20. Rome: Food and Agricul-

ture Organization.

Reuther W, Webber HJ and Batchelor LD (eds) (1967) The

Citrus Industry, vol. 1. Berkeley, CA: University of

California.

Saunt J (2000) Citrus Varieties of the World an Illus-

trated Guide. Norwich, UK: Sinclair International

Limited.

Sinclair WB (1984) The Biochemistry and Physiology of the

Lemon and other Citrus Fruits, pp. 711–718. Berkeley,

CA: University of California.

Swingle WT and Reece PC (1967) The botany of Citrus and

its wild relatives. In: Reuther W, Webber HJ and Batch-

elor LD (eds) The Citrus Industry vol. 1. Berkeley, CA:

University of California.

USDA (1999) World fresh citrus situation. In: World Horti-

cultural Trade and US Export Opportunities, Circular

Series FHORTH, pp. 18–32. USA: Foreign Agricultural

Service.

Young RH (1986) Fresh Citrus Cultivars. In: Wardowski

WF, Nagy S and Grierson W (eds) Fresh Citrus Fruits,

pp. 110–125. Westpoint, CT: AVI Publishing.

Clams See Shellfish: Characteristics of Crustacea; Commercially Important Crustacea; Characteristics of

Molluscs; Commercially Important Molluscs; Contamination and Spoilage of Molluscs and Crustaceans;

Aquaculture of Commercially Important Molluscs and Crustaceans

fig0005 Figure 5 (see color plate 33) Moroccan clementine exports in

open 10-kg packages.

1378 CITRUS FRUITS/Mandarins

CLEANING PROCEDURES IN THE FACTORY

Contents

Types of Detergent

Types of Disinfectant

Overall Approach

Modern Systems

Types of Detergent

H M J van Eijk and F A Majoor, Unilever Research

Vlaardingen, Vlaardingen, The Netherlands

Background

0001 A wide variety of chemicals can be used in the

cleaning process, and these are generally classified as:

0002 water, which acts as the transport medium for

chemicals and soil as well as delivering thermal

and mechanical energy;

0003 cleaning agents, chemicals whose function is to

remove soil.

Water

0004 Water in general makes up the great majority of the

cleaning solution (> 90%), and must therefore be

given careful consideration. In most cases, the water

used for making up the cleaning solution is also used

for intermediate and final rinses and must therefore

be of suitable microbiological quality. Particular at-

tention should be also given to the content of inor-

ganic material. If the hardness of the water is high

(> 60 mg of Ca

2þ

per liter), it might be less suitable for

cleaning purposes, and partial softening should be

considered.

Cleaning Agents

0005 Although water is important during cleaning, it

cannot always remove all soils, particularly those

encountered in the food industry, and therefore, de-

tergents are required. Since no one detergent or com-

bination of detergents possesses all the properties

required for the removal of all types of soil at min-

imum cost, a selection must be made of the most

appropriate for the application being considered.

Materials used must be acceptable to regulatory

agencies, especially with regard to biodegradability

and the effect on the environment when discharged

into surface waters. Typical components of a deter-

gent formulation will include some of the following:

0006alkalinity;

0007surfactant/antifoam;

0008sequestrant;

0009threshold agents;

0010hydrotropes;

0011specialties;

0012acids.

Many cleaning formulations are currently being

reviewed in light of environmental concerns. It is

probable that there will be an increasing use of low-

phosphate, completely biodegradable products and a

reduced use of sequestrants such as ethylene diamine-

tetraacetic acid (EDTA). Such changes in cleaning

chemicals may well affect the other cleaning para-

meters such as the time and temperatures used.

Alkalis

0013Alkaline compounds are effective for the dissolution

of proteins and removal of fats. Strong alkalis result

in hydrolysis of the protein, forming water-soluble

compounds. Examples of alkalis are sodium hydrox-

ide (caustic soda) and potassium hydroxide (caustic

potash). These compounds, being hazardous to per-

sonnel, are more widely used in cleaning in-place than

in open-plant cleaners and, where used, should be in

combination with automatic dosing equipment.

0014Further strong alkalis are:

0015sodium orthosilicate;

0016sodium metasilicate.

Milder alkalis include:

0017sodium triphosphate;

0018triethanol amine;

0019sodium carbonate.

The milder alkalis possess some degree of protein

hydrolysis and fat-removing capabilities but mainly

CLEANING PROCEDURES IN THE FACTORY/Types of Detergent 1379

act as builders or sequestrants to soften water. In this

respect, alkalis act to suspend and disperse the soil

deposit in solution.

Surfactants/Wetting Agents

0020 Surfactants are chemicals that lower the surface ten-

sion of water, and thus aid the ‘wetting’ of surfaces.

For this reason, they are commonly called wetting

agents. They also aid the penetration of the cleaning

solution into the deposit.

0021 Surfactant molecules consist of a hydrophobic

(water hating) tail and a hydrophillic (water loving)

head, as shown in Figure 1. The hydrophobic part of

the molecule has an affinity for fats and oils, whereas

the hydrophilic part of the molecule has an affinity

for water. These molecules therefore emulsify and

disperse oils, fats, waxes, and pigments. Some will

precipitate at high pHs (> 12) and are unsuitable for

use in combination with strong alkalis.

0022 The polar nature of water molecules creates a high

surface tension, and as a result, water forms droplets

on a surface (Figure 2a). When a surfactant is added,

the hydrophillic heads are attached by the water at a

water/air or water/substrate interface (Figure 2b). The

orientation of the surfactant molecules at the interface

lowers the surface tension and results in spreading of

the water droplet (Figure 2c). In a formulated deter-

gent, these effects of the surfactant result in better

penetration of that detergent into the soil deposit.

0023 At a water/substrate interface, the same orientation

of the surfactant molecules also occurs. This allows

surfactants to solubilize or emulsify fats. On contact

with a fatty soil, the hydrophobic ends of the surfac-

tant enter the fat. As more such hydrophobic ends

enter the fatty soil, the soil comes to occupy the center

of a micelle molecular array, resulting in solubiliza-

tion of the fat (Figure 3).

0024Surfactants are classified into three groups based

on the charge of the active part of the molecule (in

solution).

Anionic Surfactants

0025The active part of an anionic surfactant molecule

carries a negative charge. Included in this group are

the fatty acid salts and the sulfated and sulfonated

derivatives of fatty acids. Anionic surfactants act in

the same way as soaps, except that they are less

affected by hard water ions and are generally high

foaming.

Cationic Surfactants

0026The active part of a cationic surfactant molecule

carries a positive charge. Included in the cationic

surfactants are the quaternary ammonium com-

pounds (quats). These compounds have limited deter-

gent characteristics but have found an effective use as

disinfectants.

Nonionic Surfactants

0027The nonionic surfactants do not ionize, and therefore,

no charged species are formed. A wide range of non-

ionics exist, and consequently, these surfactants have

a wide range of chemical properties. Nonionics can

be low foaming and very penetrative wetting agents,

making them particularly effective at removing oils.

Sequestrants

0028Sequestrants serve to enhance the effectiveness of the

detergent by forming chelate complexes with metal

ions in the deposit, or in the water itself. The metal

ions mostly encountered are calcium and magnesium.

If these ions are not complexed, they will readily form

deposits on surfaces and will make the removal of fats

more difficult.

0029Sequestrants commonly used are:

0030phosphates;

0031EDTA;

0032nitrilotriacetic acid (NTA);

0033gluconate.

Hydrophobic tail Hydrophillic head

fig0001 Figure 1 Surfactant molecule.

a) Water droplet b) Water plus surfactant c) Spreading of water

droplet on surface

fig0002 Figure 2 Wetting effect of surfactants.

1380 CLEANING PROCEDURES IN THE FACTORY/Types of Detergent

The sequestering power of EDTA is sufficiently high

that even calcium salts can be redissolved.

Threshold Agents

0034 Threshold agents prevent the deposition of hard

water salts by disrupting the (calcium carbonate)

crystal growth. These agents are added to detergents,

not to prevent the deposition of hard water salts

during cleaning (this is done by the sequestrant) but

during the rinse stage. Threshold agents are used at

very low concentrations (5–20 mg l

1

), which is suffi-

cient to prevent deposition of hard water salts.

Hydrotropes

0035 Hydrotropes are used to stabilize the neat product to

ensure an adequate storage life. Liquid detergents

generally contain a significant number of chemically

active species, and special chemicals are necessary to

prevent separation or sedimentation during storage.

Specialties

0036 Further additions to detergents consist of corrosion

inhibitors, tracers, and dyes.

Acids

0037 Acids, both organic and inorganic, are commonly

used for the removal of mineral deposits such as

hard water scale or milkstone. Examples of inorganic

acids are phosphoric, nitric, and sulfamic acid, and

examples of organic acids are gluconic, hydroxyace-

tic, citric, and formic acid.

0038 Whilst extremely effective at solubilizing mineral

salts, acids are potentially corrosive to construction

materials and must be used with care. Hydrochloric

acid and fluoric acid are too corrosive (even to stain-

less steel), and they should not be used for cleaning in

the food industry. A summary of the main functions

of the chemicals is given in Table 1.

See also: Cleaning Procedures in the Factory: Types of

Disinfectant; Overall Approach; Modern Systems;

Factory Construction: Materials for Internal Surfaces

Further Reading

Imholte TJ (1984) Engineering for Safety and Sanitation.

Crystal, MN: Technical Institute of Food Safety.

Karlsson CA-C (1999) Fouling and Cleaning of Surfaces –

The Influence of Surface Characteristics and Operating

Conditions. Lund, Sweden, Lund University.

Lelieveld HLM (2000) Hygienic design of factories and

equipment. In: The Microbiological Safety and Quality,

pp. 1656–1690. Gaithersburg, MD: Aspen.

Shapton DA and Shapton NF (eds) (1998) Principles and

Practices for the Safe Processing of Foods. Cambridge,

UK: Woodhead.

Wilson DI, Fryer PJ and Hasting APM (eds) (1999) Fouling

and Cleaning in Food Processing ’98. Proceedings

of a Conference at Jesus College, Cambridge. Brussels:

Directorate-General Science, Research and Develop-

ment.

tbl0001Table 1 Main functions of chemicals in detergents

Type Chemical Function

Strong alkalis Sodium hydroxide Removal of fat and

protein

Potassium hydroxide Removal of fat and

protein

Orthosilicate Emulsification

Metasilicate Corrosion inhibition

Mild alkalis Sodium triphosphate Dispersion

Sodium carbonate Alkalinity

Surfactants Anionics Wetting and foam

Cationics Corrosion inhibition

Nonionics Wetting and antifoam

Sequestrants Polyphosphate Prevention of Ca

deposits

Gluconate Prevention of Ca

deposits

Na.NTA Prevention of Ca

deposits

Na.EDTA Dissolution of Ca

deposits

Threshold agents Phosphonates Prevention of Ca

deposits during

rinse

Polyacrylates

Inorganic acids Phosphoric acid Removal of inorganic

scale

Nitric acid

Sulfamic acid

Organic acids Hydroxyacetic acid Removal of inorganic

scale

Gluconic acid

Citric acid

Formic acid

Fat droplet

Water

fig0003 Figure 3 Solubilization of fat in water.

CLEANING PROCEDURES IN THE FACTORY/Types of Detergent 1381

Types of Disinfectant

J Fisher, Diversey Ltd, Riddings, UK

This article is reproduced from Encyclopaedia of Food Science,

Background

0001 In food factories, the detergent stage is normally

followed by a disinfecting stage. The detergent stage

is required to remove all the soil, leaving a chemically

clean surface. The disinfectant stage is used as an

extra guarantee of cleanliness and to prevent recon-

tamination in some cases. It does not compensate for

a bad detergent stage or badly designed process or

cleaning equipment.

Disinfection

0002 The definition of disinfection taken from BS5283

(1986) states ‘The destruction of microorganisms,

but not usually bacterial spores. It does not neces-

sarily kill all microorganisms but reduces them to a

level acceptable for a defined purpose, for example a

level which is harmful neither to health nor to the

quality of perishable goods.’ The acceptable level of

microbial contamination on a surface or piece of

equipment has to be determined; obviously, no patho-

gens should be found. (See Spoilage: Bacterial Spoil-

age; Molds in Spoilage; Yeasts in Spoilage.)

0003 The state of sterility is defined as free from all living

microorganisms. This is not achievable in the food

factory by using acceptable chemicals (‘acceptable’

meaning safe for humans, plant materials and prod-

ucts).

0004 Disinfectants are used after the detergent applica-

tion in cleaning-in-place (CIP) operations where the

term ‘terminal sterilant’ may be used. They are also

used after hand cleaning. Equipment should be left in

a soak bath until it is ready to be used, thus ensuring

that it remains free from recontamination.

0005 There are a wide range of disinfectants available.

The choice of disinfectant depends on the user’s

requirements, the type of processing and cleaning

equipment, the method of use, and, to some extent,

the personal preference of the user.

Types of Disinfectant

0006 Disinfectants can be split into two broad groups,

oxidizing and nonoxidizing. Oxidizing disinfectants

include the halogens, chlorine, iodine, bromine,

and chlorine dioxide, and oxygen-releasing materials

such as peracetic acid and hydrogen peroxide.

Nonoxidizing disinfectants are as follows: quaternary

ammonium compounds, amphoterics, biguanides,

and acid anionics.

Physical and Chemical Properties

Oxidizing Disinfectants

0007Halogens Chlorine and iodine have been used as

terminal disinfectants for many years. More recently,

bromine and chlorine dioxide have been introduced.

0008Chlorine Chlorine was first used as a gas for fumi-

gation in hospitals in 1791, but this application has

one obvious drawback – chlorine gas is toxic. Active

chlorine is available from two types of material:

0009Inorganic compounds containing hypochlorite

ions either as a liquid, e.g., sodium hypochlorite

(NaOCl), or as a powder, e.g., chlorinated triso-

dium phosphate

ððNa

:11H

OÞ

NaOCl, NaClÞ:

0010Powdered organic chlorine release agents, e.g.,

trichloroisocyanurate (Figure 1).

In solution, both types hydrolyze to produce hypo-

chlorous acid and/or hypochlorite ions, depending on

the pH.

Acid Alkaline

Ð HOCl Ð OCl



Chlorine gas Hypochlorous acid Hypochlorite ion

In the food industry, sodium hypochlorite is used as a

general-purpose disinfectant. It is most stable in a

slightly alkaline solution, and it is for this reason that

the concentrate is supplied stabilized with sodium

hydrocide at a pH of up to 12. An in-use solution of

between 50 and 300 p.p.m. will have a pH between 7

and 9. The optimum pH for disinfection is pH 5.0, but

fig0001Figure 1 Trichloroisocyanuric acid. Reproduced from Cleaning

Procedures in the Factory: Types of Disinfectant, Encyclopaedia of

Food Science, Food Technology and Nutrition, Macrae R, Robinson

RK and Sadler MJ (eds), 1993, Academic Press.

1382 CLEANING PROCEDURES IN THE FACTORY/Types of Disinfectant

the solution is less stable. Below pH 5.0, chlorine gas

will be produced.

0011 Applications for sodium hypochlorite in the food

industries are CIP, soak, and spray. Sodium hypo-

chlorite has many advantages: it is nonfoaming; it is

not affected by water hardness; it does not leave an

active residue, and it has a wide antimicrobial spec-

trum, which includes activity against bacterial spores

and viruses. It is also fast-acting and cheap.

0012 However, it also has numerous disadvantages: it

can be corrosive to a wide range of components,

including stainless steel; it is irritating to the skin

and eyes; the in-use solution is unstable; it is inacti-

vated by organic materials, and it may give rise to

taint problems.

0013 Chlorine dioxide Chlorine dioxide (ClO

) is an un-

stable and toxic gas that is soluble in water. When

chlorine dioxide is generated in solution, as shown

below, it is a very effective water disinfectant at point

of use.

5NaClO

þ 4HCl Ð 4ClO

þ 5NaCl þ 2H

Chlorine dioxide at use concentrations (0.5–1 p.p.m.)

overcomes some of the disadvantages of hypochlorite

in that it is nontainting, noncorrosive, and nontoxic.

Its sole use at present is in water disinfection.

0014 Iodine Iodine itself is not very soluble in water, and

the vapor is irritating to the eyes, making it difficult to

handle. Iodine is a very reactive element, and it is this

reactivity that makes it a good disinfectant.

0015 Iodine compounds used in the food industry con-

tain iodine complexed with polyvinylpyrrolidone and

other surface active agents, usually in an acid solu-

tion. These are known as iodophors and were first

introduced in 1949.

0016 The complexes formed between iodine and carrier

molecule are water-soluble and overcome the hand-

ling difficulties of iodine whilst retaining the disin-

fecting power. On dilution, the iodophors release

iodine gradually, and it is the free iodine that acts as

the disinfecting agent. The optimum pH for microbial

activity is pH 5.0.

Acid Alkaline

Ð HOI Ð OI



Ð IO



Greatest Some Inactive Inactive

activity activity

The surface-active agents provide better wetting

and organic soil penetration, thus making iodophors

less affected by soil than hypochlorite. The choice of

surface-active agent may lead to foam generation in

applications such as CIP.

0017Iodophors have a broad antimicrobial spectrum

that is similar to hypochlorite, although they are less

active against bacterial spores. In common with

sodium hypochlorite, they are fast-acting but are

more expensive. Iodophors are used in soak baths

and spray application at up to 10 p.p.m. available

iodine. In solution, iodophors are yellow-brown in

color. This color can be an advantage: in a soak

bath application, the color indicates the presence of

iodine; the in-use solutions are unstable, so that as the

iodine dissipates, the solution will become colorless.

0018Staining may be a problem, especially with some

plastics, and this may also result in taint problems.

Iodophors can be corrosive; it is therefore necessary

to ensure that the correct dilution is used; otherwise,

damage to plant and personnel may occur.

0019Bromine Bromine itself is not used as a disinfectant,

mainly because of its handling difficulties. Bromo-

chlorodimethylhydantoin is supplied as a powder or

a solid. In solution, it releases hypobromous and

hypochlorous acids.

0020Oxygen-releasing compounds 0020

Peracetic acid Peracetic acid was introduced in

1955. The material is supplied as an equilibrium mix-

ture:

Cð¼¼ OÞOOH þ H

O Ð CH

Cð¼¼ OÞOH

Peracetic acid Water Acetic acid

þH

Hydrogen peroxide

It is soluble in water and is completely biodegradable,

breaking down to harmless products:

2CH

Cð¼¼ OÞOOH ! 2CH

Cð¼¼ OÞOH þ O

As supplied, peracetic acid is corrosive and has a very

irritating smell, similar to vinegar; because of these

properties, it is unpleasant to handle, and manual use

is not recommended. It is suitable for CIP, as it is

nonfoaming.

0021Peracetic acid is a highly reactive material. As an

in-use solution, it is not very stable and will react with

organic materials. Peracetic acid may attack plant

materials, such as rubber gaskets, and at higher con-

centrations, corrosion may be a problem.

0022Peracetic acid has a wide antimicrobial spectrum,

which includes bacterial spores and viruses. This ac-

tivity is fast and is maintained at temperatures lower

than ambient.

0023Hydrogen peroxide Hydrogen peroxide (H

)

was introduced as a disinfectant in 1887. It is supplied

in solution, which has a tendency to decompose:

CLEANING PROCEDURES IN THE FACTORY/Types of Disinfectant 1383

! 2H

O þ O

Manual use of hydrogen peroxide is not recom-

mended, but it is used in spray applications such as

aseptic packaging. Hydrogen peroxide is both bac-

tericidal and fungicidal. Some bacteria and fungi are

less sensitive because of catalase activity, which des-

troys H

. Hydrogen peroxide is slow-acting, so

that a long contact time or elevated temperature is

required for effective disinfection.

Nonoxidizing Disinfectants

0024 Quaternary ammonium compounds Quaternary

ammonium compounds (QACs) were first introduced

in 1917 and are probably the best known cationic

surface-active agents. Their general formula is as

follows:

−

X is usually a halide but sometimes a sulfate ion. R

, and R

may be a variety of alkyl or aryl

groups.

0025 QACs are generally poor detergents but good wet-

ting agents. In solution, they ionize to produce a

cation, the substituted nitrogen part of the molecule,

which provides the surface-active property. The

length of the carbon chain in the R groups affects

the disinfectant ability; usually, C

to C

are the

most effective.

0026 The surface-active nature of these molecules tends

to make them too high-foaming for CIP use, but they

can be used for soak and manual cleaning at 200–

400 p.p.m. active. The optimum activity is around

neutral pH, but QACs are active between pH 3.0 and

10.0. Activity may be inhibited by water hardness.

0027 QACs are noncorrosive and are stable at in-use

dilution. Their major disadvantages are that they are

affected by organic soil and that they tend to cling to

surfaces, so that they may be difficult to rinse off,

resulting in possible taint problems.

0028 The antimicrobial range of QACs is less than that

of the oxidizing disinfectants. They are less effective

against Gram-negative bacteria than against Gram-

positive bacteria. They also have limited activity

against bacterial spores and very little activity against

viruses. To be effective against yeasts and molds, a

higher concentration is required.

0029 Biguanides Biguanides with antimicrobial activity

were first reported in 1933. The biguanides are

derivatives of guanidine, a naturally occurring sub-

stance found in vegetables such as turnips and cereals:

NNH

Biguanides are usually supplied as polymers in the salt

form, mostly as the hydrochloride. Optimum activity

liesbetweenpH3.0andpH9.0.BelowpH3.0,activityis

suppressed, whilst above pH 9.0, they are precipitated.

0030They are cationic in nature but are not regarded as

surface-active. Biguanides do not foam and are, there-

fore, suitable for CIP; they may also be used for soak

and manual cleaning. They are noncorrosive but taint

may be a problem if not properly rinsed. The in-use

solution is stable but is affected by organic soil and, to

some extent, by hard water.

0031Most biguanides have equal antibacterial activity

against Gram-positive and Gram-negative microor-

ganisms. They are less effective against molds and

yeasts, and are ineffective against bacterial spores

and viruses.

0032Amphoterics Amphoterics have been in use as dis-

infectants since the early 1950s. They are based on a

substituted amino acid, usually glycerine. The term

ampholyte is often used to describe them because in

solution they ionize to produce cations, anions, or

zwitterions, depending on the pH:

RN

CH

Cð¼¼OÞ OH

Acid cation

RN

CH

Cð¼¼OÞ O



Zwitterion

R  NHCH

CH

Cð¼¼OÞ O



Alkaline anion:

Only certain amphoterics have a disinfecting ability

and surface activity. The disinfecting ability appears

to increase with the increase of basic groups.

0033Amphoterics tend to be viscousliquids that are freely

soluble in water. They are generally too high-foaming

for use in CIP, but are suitable for soak, spray, and hand

use. Amphoterics are equally effective against Gram-

negative and Gram-positive bacteria; they are less ef-

fective against yeasts and molds, and have very little

effect against bacterial spores and viruses. The opti-

mum activity lies between pH 3.0 and 9.0.

0034Properties such as soil tolerance and corrosion vary

with the amphoteric concerned. Corrosion is not

usually a problem. The in-use solution, usually

1000 p.p.m. active, is stable.

1384 CLEANING PROCEDURES IN THE FACTORY/Types of Disinfectant

0035 Acid anionics The active molecule in acid anionics

varies considerably. There are two main types: those

based on carboxylic acids, which include fatty acids

and derivatives, and those based on anionic surfac-

tants combined with mineral acid.

0036 Acid anionics tend to be formulated products with

additions to aid activity or solubility. Properties will

vary with product, but they tend to have some deter-

gent and wetting ability. The higher-foaming products

are unsuitable for CIP, so that their general use is for

spray. They are not suitable for hand use, since a pH of

2 is required for optimum antimicrobial activity.

0037 The antimicrobial activity is against Gram-

negative and Gram-positive bacteria, but they are

less effective against bacterial spores and viruses.

Certain carboxylic acid types are active against yeasts

and molds. Both types are affected by organic soil and

water hardness, but again, both properties will vary

with the product. The in-use solutions are stable.

Effluent Problems

0038 The oxidizing disinfectants are degraded very easily

by organic soil to ineffective products. Peracetic acid

and hydrogen peroxide break down to the products

that have been described earlier.

0039 The breakdown products from the halogens vary

with pH of the effluent, but in general, halide ions will

be produced. The halogens should not be mixed with

acid products, as chlorine will react with organic

chemicals to produce organo-chloro compounds,

which may be carcinogenic. The nonoxidizing disin-

fectants in modern products tend to consist of bio-

degradable compounds. The cationic products will

adsorb on to organic material. The biguanides are

incompatible with alkaline chemicals and will form

a precipitate. (See Effluents from Food Processing:

On-Site Processing of Waste; Disposal of Waste

Water; Composition and Analysis.)

Analysis of Disinfectants in Waste Water

0040 Obviously, detection will tend to depend on the con-

centration of disinfectant present. The oxidizing dis-

infectants are unlikely to be detected. Halide ions can

be detected but cannot be identified as coming from

the disinfectant.

0041 Using an available chlorine probe, chlorine may

be detected up to 200 p.p.m., but because of the

presence of organic material and other chemicals,

the presence of available chlorine may not be detected.

As with chlorine, available iodine can be detected using

a probe, but iodine is converted very quickly to iodide.

The breakdown products of peracetic acid and hydro-

gen peroxide are unlikely to be detected.

0042For the quaternary ammonium compounds, the

biguanides and the amphoterics, it would be neces-

sary to know the specific active molecule to be able to

quantify these activities in effluent. The active content

could then be determined by HPLC.

0043Acid anionics can be detected in the effluent by

determining the anionic content.

Comparison with Steam

0044There is no chemical suitable for use as a disinfectant

in the food factory that can compete with steam. It

is effective against bacteria, molds, yeasts, bacterial

spores, and viruses. It is not affected by soil and hard

water. There are no corrosion or stability problems,

and it leaves no residues. The drawbacks are that it

cannot be used with heat-sensitive plant materials,

and it needs careful use to avoid human contact.

See also: Effluents from Food Processing: On-Site

Processing of Waste; Disposal of Waste Water;

Composition and Analysis; Spoilage: Bacterial Spoilage;

Molds in Spoilage; Yeasts in Spoilage