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

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a means of removing surplus shell eggs from the

market. Therefore, the major use of fresh eggs is in

their original form sold to consumers in shell as a

food.

Storage and Shelf-Life Problems

0006 Shell eggs are a fresh, perishable food and conse-

quently are liable to the same deterioration in quality

over a comparatively short period of time that can be

associated with any other fresh food product. The

problem in the case of eggs is increased by the fact

that the shell of the egg is porous and, therefore, the

internal contents, which represent the consumable

part, are not totally protected from the external en-

vironment. This comes about because the origins of

the egg were not as a human food but as a source

of propagation for the bird and the egg represents

a development chamber for the growing embryo.

Therefore, the need for gaseous exchange across the

shell is inbuilt into the egg via the porous nature of

the shell.

Storage Conditions

0007 The conditions under which the fresh egg is stored

will influence the rate of deterioration of its quality.

However, even the most carefully controlled storage

conditions can do no more than slow down the rate of

subsequent deterioration. Ideally, eggs should not be

stored for more than a few days, although they can

remain consumable for up to 21 days after packing.

0008 The rate of deterioration is closely related to the

loss of carbon dioxide through the shell and the con-

sequent increase in alkalinity of the albumen. At

higher temperatures the rate of carbon dioxide loss

is increased and the egg appears stale within a few

days. Lower temperatures result in a slight loss and

the structure of the egg is maintained at an acceptable

level for several weeks.

0009This tendency towards a deterioration in quality

leads to a number of problems with the storage of

hen eggs for human consumption. Quality loss mani-

fests itself primarily as the loss of moisture through

the shell. There is a breakdown of the egg albumen

(white), causing it to spread on breaking the egg, a

characteristic not popular with consumers. Essen-

tially it is the thick gel-like albumen which slowly

breaks down, resulting in more and more thin, watery

albumen. These changes, occurring in the rest of the

egg, are associated with a change in proportion of

thick to thin albumen.

0010The egg yolk becomes enlarged, flattened, and

mottled and the cushioning effect of the thick albu-

men is decreased. With advancing deterioration, the

yolk becomes detached from any remaining thick

albumen. These changes give the egg a stale appear-

ance which is unacceptable.

0011As the storage temperature is raised the rate of

quality deterioration accelerates. At a constant tem-

perature, quality loss is most rapid in the first 2 or 3

days. At high temperatures, the albumen deterior-

ation is substantial and occurs within hours of the

egg being laid. Consequently if eggs are to be stored

they must be collected frequently and placed in a low-

temperature store as soon as possible.

Egg Weight Loss

0012The porous nature of the egg shell results in egg

weight loss under storage conditions. The most im-

portant factors influencing egg weight loss are tem-

perature and humidity. As the temperature rises,

weight loss becomes increasingly rapid. Relative

humidity also influences weight loss and this effect

is particularly important at high temperatures. After

the first 3 days the weight loss of eggs stored at both a

constant temperature and constant relative humidity

is almost linear – the same amount is lost each day.

Egg Storage

0013Egg storage needs to be considered from the point of

view of short-, medium-, or long-term storage. Egg

quality deterioration and weight loss, as described

above, only become excessive when the storage tem-

perature approaches 21



C. In many countries around

the world this temperature is not achieved for pro-

longed periods of time and is therefore not a problem

in the context of short-term egg storage. If higher

temperatures are a problem, or longer-term storage

is planned, then sophisticated cooling techniques are

tbl0002 Table 2 European Community egg consumption (number per

head per year)

1994 1995 1996 1997 1998

Belgium/Luxenbourg 225 227 227 229 240

Denmark 258 254 225 244 238

Eire 151 156 130 127 122

France 253 264 263 257 252

Greece 218 212 214 214 213

Italy 218 219 221 222 225

Netherlands 173 175 175 176 178

UK 172 167 170 171 166

Germany 219 224 225 227 225

Spain 258 266 250 259 249

Portugal 158 133 145 144 142

Austria 230 230 232 241 240

Finland 168 190 177 167 165

Sweden 204 205 200 200 201

EU-15 (average) 214 217 210 211 211

Source: Anon. (1999c) Poultry World.

EGGS/The Use of Fresh Eggs 1997

needed and the procedure for egg handling is

governed by the requirements of the stored eggs.

The longer the storage period, the more precise must

be the environmental control.

0014 If the eggs are maintained at a temperature of

8–10



C and a relative humidity of 85%, the quality

deterioration and weight loss are slow. Providing

the initial egg quality is good and that only intact

and naturally clean eggs are stored, they can be

held under these permitted controlled conditions for

6–8 weeks and still remain acceptable. Once eggs

are removed from such storage conditions to an

environment compatible with that found in a super-

market, egg quality deterioration and weight loss

are rapid.

0015 Refrigeration is the only means by which eggs

can be stored for long periods of time (several

months). A temperature of 0



C and a relative humid-

ity of 85% close to the eggs is essential. Such storage

is not encouraged within the European Union (EU)

and a regulation states that eggs which have been

refrigerated in premises artificially maintained at a

temperature less than 5



C shall not be sold as class

A, first-quality eggs.

0016 A further problem associated with egg storage is

the persistent risk of condensation on the egg surface

which can result in mold growth. If warm, moist air is

allowed on to the eggs while in store or as they are

being removed from the store, condensation or

sweating will occur at certain temperature and rela-

tive humidity combinations.

0017 Within the EU eggs that have been washed also

cannot be sold as class A first-quality. This regulation

applies because of the negative effect on microbio-

logical keeping quality resulting from washing. In

some countries, particularly the USA and Australia,

egg washing is routinely carried out on all eggs pro-

duced for human consumption. Where practiced, egg

washing should be carried out to strict standards in

terms of water temperature and hygiene.

0018 In some countries eggs are sprayed with an odor-

less, colorless vegetable oil to prevent loss of mois-

ture and carbon dioxide from the egg during

storage. As summer temperatures in several coun-

tries can exceed the optimum storage temperature

for eggs for prolonged periods of time, this tech-

nique helps to prevent rapid deterioration of egg

quality but does not improve microbiological keep-

ing quality of eggs kept dry in stores. The oil is

generally applied as the eggs move from the washer

to the grader or as they move in their boxes along

the packing line. The application of the oil is by

finely calibrated spray, usually from above, and

the oil runs down the egg to give it a complete

covering.

Handling and Marketing of Fresh Eggs

0019In recent years there has been a marked change in

attitude and requirements in relation to egg marketing

which has significantly influenced the way that eggs

are handled over the last 10 years.

0020Major retail groups (supermarkets) account for

a large proportion of the sales of the eggs produced

in the UK and, consequently, the requirements laid

down by these groups very much influence the policy

of the industry as a whole within the UK. It is likely

that the market share of such retail groups will con-

tinue to increase as consumers respond to quality

assurances offered by such groups.

0021The handling policy now implemented by major

egg-marketing companies is one of getting eggs

from the point of production to the point of sale

as quickly as possible. Eggs have to be treated as

a fresh food. A typical time scale now applied

would be 48 h at most from production site to

retail outlet.

0022This means that production sites may well be dir-

ectly linked to, or be situated close to, a packing and

quality control center. Where the production facility

is not close to a packing center, or eggs have to be held

for any period of time (maximum 3 days) prior to

packing, they will be held in a short-term store con-

trollable, to provide conditions in line with those

described above, to insure the maintenance of

optimum quality standards.

0023Mechanical handling of eggs is now a feature of

any modern production and packing plant. Eggs

would be transferred from the point of laying

via narrow belts to slatted cross-conveyors capable

of carrying 150 eggs per meter run of conveyor,

moving at a speed of around 4 m min

1

. Depending

on the production facility, the conveyor would either

take the eggs directly into a grading and packing

machine or to a farm packing machine which would

place the eggs in trays containing either 20 or 30 eggs

for subsequent transfer to a plant for grading and

final packing. In the latter case the eggs would be

stacked on pallets or trollies, each holding around

3200 eggs for easy handling by forklift truck or

other means. The eggs would be transferred to the

packing plant in temperature-controlled vehicles in

most cases (Figure 1).

0024Eggs are a fragile product and are very suscepti-

ble to damage. Approximately one in 10 eggs (10%)

fails to reach the market place as a grade A, first-

quality egg, and the majority of those downgraded

eggs are substandard as a result of shell damage or

faults. Therefore, correct handling procedures at all

stages of the egg collection and handling processes are

fundamental to maintaining egg quality.

1998 EGGS/The Use of Fresh Eggs

Egg Packing

0025 On arrival at the packing plant the eggs are trans-

ferred from the main conveyor, if the production

plant is close by, or from the pallets or trollies on to

the grading and packing machine (Figure 2). The

Dutch and Americans dominate the world market

for egg-grading and packing equipment and such ma-

chines can grade and pack up to 100 000 eggs an

hour. On such machines, egg quality is assessed by

a combination of computer-controlled detection of

cracks, dirt, and internal blood spots with visual

candling involving one or two operators. This process

involves shining a light into the whole egg while

rotating it to emphasize shell faults and make some

of the contents visible to the naked eye. The eggs are

then automatically sorted into various sizes by weight

prior to packing and selling. Electronics and compu-

terization are playing an increasing role in the oper-

ation of a modern egg-grading and packing machine.

0026 The EU operates a four-weight category system

ranging from eggs weighing less than 53 g (small) up

to eggs in excess of 73 g (extra large). The weight sizes

are separated by 10 g bands, 53–63 g being medium

and 63–73 g large. The USA operates a six-grade

system with a minimum net weight per dozen as

follows: jumbo (30 oz.), extra large (27 oz.), large

(24 oz.), medium (21 oz.), small (18 oz.), and peewee

(15 oz.). In some countries, typically the Middle and

Far East, eggs are not graded into sizes prior to sale

but are sold by the kilo.

0027 A typical modern UK egg-packing station or plant

should be built to food factory specifications and

regularly inspected by its customers and DEFRA

(Department for Environment, Food and Rural

Affairs) egg inspectors, who will check for compli-

ance with EU regulations relating to egg marketing. It

would ideally be situated with no production source

further than 75 miles (120 km) away, although its

market could be several hundred miles away. Eggs

can be laid and packed within 24 h, and with the

customer within a further 24 h in recognition of the

need for a fresh product at consumer level. This re-

quires, and enables, full benefit to be made of egg

cooling and the development of a ‘cool chain’ from

producer to retailer. In the UK at least, eggs are not

displayed in cool cabinets in retail stores.

0028A modern egg-packing plant in the UK selling eggs

to major retailers could handle 800 combinations of

eggs and packaging, taking into account sizes,

brands, and pricing. A single plant could be servicing

2100 retail outlets, but only 10 major customers, and

packing some 1.6 million eggs a day. The operation,

including distribution, could require a staff of 220

working an 8-h shift 5 days a week. Five hours a

day would be spent on cleaning operations and the

maintenance of hygiene. It should of course be re-

membered that many much smaller operations exist

in any egg production industry around the world and

the standards set and achieved may vary considerably.

0029The management of a large, modern operation

needs to coordinate the supply, packing, and distribu-

tion and would depend very much on computer tech-

nology to do this. Sales information and analysis

would be produced and a rolling 5-year plan would

be maintained.

Packaging

0030Egg packaging is an important aspect of handling and

selling and represents about 50% of total packing

costs. There are many different types of egg pack-

aging, ranging from fiber trays holding 20 or 30

eggs to specific packs made from fiber, plastic, or

polystyrene, or even biodegradable materials to

comply with concerns of environmentalists. Such

packs would generally contain six, 10, 12, or 18

eggs. Niche markets, such as organic and eggs rich

in omega-3 fatty acids, have developed for shell eggs

as well as those from alternative production systems

such as free-range and barn, and the packaging will

be used to sell eggs and the egg concept (Figure 3).

fig0001 Figure 1 A temperature-controlled egg transporter. Courtesy

of Thames Valley Foods Ltd.

fig0002Figure 2 A modern egg-grading and packing machine.

Courtesy of Deans Food Group Ltd.

EGGS/The Use of Fresh Eggs 1999

Egg packs are and will be used to promote an image

giving more information on the production system

and methods. Value-added shell egg products, such

as extra fresh, can only be promoted through the

packaging design.

Eggs from Other Species

0031 Traditionally, it is the hen’s egg that is most widely

used for human consumption and around which

modern poultry breeding and egg-marketing tech-

niques have been developed. Eggs from other

species, if consumed, tend to be a specialist product

sold in exclusive restaurants or stores. A typical

example of this would be quail eggs in aspic. Turkey

eggs are not generally sold for human consumption

and are used more for breeding to produce turkey

meat for human consumption. Human consumption

of duck, goose, and pheasant eggs is negligible and

of no commercial significance today. Eggs from

waterfowl are nutritionally richer than those of do-

mestic fowls as their yolks comprise about 36% of

the egg’s total weight, compared to 30% for hens.

The consumption of duck eggs declined significantly

because of fears relating to salmonella associated

with them.

See also: Eggs: Use in the Food Industry; Structure and

Composition; Dietary Importance; Microbiology

Further Reading

Anonymous (1983) Table Egg Storage on the Farm. Leaflet

563 (revised 1983). London: MAFF Publications.

Anonymous (1988) A Guide to Using Mechanical Egg Col-

lection Systems. Springhill, Arley, Coventry: CES Potters.

Anonymous (1999a) Watt Poultry Statistical Yearbook.

Poultry International. Mount Morris, IL: Watt.

Anonymous (1999b) Diamond’s 65 years of eggs handling

success. Poultry World 153: 25.

Anonymous (1999c) A series of hard knocks. Poultry World

153: 13.

Austic RE and Nesheim MC (1990) Poultry Production,

p. 268. Lea & Febiger, Philadelphia.

Use in the Food Industry

C G Belyavin, Chris Belyavin (Technical) Ltd, Newport,

Shropshire, UK

Introduction

0001The majority of eggs produced in the world are sold in

shell for consumers to utilize in the home in trad-

itional ways or for baking. In the UK only 17% of

eggs produced go into egg products and in the USA

the figure is nearer 30%.

0002Traditionally, surplus eggs not required for the shell

egg market (normally the smaller sizes) and down-

graded eggs were turned into egg products. Today,

farmers have specific contracts to produce eggs for

further processing and any egg that is damaged

cannot be used for this purpose. There are essentially

three types of egg products: liquid, dried, or frozen,

with small markets for peeled, hard-boiled and hard-

boiled pickled eggs. The main products are used

widely in the bakery and confectionery trades along

with other industries. Figure 1 illustrates the many

uses to which processed whole eggs can be put and

also shows the way in which whole eggs can be used

to produce value-added products for the food indus-

try without going through the process of pasteuriza-

tion with or without subsequent drying. Value-added

products in the USA are often made with pasteurized

eggs.

0003World trade in liquid egg is in excess of 110 000

tonnes traded annually, some 80% of which is traded

between EU member countries. Outside of this area,

the only significant major market is Japan which

purchases around 15 000 tonnes a year. The Nether-

lands are the number one exporter closely followed

by Belgium, between them accounting for about 45%

of the total world trade.

0004Some 28 000 tonnes of dried egg are marketed

internationally. Japan and European countries are

the major buyers, with the USA being the major seller.

fig0003 Figure 3 Egg-packaging material used for the distribution and

marketing of eggs. Courtesy of Thames Valley Foods Ltd.

2000 EGGS/Use in the Food Industry

0005 When setting up an egg-processing plant it should

ideally be located close to its supply of eggs. A con-

stant supply of eggs is important in the efficient oper-

ation of the plant. The correct location enables the

eggs to arrive at the plant in good condition, thus

insuring that the resulting product is of good quality.

Liquid Egg Products

0006 The production of liquid egg products takes place

in specialist, large plants specifically designed for

the purpose. Such a plant could process in excess

of 36 million eggs a year. Mechanical equipment

is used to break the eggs automatically and, if neces-

sary, separate the egg yolk from the albumen. Such

systems can handle up to 108 000 eggs an hour

with electronic detectors to make sure that no yolk

ends up in the white at the time of separation. A

temperature of 10



C is optimum for breaking and

separating.

0007 Further processing of eggs into liquid product is not

a means of disposing of poor-quality eggs. In fact, the

increasing concern about food safety and quality

has meant that only surplus first-quality eggs and

uncracked seconds are used in breaking plants.

0008 At the time of breaking each egg will be visually

inspected, either automatically or by an operator, to

insure that no undesirable material is passed into the

further processing line. Any eggs seen to be unsuitable

will be rejected from the system at this stage and

disposed of. The contents from the broken eggs are

then passed through a sieve to remove any remnants

of shell, the chalazae, which are the strands of protein

which hold the egg yolk in place, and any other

undesirable material.

0009About 50% of total liquid egg production in the

USA is in the form of whole egg (yolk and albumen)

and some may be fortified by the addition of extra

yolk to increase the ratio of yolk to albumen over and

above that found in a normal egg. The balance is

divided between production of the separate compon-

ents, i.e., either albumen or yolk. Liquid yolks may be

sold as plain yolk or special blends such as sugared

yolk or salted yolk. Such products not only meet the

needs of specific customers but the addition of these

agents to yolk also helps to maintain the consistency

of the yolk, as without these natural additives it tends

to separate into a thin liquid surrounding a congealed

core if it is frozen. Whole egg tends to be standardized

to a solids content of 24.7%. Separate egg white

should not contain more than 0.03% yolk on a liquid

basis and yolk tends to be standardized to a solids

content of 43%.

0010In the past all these products would have been

frozen rapidly in a blast-air freezer and held in this

form until used. However, there has been a tendency

in large-scale plants to chill the products and handle

them as a fresh food, transporting them in refriger-

ated vehicles to their point of use. In this case, whole

egg and yolk liquids are chilled to 4.4



C and egg

albumen to less than 7



C. In this form the shelf-life

of the product is only about 4 days but the costs of

canning and freezing are avoided. Freezing is still

adopted for small-scale use of liquid egg.

0011Bakeries as a group are the largest users of

whole egg and separate albumen. Mayonnaise

Shell eggs

Value-added products

Scrambled egg

Egg macmuffins

Boiled eggs

Pickled eggs

Sandwich fillings

Egg roll (long egg)

Omelette mix

Egg and apple drink

Burger egg/fried egg

Pasteurized

Dried

Whole egg

Albumen

Yolk

Whole egg

Fortified

Albumen

Yolk

plain

blends

Bakeries

Restaurants

Cake mixes/meringues

Sweets

Salad dressings/mayonnaise

Icecream

Noodles

Baby food

Liquid

fig0001 Figure 1 Eggs in the food industry.

EGGS/Use in the Food Industry 2001

manufacturers and salad dressing makers use large

quantities of salted yolks and icecream makers use

sugared yolks. Noodle makers and processors of baby

foods use plain yolks.

0012 Liquid egg or egg products are pasteurized

(Figure 2) during their manufacture to prevent organ-

isms such as salmonella becoming a major health

hazard during their subsequent use and particularly

after the eggs are removed from storage. Legislation

to enforce this was introduced in the UK in 1964 and

in the USA in 1966. The pasteurization process in the

UK involves subjecting the product to a temperature

of 64.4



C (148



F) for 2.5 min for whole eggs. Com-

parable figures for the USA are 60



C (140



F) for

3.5 min. Albumen is more susceptible to heat and so

a slightly lower temperature is used, whereas the

reverse is the case for yolk, where any salmonella

is more heat-resistant. The alpha-amylase test is

routinely used to test for adequate pasteurization.

0013 Traditionally, liquid egg products were packed in

metal cans or transported by large tankers. Today,

modern packaging machinery enables the product to

be put in large plastic bags contained in rigid outers

and each bag can contain 500 kg of liquid egg which

is drained from the container by means of a tap

inserted in the bottom. The bag is then disposed of

and the outer is returned to the manufacturer to be

refilled. Product can be put into smaller cartons

(Figure 3) which can be supplied to retail outlets for

direct sale to consumers or larger cartons for supply-

ing to hospitals and institutions. This is an expensive

way of producing liquid egg because of the cost of the

packaging. In these cases, liquid whole egg would be

used for making scrambled egg and omelettes, for

example.

0014Over the last 10 years, the production of egg prod-

ucts has been seen as the way in which any decline in

egg consumption can be reversed. Consequently, a

more diverse range of products is now available,

including burger eggs, fried eggs, and meringue mix.

Freezing of Liquid Egg

0015If liquid egg is going to be frozen, to maintain a

quality product, it is important that the freezing

process should be rapid and that the frozen product

should be stored at a low temperature. Cans of chilled

egg should be subjected to an air blast at 30 to

40



C to insure total freezing within 24 h, produ-

cing a uniform product without coagulation of the

yolk. Subsequent storage should be at 10 to

20



C. (See Freezing: Operations.)

Production of Egg Powder

0016The production of dried egg products is a further step

beyond pasteurization. Spray drying is now the most

common method for producing egg powder. How-

ever, some egg white is pan-dried and some whole

egg is freeze-dried. Dried-egg products have a number

of advantages which are listed below.

0017They can be handled and stored with ease and at

low cost.

0018They are ready to use immediately with no

thawing.

0019They are easy to handle in a hygienic way.

fig0002 Figure 2 A liquid egg pasteurization plant. Courtesy of

Oasters–Fridays (Cranbrook) Ltd.

fig0003Figure 3 Liquid egg being packed into small cartons for retail

sale. Courtesy of Oasters–Fridays (Cranbrook) Ltd.

2002 EGGS/Use in the Food Industry

4.0020 They are easy to remove from the container

without scraping.

0021 No bacterial growth can occur in powder at

room temperature providing it is kept dry.

0022 There is good uniformity.

0023 There is precise control over the amount of water

used in formulation.

0024 There is no loss when used because dried egg is

usually added directly to the batch.

0025 No special transfer or storage equipment is

needed.

10.

0026 Because the moisture content is reduced from

around 74% to 2–4% by weight, there is a re-

duction in weight and volume and a concentra-

tion of food value.

A possible disadvantage of powder compared to

liquid egg is a loss of ‘fresh flavor’ and a loss of

certain functional properties such as aerating power

unless treated with nonreducing sugars prior to

heating. This, however, limits its use because of the

sweetened nature of the powder.

0027 There are now several different types of dried-egg

products available which can be summarized under

four major headings: dried egg white, dried plain

whole egg and yolk, dried blends of whole egg and

yolk with carbohydrates, and special types of dried-

egg products.

0028 The growth in egg drying is well illustrated

by reference to the USA. Prior to 1941, less than

1% of the eggs produced went to drying plants. Gov-

ernment purchases stimulated drying operations to

such an extent that 20 400 tonnes were produced

in 1941, 107 000 tonnes in 1942, 118 000 tonnes in

1943, and 146 000 tonnes in 1944. The current

annual volume is over 180 000 tonnes. A 30-dozen

case of shell eggs will yield about 18 kg of liquid

whole egg or 4.5 kg of dried product containing

2.5% moisture.

0029 The handling of shell eggs prior to drying is no

different from the handling of eggs that are to be

kept liquid. The liquid material is put through a clari-

fier to remove any bits of shell and is then screened to

remove the chalazae and vitelline membranes. Pas-

teurization is important, not only to control salmon-

ella infection, but also to preheat the liquid so as to

insure a low-moisture powder that will not show any

scorching. A typical egg-drying plant is shown in

Figure 2.

0030 The liquid egg is then pumped under pressure

of 17 250–34 500 kPa (2500–5000 lbf in

2

) to nozzles

through which it is released into a large chamber

where it immediately comes into contact with a

stream of air that has been heated to temperatures

of 120–175



C. The enormous surface area created

by atomization causes instantaneous evaporation

of most of the moisture from the egg material and

the formation of powder which falls to the floor as

a fine powder while the moist air passes on out of

the drying chamber at a temperature of 65–71



C. It

is important that the spray drier is designed so that

the product stays at relatively low temperatures

throughout the drying system and that the dried

product is removed from the hot-air stream as rapidly

as possible.

0031Modern driers produce a powder in which the

moisture content does not exceed 2%. The tempera-

ture of the powder as it leaves the drier may be 65



or higher, and this must be reduced quickly to less

than 29



C if the product is to have good keeping

qualities. Since the powder is extremely hygroscopic,

the temperature must be reduced by contact cooling

rather than by exposure to cold air. Two different

powder-cooling methods are commonly used: first

there is pneumatic conveying with cooling air and

second, mixing the powder with carbon dioxide in

the form of dry ice. After cooling, the powdered eggs

are then packed immediately in sealed containers.

Many of them are packed in carbon dioxide to

remove the oxygen and lower the pH value in order

to improve the keeping quality of the product.

0032Egg white can be dried in pans rather than through

a spray technique. Pan-dried egg white can be in the

form of flake or granular albumen or can be milled

to a powder form. This form of egg albumen tends to

have good whipping properties once reconstituted.

0033Chief users of dried-egg products are cake mix

manufacturers, sweet makers, and manufacturers of

meringue powders and, to a lesser extent, mayonnaise

makers. Most dried-egg products made for commer-

cial use are packed in polythene-lined boxes or drums.

A common pack size would contain 25 kg of product.

(See Drying: Theory of Air-drying.)

Quality of Dried-Egg Products

0034The quality of dried egg or dried-egg products can be

affected by a number of factors. Important are quality

of the eggs broken out to make the original product,

handling methods, sanitation practices, conditions

during processing, pasteurization procedures, drying,

and the conditions under which the products are held

in storage. Glucose (0.3–0.5%) is removed from

liquid egg white prior to drying by fermentation

using a yeast or bacterial culture, or by oxidation to

gluconic acid using a glucose oxidase–catalase

enzyme system. With glucose removed, dried egg

whites are completely stable. If glucose is not

removed, the product would be unstable because re-

ducing groups from the glucose would combine with

amino acids in the protein, leading to a condensation

EGGS/Use in the Food Industry 2003

reaction which would be followed by browning and

the development of insoluble proteins. There could

also be the development of off-odors and the loss of

some functional properties during storage. Plain

whole egg and yolk can be pasteurized and dried

without removal of the glucose and consequently

these are the least stable of the egg products.

0035 Physical properties important in relation to dried-

egg products are: bulk density, dispersibility, solubil-

ity, and reconstituted viscosity.

Storage of Dried-Egg Products

0036 One of the real advantages of dried-egg products is

their ease of storage. Most are relatively stable when

stored at room temperature. Dried egg whites can be

held under almost any storage conditions for an in-

definite period of time. Dried products containing

whole egg and yolk should be under refrigeration

if held for long periods of time. Some of these are

relatively stable at room temperature, particularly

those where the natural glucose has been removed

prior to drying.

Other Uses of Eggs in the Food Industry

0037 Although liquid egg and dried egg still account for the

majority of egg used in the food industry, there are

other products which have evolved during the last

10–15 years which are commercially available.

0038 The mass production of hard-boiled eggs has

developed in recent years. Normally, white eggs are

used in the process rather than brown because the

shells remove from white eggs easier than from

brown, resulting in less damage to the finished prod-

uct. In countries where brown egg production pre-

dominates, such as the UK, this means that white

eggs may have to be imported for the process from

countries such as Denmark. However, in recent years

flocks of white-egg-laying hens have been established

in the UK specifically to supply the processing industry.

0039 Again, only good-quality eggs are used in the pro-

cess so that the final product is also of good quality.

Normally in European Union countries small eggs

would be used (under 53 g) for boiling as there is little

demand for these sizes of egg in the shell egg market.

0040 The eggs are gradually boiled as they move around

a trough arrangement containing high-temperature

water, with the objective of them being hard-boiled

by the time they have completed a single circuit of the

trough. The eggs are then removed, deshelled, and

cooled. Once hard-boiled, the eggs can be used for a

number of products. They can be pickled in jars in

plain vinegar or with spices. They can be used in pies

or salads and a major use in this form is in airline

meals. Eggs damaged during the boiling or shelling

processes would not necessarily be discarded. They

can be diverted to the manufacture of sandwich fill-

ings, such as egg mayonnaise, which can be packed

into 5-kg tubs for distribution to sandwich manufac-

turers and the catering trade.

0041Problems associated with large-scale boiling of

eggs, apart from that of deshelling, include optimiz-

ing the temperature for both the boiling and cooling

processes, effluent discharges, and the prevention of

black rings occurring at the junction between the yolk

and the albumen. This is associated with the break-

down of sulfur-containing amino acids in the albumen

producing hydrogen sulfide which reacts with iron

released from the yolk to form iron sulfide.

Hygiene Measures

0042In all egg-processing plants producing egg products

for human consumption a strict code of practice

relating to hygiene is essential. Conventional egg

products must now meet strict chemical, physical,

and functional specifications which include moisture,

fat, protein, ash, glucose, reconstituted viscosity,

whipping ability, as well as functional performance

in the foods in which they are used. Also included are

microbiological standards for total plate count, coli-

form, yeast and mold, Escherichia coli, salmonella,

coagulase-positive staphylococcus, and Clostridium

perfringens.(See Clostridium: Occurrence of Clostri-

dium Perfringens.)

0043Many plants have a resident food technologist

responsible for implementation of a quality control

program using an inhouse quality control and micro-

biology laboratory. Every batch of product produced

would be tested for contamination and production

plants would be swabbed twice a week to test for

the presence of undesirable organisms within such a

program.

See also: Eggs: The Use of Fresh Eggs; Structure and

Composition; Dietary Importance; Microbiology