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

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higher (60–70



C), which may kill the yeasts and

many other bacteria.

0049 Mycotoxin formation is more sensitive to a reduc-

tion in a

than is the growth of the mold forming it.

To prevent the formation of bacterial toxins or the

development of organisms pathogenic to humans, the

food product should be dried at temperatures where

growth is unlikely to occur. At temperatures of 50



it is probably the minimum. Where some heating

below this temperature is unavoidable because of

loss of quality in the product, the period of dehydra-

tion should not exceed 4 h. Bacterial growth generally

does not occur in foods containing less than 15%

water. Foods at a

levels below 0.78–0.80 are not

hazardous. They also indicate that mold species are

generally more osmotolerant than bacterial species,

both in their ability to grow and produce toxins at

low a

levels. Staphylococcus aureus, the bacterial

species capable of growth at the lowest a

, has been

exploited in some food regulations. Foods can be

protected against microbial deterioration by keeping

their a

below a certain value. The approximate

lower limits of a

at which bacteria, yeast, and

molds can grow are 0.91, 0.88, and 0.80, respectively.

Most food-poisoning bacteria, including C. botuli-

num, Salmonella, and Shigella, are unable to grow

or produce toxins below a

of 0.95 in foods. Some

aerobic sporeforming bacteria such as Bacillus cereus

can tolerate much lower a

(0.93) and the most xer-

otolerant species, like B. subtilis, are able to develop

at a

0.90. Staphylococcus aureus is the most xero-

tolerant and toxin-producing bacterium. The limit of

growth in laboratory media is 0.86, but enterotoxin

A, which is frequently encountered in foods, is not

produced below a

of 0.88 at 25



C. Such a difference

between a

levels permitting growth and those

allowing the production of toxins is also frequent

for mycotoxins produced by toxigenic molds.

0050 As a guide to the storage stability of dried foods, the

‘alarm water content’ hasbeensuggested.Thisisthe

water content which should not be exceeded if mold

growth is to be avoided. Although drying stops growth,

it does not kill all bacteria in the foods. The ‘alarm

water’ contents for some foods are given in Table 3.

These values are equivalent to an a

of 0.7, at which

point microbiological stability can be expected.

0051Several organizations are specialized in producing

guidelines and standards for food-processing plants.

Organizations in the USA and Europe attempt to

harmonize hygienic design standards and guidelines,

facilitating international trade. Specifically, the USA-

based 3-A organization (3-A Sanitary Standards

Committees, St Paul, Minnesota, USA), NSF Inter-

national (NSF International, Ann Arbor, Michigan,

USA), and the European Hygienic Equipment Design

Group (EHEDG) (EHEDG Foundation, Brussels, Bel-

gium) have established cooperation by exchanging

staff and by participation in joint working groups.

See also: Cleaning Procedures in the Factory: Types of

Detergent; Types of Disinfectant; Overall Approach;

Modern Systems; Factory Construction: Environmental

Considerations; Materials for Internal Surfaces; Food

Poisoning: Classification; Meat: Hygiene; Metals Used

in the Food Industry; Plant Design: Basic Principles;

Designing for Hygienic Operation; Spoilage: Bacterial

Spoilage; Water Activity: Principles and Measurement;

Effect on Food Stability

Further Reading

Adams D and Agarwal D (1988) Clean-in-place system

design. Biopharm 2(6): 48–57.

Alur MD and Venugopal V (1999) Dried foods. In: Encyc-

lopedia of Food Microbiology, pp. 530–537. London:

Academic Press.

Chisti Y (1999) Modern systems of plant cleaning. In:

Encyclopedia of Food Microbiology, pp. 1806–1815.

London: Academic Press.

Curiel GJ, Van Eijk HMJ and Lelieveld HLM (1999) Risk

control of airborne contamination. In: Encyclopedia of

Food Microbiology, pp. 1816–1822. London: Academic

Press.

EHEDG Guideline no. 1 (1993) Hygienic equipment design

criteria. Trends in Food Science Technology 4: 225–229.

EHEDG Guideline no. 2 (1993) Welding stainless steel to

meet hygienic requirements. Trends in Food Science

Technology 4: 306–310.

EHEDG Guidelines no. 3 (1994) Hygienic design of equip-

ment for open processing. Trends in Food Science and

Technology 6: 305–310.

Gurakan GC and Bozoglu TF (1999) Designing for hygienic

operation. In: Encyclopedia of Food Microbiology,

pp. 1790–1794. London: Academic Press.

Hayes PR (1985) Food Microbiology and Hygiene.

London: Van Nostrand.

Hobbs BC and Roberts D (1987) Food poisoning and

food hygiene. In: Javitt R (ed.) Hygienic Design and

Operation of Food Plant, Connecticut: AVI.

tbl0003 Table 3 The ‘alarm water’ content of some foods

Foodproduct Water (%)

Dehydrated fruits 18–25

Starch 18

Dehydrated vegetables 14–20

Pulses, milk powder, dehydrated meat 15

Rice, wheat flour 13–15

Dehydrated whole eggs 10–11

Whole milk powder 8

Reproduced from Alur MD and Venugopal V (1999) Dried foods. In:

Encyclopaedia of Food Microbiology, pp. 530–537. London: Academic Press,

with permission.

1956 DRYING/Hygiene

Hyde JM (1985) New developments in CIP practices.

Chemical Engineering Progress 81(1): 39–41.

International Association of Milk, Food and Environmental

Sanitarians. 3-A Sanitary Standards. US Public Health

Service Dairy Industry Committee.

International Commission on Microbiological Specifica-

tions for Foods (1996) Microorganisms in Foods 5:

characteristics of Microbial Pathogens. Blackie Aca-

demic & Professional.

ISO/DIS14159. (1998) Safety of Machinery. Hygiene

Requirements for the Design of Machinery.

Mostert MA and Lelieveld HLM (1999) Overall approach

to hygienic processing. In: Encyclopedia of Food Micro-

biology, pp. 1802–1805. London: Academic Press.

Ramesh A (1995) CFTRI Annual Conference – CAC’95,

pp. 49–54.

Robson JN and Barnes G (1980) Hygienic Design and

Operation of Food Plant, pp. 121–124. Connecticut:

AVI.

Stewart JC and Seiberling DA (1996) Clean in place.

Chemical Engineering 102(1): 72–79.

Equipment Used in Drying

Foods

J G Brennan, The University of Reading, Reading, UK

Drying in Heated Air

0001 A wide range of equipment is used in air-drying foods,

including the following.

Cabinet or Tray Drier

0002 This is a batch drier consisting of an insulated cabinet

fitted with a fan, an air heater, and baffles to direct

the flow of the heated air between trays of food or

through perforated trays and layers of the food ma-

terial. Dampers control the intake of fresh air and the

outflow of the exhaust air. These driers vary in size

from small bench units, which house a few trays and

are used to carry out laboratory studies, to large

industrial installations which may take up to 25

large trays. In the case of industrial driers, the trays

are usually loaded on to trolleys which are wheeled

in and out of the cabinet. For large throughputs, a

number of cabinets may be used in parallel with a

staggered loading sequence. Such plants can handle

several thousand kilograms of fresh vegetables in a

24-h period. Cabinet driers are used to dry sliced and

diced vegetables and fruits, cubed or minced meat,

and many other types of food.

Tunnel Drier

0003This type of drier can handle large quantities of vege-

tables and fruits on a continuous or semicontinuous

basis. It consists of an insulated tunnel, up to 25 m

long and 2 m 2 m cross-section. Prepared food is

spread in even layers on trays which are stacked on

trolleys. When a trolley of fresh food is introduced

into one end of the tunnel a trolley of dried material

exits the other end. Heated air flows mainly between

the trays, although some throughflow may occur. In a

concurrent tunnel both the air and the fresh food

enter the tunnel at the same end, the ‘wet end,’ and

travel concurrently along the tunnel to exit at the ‘dry

end’ (Figure 1a). This design of tunnel features high

initial rates of drying. As the air moves along the

tunnel its temperature falls and it becomes more

humid. Consequently, the drying conditions at the

dry end are poor and it may be difficult to attain

low moisture contents. In the countercurrent tunnel

(Figure 1b), the air is introduced at the dry end and

travels countercurrent to the feed exiting at the wet

end. The initial drying rate is lower than that in the

concurrent design, but at the dry end the fresh, hot air

meets the almost dry food. Hence, low moisture con-

tents can be attained but there is a danger of heat

damaging the food. Two tunnels may be used in

series. The food first passes through a relatively

short concurrent tunnel and then through a longer

countercurrent tunnel. Thus, high initial drying rates

can be achieved and, by using relatively cool but dry

air in the countercurrent tunnel, low moisture con-

tents can be attained without heat damaging the food.

These features can be included in a single tunnel

(Figure 1c), known as a center exhaust tunnel. In a

cross-flow tunnel (Figure 1d), the air travels at

right angles to the direction of flow of the feed. This

facilitates uniform drying.

Conveyor or Belt Drier

0004In this type of drier the food is carried through a

drying tunnel on a moving belt made up of hinged,

perforated metal plates or wire mesh. The conveyor is

2–3 m wide and up to 50 m long. The drying air is

usually directed through the belt and layer of food,

which may be 75–150 mm deep. Usually the air

travels upwards in the early stages of drying and

downwards in the later stages. Such throughflow

driers may only be used for solid particles that

form a porous bed. The throughput per unit floor

area is much less than that of a conventional tunnel

drier. Using two or more conveyors in series, with

solids being redistributed on to the following belt,

can increase the throughput and result in more

uniform drying, compared to a single-stage drier.

DRYING/Equipment Used in Drying Foods 1957

Heater

Baffles

Exhaust air

out

Air in

Fan

Trucks in

Trucks

out

(a)

(b)

Trucks in

Exhaust air

out

Baffles

Heater

Fan

Air in

Trucks out

Exhaust air out

Heater

Air in

Trucks

out

Trucks

Air in

Heater

(c)

(d)

Trucks

Exhaust

air out

Air heaters

Air in

Trucks

out

fig0001 Figure 1 Tunnel driers: (a) concurrent; (b) countercurrent; (c) center exhaust, (d) cross-flow. Adapted from Brennan JG, Butters JR,

Cowell ND and Lilly AEV (1990) Food Engineering Operations, 3rd edn. London: Elsevier Applied Science.

1958 DRYING/Equipment Used in Drying Foods

Nevertheless, it is a relatively expensive method of

air-drying. Such a drier may be used to part-dry a

food, e.g., diced vegetables down to 10–15% mois-

ture. The final drying is carried out in less expensive

equipment, such as a bin drier.

Bin Drier

0005 This is a deep-bed, throughflow drier which is often

used to finish off products that have been partly dried

in tunnel or conveyor driers. It consists of a vessel

fitted with a perforated base. Partly dried particles are

placed in the bin to a height of up to 2 m. Dry air at

relatively low temperature passes up through the bed

of particles, at a relatively low velocity. Drying takes

place over a period of up to 36 h. Moisture migration

between particles can lead to a uniform moisture

content in the product. Large bins are fitted with

their own fan and heater. Smaller portable bins may

be filled with partly dried particles direct form the

first drier then moved and connected to a common air

supply.

Fluidized-bed drier

0006 This type of drier is being used increasingly for drying

of foods. (See Drying: Fluidized-bed Drying.)

Pneumatic or Flash Drier

0007 In this type of drier, food particles are fed into a fast-

moving stream of heated air. They are carried in the

air stream through ducting which is of sufficient

length to give the required drying time. The dry par-

ticles are recovered from the air stream by a cyclone

separator or filter. The ducting may be arranged ver-

tically, known as air-lift driers, or horizontally. Rela-

tively high air temperatures are used to reduce the

length of the ducting. Expansion chambers may be

incorporated into the ducting to facilitate control

over the air temperature. Two or more of these driers

may be used in series, with fresh air being introduced

to each stage. To reduce the length of the ducting a

closed-loop or ring drier may be used. The food par-

ticles circulate a number of times around the loop

until they reach the required moisture content. They

are then recovered from the air stream by a cyclone.

There is a continuous supply of fresh air and feed to

the drier and dried product is discharged continu-

ously. Pneumatic driers are used to dry relatively

small particles such as grains and flours and as after-

driers on spray drier installations.

Rotary Drier

0008 This consists of a cylindrical shell which rotates at an

angle to the horizontal. The feed, consisting of par-

ticulate material, is introduced at the raised end of the

shell and the product is discharged over a weir at the

lower end. The shell is fitted with flights internally. As

the shell rotates, the flights lift the material up and

then it falls down through a stream of heated air,

which may flow concurrently or countercurrently to

the movement of the material. Rotary driers are not

widely used for food dehydration. They are applied to

grain drying and removing surface moisture from

sugar and salt crystals.

Spray Drier

0009This type of hot-air drier is very widely used in the

food industry for drying liquids and slurries. (See

Drying: Spray Drying.)

Drying by Direct Contact with a Heated

Surface

0010When a wet material is placed in contact with a

heated surface, the necessary sensible and latent heat

of evaporation is supplied to the material, mainly by

conduction, and drying will take place. The general

pattern of drying is similar to that of hot-air drying.

There are two stages: an initial constant rate period

followed by a falling rate period. However, if drying

takes place at atmospheric pressure, the temperature

attained by the material will be higher than that

reached during hot-air drying, as the evaporative

cooling effect will be less. To minimize heat damage,

when drying at atmospheric pressure, the material is

applied to the hot surface in a relatively thin layer.

This results in short drying times, usually in the range

2–30 s. The drum drier is widely used for drying food

liquids and pastes at atmospheric pressure. Alterna-

tively, drying can be carried out at a pressure below

atmospheric, i.e., vacuum drying, thus reducing the

temperature at which drying takes place.

Drum, Film, or Roller Drier

0011A single-drum drier consists of a hollow metal cylin-

der rotating about a horizontal axis and heated in-

ternally, usually by steam. The feed is applied in a thin

layer to the surface of the drum. As the drum rotates,

drying takes place. The dried material is scraped off

the drum surface by a knife some two-thirds to three-

fourths of a revolution from the point of application

of the feed. The drum may dip into the trough of feed

material (Figure 2a) which boils on to the drum sur-

face. This can lead to heat damage to the feed. Alter-

natively, two unheated rollers may apply the feed to

the drum surface (Figure 2b). This method reduces

the possibility of heat damage to the material. In

the case of starchy materials, a number of rollers

may be used to apply the feed (Figure 2c). The feed

DRYING/Equipment Used in Drying Foods 1959

is introduced between the first and second roller. The

starch gelatinizes and the feed forms a rotating cylin-

der. Each of the other rollers applies a layer of the

gelatinized material to the drum surface. Up to five

rollers may be used.

0012A double-drum drier consists of two cylinders ro-

tating towards each other at the top. The feed enters

the trough between the rollers and boils on to both

drums. The clearance between the drums may be

adjusted to alter the thickness of the layer applied to

the drums. This type of drum drier is used for low-

viscosity materials that are not very heat-sensitive.

The drum diameter ranges from 15 to 150 cm and

length from 20 cm to 300 cm. The speed of rotation

ranges from 3 to 20 rpm and surface temperature

from 110 to 165



C. They are usually made of

chromium-coated cast iron or stainless steel. Potato

flakes, instant breakfast cereals, made from an oat

flour slurry, and ingredients for dried baby foods are

some of the products made by drum drying. For very

heat-sensitive materials vacuum-drum driers may be

used. The drum is enclosed in a vacuum chamber and

the pressure reduced to lower the temperature at

which drying takes place. However, these driers

have high capital and running costs and are not

widely used in the food industry.

Vacuum Shelf or Tray Drier

0013This type of drier consists of a vacuum tight chamber,

usually cylindrical and fitted with hollow shelves.

These shelves are heated internally by steam, hot

water, or some other thermal fluid which is circulated

through them. The shelves typically measure

2.0 1.5 m and the cabinet may contain up to 24 of

them. The food is placed on trays which sit on the

heated shelves. The chamber is sealed and the pres-

sure inside is reduced to 5–30 kN m

2

absolute, by

means of a condenser and vacuum pump. The shelves

are heated to 35–80



C. This type of drier can be used

for heat-sensitive liquid or solid foods. However, the

capital cost, including the condenser and vacuum

pump, is relatively high, and so are the maintenance

costs. It is only used to dry materials that can bear the

high costs of drying. It has been used for fruit juice

concentrates, chocolate and malt-based drinks, choc-

olate crumb, yeast extract, and minced cooked meat

for inclusion in ready meals or soup mixes.

Vacuum Band or Belt Drier

0014In this type of drier a continuous stainless-steel band

or a belt made up of wire mesh or hinged metal plates

moves clockwise over a heating and cooling drum,

inside a vacuum chamber (Figure 3). Additional heat

may be supplied by heated platens or radiant heaters.

The feed, which must be a liquid or paste, is applied

to the band by spraying or by means of a roller. The

cooled product is scraped from the band by means of

Feed in

Scraper

knife

Product

out

Feed in

Scraper

knife

Product

out

(a)

(b)

(c)

(d)

Feed in

Feed rolls

Drum

Knife

Product

Feed in

Scraper knife

Scraper

knife

Product

out

fig0002 Figure 2 Drum driers – different feeding arrangements: (a)

dip feed; (b) unheated roller feed; (c) multiroller feed; (d) double

drum with trough feed. Adapted from Brennan JG (1994)

Food Dehydration ^ A Dictionary and Guide. London:

Butterworth-Heinemann.

1960 DRYING/Equipment Used in Drying Foods

a knife and removed from the vacuum chamber via a

sealed conveyor or rotary valve. The pressures and

temperatures are similar to those used in the vacuum

shelf drier. The vacuum band drier is costly to pur-

chase and maintain and so is only used to dry rela-

tively expensive materials, similar to those examples

of liquid foods given above.

Drying by the Application of Radiant Heat

0015 Apart from sun or solar drying (See Drying: Drying

Using Natural Radiation), radiant energy is not

used in industry to remove water in bulk from food

materials. However, it has been used to remove

small amounts of water from granular or powder

materials.

Infrared Drier

0016 In this type of drier a moving belt or vibrating deck

conveyor carries the granular material beneath a

bank of infrared heaters. Short-wave lamps are used

for very heat-sensitive materials while long-wave bar

heaters are used for less sensitive foods. Breadcrumbs,

starches, tea, spices, cake mixes, and nuts are among

the materials dried in this way.

Drying by the Application of Microwave

Energy

0017(See Drying: Dielectric and Osmotic Drying.)

Freeze Drying

0018(See Freeze-drying: The Basic Process.)

Osmotic Drying

0019(See Drying: Dielectric and Osmotic Drying.)

See also: Drying: Drying Using Natural Radiation;

Fluidized-bed Drying; Spray Drying; Dielectric and

Osmotic Drying; Freeze-drying: The Basic Process

Further Reading

Brennan JG (1994) Food Dehydration – A Dictionary and

Guide. London: Butterworth-Heinemann.

Brennan JG, Butters JR, Cowell ND and Lilly AEV

(1990) Food Engineering Operations, 3rd edn. London:

Elsevier Applied Science.

Greensmith M (1998) Practical Dehydration, 2nd edn.

Cambridge: Woodhead.

Ducks See Poultry: Chicken; Ducks and Geese; Turkey

Stainless-steel belt

Radiant heater

Heated

drum

Cooled

drum

To vacuum system

Vacuum chamber

Scraper

knife

Feed in

Product out

fig0003 Figure 3 Vacuum band drier. From Brennan JG, Butters JR, Cowell ND and Lilly AEV (1990) Food Engineering Operations, 3rd edn.

London: Elsevier Applied Science.

DRYING/Equipment Used in Drying Foods 1961

E-numbers See Food Additives: Safety

Eating Disorders See Anorexia Nervosa; Bulimia Nervosa

EATING HABITS

H L Meiselman and R Bell, US Army Natick Soldier

Center, Natick, MA, USA

Background

0001 Eating habits refer to the wide spectrum of attitudes

and behaviors associated with eating. These areas are

sometimes comprised in the fields of study referred to

as food habits or food choice. Eating habits can be

outlined as follows: food attitudes, food acceptance,

food selection, food consumption, and food waste.

This follows the temporal sequence of eating, begin-

ning with the attitudes that lead to the selection and

consumption of food, through to what is not eaten

(i.e., wasted). This section on eating habits will follow

this temporal sequence and will end with a treatment

of meals and meals patterns, since, ultimately, food

selection results in the construction of meals that

combine all of the influences on eating habits.

Attitudes

0002 Attitudes are related to whether people eat, what they

eat, and how much they eat. Attitudes are usually

defined as psychological tendencies containing an

element of evaluation. The evaluative component

is considered to be an important part of what

constitutes an attitude. Attitudes are both long-

lasting and short-lasting. The long-lasting attitudes

are also called traits, which represent the ways in

which people differ from one another and tend to be

stable over time and over situations. Some of the

attitudes that have been considered with respect to

eating are these long-term traits. Expectations are the

attitudes that products will possess certain sensory

attributes at certain intensities or, more generally,

the beliefs that products will be liked or disliked to a

certain degree. Modern cognitive theories argue that

the effective stimulus in any situation is not solely the

physical stimulus, but rather is the relationship be-

tween the objective stimulus and the preexisting cog-

nitive basis against which the stimulus is judged. This

makes the area of food acceptance more complex,

because we need to consider the response to the actual

food as well as the expectation of that food.

Specific Attitudes and Traits

0003A number of measures, or scales, have been developed

to assess attitudes and traits toward foods. By meas-

uring these attitudes and traits, one can apply them in

research studies to learn what factors influence them

and, in turn, how they influence eating behaviors. The

measures are also valuable for segmenting consumers

into subgroups, in which different variables might

operate, or in which the same variables might operate

differently. These measures come from various fields

such as market research, social psychology, and ab-

normal psychology. Several important criteria are

involved in the assessment of such measures. In add-

ition to the usual criteria of validity and reliability,

one must examine the nature and size of the sample

on which the measure was developed and validated,

whether the measure has been used to predict specific

behaviors, and whether the measure has been tested

on diverse populations. Below are some of the major

scales being used.

0004 The Variety Seeking Tendency Scale (VARSEEK) is

a measure of the intrinsic tendency to seek variety in

the diet and was developed by van Trijp and Steen-

kamp in 1992 as a special case of general variety

seeking by consumers. The scale has eight items,

each of which is rated on a five-point scale (dis-

agree–agree). Individuals who score higher in variety

seeking tendency have shown more exploratory ten-

dencies in purchase behavior and more vicarious

exploration, and use innovativeness more than those

who score lower on the scale. Certain product char-

acteristics, such as the sensory variation between

alternatives being offered, may determine whether

the intrinsic desire for variety is expressed when

making a food selection.

0005 The Food Neophobia Scale (FNS) is a measure of

avoidance of novel foods, or foods to which people

have not previously been exposed. It consists of 10

items, five positively worded and five negatively

worded. Each is rated on a seven-point scale (agree–

disagree). This measure has been shown to be a good

predictor of an individual’s propensity to avoid foods

they have not tried previously. In addition, by pre-

senting information that reduces the uncertainty

about how a novel food might taste, those individuals

with higher levels of food neophobia become more

inclined to try that novel food. The Food Neophobia

Scale has potential application within the area of new

product development of nontraditional food items.

Variety-seeking tendency and food neophobia tend

to measure the opposites of food seeking and food

avoiding; this is reflected in their negative correlation

of approximately 0.7.

0006 Dietary restraint refers to the degree to which one

tries to control one’s eating. It is not a measure of how

well one controls eating, but whether one pays atten-

tion to eating in an attempt to control it. Dietary

restraint has received attention by obesity researchers

and others and can be measured by several different

scales. Females usually exhibit more dietary restraint

than males. The Restrained Eating Scale of the Dutch

Eating Behavior Questionnaire consists of 10 items

with a temporal response format (seldom, sometimes,

often, very often). Stunkard and Messick (1985) also

developed a dietary restraint scale as part of their

three-factor eating questionnaire, and Herman and

Polivy (1975) used a scale comprising a series of

statements that allow for the classification of a sub-

ject as being either a dieter or a nondieter. Dietary

restraint has been used extensively within obesity

research, but has broad applicability within eating

habits research and with product development aimed

at the diet-conscious eater.

0007It has been shown that measures of variety-seeking

tendency, food neophobia, and dietary restraint

are stable over long periods of time, and are thus

valuable indicators of a group’s or individual’s ten-

dencies.

Food Preferences

0008Food preferences are the evaluative attitudes that

people express toward foods. Food preferences in-

clude the qualitative evaluation of foods, and also

how much people like and dislike them. Quantitative

food preference measurement has been a part of the

field of food habits at least since the 1940s, when

the US Army undertook it for menu planning pur-

poses. These studies were summarized by Meiselman

in 1988. Of course, nonquantitative food preference

measurement has been around since any mother

asked their family what they wanted to eat. Food

preferences are usually reported either on a hedonic

scale (‘how much do you like or dislike a food?’) or

on a preferred frequency scale (‘how often do you

want to eat a food?’). The nine-point hedonic scale,

designed to measure food acceptability, is also used

for food preference measurement. (See Food Accept-

ability: Affective Methods.)

0009Food preferences have been analyzed in terms of a

number of demographic variables, including race,

gender, geography, age, taste physiology, and many

disease states. Differences in food preferences have

been reported with differences in age, gender, race,

and other variables. One of the early theories of

obesity argued that obese people had different taste

preferences than nonoverweight people. However,

this has been shown not to be the case. While gender

differences in food preferences have been known for

some time, Drewnowski and colleagues have put

these differences into a different context, arguing

that males prefer salty foods, and females prefer

sweet and fatty foods (1997).

0010One of the main differentiators of food preferences

is culture. Elizabeth Rozin has argued that different

food preferences are basically rooted in differing

flavor principles among cuisines. Flavor principles

are the unique flavor components of foods of

differing cultures. For example, Greek cuisine is char-

acterized by the combination of olive oil and lemon,

whereas southern French cuisine is characterized by

1964 EATING HABITS

olive oil and herbs. Japanese cuisine is characterized

by the use of soy sauce. These traditional flavors help

the consumer to identify culturally acceptable foods,

and the incorporation of these flavor principles can be

used to overcome neophobia to new foods.

0011 Food preference measurement can be linked to

menu planning. Beginning in the 1970s, modelers

have calculated the contribution of various meal com-

ponents to overall meal acceptability. This has usually

been done with paper and pencil tests, rather than

with actual foods and meals. The overall results of

these studies show that that the main dish in a meal

accounts for the major portion of a meal’s acceptabil-

ity, often 50% or more. Hedderly and Meiselman

(1996) used acceptance ratings of actual college

meals to conduct these regression analyses, showing

that meal components change in their contribution to

overall meal acceptance when the style of meal is

changed from full plated meals to sandwich meals to

pizza meals. Moskowitz and others have also mod-

eled food combinations, boredom in menus, and time

preference relationships in menus, trying to predict

how much consumers would like an item if they had

eaten the item recently or a long time ago.

Food Acceptance

0012 Food acceptance, or the level of liking for a particular

food, has been extensively researched and has been

covered elsewhere in this volume. (See Food Accept-

ability: Affective Methods.) In this section, we will

briefly discuss the role of food acceptance in influ-

encing eating habits.

0013 How much someone likes a food should be an

important factor in influencing the selection and con-

sumption of food, that is, eating habits. Few people

would argue with this rational assumption. However,

despite many studies of food acceptance, very few

have shown a strong relationship of acceptance with

either food choice or food consumption. This is be-

cause food consumption and food selection are ex-

tremely complex behaviors; complete models to

predict food selection and food consumption might

need dozens, hundreds, or even thousands of vari-

ables. Food acceptance is only one of these variables,

although it is probably one of the most powerful.

Another reason is that food consumption and food

selection are not always rational behaviors. In gen-

eral, people do not spend a large amount of time

thinking about what to eat at every eating occurrence,

and many other factors (availability of time and prod-

uct) may be more instrumental in driving any one set

of food selections. So, by itself, acceptance is merely a

good measure of how much someone likes a food, and

not a predictor of selection or consumption; but in

conjunction with measures of other variables, accept-

ance can be part of a series of factors that operate

together to control eating habits.

Food Selection

0014Food selection, or food choice, is the study of those

factors that influence choice. Several fields of research

have examined this relationship, including physi-

ology, psychology, economics, and consumer behav-

ior, to name a few. This chapter focuses on food

selection as being a function of the interactive com-

bination of the person, the product and the situation

in which a food selection is made. Several authors

have attempted to model the factors involved in the

complex food selection or food choice process.

0015One difficulty in studying food selection is that it is

nearly impossible to control for all factors that might

influence choice in a real food choice setting, such as

a restaurant or supermarket, or even in the home.

Therefore, many studies have tried to explain food

selection by using controlled studies in the laboratory.

The problem is, once you take away the key elements

that might come into play in a real setting, all of

which tend to confound the control of a laboratory

study, you are no longer examining the very variables

that might be the most critical in affecting selection.

There is no easy resolution to this controversy, but

one approach is to do both laboratory and natural

setting research, using the laboratory as a way of

generating hypotheses and testing relationships that

would identify salient factors influencing choice that

could easily translate to real settings, then following

up by introducing manipulations of these salient

factors in a natural choice environment.

0016A number of variables have been shown to influ-

ence food choice. Habitual behaviors can influence

food usage, in certain instances even more so than

food acceptability. Familiarity with specific foods,

obtained with prior experience, is a strong contribu-

tor to food acceptance and food selection, especially

for people who are slightly neophobic. Attitudes and

traits and expectations also influence acceptability

and choice. Persistent negative expectations or stereo-

types are important in understanding the critical

evaluations of institutional foods and other foods

that are regularly criticized such as airline food. In

addition, several of the attitudes and traits described

earlier (e.g., food neophobia, dietary restraint) also

function to drive food choice behavior.

0017A number of environmental or situational variables

have been shown to influence food selection. In-

creased effort required to obtain food leads to de-

creases in food selection of that item, and often

increased selection of another item to take its place.

EATING HABITS 1965

The presence of other people leads to increased con-

sumption, probably because meals are longer when

eaten with other people present. Food packaging, the

information contained on the package or on the food

shelf, as well as the placement of the food in relation

to other products can influence selection. Finally, the

cor, design, and visual and auditory elements of the

food selection facility can influence choice.

Food Consumption

0018 No other topic has occupied more research within

eating habits than the research devoted to measuring

food consumption. This seemingly simple question of

how much people eat and why has still not been

conclusively settled, leading to numerous books con-

taining plans for healthy nutrition and dieting. Other

sections of this book deal with the complexities of

food-intake measurement.

0019 Food acceptance or palatability has been shown to

be a major determinant of eating habits. People eat

larger meals when they are eating food that they like.

This has been demonstrated in studies of individuals

based on their own food preferences, and in studies in

which the food has been manipulated to make it less

acceptable. Palatability is a significant factor for meal

studies involving both single courses and multicourse

meals, as well as for sandwiches and snacks. The

palatability effect has been studied in adults as well

as neonates and children. Palatability not only affects

what you eat, but how you eat. More palatable meals

are eaten faster, and people take bigger bites and chew

less time with more palatable foods.

Food Waste

0020 Food waste, or the disposal of food, has received

much attention in both the sociological and economic

literature. In the former area, the study of waste is

based on the notion that we are all involved in a

world of goods in which we desire to be affiliated

with a social structure that has us participating in

the process of disposal of food in social and cultural

contexts. In economics, the research issue is the cost

of food waste in financial terms. In the context of

eating habits that we have framed in this chapter,

food waste becomes a measurement by which we

can infer food consumption, and also a measure of

food acceptance.

0021 Food waste is sometimes measured while measur-

ing consumption, because often consumption is meas-

ured as the difference between what is provided and

what is wasted. The measurement of waste is difficult

and time-consuming, because edible food waste must

be separated from inedible food waste such as bones.

This type of quantitative research has taken place in

studies of clinical nutrition and in studies of military

ration testing. In the former, subjects are offered foods

in a laboratory or clinic. Meal and edible plate waste

are analyzed using specialized instruments for esti-

mating the nutrient content of the uneaten foods.

Measures include moisture, crude protein, crude

lipid, ash, and fiber content; total carbohydrates are

then calculated by the difference between what was

offered and what remains after analysis. In military

ration testing, soldiers in the field are fed a measured

and controlled amount of food for a particular meal,

set of meals, or days. Other sources of food are con-

trolled. By weighing the food prior to consumption

and weighing the leftovers or waste, one can subtract

to obtain the weight of the food eaten. Approxima-

tions of protein, fat, carbohydrates, micronutrients,

or even particular foods, can be made based on the

weight of the disposed food.

Meals and Meal Patterns

0022The patterns of eating in humans are a function of the

combination of many, if not all, of the variables men-

tioned in this chapter. Determining exactly what

factors influence meal patterns depends upon how

one defines a ‘meal’ and a ‘meal pattern.’ This seem-

ingly simple problem is complex because the defin-

ition of a meal depends on your perspective. The

nutritionist sees meals as combinations of nutrients,

the chef sees meals as combinations of courses and

dishes, the social scientist sees meals as opportunities

for individual expression and for social interaction,

and so on. Following this, meal patterns have been

defined in several ways, including the macronutrients

or energy content in an individual’s diet, the amount

of food consumed per meal, the interval between

meals, and the presence of social interaction.

0023One of the most interesting parts of the daily meal

pattern is the breakfast, the first and smallest

meal of the day, following the longest fast of the

day. Although there is great variability from person

to person in the types of breakfasts chosen, in general,

breakfast is different in make-up from the other

meals; midday and evening meals are often composed

of meat or fish along with starch and vegetables.

Breakfast is not similarly composed. Further, break-

fast differs greatly from culture to culture. Breakfast

ranges from the often-chosen roll and coffee in South-

ern Europe to the more traditional large cooked

breakfasts of England and parts of America. Break-

fast is also the meal most often skipped, and the meal

most often eaten alone. One can question whether

sipping a coffee while walking down the street consti-

tutes a meal and a breakfast.

1966 EATING HABITS