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

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systems. In essence, these contentions may be sum-

marized as follows:

0011 The long-term survival of a system will depend on

how well it ‘interacts’ with its environment, that is to

say, how efficiently it acquires appropriate inputs

and how ideally the output it produces match the

current and potential demands of the environment.

0012 The efficiency with which a system works, and

therefore thrives, will depend on ensuring that its

subsystems work harmoniously towards common

goals that contribute to, and are congruent with,

the objective/s of the organization.

Catering systems, therefore, have been defined either

in terms of the markets that they serve, that is against

the context of their environment, or in terms of the

differentiation in their internal processes or subsys-

tems. There follows a brief summary of the classifica-

tions that can be applied to catering systems in

relation to these perspectives.

Catering Systems Defined in Terms of

Their External Environment

0013 Catering organizations, as with all ‘systems,’ interact

with their environment. In an ideal world, a catering

system will produce the exact outputs the ‘environ-

ment’ demands in terms of both quantitative and

qualitative requirements. A key task in managing

such systems involves matching systems output to

the requirements of the environment in such a way

as to maximize the systems potential to do work.

Thus, catering systems have typically been classified

in terms of the sector of the environment they serve.

0014The two major sectors into which catering systems

are divided are the ‘Cost Sector,’ which, broadly

speaking, incorporates all not-for-profit catering ac-

tivities, and the ‘Profit Sector,’ which includes all

profit-orientated organizations.

0015The ‘Cost Sector’ typically includes all catering

systems in the following subsectors:

0016Healthcare, e.g., hospitals;

0017Education, e.g., schools and colleges;

0018Business and Industry, e.g., staff-feeding oper-

ations;

0019Public Services, e.g., the police and armed services.

In 1996, the value of purchases (which equate with

sales) in this sector, in the UK, was almost £1.5

billion, ‘Healthcare’, ‘Education,’ and ‘Business and

Industry’ sectors each having similar values of £460–

475 million.

Feedback from

Environment (Market)

Environment

Meals

Satisfied

customers

Profit

(waste and

by-products)

Outputs

Inputs

Food

Equipment

Labor

Finance

Management

Information

(Feedforward)

Market

Information

(Feedback)

Subsystems

e.g. Process

subsystems

•

↓

•

↓

•

↓

•

↓

•

↓

•

↓

•

↓

•

Receiving

Storing

Issuing

Preparing

Cooking

Holding

Serving

Clearing

Catering system

fig0001 Figure 1 Simple model of a catering system.

976 CATERING/Catering Systems

0020 The ‘Profit Sector’ includes catering systems in the

subsectors listed below:

0021 Hotels;

0022 Restaurants;

0023 Fast Food;

0024 Cafes and Takeaways;

0025 Public Houses;

0026 Travel Organizations (e.g., on-board and in-flight

catering);

0027 Leisure Operations.

In 1996, the value of purchases in the profit sector

was over £6 billion, and sales were in excess of

£18 billion. The Hotel sector alone accounted for

£4.7 billion sales, with Public Houses being the

second largest subsector having sales just less than

£4 billion.

0028 These figures serve to confirm the economic im-

portance of catering systems to the UK economy,

which reflects a global pattern in the developed world.

Catering Systems Defined by Their

Subsystemic Differentiation

0029 Catering systems may be defined in terms of the

differences in the subsystems they contain. Subsys-

tems can be defined in many ways, depending on the

analysis being undertaken. In the example of ‘process

subsystems’ alone, the possible permutations that can

be identified mean that there are potentially innumer-

able variations in operational systems. Attempts have

been made to resolve these variations into viable

‘generic’ groups. There are essentially three major

classifications of catering systems into which the

minor ‘generic’ variations may all be fitted. These

can be summarized as follows, and their key charac-

teristics are outlined in Figure 2.

0030 ‘Cook–serve’/Integratedfood-servicesystems,where

both the preparation of food and its service are an

integral function carried out in a single operation,

and there is little delay between preparation and

food service. The majority of the catering industry

still operates conventional systems of this kind.

0031 Food-manufacturing systems, where the produc-

tion of food and meals is separated or ‘decoupled’

from the service of meals. Such systems encompass

the use of chilling and freezing methods to preserve

the food and in the past have been referred to as

‘technological catering systems.’

0032 Meals-assembly/food-delivery systems, a recent

systems development, in which little or no actual

food preparation takes place in the system and the

operation focuses on the assembly, regeneration,

and service of meals.

Cook–Serve Catering Systems

0033The cook–serve or integrated catering system repre-

sents the conventional approach to catering. These

systems operate over a short time scale with the

minimum feasible period or ‘time buffer’ between

cooking and food service (see Figure 2). Where food

is cooked to order, or produced in small batches to

suit expected demand, it is quite easy to minimize the

‘time buffer,’ but this can be more difficult where food

is made in bulk quantities for large numbers such as in

institutional food services. The period, over which

food is held hot, which, according to UK legislation,

must be at a temperature above 63



C, is largely dic-

tated by the logistics of serving individual customers

in each situation.

0034In cook–serve systems, should food need to be held

hot for any appreciable period, time- and tempera-

ture-dependent changes occur that reduce both the

sensory and nutritional properties of food. Adverse

sensory changes can affect the color, texture, and

flavor of foods. Losses in heat-labile vitamins such

as thiamin and vitamin C also occur.

0035In research, the loss of vitamin C (as measured

using the ‘Fluorimetric method’) has frequently been

used as an indicator of food quality, as its destruction

is time- and temperature-dependent and is accompan-

ied by losses in sensory qualities. The effect of differ-

ent cooking periods and hot holding times on the

retention of vitamin C in Brussels sprouts is shown

Time buffer Time buffer

Time buffer

Cooking

Preparation

Delivery of

raw materials

(Integrated)

Cook-serve

Chilling/freezing

and

storage for

days or months

Chilling/frozen

storage for

days or months

Manufacturing

(Cook−freeze/

Cook−chill/Sous-vide)

Delivery of

raw materials

Delivery of

manufactured meals

(Food delivery)

Meals Assembly

Preparation

Cooking

Short hot holding

time (mins)

Food service

Regeneration

Assembly of meals

Food service

fig0002Figure 2 Major types of catering systems.

CATERING/Catering Systems 977

in Table 1. Extended cooking times and hot holding

period cause substantial losses not only in cook–serve

systems but also in the other systems discussed.

0036 It can be imputed that cook–serve systems in many

areas of catering have their limitations. This is par-

ticularly the case in large-scale institutional catering

such as in the healthcare sector. Large hospital food-

service operations formerly using traditional cook–

serve methods and experiencing associated quality

problems owing to extended hot holding before

service, have been at the forefront of the change to

food-manufacturing and delivery systems.

Food-manufacturing Systems

0037 Food-manufacturing systems avoid prolonged hot

holding of foods as they incorporate a substantial

‘time buffer’ between cooking and food service. This

is achieved by chilling or freezing the prepared meals

followed by appropriate storage. In this case, a ‘time

buffer’ is effectively used to ‘decouple’ the production

subsystems of the operation from food assembly and

service (see Figure 2).

0038 In food-manufacturing systems, food items are pre-

pared in quantity in a large kitchen or centralized

production unit, then chilled or frozen usually in

multiportion packs, in effect preserving food until

required. Products can be regenerated in the required

amounts in a satellite kitchen, or using specialized

reheating equipment close to the point of service

(e.g., in large institutional operations) or within indi-

vidual units (e.g., in an aeroplane’s galley kitchen in

in-flight catering). This approach minimizes the time

food is actually hot-held as it should take only the

time required to serve food to customers immediately

after regeneration, which will minimize potential

deterioration.

Meals-assembly/Food-delivery Systems

0039Food-delivery systems take the concept of ‘decoup-

ling’ to a logical conclusion in that the manufacturing

subsystems are completely removed. Food products

are ‘bought in’ from specialist manufacturers produ-

cing frozen menu items for assembly and regeneration

in simple kitchens consisting essentially of reheating

equipment, or close to the consumer using specially

designed heated trolleys. These catering systems,

which do not require the traditional kitchen, may be

referred to more aptly as ‘meals assembly systems’ as

they only consist of the storage, assembly, regener-

ation, and service subsystems (see Figure 2).

0040The length of the ‘time buffer’ in these systems is

determined by the preservation technique used, being

up to 5 days for standard chilled foods and a year for

frozen foods. Thus, the time buffer decouples produc-

tion from service and potentially preserves food qual-

ity. This potential can be lost if the food is subjected

to another period of hot holding after regeneration.

UK guidelines recommend that it should take no

longer than 15 min for meals to be served after regen-

eration is complete. Table 1 shows the damaging

effect on vitamin C content if extended periods of

hot holding do occur.

0041Whilst the food-manufacturing approach aims to

improve efficiency by decoupling the major subsys-

tems, ‘meals assembly’ actually simplifies a catering

system by removing the preparation and cooking

tbl0001 Table 1 Comparison of the percentage overall losses of vitamin C in Brussels sprouts at the end of different periods of hot holding, in

four different catering systems

System Overallpercentagevitamin Closs at end of stages duringhotholding (min)

15 30 45 60 90

Cook^serve

‘Ideal’ cook–serve 17.2 26.9 * * *

‘Abused’ cook–serve 25.3 32.3 * 42.7 51.4

Cook^chill

2-day storage 34.5 41.0 50.7 * *

3-day storage 39.8 48.1 54.3 * *

4-day storage 46.6 53.6 60.0 * *

5-day storage 55.7 61.9 67.5 * *

Cook^chill sous vide

4-day storage 32.9 38.6 45.8 * *

5-day storage 32.7 41.4 48.3 * *

Meals assembly 43.8 55.1 63.8 * *

*no data available.

‘Ideal’ represents 15-min steaming.

‘Abused’ represents 30-min steaming.

From West A, Walker A and Lawson JM (1998) The effects of food processing in hospital catering systems. In: Edwards JSA (ed.) Culinary Arts and

Sciences 2. Global and National Perspectives, pp. 283–289. London: Computational Mechanics Publications.

978 CATERING/Catering Systems

subsystems completely. This allows the caterer to

focus on food service and the monitoring of food

safety and quality.

Preservation Methods in

Food-manufacturing and

Meals-assembly Catering Systems

Cook–Freeze

0042 Freezing is a reliable method of preservation as it

includes the barrier of the latent heat plateau seen in

any time/temperature graph during the thawing of

frozen food. This phase change provides a safety

factor against temperature abuse, although any par-

tially thawed foods at the surface could potentially

cause food-safety and sensory problems.

0043 A variation of this is the cook–freeze–thaw system

introduced because, once thawed, the food can be

treated as for cook–chill. However, the system can

be potentially hazardous unless the temperatures are

tightly controlled.

Cook–Chill

0044 Cook–chill systems have gained acceptance through

consumer preference for minimally processed foods.

These are, however, more susceptible to tempera-

ture abusein only having a smallbarrier to temperature

change. Precise temperature control is necessary

throughout the whole system. The time and tempera-

ture requirements currently specified under UK legis-

lation are identified in italics in Figure 3.

Sous Vide

0045 Sous vide is a specialist form of cook–chill system (see

Figure 3) in which product shelf-life is extended from

the normal 5 days up to as long as 42 days. Sous vide

cooking is semicontinuous when operated on a large

scale but discontinuous in smaller operations. There

are particular concerns that all systems employing

this method must have appropriate technical expert-

ise to ensure that all the processing equipment and

operating procedures are adequately designed so that

products receive sufficient heat treatment.

0046 Questions about food safety and quality in sous

vide operations have been raised. Food is cooked

in sealed plastic bags under a partial vacuum, which

slows the rate of heat transfer and could result

in underprocessing. This has led to concerns

that psychrotrophic pathogens, such as Listeria

monocytogenes, Yersinia enterocolitica, Clostridium

botulinum, and the like could survive. The most haz-

ardous of these is Clostridium botulinum, some

strains of which produce a toxin at temperatures

as low as 3.3



C. Although the vegetative cells of

Clostridium botulinum are destroyed by heat treat-

ment of not less than 70



C for 2 min at the coldest

spot, foods should be heated to 90



C for 10 min to

ensure destruction of spores.

0047Concerns about the safety of vacuum-packaged

and modified atmosphere-packaged products have

led the Advisory Committee on the Microbiological

Safety of Food in the UK to issue a Code of Practice

that recommends the use of additional hurdles and

the application of the HACCP technique in the manu-

facture of all such products.

0048The retention of most of the original juices within

the package after cooking has led to claims that sous

vide processed foods have enhanced sensory qualities.

This claim has not been fully supported by research

findings to date.

Further Developments in Cook–Chill

0049As there is doubt that chilled storage alone can assure

the safety of sous vide products, recent work has

focused on the formulation of products with add-

itional hurdles. This involves the combination of

several factors together, which collectively ensure

Delivery of raw

materials

Delivery of raw

materials

Delivery of raw

materials

Cook-Freeze Cook- Chill Sous Vide

Storage,

ambient, chill,

frozen

Storage,

ambient, chill,

frozen

Storage,

ambient, chill,

frozen

Preparation Preparation

Preparation

(Pre-cooking)

Portioning

Vacuum packing

Cooking

(Pasteurization)

Freezing

to −5 ⬚C within 90

mins, then to −18 ⬚C

Frozen storage

−18 ⬚C for, weeks−1 year

Chilled storage

0−3 ⬚C for 5 days

Chilling

to 0−3 ⬚C within

90 mins

Rapid chilling

Chilled storage

Distribution Distribution

Distribution

Regeneration

to 70 ⬚C for 2 mins

Regeneration

to 70 ⬚C for 2 mins

Regeneration

Food service Food service Food service

Cooking

70 ⬚C for 2 mins

Cooking

70 ⬚C for 2 mins

fig0003Figure 3 Stages involved in food-manufacturing systems.

CATERING/Catering Systems 979

the microbial safety of food, even though each hurdle

on its own might be insufficient to maintain safe food.

0050 Examples of hurdles are low water activity, low pH,

use of modified atmospheres (See Chill Foods:Effectof

Modified-atmosphere Packaging on Food Quality)

irradiation, added organic acids and protective cul-

tures. The incorporation of such adjuncts provides

hurdles to microbial growth and can also impact posi-

tively on safety, nutritional, and sensory aspects.

0051 Research indicates that cook–chill produces a

product that is inferior in sensory qualities to that

produced in cook–serve systems in ideal conditions,

but better than that produced in the nonideal or

abused situations often found in catering systems.

Meals-assembly Techniques

0052 The main stages in food delivery or meals assembly

systems are shown in Figure 2. In this type of system,

menu items are prepared and processed by food manu-

facturers to a specification prepared by a caterer. Typ-

ically, these menu items will include main courses,

vegetables, and puddings, plus accompaniments such

as sauces. The meals are chilled or frozen, and pack-

aged in bulk foil containers suitable for use in com-

mercial catering operations. After delivery to the

catering unit, food is stored appropriately until requi-

sitioned. Meals are then assembled, regenerated usu-

ally using forced-air convection ovens, and served.

0053 Meals assembly represents a radical change in

catering systems. By the year 2000, such systems

were being used by almost a fifth of UK NHS hos-

pitals as well being more widely adopted within the

profit sector, particularly by pub and fast-food oper-

ations. This type of system has proven popular in

healthcare catering, because it offers cost savings by

reducing the need for skilled labor and expensive

plant and equipment.

0054 The meals-assembly system allows the catering

manager to concentrate on food-service techniques

and monitoring methods, in particular to control time

and temperature factors. A quality-management

approach is essential for both the manager’s own oper-

ation and for their suppliers, the food manufacturers.

0055 The final quality of food produced using these new

systems is governed by the control of time–tempera-

ture parameters throughout the system. Potentially,

regeneration is the stage that can affect food quality

most adversely, as primary cooking is common to all

types of system.

Regeneration

0056 In a meals-assembly system, regeneration usually in-

volves a standard reheat cycle in which a mixed load

of chilled or frozen meals is regenerated in a specially

designed oven. This means that food can be under- or

over-heated as different foods have different thermal

characteristics. Owing to food-safety concerns food,

is often effectively overheated, with core food tem-

peratures at the end of regeneration in excess of 80



being usual. The time spent at this temperature level is

particularly detrimental to food quality, causing both

heat-labile vitamin losses and sensory losses. There is

often potential to reduce the severity of the regener-

ation process whilst still maintaining safety, yet pre-

serving sensory and nutritional quality, but reliable

control and monitoring methods are vital.

0057Various types of equipment can be used for regener-

ating assembled meals, the most common currently

being forced-air convection ovens. Forced-air convec-

tion technology gives a fast regeneration time

owing to constant air velocity and even temperature

distribution. Hot-air convection currents being

forced to circulate the oven cavity by a fan achieve

this. These currents remove the steam layer from

the surface of the food quickly and enable heat to

reach the food directly, thus causing a rapid rise in

temperature.

0058The heating effect can be enhanced further by the

incorporation of steam injection into the oven cavity.

The latent heating effect of condensing steam on

the surface of the food package promotes faster

reheating.

0059The use of microwaves in regeneration is less

common but can be successfully combined with

forced-air convection technology. Microwaves alone

are better for reheating chilled, rather than frozen,

foods because of the different absorbency of micro-

waves by ice and water, which can cause thermal

runaway, leading to hot spots and cold spots in the

product. This can still occur in chilled products be-

cause of different dielectric properties in foods of

varying compositions. (See Chill Foods: Effect of

Modified-atmosphere Packaging on Food Quality;

Chilled Storage: Principles; Attainment of Chilled

Conditions; Quality and Economic Considerations;

Microbiological Considerations.)

0060The newer systems of food manufacture and food

delivery require strict control throughout heat pro-

cessing to ensure food safety and maintain consistent

quality. New approaches to equipment design include

the application of computational fluid dynamics and

the use of model-based control design.

Food-safety Issues in Catering Systems

(

See

Food Safety)

0061Temperature control in catering systems is impera-

tive, and monitoring systems have consequently

980 CATERING/Catering Systems

been developed in recent years. Larger units can

have computer-controlled temperature-monitoring

devices, whereas smaller operators generally rely on

making manual checks and keeping manual records.

0062 Failure to control time and temperature remains

a problem responsible for the majority of food-

poisoning cases caused by the catering industry. In

the UK, there is a mandatory requirement for caterers

to identify the steps in the system where hazards can

arise and put appropriate control and monitoring

measures in place. This relates to the implementation

of Hazard Analysis Critical Control Point (HACCP)

techniques. Caterers are encouraged to develop modi-

fied HACCP approaches based on the Assured Safe

Catering methods, but this is expected to be a slow

process that will take place over several years. (See

Hazard Analysis Critical Control Point.)

0063 There is a need to address the safety of individual

foods as caterers continue to cause outbreaks of food

poisoning owing to the use of contaminated fresh

shell eggs. The UK Government has recommended

that caterers should make use of heat-treated egg

products, pasteurized to eliminate Salmonella enter-

itidis.(See Salmonella: Properties and Occurrence;

Detection; Salmonellosis.)

0064 Systems used in the catering industry can be seen

as a continuum of the techniques used in the food-

manufacturing industry and therefore can employ

similar methods of control. For example, the concept

of quality management can be usefully applied. As

more food-manufacturing techniques are adopted,

and encouraged by regulatory authorities, these tech-

niques should accompany the HACCP approach so

that safety and quality issues are both addressed.

Catering Systems in Conclusion

0065 There is a need for further research to confirm claims

of improved sensory qualities, safety, and nutritional

values in food manufacturing and meals assembly

systems. Quality changes can occur rapidly, but

many variables affect the end result that is often

product-specific. The lack of control and standard-

ization in both the catering industry and experimental

methods makes comparisons between studies diffi-

cult. The fact that technological innovations in

catering systems have not introduced new methods

of food production but rather, as some have noted,

introduced systems of food preservation has not been

proven to have had a positive impact on food quality

predicted, as a matter of course.

0066 Generally cook–serve catering systems still pre-

dominate throughout the food-service industry. It

has been found that increased size, certainly in the

healthcare sector, tends to dictate whether or not

food-manufacturing systems have been adopted.

However, recent surveys have indicated that around

three-quarters of hospitals in the USA and almost the

same proportion in the UK still operate conventional

food-service systems.

0067In recent years, the emergence of food-delivery/

meals-assembly systems has offered the opportunity

for many smaller catering operations to adopt this

type of system. Whilst this development means that

catering systems can provide a wider menu with less

skilled staff and reduced equipment needs, it has been

observed that quality suffers if regeneration of prod-

ucts is poorly controlled and if the aesthetics of meals

assembly and customer service expectations are over-

looked.

0068It is pertinent to recall that the term ‘catering

system’ emerged from the application of systems

theory to the management of food-service operations.

It should not be forgotten, therefore, that the systems

approach is ‘holistic,’ and that any innovation that

affects one or more subsystems will also affect the rest

of the system, its inputs, and the efficiency and effect-

iveness with which it produces its outputs.

See also: Chilled Storage: Principles; Chill Foods: Effect

of Modified-atmosphere Packaging on Food Quality;

Chilled Storage: Packaging Under Vacuum; Food

Poisoning: Classification; Tracing Origins and Testing;

Statistics; Economic Implications; Food Safety; Hazard

Analysis Critical Control Point; Legislation: History;

International Standards; Additives; Contaminants and

Adulterants; Codex; Quality Assurance and Quality

Control

Further Reading

Creed PG and Reeve W (1998) Principles and applications

of sous vide processed foods. In: Ghazala S (ed.), pp.

25–51. Sous Vide and Cook–Chill Processing for the

Food Industry. Gaithersburg, MD: Aspen.

Department of Health (1999) Assured Safe Catering. A

Management System for Hazard Analysis. London: The

Stationery Office.

Department of Health and Social Security (1989) Chilled

and Frozen – Guidelines on Cook–Chill and Cook–

Freeze Catering Systems. London, UK: HMSO.

Johns N and Jones P (1999/2000) Parts 1, 2 and 3 – Systems

and management. The Hospitality Review July 1999: 43

et seq., Oct. 1999: 40 et seq., Jan. 2000: 47 et seq.

Jones P (1994) Catering Systems. In: Davis B and Lock-

wood A (eds) Food and Beverage Management – A

Selection of Readings, pp. 131–144.

Kirk D and Pine R (1998) Research in hospitality systems

and technology. International Journal of Hospitality

Management 17: 203–217.

Reeve WG and Edwards JSA (1996) Catering systems re-

visited. In: Edwards JSA (ed.) Culinary Arts and Sciences

CATERING/Catering Systems 981

Global and National Perspectives, pp. 117–127.

London: Computational Mechanics Publications.

West A, Walker A and Lawson JM (1998) The effects of

food processing in hospital catering systems. In:

Edwards JSA (ed.) Culinary Arts and Sciences 2. Global

and National Perspectives, 283–289. London: Compu-

tational Mechanics Publications.

Nutritional Implications

A G Smith and C Hunt, University of Huddersfield,

Queensgate, Huddersfield, UK

Introduction

0001 The catering or food service industry incorporates a

wide range of organizations engaged in the provision

of food products for customers within either the com-

mercial or welfare sectors (See Catering: Catering

Systems). Catering operations have been defined as:

‘establishments whose main business comes from the

sale of meals . . . refreshments . . . alcoholic drinks . . .

or the provision of accommodation.’ The following

article focuses specifically on the aspect of the provi-

sion of meals by food service systems. The process

subsystems involved in typical catering operations are

identified and the consequent nutritional implica-

tions, both positive and negative, that these processes

might have for the final food products is then

considered.

0002 It is the preparation and cooking of raw food

ingredients that renders the nutritional benefit of

food available to the consumer. In this sense,

the food service system may be seen as both positive

and necessary for the acquisition of necessary nutri-

tion by human consumers within today’s society,

where an increasing number of meals are consumed

outside the domestic setting. However, there are

many opportunities for an inadequately managed

food service system to contribute to the avoidable

deterioration of the nutritional content of food items.

General Nutritional Considerations

0003 Nutrients can be subdivided into macronutrients

(fats, protein, and carbohydrate) and micronutrients

(minerals and vitamins).

0004 Macronutrients are relatively stable during storage

and heat processing. Commodities such as meats and

dairy products provide macronutrients such as pro-

teins and fats. They may also provide fat-soluble

vitamins. These nutrients are relatively stable, al-

though they can be broken down by certain activities,

such as the natural digestive process, whereby they

can be utilized by the body.

0005Cereal products are key sources of carbohydrate in

the diet. Processed cereal products such as pasta and

breads hence are also a major provider of this essen-

tial energy fuel. Carbohydrates are relatively stable

and, if commodities such as those outlined are

stored and handled correctly, then little deterioration

should occur whilst the products are processed by a

food production or service system.

0006Of the micronutrients, minerals, which occur in a

variety of foods, are heat-stable and will not be

destroyed by cooking, Nevertheless, some loss can

occur by water leaching.

0007Vitamins vary considerably in terms of stability.

The fat-soluble vitamins (A, D, E, and K) found in

meats, nuts, and yellow fats, for instance, are rela-

tively stable. The B-complex of vitamins and vitamin

C, which are largely supplied by fruit and vegetables,

are the nutrients most vulnerable to loss during

storage and processing. These water-soluble vitamins

are also generally unstable to heat and liable to

oxidation.

A Catering System – Defined in Process Terms

0008Amongst the many ways in which catering systems

can be defined (See Catering: Catering Systems), per-

haps the most useful of these, when considering the

production elements of catering, is to view a catering

system in terms of process subsystems (Figure 1).

Receipt of food supplies

Raw/part-prepared/prepared foods ordered/delivered

Storage of food (prior to requisition/use)

Dry Chilled

Chilled

Preparation

Holding

(prior to service)

Storage

(for later use regeneration)

Hot Chilled

Service of finished product

Cooking/regeneration of preprepared food

Frozen

fig0001Figure 1 Process subsystems within a typical catering

(production) system.

982 CATERING/Nutritional Implications

0009 To consider the nutritional impact on food items as

they are transformed from raw products into finished

dishes for the consumer, each process stage is dis-

cussed below.

Ordering and Receipt of Food Supplies –

Nutritional Considerations

0010 The first process undertaken by all food service

systems is generally that of ordering and receiving

the raw materials or part-processed goods that

will be used to make finished products. Whilst

there are aspects of efficiency in the undertaking of

this process that should be considered in order to

insure that foods retain their maximum nutritional

value, it is apposite to consider initially the

nutritional quality of the foodstuffs when received

by the caterer.

0011 Many factors affect the incoming nutritional value

of food materials, which may ultimately have more

impact on the final nutritional profile of manufac-

tured food products than the following prepara-

tion activities might have. These influences vary

depending on the commodity, so that animal-based

raw materials such as meats may display different

nutritional values for different reasons to plant-

derived foodstuffs such as vegetables.

0012 Key influences on the nutritional content of these

major commodity areas are listed in Table 1.

0013 In order to insure that goods received are of appro-

priate quality, it is important that food produc-

tion and service systems draw up comprehensive

purchase and product specifications. Even so, it will

not be possible to avoid the substantial effects on

nutrient values that certain natural occurrences or

agricultural practices instigate.

Receiving Procedures – Impact on Nutrition

0014 Receiving procedures for food items arriving at a

food service operation can have a negative impact

on nutritional value if not planned and executed

efficiently. All food service systems should have

procedures that incorporate staff accountability and

immediate checking and transfer to appropriate

storage facilities for foodstuffs at the time of delivery.

0015Accountability is important for retracing the chain

of events if there should be any problems with food

materials found in storage, hence a responsible

member of staff should be appointed to undertake

the receipt of deliveries.

0016If food is held at the point of receipt prior to

appropriate storage then time- and temperature-

related factors can lead to rapid onset of deterior-

ation. Foods that are not properly stored immediately

on receipt may be open to contamination or infest-

ation, leading to hygiene and food safety-related

problems and an adverse impact on nutritional value.

Nutritional Implications of Storage of Food

0017There are essentially three key forms of storage of

food items that most, if not all, food production and

service systems utilize for keeping food prior to prep-

aration into finished products. Items may be held as:

0018dry goods

0019chilled goods

0020frozen goods

Each of these categories of stored goods may be sub-

ject to nutritional deterioration whilst being held

prior to use. The amount of deterioration that takes

place will largely depend on the following factors:

0021the food item itself

0022the nature of the item’s nutritional make-up

0023the type of storage

0024the length of time it is held in storage

Given that the nutritional content for key com-

modities can vary on delivery due to many factors

whilst stored pending use, in most cases further

deterioration will be largely time- and temperature-

dependent. The higher the temperature stored and the

longer the item is held, the more the nutritional value

of some foods will decline. The likelihood that food

will exhibit nutritional deterioration depends on the

nature of the major nutrients that food contains.

0025As mentioned earlier, vitamin C is the nutrient

which is most susceptible to loss, so measurement of

the extent of its retention during storage or processing

has come to be used as an indicator of the efficiency of

food production systems. If the proportion of vitamin

C retained in the food is good, then this indicates that

the levels of the less unstable nutrients will be also be

good. (See Catering: Catering Systems.)

0026The major food commodities that supply vitamin C

are fruit and vegetables. Fruit and vegetables should

not be stored above 8



C, with optimal storage tem-

perature within the range 0–3



C. Many fruit and

tbl0001 Table 1 Factors influencing nutritional value of food

comU

modities prior to processing

Animal origin (e.g., meats) Plant origin (e.g., vegetables)

Breed/strain/genetic make-up

of animal

Variety of plant

Climate variations

Age of animal at slaughter Seasonal factors

Feedstuffs used during growth Quality of soil

Quality of grazing pasture Use and nature of fertilizers

Other seasonal variations Growing conditions

Use of growth stimulators Degree of maturity of crop

CATERING/Nutritional Implications 983

vegetable products are stored prior to delivery in a

controlled atmosphere where the environmental gas

mixture contributes to the lengthening of shelf-life.

Products delivered to food service systems are often

supplied in modified-atmosphere packaging (MAP).

MAP should be retained intact until the stocks are

issued, as the gas mixture used in the packing process

can increase shelf-life of fruit and vegetables from

between 2 and 7 days to up to 35 days, depending

on the item. The inhibition of the ripening process

and enzyme activity preserves the organoleptic qual-

ity and nutritional value of foods held in storage

pending use. (See Chill Foods: Effect of Modified

atmosphere Packaging on Food Quality.)

0027 For food items that provide a source of the rela-

tively stable nutrients, the nutritional profile of the

foods will be adversely affected if storage is inappro-

priate such that loss due to spoilage renders the food

unfit to eat. This means that the nutrient value of the

food would no longer be available for safe consump-

tion. For instance, over time poorly stored foods

which contain fats will become rancid. This will

occur more rapidly if temperatures are too high, and

the product is poorly wrapped, allowing oxidation

to occur. Protein-rich foods such as meats quickly

become subject to contamination, hence unsafe to

eat, if stored at temperatures and in conditions that

allow the establishment of bacterial colonies that

thrive on the same sources of protein as humans.

0028 In the case of carbohydrate sources, such as cereals,

grains, pasta, and flour, it is essential that these items

are kept dry and in containers that are impervious

to insect pests. The nutrient value per se will not

deteriorate but poor storage can lead to spoilage or

contamination, rendering the food unfit to eat.

Food Preparation Techniques and Impact

on Nutrient Content

0029 Many food items delivered to catering systems re-

quire preparation before they can be utilized. Fruit

and vegetables will need washing and peeling and

may be further prepared, by chopping or slicing, for

example, prior to cooking. Raw meats may require

differing amounts of preparation depending on how

much has already been done by the butchers prior to

delivery and according to what use is to be made of

the item.

0030 Whilst the purpose of preparation of foodstuffs is

either to remove any inedible parts or generally to

enhance the eating quality of the ingredient, any prep-

aration process can lead to a reduction in overall

nutritional value of the food.

0031 The process of peeling fruit and vegetables, whilst

enhancing visual appeal and possibly eating quality,

will normally result in the reduction of overall nutri-

ent content. If any proportion of the preparation

waste would originally have been edible, overall nu-

trient value will be reduced. It has also been shown

that peeling vegetables can lead to increased vitamin

loss as a result of leaching during the cooking process.

0032In the preparation of meat it is increasingly likely

that, due to healthy-eating advice, the larger propor-

tion of surface fat will be removed from raw meats

during the preparation stages. In effect, the overall

potential nutritional value of the meat is reduced by

doing this. However this might be viewed as accept-

able nutritional loss in the light of the potential

contribution this makes towards achieving healthier

diets.

0033It can be argued that the consequent improvement

in final eating quality of a product achieved by pre-

paring ingredients appropriately could result in more

of the total finished product being consumed than if

such preparation had not been undertaken. This im-

plies that good preparation may lead to more efficient

consumption of the nutritional potential of foods

items made for consumption. However, for the man-

ager of a food-manufacturing or catering operation it

is imperative that good staff training emphasizes the

importance of minimizing waste during the prepar-

ation stages in food production. This will mean

that both nutrient contents and potential profits are

preserved.

Cooking Processes and Nutritional

Implications

0034In general, cooking has the biggest nutritional impli-

cations of any single process undertaken within a

typical catering system. The impact of cooking on

nutrients varies according to the method of cookery,

the length of time food is cooked for, and the tem-

peratures employed.

0035Broadly, the shorter the cooking time and the

more quickly food is consumed after it is prepared,

the less the unstable nutrients will have declined.

However, the methods of cookery that are used in

most systems are dependent upon the nature of the

foods themselves. The nutritional implications of

the methods of cookery are briefly considered below.

Dry-Heat Cooking

0036These cooking methods are largely applicable to pro-

teinaceous foods and to certain carbohydrate

nutrient sources. Meats, poultry, and fish, as major

protein sources, can be baked, roast, or grilled, for

instance. Cakes and bread are baked, whereas pota-

toes are often baked or roasted: all these are import-

ant sources of carbohydrates.

984 CATERING/Nutritional Implications

0037 These dry-heat cooking methods generally require

quite high temperatures (150–400



C) and the period

for which heat is applied is directly related to the size

and density of the food being cooked. However, pro-

teins and carbohydrates are quite stable and efficient

cooking results in positive changes taking place

during cooking that increase the edibility and digest-

ibility of these nutrients.

0038 When carbohydrate-rich foods are dry-cooked, the

starches are turned to easily digested sugars called

dextrins which darken as they cook. This accounts

for the browning of toast and the surface of potatoes,

as dextrins caramelize, and which shows when a food

is cooked. When such foods are overcooked, the

sugars char, which can impart unpleasant visual and

flavor characteristics, making foods less palatable

and resulting in the destruction of the carbohydrates

that have been burnt. B-vitamins can also be lost in

the toasting process, e.g., toasting bread results

in considerable loss of thiamin.

Moist-Heat Cooking

0039 These methods are generally applied to:

0040 Delicate foods such as vegetables that contain a

high percentage of water in themselves, and must

be kept moist to insure that they are edible and

digestible. This also applies to delicate protein

foods, such as fish. The final eating quality of

these foods can benefit from gentle moist cooking

for a relatively short period of time.

0041 Tougher protein foods such as stewing meat and

boiling fowl, which require moderate tempera-

tures for longer times to retaining moistness and

achieve a tender, palatable product.

For vegetables this method of cookery can be prob-

lematic because they are often a source of the least

stable vitamins, such as vitamin C and B-vitamins

such as folate. Vegetables commonly lose around

half of their vitamin C content on boiling, mostly

due to the vitamin dissolving into the cooking liquor

by leaching out of the cut or peeled vegetables.

Similarly, almost a third of folate is lost on boiling.

In contrast, it has been shown that steaming

vegetables considerably reduces such losses (vitamin

C10–20%; folate 0–10%) because it involves a lot

less water so there is less opportunity for leaching to

occur.

0042 Nutritional analyses have shown that vegetables

lose considerably higher proportions of these vulner-

able vitamins when they are peeled and when they are

chopped up. New potatoes lose only about 5% of

vitamin C on boiling when their skins are left on, as

opposed to up to 50% loss when peeled. As the skin

acts as a natural barrier to vitamin leaching, caterers

should consider retaining edible peels whenever

possible during cooking. It is also advisable to min-

imize the chopping of vegetables within reason,

as whole items retain vitamins much more success-

fully because the cellular structure of the vegetables

remains intact and cell contents are less likely to leak

into the cooking liquor.

0043Although heat in combination with exposure to

oxygen in the air will result in permanent destruction

of a proportion of vitamins during the cooking of

vegetables, by far the greater amount of ‘lost’ vita-

mins will simply be dissolved into the cooking liquor.

It is for this reason that caterers should make it

common practice to incorporate cooking liquors

into stocks, sauces, and gravies wherever possible as

this will insure that such ‘lost’ vitamins are retained

for potential consumption.

0044Many vegetables also provide important carbohy-

drates and fiber in the diet. Moist cooking methods

help to gelatinize carbohydrates, which aids their

digestion. Fiber, in the form of cellulose, also needs

to be softened by such cooking to make the

vegetables more palatable. The more cellulose there

is, the longer cooking time is required. Hence carrots

need longer cooking than some delicate green vege-

tables. This has implications for the caterer who

wishes to achieve the optimum balance of color,

flavor, and digestibility, along with retention of

maximum nutritional value.

0045Delicate protein foods such as fish may be poached

or steamed to achieve moist and palatable results.

Flavors will not intensify as much as they might

during dry cooking, which effectively dehydrates

foods and hence concentrates flavor elements.

Natural mineral salts are also dissolved into the

cooking liquor and these are not only important

nutrients but also key to the development of flavor.

There may also be some minor loss of proteins into

the cooking liquor. Once again, using any resultant

stock, after cooking is complete, to make sauces to be

served with the dish will recoup the majority of these

nutrients.

0046When moist cooking methods are applied to

appropriate cuts of meat in the process of making

stews, pie fillings, or casseroles, for example, this

helps to turn the tough collagen in the meat to gelatin.

Gelatin is more easily digested because it is a soluble

protein, hence the cooking process not only improves

palatability but also makes the nutrients more readily

available to the consumer of the product. Once again,

it is imperative that the cooking liquor becomes part

of the dish, in the form of sauce or gravy, because

flavorsome, nutritionally valuable natural mineral

salts as well as some proteins will be dissolved or

suspended in it.

CATERING/Nutritional Implications 985