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

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its ubiquitous use and popularity, an enormous

investment has been made to examine health issues

associated with its regular use.

Caffeine Consumption

0005 There are various vehicles for caffeine consumption:

some are internationally recognized, such as tea and

coffee, but others are only locally consumed, e.g.,

mate

in South America and miang in Thailand.

Worldwide, the average caffeine consumption is esti-

mated at 50 mg per day.

0006 The properties of caffeine have been known since

preliterate times, when its use was confined to specific

areas – those where coffee plants grew wild (e.g., Ethi-

opia), until the time of European colonization, in the

seventeenth century. At this time, caffeine-containing

products were cultivated and subsequently became

widely distributed. The combined physiological and

psychological impact of caffeine depends on the pattern

and degree of exposure to the drug. Thus, there has

been extensive investigation into the caffeine content of

widely consumed beverages and their consumption.

Caffeine Content of Beverages and Food

0007 There is a marked variation in the estimates of caf-

feine content in different beverages. This arises from

differences in:

0008 methods of preparation, e.g., methods of brewing

tea and coffee;

0009 product source, e.g., black or green tea;

0010 reference volumes; and

0011 analytical methods.

Table 1 lists standard values that are widely quoted

with respect to caffeine content.

Caffeine Consumption Studies

0012 It is estimated that at least 80% of the adult popula-

tion in the majority of countries worldwide consume

caffeine on a regular (daily) basis. Variation exists in

the nature of the caffeine vehicle. In the UK, 81% of

adults drink tea, whereas in France, 81% drink

coffee. In the USA, it is estimated that only 52.1%

drink coffee, but more soft-drink beverages are con-

sumed than in other countries.

0013Data for estimating a population’s caffeine intake

have been available from prospective and retrospect-

ive studies. In general, the former has gained more

credence, and it has been shown repeatedly that there

is a good correlation between reported caffeine intake

and subsequent appropriate measurement of caffeine

or caffeine metabolite levels. Table 2 shows the esti-

mated mean intake of caffeine in several countries.

Pharmacokinetics of Caffeine

Absorption

0014Caffeine absorption from the gastrointestinal tract is

rapid. About 90% of the caffeine in a cup of coffee is

cleared from the stomach in 20 min, although the

stomach is also able to absorb this substance. A

wide variation in the time to reach peak plasma con-

centrations has been reported in humans (i.e., 15–

120 min). However, absorption may be slowed by

the presence of food in the intestine or when large

amounts of the drug are ingested. On an empty stom-

ach, the time taken is around 40 min, with 99%

absorbed after 45 min.

Distribution

0015Once absorbed, caffeine, because of its hydrophobic

properties, can pass through all biological mem-

branes, including the blood–brain barrier. Salivary

caffeine concentrations have been shown to correlate

closely with plasma concentrations, reaching up to

85% of plasma levels.

0016After oral ingestion of 5–8mgkg

1

in humans,

the peak plasma caffeine concentration equals 8–

10 mg l

1

. From this, it can be estimated that inges-

tion of a single cup of coffee, which provides a dose of

0.4–2.5 mg kg

1

, would give a peak concentration of

0.25–2.0 mg l

1

. In normal adults, the plasma half-

life is between 3 and 7 h. Whereas there is little or no

difference with increasing adult age, premature and

full-term neonates show a markedly increased plasma

tbl0001 Table 1 Caffeine content of beverages and foodstuffs

Drink Caffeine content

Coffee

Ground roast 85 mg per 150 ml

Instant 60 mg per 150 ml

Decaffeinated 3 mg per 150 ml

Te a

Leaf or bag 30 mg per 150 ml

Instant 20 mg per 150 ml

Cola 18 mg per 180 ml

Caffeine-free cola 0

Cocoa (hot chocolate) 4 mg per 150 ml

Chocolate milk 4 mg per 150 ml

Chocolate candy 5–20 mg per 100 g

tbl0002Table 2 Estimated average daily consumption in certain

countries

Country Meanintake (mg kg

1

)

USA 4

UK 3

Denmark 7

746 CAFFEINE

half-life, owing to the lower activity of cytochrome

P450 and the relative immaturity of some elimination

pathways. This state continues for up to 12 months

but is then essentially stable throughout life.

0017 Although the clearance rate is overall similar for

men and women, it is related to the menstrual cycle,

being slower in the luteal phase (6.85 h luteal vs.

5.54 h follicular). In the third trimester of pregnancy

there is a significant prolongation of the plasma half-

life (up to 15 h). In adult males who smoke, the caf-

feine half-life is decreased by up to 50% compared

with nonsmokers.

Caffeine Metabolism

0018 Caffeine is metabolized by the cytochrome P450

enzyme system. The major process is demethylation

at the C3 position to produce paraxanthine, which

accounts for up to 80% of caffeine metabolism. The

other 24 excretory products include theophylline

(1,3-dimethylxanthine), theobromine (3,7-dimethyl-

xanthine), and both uric acid and uracil derivatives.

Many of the metabolic steps may be saturable in

humans, as the elimination half-time for caffeine

and some of its metabolites is dose-dependent. Less

than 2% of the ingested dose of caffeine is recover-

able from the urine unchanged.

Mechanism of Caffeine Action

0019 Caffeine exerts a variety of pharmacological actions

at diverse sites, both central and peripheral. Whilst

several processes have been investigated as being

responsible for these effects, the mechanism must be

activated by caffeine consumption within normal

human amounts. This effectively rules out some

hypotheses (Table 3).

0020 Thus, the general consensus now is that the only

known mechanism that is significantly affected by the

relevant doses of caffeine (i.e., able to achieve an

extracellular concentration of 10–50 mM) is binding

to adenosine receptors and competitive antagonism

of adenosine. Although the effects of caffeine on be-

havior have been well documented, understanding of

its cellular mechanisms of action remains incomplete.

0021Adenosine receptors are widely distributed

throughout the body, which befits the mechanism of

caffeine action because of the substance’s wide range

of effects. For example, adenosine causes broncho-

constriction and negative inotropic effects on the

heart, and inhibits gastric secretions, lipolysis, and

renin release, all of which are the opposite of the

effects of caffeine. Centrally mediated effects of

adenosine are also the reverse of caffeine.

0022Four distinct adenosine receptors have been identi-

fied and cloned: A

, and A

. In humans, A

and A

have been shown to be important, as the

other two are only stimulated with toxic concentra-

tions of caffeine. Whereas caffeine is equally active at

adenosine A

and A

receptors, it has been shown

recently that the stimulatory central action of caffeine

is mainly mediated through an inhibition of transmis-

sion of adenosine A

receptors.

Physiological Effects of

Caffeine – General

0023The effects of caffeine are legion. Table 4 summarizes

the effects of caffeine on the body, with the following

sections describing the physiological effects on the

functions of the cardiovascular, central nervous, and

neuroendocrine (including adrenomedullary) systems.

Psychological effects are considered separately.

Physiological Effects of Caffeine on the

Cardiovascular System

0024The effects on caffeine on the cardiovascular system

have been extensively researched in both experimen-

tal and epidemiological studies. It has generated

much interest because of the debate regarding the

tbl0003 Table 3 Mechanisms of caffeine action

Potentialmechanismof caffeine action Reference Relative caffeine

concentration required

for effectiveactivation

(1 ¼a cup of coffee)

Adenosine receptor antagonism Fredholm (1980) 1

Inhibition of phosphodiesterase 10

g-Aminobutyric acid receptor blockade Marangos et al. (1979) 20

Mobilization of intracellular Calcium McPherson et al. (1991) 500

Fredholm BB and Hedqvist P (1980) Modulation of neurotransmission by purine nucleotides and nucleosides. Biochemical Pharmacology 29(12):1635–

1643. Marangos PJ, Paul SM, Parma AM, Goodwin FK, Syapin P and Skolnick P (1979) Purinergic inhibition of diazepam binding to rat brain (in vitro). Life

Science 24(9): 851–857. McPherson PS, Kim YK, Valdivia H et al. (1991). The brain ryanodine receptor: a caffeine-sensitive calcium release channel.

Neuron 7(1):17–25.

CAFFEINE 747

involvement of caffeine in cardiovascular disease.

Experimental studies have investigated the effects

of controlled caffeine exposure, whereas epidemi-

ological studies have addressed the relationship of

caffeine to cardiovascular disease.

Caffeine and Blood Pressure

0025 The major cardiovascular effect of caffeine is periph-

eral vasoconstriction, resulting in elevated blood

pressure, which is not accompanied by an increase

in cardiac output. Acute tolerance to the pressor

response does occur in regular consumers but is

reinstated by a brief period of abstinence, as demon-

strated by the referenced studies. This may be as short

as 3 h. Other evidence has demonstrated that a second

cup of coffee induces a pressor effect, albeit dimin-

ished. Finally, ambulatory blood pressure measure-

ments on days of caffeine intake compared with

placebo days are higher in usual caffeine consumers.

Both systolic and diastolic blood pressures have been

reported as being more significantly affected by an

acute caffeine challenge.

0026 In addition, caffeine increases cardiovascular

responses to stress. This includes the pressor response

to mental or physical stress, as well as other

responses, e.g., cardiac output and forearm blood

flow. As caffeine has pressor effects, it has been rec-

ommended as a treatment for orthostatic and post-

prandial hypotension.

Caffeine and Heart Rate

0027 The effect of caffeine on heart rate is less well

defined. Consumption within normal limits has

been reported as being associated with a decrease,

an increase or no change in heart rate. Whilst

caution is advised with regard to tachyarrhythmias

induced by caffeine, this is associated with excessive

doses or underlying cardiac disease. Interestingly,

it is widely believed that caffeine is associated

with palpitations, tachycardia, and arrhythmias, by

physicians.

Physiological Effects of Caffeine on the

Central Nervous System

0028The physiological effects on the central nervous

system are manifold. These include the effects of caf-

feine on cerebral blood flow, cerebral metabolism,

and electrophysiological activity. The psychological

effects will be considered separately.

Cerebral Blood Flow

0029Caffeine causes cerebro-vasoconstriction 30 min after

ingestion, via antagonism of the vasodilatory proper-

ties of endogenous adenosine. This effect was first

demonstrated over 60 years ago. A dose of 250 mg

of caffeine causes a decrease in cerebral blood flow of

15–18% as measured by the Xenon inhalation tech-

nique. The effects of caffeine on cerebral blood flow

have been demonstrated to last for 90 min and are

independent of mood and arterial partial pressure of

carbon dioxide.

Cerebral Metabolism

0030Following caffeine administration, the stimulant

effects on the central nervous system (CNS) are asso-

ciated with changes in local rates of cerebral

energy metabolism. In rat studies, a caffeine dose of

10 mg kg

1

causes increases in the motor and limbic

systems, as well as the thalamus (specific nuclei only),

substantia nigra, ventral tegmental areas, locus

ceruleus, and raphe nuclei. These changes in glucose

utilization correlate with changes in locomotor activ-

ity in rats and other behavioral modifications. The

multiple areas of the brain that are affected by caf-

feine mean that, although the primary action of caf-

feine is to block adenosine (a neuromodulator), other

neurotransmitters such as dopamine, norepinephrine,

serotonin, acetyl choline, and glutamate are involved.

Neuroelectrophysiology

0031Caffeine is a cerebral stimulant, and thus its effects

can be measured on an electroencephalograph. The

tbl0004 Table 4 Summary of the physiological effects of caffeine on the body

Effectof caffeine

Gastrointestinal system Increases gastric acid secretion in susceptible individuals, not related to gastric ulcers

Hepatic dysfunction increases caffeine half-life

Digestive absorption of alcohol is increased when caffeine is consumed beforehand

Respiratory system Relaxes bronchial smooth muscle

Increases CNS sensitivity to carbon dioxide

Renal system Stimulates renin release

Diuresis resulting from increased glomerular filtration rate and decreased tubular reabsorption

Adipose tissue Stimulates lipolysis

Bone tissue In large amounts, coffee can contribute to a negative calcium balance in those with a low calcium intake

748 CAFFEINE

most consistent results from a number of studies is

that moderate doses of caffeine effect the decrease in

spectral power in the lower alpha and theta ranges. In

addition, P300 amplitude increases with confidence,

attention, arousal level, and reward. Such changes

have been demonstrated with caffeine consumption.

Physiological Effects of Caffeine on the

Neuroendocrine Function

0032 The effects of caffeine in humans on the endocrine

system appear to be confined to the endocrine res-

ponse to stress, especially production of catechol-

amines and cortisol, although other hormones may

be important too, e.g., growth hormone. Plasma con-

centrations and urinary excretion of epinephrine and

norepinephrine are increased by caffeine consump-

tion. Although the methods of augmentation have

not been described in detail, it has been suggested

that caffeine-stimulated release of adrenomedullary

catecholamines is mediated by peripheral sympa-

thetic nerves. Thus caffeine antagonism of adensoine

receptors may result in increased sympathetic stimu-

lation of the adrenal gland, leading to increased thy-

roxine hydroxylase activity and thus catecholamine

synthesis. Like increased adrenaline production, nor-

epinephrine synthesis is controlled centrally by sym-

pathetic outflow.

0033 Cortisol production is similarly augmented by caf-

feine and stress. This is thought to be mediated by an

increase in adrenocorticotrophin. This action could

also be partly due to caffeine’s action on prosta-

glandins. The effects of caffeine on growth hormone

and prolactin are less well defined.

Psychological Effects of Caffeine

Consumption

0034 Having previously discussed the effects of caffeine at

a receptor and neuronal level, this section discusses

the effects of caffeine on psychological responses. A

large number of functions are affected, which would

be beyond the range of this review, and so three

specific functions are considered.

Behavior

0035 Caffeine is erratically self-administered in animal

models of drug self-administration. In humans, both

self-administration and choice procedures have

shown that caffeine acts as a reinforcer. In choice

studies, subjects typically first sample caffeine or pla-

cebo and later have the opportunity to choose to self-

administer one. Caffeine is chosen in preference to

placebo in subjects with or without a prior history of

caffeine consumption and is especially marked in

those with a history of drug abuse. To date, the mech-

anism of action of caffeine on behavior in humans has

not been extensively investigated. It is likely that an

interaction between adenosine and dopamine recep-

tors is important.

Performance

0036Owing to the enormous consumption of caffeine

worldwide, there has been a vast amount of work

on the performance effects of caffeine. It is far from

clear how the benefits and drawbacks of its consump-

tion balance out. In this section, the evidence for the

psychostimulant effects of caffeine on performance is

considered, as these are widely held to be the main

benefits of caffeine use.

0037Numerous placebo-controlled studies have been

published. Although the results are varied, with

some studies showing no effect of caffeine, taken as

a whole, they confirm a psychostimulant action of

caffeine.

0038Whilst a wide spectrum of cognitive tests have been

investigated in the above studies, usually, prior ab-

stinence of caffeine was required at least overnight.

This limits the relevance to caffeine consumption in

everyday life. The problem with caffeine deprivation

prior to testing, especially for a short period, means

that symptoms of caffeine withdrawal can be

invoked. Thus, it is not possible to describe the net

effects of caffeine with these studies, especially as

caffeine withdrawal has also been shown to decrease

performance in both humans and animals. However,

evidence in this area is inconclusive. A caffeine chal-

lenge of only 70 mg with 1.5 h of caffeine deprivation

has been shown to improve simple reaction time.

0039Another standpoint in this discussion is founded

on the demonstration of improved psychomotor

performance in noncaffeine-deprived individuals. A

large (9003 subjects) correlational study showed that

there was a relationship between habitual caffeine

consumption and performance (reaction time –

simple and choice, verbal memory, and visuospatial

reasoning), even when all variables were controlled

for.

Mood

0040The effects of caffeine on mood have been studied

extensively, and the results of these studies have been

more consistent than in other areas of caffeine re-

search. Caffeine in lower doses (up to 250 mg) has

positive effects on mood in both caffeine-deprived

and caffeine-tolerant studies. From these and many

other studies, the benefits of acute caffeine ingestion

on mood include an increase in energetic, confident,

and alert feelings, as well as motivation to work,

concentrate, or socialize.

CAFFEINE 749

Caffeine Withdrawal

0041 The phenomenon of the caffeine withdrawal syn-

drome is well substantiated and characterized in

detail. Table 5 lists the symptoms identified to occur

in the caffeine-withdrawn state.

0042 It is noteworthy that the prevalence of headache in

the general population is 27%, yet only 6% coffee

drinkers and 6% tea drinkers associate headache with

omission of caffeine intake.

0043 The time course for these symptoms to develop is

short. Overnight abstinence is part of the usual pat-

tern of caffeine consumption, and it is usual for with-

drawal symptoms to develop. The symptoms increase

for 24–48 h and then begin to improve. Usually, they

have subsided by day 7. A high daily intake of caf-

feine can lead to a prolongation of the symptoms for

up to 10 days or more. This may be explained by the

fact that the rate of caffeine metabolism may vary by

13-fold throughout the population. It has been shown

that caffeine consumption is directly related to the

symptoms of caffeine withdrawal. A dose of 100 mg

of caffeine per day is sufficient for caffeine with-

drawal symptoms to occur. Three days of caffeine

consumption is required before withdrawal symp-

toms occur.

0044 Much work has been published on the subjective

effects of caffeine withdrawal, but less work has con-

sidered performance. Although psychomotor impair-

ment is not associated with up to 18 h of caffeine

deprivation, impairments have been reported in a

variety of tasks after 24 h.

0045 The above summarizes the parameters whereby

caffeine withdrawal occurs in an otherwise healthy

population. It can be so disruptive to life that in 1994,

the American Psychiatric Society included it in the

DSM IV, although only as a ‘proposed,’ rather than

an official, category.

Therapeutic Uses

0046 A number of clinical uses have been suggested for

caffeine. However, the only widespread therapeutic

use at present is stimulating apneic premature infants.

Initially, theophylline was identified to increase the

respiratory rate, but caffeine had succeeded this

because of its wider therapeutic index. Following a

loading dose of caffeine, plasma caffeine levels are

maintained carefully between 10 and 20 mg l

1

0047Other applications for caffeine include treatment

of asthma and chronic obstructive pulmonary dis-

ease, because of its bronchodilatatory effects. In add-

ition, it has been used to extend the duration of

seizure, induced by electroconvulsive therapy. Uses

in hypotension and allergic rhinitis have also been

described. Caffeine may also aid the recognition of

hypoglycemia induced by treatment of diabetes mel-

litus. Finally, caffeine is available in over-the-counter

medicines for simple analgesia, cold remedies, and

stimulatory preparations.

See also: Behavioral (Behavioural) Effects of Diet;

Cocoa: Chemistry of Processing; Production, Products,

and Use; Coffee: Green Coffee; Roast and Ground;

Instant; Analysis of Coffee Products; Decaffeination;

Physiological Effects; Hormones: Adrenal Hormones;

Thyroid Hormones; Steroid Hormones; Hypertension:

Hypertension and Diet; Tea: Types, Production, and

Trade; Chemistry; Processing; Analysis and Tasting

Further Reading

Barone J and Roberts H (1996) Caffeine consumption.

Food and Chemical Toxicology 34: 119–129.

Debry G (ed.) (1994) Coffee and Health. Paris: John Libbey

Eurotext.

Nehlig A (1998) Are we dependent upon coffee and caf-

feine? A review on human and animal data. Neurosci-

ence and Biobehavioral Reviews 23: 563–576.

Silverman K, Evans SM, Strain EC and Griffiths RR (1992)

Withdrawal syndrome after the double blind cessation

of caffeine consumption. New England Journal of Medi-

cine 327: 1109–1114.

tbl0005Table 5 Symptoms of caffeine withdrawal

Increased Decreased

Irritability Well-being

Blurred vision Desire to talk/socialize

Drowsiness/sleepiness Urge to do work-related tasks

Yawning Energy/active

Lethargy/fatigue/tiredness/

sluggishness

Contentment

Thick head Flu-like feelings

Headache

Self-confidence

Heavy feeling in arms and legs

Hot or cold spells

750 CAFFEINE

CAKES

Contents

Nature of Cakes

Methods of Manufacture

Chemistry of Baking

Nature of Cakes

S P Cauvain, Campden and Chorleywood Food

Research Association, Chipping Campden, UK

Definition

0001 The definition of cake will vary slightly in different

parts of the world but essentially the term refers to

products which are characterized by formulations

based on (wheat) flour, sugar and (whole) eggs and

other liquids (milk), to which fat or oil may be added.

The level of added liquids is such that a low-viscosity

batter is formed rather than a dough. A key difference

between cake and bread is that the former is most

commonly baked in a mold, pan, or tin in order to

contain the batter and to form a product of a given

shape. Minimal processing of the batter is required

before baking.

0002 There is no significant gluten formation in cake

batters and, indeed, cake-making technology exploits

positive steps to prevent gluten formation. Modern

cakes are produced by forming a complex emulsion

and foam – the batter – which is processed by being

heat-set. As a broad generalization, modern cake

batters can be considered as fat, or oil, in water

emulsion systems. The aqueous phase contains the

dissolved sugar and suspended flour particles. In

many batter systems air bubbles are incorporated by

entrainment in the solid fat and they are held there

rather than the aqueous phase. However, as the batter

warms during baking, the air bubbles transfer from

the fat to the aqueous-phase foam and expand. Later

in the baking process the foam sets to yield the cake

structure.

0003 The key structure-forming component of cakes is

the starch contributed by wheat flour and the modifi-

cation of its gelatinization characteristics through the

addition of sugars and high levels of liquids (egg,

milk, water).

0004 Cakes are characterized by being relatively high-

density products, typically 0.4–0.7 ml g

3

, with a

tender-eating, friable crumb, and sweet taste. Their

final moisture contents typically lie in the region of

18–28%, lower than that of bread but higher than

that of pastries, biscuits, and cookies. The organolep-

tic and mold-free shelf-life of cake products varies

according to their formulations.

A Brief History of Cake Making

0005Representations of products described as ‘cakes’ are

known from the twelfth century bc in Egypt. To what

extent the products depicted equate to our modern

view of cake is uncertain. Baking molds appear to

have been used, since many of the products take the

form of animals of the time. For example, a fried

product resembling a snake is described. The first

likely use of sweet substances in cooking/baking

appears to belong to the ancient Greeks who knew

of the special properties of the ‘sackharon’ or ‘sweet

reed’ (sugarcane) from the Indian subcontinent. The

advance of cane sugar into the Middle East was com-

plete by about 700 bc. Sugar consumption continued

to rise and spread, first with the expansion of the

Roman Empire and later throughout medieval

Europe.

0006Early cake recipes were probably based on the use

of honey and in Roman times such confections were

made for special occasions such as the Saturnalia and

the New Year’s fair. Recipe books of the time

record the addition of honey to dough to make such

cakes. In the medieval period cake recipes and their

production are recorded in many European contexts.

Access to sugarcane gradually improved with the

voyages of discovery to the east and the Americas

and the production of sweetened cakes increased

and their forms proliferated through the sixteenth,

seventeenth, and eighteenth centuries ad.

Types of Cakes

0007The term ‘cake’ is taken to include the forms listed in

Table 1 and variants thereof. Cakes may be classified

into six arbitrary categories:

0008Low-fat sponges, containing less than 5% fat.

0009High-fat sponges, containing more than 5% fat.

CAKES/Nature of Cakes 751

.0010 Low-ratio cakes, in which the levels of sugar and

liquids in the formulation are individually less than

the flour weight.

0011 High-ratio cakes, in which the levels of sugar and

liquids in the formulation are individually greater

than the flour weight.

0012 Fruited cakes, which have a proportion of dried

vine fruits, fresh fruit, nuts, or other particulate

materials in the formulation.

0013 Chocolate cakes, containing a proportion of cocoa

solids.

Some examples of typical sponge and cake formula-

tions are given in Table 1.

The Nature and Roles of the Ingredients

Used

Flour

0014 Cakes can be manufactured with most types of wheat

flour. The most important contribution of the wheat

flour is the starch, the gelatinization of which forms

the major structural component of cakes. The hy-

drated wheat flour proteins form a significantly

weaker gluten structure in cake batters than in

bread dough because of the disruptive effects of the

recipe sugars and fats in the cake formulation. In

addition, the high levels of recipe liquids produce a

low-viscosity batter which reduces the ability of the

mixing action to impart the necessary energy for

gluten formation. A protein continuum may form in

the batter and this does make a small contribution to

cake strength and gives a firmer eating quality.

0015 Most commercial cake flours are characterized by

the following key features:

0016 Particle size – improved cake quality is obtained

when the particle size is reduced below that nor-

mally obtained from a standard flour-milling pro-

cess. This is usually accomplished by regrinding the

flour or through the application of air-classification

techniques. The aim of both methods of particle

size reduction is to free the starch granules from the

enveloping protein matrix. Ideally, the maximum

particle size of cake flours should be < 90 mm.

0017Postmilling treatment – the most common forms of

treatment are exposure to chlorine gas and dry-heat

treatment. Although the two treatment methods

are quite different, the resulting change in flour

properties is quite similar–notably, they cause

changes in the hydrophobicity of the starch gran-

ules. The treatment makes the flours more suited to

the production of the high-ratio type of cake. (Note

that treatment of cake flours with chlorine gas is

not now permitted in many countries.)

Sugars and Sweeteners

0018Sugar provides sweetness in cakes but also plays a

significant role in batter aeration and structure for-

mation. The influence on structural formation comes

from the effect of the sugar solution formed in the

batter on the gelatinization temperature of the starch.

The higher the sugar concentration, the higher the

starch gelatinization temperature and therefore the

longer the time that the batter has to expand before

it sets. Figure 1 illustrates the effects of increasing

sugar level.

0019The most common sugar used in cake making is

sucrose, though glucose and other sugars may be

used. If reducing sugars are used, there is a tendency

for discoloration of the crumb to occur at higher rates

of addition.

Eggs

0020Whole egg is a common component of cakes, provid-

ing color, flavor, aeration, and structure-forming

properties. The aeration and structure-forming prop-

erties come from the proteins which are present in the

egg white. The addition of fat will interfere with the

aeration power of egg proteins.

0021Some cake types, e.g., angel cake, may be made

without the use of egg yolks. Using only the egg

white confers a white color to the final product.

Milk

0022Milk products are commonly used to provide flavor

and a source of water to dissolve the added sugar.

Dried-milk products may also be used, provided an-

other source of water is added in the recipe. Skimmed

milk powder can be used for color and flavor. The

powder should have been heat-treated before use,

otherwise it may adversely affect product volume.

The heat treatment is required to denature the globu-

lins which are present, otherwise they can interfere

with the stability of the gas bubbles in the batter and

cause loss of product volume.

tbl0001 Table 1 Examples of cake formulations

Sponge cake High-ratio

cake

Chocolate

cake

Fruited cake

Flour 100 100 100 100

Sugar (sucrose) 105 115 130 120

Fat/oil 5 35 55 50

Baking powder 3 5 5 3

Whole eggs 50 30 30 45

Milk solids 5 6 8 5

Water 65 100 120 65

Cocoa powder 25

Dried vine fruits 140

Recipes are based on 100 parts (e.g., 100 g, 100 kg, 100 lb) of flour.

752 CAKES/Nature of Cakes

Water

0023 Water may be added to dissolve the recipe sugars,

especially if liquid milk products are not used.

Fats and Oils

0024 The addition of solid fat to a cake formulation is used

to provide tender eating qualities and restrict the

potential for gluten formation. The solid fat also

aids the incorporation and stabilization of air bubbles

in the batter. Polarization microscopy shows that,

when subjected to agitation, the fat crystals align

themselves around the air bubbles, thereby entrap-

ping and stabilizing them. This is possible because

the oil fraction in the fat allows the fat crystals to

move and at the same time adhere to one another like

links in a chain. It is apparent that in such a mechan-

ism the ratio of liquid to crystalline fat and the size of

the individual crystals are very important. If oil is

used in the batter, the bubble stabilization effects

will be absent and the cake will lack volume.

0025 The crystalline form of the fat is important in pro-

moting batter aeration. The three fat polymorphs of

concern are the alpha, beta-prime and beta. Air in-

corporation in cake batters is greatest with fats in the

beta-prime form, less with the alpha form, and least

with the beta form.

Emulsifiers

0026 Emulsifiers are used to aid the incorporation and

stabilization of air bubbles in the batter, especially in

the presence of fats or oils. The most commonly used

emulsifiers for this purpose are glycerol monostearate

(GMS) and polyglycerol esters, with the former being

the more effective of the two on a weight-for-weight

basis. Both emulsifiers are commonly used in a paste

form, i.e., dispersed in water with other ingredients

which promote gel stability. Emulsifiers like GMS

may exist in a number of forms when dispersed in

water and it is important it is in the active alpha-gel

form when used for cake making.

0027Without GMS the egg protein will largely stabilize

the air bubbles and the sponge will have a reasonable

volume, but often with an area of coarse open-cell

structure in the crumb. The addition of a small level

of GMS somewhat unexpectedly produces a worse

cake, with a dip in the top surface. It is apparent

from this result that the GMS and the egg proteins

do not combine their stabilizing power. At low levels

the GMS is able to stabilize the bubbles at low tem-

peratures, but it cannot continue to do so as the

temperature rises and the bubbles expand during

baking. Further increases in the level of added GMS

eventually provide a stable batter and improved cake

quality.

Baking Powders

0028A significant proportion of the final baked cake is

air. This is a mixture of gases, partly air incorporated

during mixing, and partly carbon dioxide generated

from the action of sodium bicarbonate with a suitable

food acid. The production of carbon dioxide gas

and its release when the batter first enters the

oven is an important part of the cake expansion

mechanism. Without this extra release of gas the

batter can only expand from the temperature effect

on the air trapped in the batter and the cake will

remain small in volume. Providing an extra release

of gas produces a larger cake specific volume and

gives it a more tender eating quality. The relative

importance of mechanical and chemical aeration is

shown in Figures 2 and 3.

fig0001 Figure 1 (see color plate 14) Cakes with (left) 57.5, (middle) 86 and (right) 115% sucrose based on flour weight.

CAKES/Nature of Cakes 753

0029 The action of the baking acid on the sodium bicar-

bonate normally proceeds to completion, i.e., to re-

lease all of the carbon dioxide gas from the mixture.

The flavor of the cake is influenced by the residual

salt from the acid–base reaction. The rate at which

carbon dioxide is released from the baking powder

reaction is controlled by using acids of different types.

The most commonly used baking acids and their rates

of addition to achieve neutrality with one part of

sodium bicarbonate are:

0030 Tartaric acid, 0.89, fast reaction

0031 Potassium hydrogen tartrate (cream of tartar),

2.25, fast reaction

0032 Acid calcium phosphate (monocalcium phos-

phate), 1.25, moderately fast reaction

0033Glucono-delta-lactone, 2.10, moderately fast reac-

tion

0034Sodium acid pyrophosphate, 1.33, slow reaction

0035Sodium aluminum phosphate, 1.00, slow reaction

Other Dry Ingredients

. 0036Whey solids may be used for color and flavor. The

powder should have been heat-treated before use

otherwise it may adversely affect product volume.

0037Cocoa powder is used in the production of choc-

olate cakes. It can come in several different forms.

0038Salt may be used for flavor and improving product

mold-free shelf-life.

0039Humectants such as glycerol and sorbitol may be

used to extend product mold-free shelf-life.

fig0002 Figure 2 (see color plate 15) Cake (left) with and (right) without chemical aeration.

fig0003 Figure 3 (see color plate 16) Cake (left) with and (right) without mechanical aeration.

754 CAKES/Nature of Cakes

.0040 Dried vine fruits are used in the production of

fruited cake varieties.

0041 Candied orange and lemon peel and glace

cherries

may be used in the production of fruited and speci-

ality cakes.

0042 Dried nuts may be added to fruited and speciality

cakes.

The Importance of Recipe Balance

0043 The final quality of cakes is strongly influenced by

the proportions of the ingredients that are used in the

recipe. Since the wheat flour provides the main struc-

ture-forming component – the starch – it is common

practice to construct the recipe based on the flour

weight and express the mass of other ingredients as

‘percentage flour weight’. This method of determining

ingredient levels has the advantage that it is possible to

deduce a series of ‘rules’ by which any cake recipe can

be constructed and the causes of quality losses rectified.

0044 Typical of the rules which are applied to cake

making include the following:

0045 The level of sugar will lie between 95 and 135%

flour weight for high-ratio cakes and 65 and 95%

for low-ratio cakes.

0046 The level of water should be equal to and not

exceed 1.25 times the sugar weight.

0047 The level of fat should not exceed the level of total

egg used (i.e., solids and water combined).

0048 The level of fat should not exceed the level of sugar.

Imbalances in ingredient ratios will manifest as qual-

ity losses in the baked product. Many more

specialized rules exist whereby the level of other func-

tional ingredients, e.g., baking powder, may be deter-

mined. The range of acceptable ingredients ratios

varies according to the type, size, and shape of cake

being made.

Cake Shelf-Life

Water Activity

0049 Cakes are commonly referred to as intermediate-

moisture food products because the moisture content

of typical cake products (approximately 18–28%) is

high enough to confer soft and tender eating proper-

ties. At such moisture contents cakes are susceptible

to microbial spoilage within a few days or weeks.

However, it is the water activity of a cake product

that controls the products microbial shelf-life rather

than the moisture content alone. Examples of water

activity in cakes are given in Table 2.

0050 The formulation of the cake recipe is the main

factor which affects its water activity and thus

its microbial shelf-life. Particularly important in con-

trolling water activity is the ratio of recipe water

to the soluble materials. The latter will include salt

and sugars. In addition, some other ingredients

which do not go into solution but which have the

ability to hold water and reduce its availability for

microbial activity may be present. An example of the

latter is flour which hydrates during mixing because

of the presence of proteins and damaged starch. On

baking, the flour proteins coagulate and the starch

gelatinizes.

0051When soluble materials like salt and sugar dissolve

in water they both reduce the vapor pressure of the

solution. The potential effect of a particular ingredi-

ent depends on its individual chemistry. For example,

salt is ionic and has a great affinity for water. Sucrose

and other sugars (e.g., glucose) do not possess that

same affinity of water and so for a given weight is less

effective than salt at locking up water. The sucrose

equivalent of an ingredient is often used to identify its

likely affect on cake water activity. Some typical su-

crose equivalents for cake ingredients are given in

Table 3. The sucrose equivalent is based on a method

which assigns a value of 1 to sucrose and compares all

ingredient effects on an equal-weight basis. Thus, in

Table 3 the value for salt is 11, which indicates that,

weight for weight, salt is 11 times more effective at

lowering product water activity than sucrose. Other

materials worthy of note are glycerol four times more

effective, sorbitol twice, and dextrose monhydrate

1.4. Many ingredients are much less effective than

sucrose and therefore have values of less than one.

Spoilage Inhibitors

0052Where the microbial shelf-life of cake products is

insufficient it is common practice to add a suitable

mold inhibitor to add to the effect of product water

tbl0002Table 2 Examples of water activity in cakes

Cake product Water activityrange

High-moisture cakes, such as carrot cake 0.9–0.95

Yellow, white, chocolate, and layer cakes 0.8–0.89

Fruited cakes 0.7–0.79

Celebration cakes 0.6–0.69

tbl0003Table 3 Sucrose equivalent of some bakery ingredients

Ingredient Sucrose equivalent

Salt 11.0

Glycerol 4.0

Sorbitol solids 2.0

Dextrose monohydrate 1.4

Sucrose 1.0

Flour 0.2

CAKES/Nature of Cakes 755