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

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contain up to 4% (1,2)-a-rhamnopyranose units

which give rise to kinks. l-Arabinose, d-galactose,

and d-xylose (10–15%) are linked to the rhamnose

units forming ramified side chains which are referred

to as ‘hairy regions’ along the otherwise smooth

galacturonan backbone. If the degree of esterification

(DE) is > 50% it is referred to as high-methoxyl (HM)

pectin. Deesterified pectin with DE < 50% is pro-

duced by mild acid or alkali treatment and is referred

to as low-methoxyl (LM) pectin. If the alkali used is

ammonia, amidated pectin is formed. Pectin is soluble

in water and is most stable at pH 3– 4. At lower pH,

the glycosidic bonds are hydrolyzed. In alkaline con-

ditions the glycosidic and ester linkages are cleaved,

yielding the free acid. Both HM and LM pectins form

gels. For HM pectin (DE 60–75%) gelation occurs at

high soluble solids content (typically 50–75% sugar)

and at pH < 3.5 over a period of time. The gels are not

thermoreversible. Junction zone formation is believed

to be as a consequence of hydrophobic association

between ester groups coupled with intermolecular

hydrogen bonding between hydroxyl groups on the

galacturonan backbone. For LM pectin (DE typically

20–40%) gelation is brought about by the addition of

divalent cations, and a high solids content and low

pH are not a prerequisite. Gelation is rapid and is

thermoreversible.

0022 Pectins are mainly used for the production of jams

and jellies. High-ester pectins find widespread use in

normal jams, whereas low-ester pectins are preferred

for low-sugar jams. LM amidated pectin is used to

stabilize fruit pulp which is incorporated into prod-

ucts such as yogurt.

0023 Konjac mannan is the soluble extract of konjac

flour obtained by pulverizing the dried tuber of

Amorphophallus konjac. It is a glucomannan and

consists of a main chain of (1,4)-b-d-mannopyrano-

syl and d-glucopyranosyl units with (1,3) linked

branches approximately every 10 sugar residues.

The ratio of mannose to glucose is 1.6:1. Approxi-

mately 1 in 19 sugar residues is acetylated. Konjac

mannan forms highly viscous solutions on dissolution

in water following heating. In the presence of alkali,

thermally irreversible gels are formed as a conse-

quence of deacetylation and aggregation of the glu-

comannan chains. In Japan, konjac mannan is made

into noodles. The process involves pumping a solu-

tion of the gum through a spinneret into a hot alkaline

bath (e.g., calcium hydroxide solution) which results

in the formation of long gel threads. The gum is also

sold in blocks of gel, known as konnyaku, for use in

traditional Japanese dishes and also as a dessert jelly.

Konjac mannan has recently been approved for food

use and is now finding application as a thickener and

gelling agent. It forms thermoreversible gels with

xanthan gum and also increases the gel strength, elas-

ticity, and clarity of kappa-carrageenan gels. For both

mixtures it has been argued that the synergistic be-

havior is due to association of carrageenan and

xanthan helices with the glucomannan chains.

Galactomannan Seed Gums

0024Locust bean (or carob), tara, and guar gums are stor-

age polysaccharides obtained from the endosperms of

leguminous seeds of Ceratonia siliqua, Caesalpinia

spinosa, and Cyamopsis tetragonoloba respectively.

They have a molecular mass of the order of 10

and

consist of a linear main chain of b-(1,4)-linked d-

mannopyranosyl units with galactopyranosyl units

linked a-(1,6) to varying degrees. The mannose-to-

galactose ratio is approximately 4.5:1, 3:1, and 2:1

for locust bean, tara, and guar gums respectively. The

galactose residues are distributed nonuniformly along

the mannan chain. The presence of galactose tends to

inhibit intermolecular association between the galc-

tomannan chains, hence, whereas guar gum is readily

soluble in cold water, tara, and locust bean gums have

to be heated to high temperatures to disrupt the ag-

gregation and achieve complete dissolution. Once

dissolved, all three yield highly viscous solutions

even at 1% concentration and as a consequence

their main application is as thickeners.

0025Locust bean gum will self-associate in solution and

will form thermally irreversible gels on freezing. It is

commonly used in combination with other polysac-

charides, particularly kappa-carrageenan, since it

leads to the formation of stronger, more elastic gels,

which have improved transparency and are less prone

to undergo syneresis. Locust bean gum also forms

strong thermoreversible gels with xanthan gum. It is

believed that interaction occurs between the carra-

geenan and xanthan helices and mannose sequences

along the backbone which are devoid of galactose

residues. This model also explains why guar gum is

not as effective.

Algal Polysaccharides

0026The carrageenans are a family of sulfated galactans

obtained from red seaweeds (Rhodophyceae) where

they have a key structural function. The traditional

method of extraction is by treatment of the seaweed

with hot alkali for 10–30 h followed by precipitation

with alcohol and then drying. The three major

types are kappa-, iota- and lambda-carrageenan.

Kappa is obtained from a species of seaweed called

Euchema cottonii and occurs together with lambda-

carrageenan in Chondrus crispus. Iota-carrageenan is

obtained from E. spinosum. They differ essentially

2998 GUMS/Properties of Individual Gums

in their degree of sulfation. The idealized structure for

kappa-carrageenan is a disaccharide repeat unit

consisting of (1,3)-b-galactopyranose-4-sulfate and

(1,4)-a-3,6-anhydrogalactopyranose residues. Iota-

carrageenan differs only in that the latter residue

is sulfated at the C2 position. Lambda-carrageenan

is further sulfated and consists of (1,4)-a-galactopyr-

anose 2,6 disulfate and (1,3)-b-linked galactopyra-

nose which is 70% substituted at the C2 position.

The carrageenans are all soluble in water but whereas

lambda forms viscous solutions, kappa and iota form

thermoreversible gels. In solution the molecules

undergo a thermoreversible coil-to-helix transition

and the helices self-associate, giving rise to a three-

dimensional gel structure (Figure 2). The temperature

of gelation increases with increasing electrolyte con-

centration. It has been shown that potassium, rubid-

ium, and cesium ions specifically bind to the helical

structure of kappa-carrageenan and hence promote

helix formation and gelation at much lower concen-

trations than other electrolytes. As a consequence,

kappa-carrageenan gels are much stronger in the

presence of potassium chloride compared to, say,

sodium chloride. This ion specificity is not observed

for iota-carrageenan, which forms weaker more

elastic gels compared to kappa. This is probably due

to the fact that the increased charge on the iota-

carrageenan chains reduces the extent of helix self-

association. Self-association results in the melting

temperature being greater than the gelation tempera-

ture and this hysteresis is more pronounced in kappa-

carrageenan.

0027Kappa-carrageenan gels are more brittle and turbid

than iota-carrageenan gels and are more prone to

syneresis. As discussed above, incorporation of locust

bean gum or konjac mannan into kappa-carrageenan

gels reduces turbidity, brittleness, and syneresis and

also increases gel strength.

0028Kappa-carrageenan is widely used in dairy prod-

ucts because it interacts synergistically with kappa-

casein and prevents wheying-off. Carrageenans are

also used extensively in meat products such as cooked

hams, poultry products, and sausages because of their

ability to bind water and control the texture and

structural integrity.

0029Agarose (the major component of agar) is also

obtained from red seaweeds, notably Gelidium and

Gracilaria spp. It is a linear neutral polysaccharide

and has a similar structure to the carrageenans, con-

sisting of alternating (1,3)-b-d-galactopyranose and

(1,4)-linked 3,6-anhydro-a-l-galactopyranose units.

It dissolves in near-boiling water and gels on cooling

to <40



C. The gelation mechanism is as described

for the carrageenans but, since the agarose chains

are nonionic, extensive helix aggregation occurs,

resulting in the formation of very strong gels. The

gels show pronounced hysteresis and melt only on

heating to 80–90



C. The use of agar is far more

restricted commercially than that of carrageenan

owing to availability and cost considerations.

0030Alginate is obtained from brown seaweeds (Phyo-

phyceae) and is a linear (1,4)-linked polyuronan con-

sisting of b-d-mannuronic and a-l-guluronic acids.

The acids are present as blocks of separate or mixed

sequences along the chain depending on the seaweed

source. Macrocystis pyriferia and Ascophyllum nodo-

sum have a high mannuronic acid content (61% and

65%, respectively), whereas Laminaria hyperborea

has a high guluronic acid content (69%). Sodium

alginate dissolves readily in water to form viscous

solutions and forms thermally irreversible gels in the

presence of divalent cations (notably calcium). It is

the guluronic acid residues that are responsible for gel

formation and their proportion and distribution

along the polyuronan chain have a major influence

on the properties of the gels produced. Adjacent dia-

xially linked guluronic acid residues form a cavity

which acts as a binding site for cations which interact

with the carboxyl and hydroxyl groups. Intermolecu-

lar cross-linking of sequences results in the formation

of junction zones and a three-dimensional gel net-

work. This mechanism is referred to as the ‘egg-box

model’ (Figure 3).

0031If a sodium alginate solution is added dropwise

into a solution containing a calcium salt, gel beads

are produced and this process is used for the produc-

tion of ‘artificial fruit’ for use in pie fillings. In order

Cooling

Heating

Cooling

Heating

Random

coil

Double

helix

Aggregate

fig0002 Figure 2 Gelation process for agarose and carrageenan in-

volving double helix formation and aggregation. Reproduced

from Gums: Properties of Individual Gums. Encyclopaedia of

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

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

GUMS/Properties of Individual Gums 2999

to produce homogeneous gels, a common practice is

to generate the calcium ions slowly in situ. Sparingly

soluble salts such as calcium phosphate are used and

the release of ions is controlled by sequesterants and

adjustment of pH. This process is used in the prepar-

ation of structured or fabricated foods such as fruit

and meat products.

Microbial Gums

0032 Xanthan gum was first discovered in the 1950s and is

now finding extensive application in the food indus-

try since its introduction in the early 1970s. The gum

is obtained from the genus Xanthomonas, notably X.

campestris by aerobic fermentation. The xanthan

molecules have a (1,4)-b-d-glucopyranose backbone

as in cellulose, but in addition have a trisaccharide

side chain on every other glucose residue linked

through the C3 position. The side chain consists of

two mannopyranosyl residues linked on either side to

a glucuropyranosyl uronic acid group. The inner

mannose residue connected to the backbone may

be acetylated while the terminal mannose residue

may be pyruvated. The molecular mass of the

xanthan molecules is very high (> 3 10

) and

the gum dissolves in water to yield highly viscous

solutions. The xanthan molecules are reported to

undergo a thermoreversible coil-to-helix transition

in solution, which is shifted to higher temperatures

by the addition of electrolyte. In the disordered coil

form the side chains are envisaged as protruding away

from the backbone into solution, while in the ordered

form the molecules form a stiff five-fold helical struc-

ture with the side chains folded in and associated with

the backbone. Most workers now believe that the

helix is double-stranded. The stiff xanthan chains

tend to associate in solution, giving rise to a very

high viscosity at low shear rates, which is sufficient

to prevent particles from sedimenting or oil drops

from creaming. The associations are readily broken

on applying shear, giving rise to a dramatic drop in

viscosity and hence the solutions readily flow. Unlike

other polyelectrolytes the viscosity of xanthan solu-

tions is relatively insensitive to addition of electrolyte

since the electrolyte will promote helix formation.

The helices are also stable over a broad range of pH.

The high apparent yield stress and pronounced shear

thinning characteristics have led to a large increase in

the use of this gum, which now finds application in a

broad range of food products such as sauces, salad

dressings, and mayonnaises.

0033Gellan gum has only recently been commercialized.

It is produced from Pseudomonas elodia by aerobic

fermentation and consists of a linear tetrasaccharide

repeat unit of (1,3)-b-d-glucopyranose, (1,4)-b-d-

glucopyranose uronic acid, (1,4)-b-d-glucopyranose

and (1,4)-a-l-rhamnopyranose. In the native form the

(1,3)-linked glucose residues contain glycerate and

acetate moieties. X-ray fiber diffraction studies indi-

cate that the gellan molecules form a threefold double

helical structure and in solution undergo a thermo-

reversible coil-to-helix transition. The transition

shifts to higher temperatures in the presence of

electrolyte. Once formed, the helices tend to self-

associate, leading to the formation of a gel, as is the

situation for agarose and carrageenan. Gels formed in

the presence of monovalent ions are usually thermo-

reversible, although the melting temperature is nor-

mally much greater than the gelation temperature – a

consequence of the extensive aggregation. If gels are

formed by the addition of divalent ions then they can

be thermally irreversible. The native form produces

soft elastic gels whereas the deacetylated material,

which is sold commercially, forms hard brittle gels.

The gum is used in fruit fillings.

See also: Cellulose; Gelatin; Gums: Food Uses; Dietary

Importance; Nutritional Role of Guar Gum; Marine Foods:

Production and Uses of Marine Algae; Pectin: Properties

and Determination; Food Use; Starch: Structure,

Properties, and Determination

Further Reading

Hill SE, Ledward DA and Mitchell JR (1998) Functional

Properties of Food Macromolecules. Gaithersburg, MD:

Aspen.

Imeson I (1992) Thickeners and Gelling Agents for Food.

Glasgow: Blackie Academic and Professional.

Lapasin R and Pricl S (1995) Rheology of Industrial Poly-

saccharides; Theory and Applications. Glasgow: Blackie

Academic and Professional.

Nussinovitch A (1997) Hydrocolloid Applications; Gum

Technology in the Food and other Industries. Glasgow:

Blackie Academic and Professional.

Phillips GO and Williams PA (2000) Handbook of Hydro-

colloids. Cambridge: Woodhead.

fig0003 Figure 3 Schematic representation of junction zone formation

in calcium alginate gels (egg-box model). The calcium ions are

represented by

. Reproduced from Gums: Properties of Individ-

ual Gums. Encyclopaedia of Food Science, Food Technology and Nu-

trition, Macrae R, Robinson RK and Sadler MJ (eds), 1993,

Academic Press.

3000 GUMS/Properties of Individual Gums

Ross Murphy S (1994) Physical Techniques for the Study of

Food Biopolymers. Glasgow: Blackie Academic and

Professional.

Stephen AM (1995) Food Polysaccharides and Their Appli-

cation. New York: Marcel Dekker.

Williams PA and Phillips GO (2000) Gums and Stabilisers

for the Food Industry 10. Cambridge: Royal Society of

Chemistry.

Food Uses

P A Williams and G O Phillips, The North East Wales

Institute, Wrexham, UK

Introduction

0001 Gums have a major influence on the structural char-

acteristics, texture, organoleptic properties, and over-

all appearance of foods, even though they are present

often at concentrations of less than 1%. On food

labels they are commonly referred to as ‘stabilizers,’

‘thickeners,’ or ‘gelling agents’ and in fact may serve a

number of functions, such as enhancing viscosity,

preventing particle sedimentation or droplet

creaming, inducing gelation, emulsifying oils, stabil-

izing foams, and inhibiting ice or sugar crystalliza-

tion. The various food sectors where gums are

commonly used are shown in Table 1 together with

an estimate of their usage levels. The high levels of

modified starch, gelatin, and guar gum used reflect

their relatively low cost.

0002 The use of gums in food products is steadily in-

creasing due to the rapid rise in the consumption of

ready-made meals and novelty foods and also because

of consumers’ growing awareness of the need to

increase the amount of fiber and reduce the amount

of fat in the diet. Gums are considered as soluble fiber

and there is evidence to indicate that they assist

plasma cholesterol reduction and promote fermenta-

tion in the large bowel. The latter yields short-chain

fatty acids, mainly acetate, proprionate, and butyrate,

which have a beneficial effect on the colon through

stimulation of blood flow and enhancement of

electrolyte and fluid absorption and muscular activ-

ity. Gums are nowadays widely used for fat replace-

ment in a wide range of low-calorie products. They

may be added in their natural form or as specifically

fabricated microparticulates and serve to enhance the

rheological properties of the lower fat products.

Rheological enhancement can also be achieved by

incorporating two or more gums. In such systems,

phase separation can occur and, if one or more of

the gums is able to form a gel, can lead to the devel-

opment of novel gel structures.

Safety of Gums used in Foods

0003The Joint Expert Committee on Food Additives

(JECFA) was first established in the mid-1950s by

the Food and Agricultural Organization (FAO) and

World Health Organization (WHO) to assess chem-

ical additives in food on an international basis. The

Codex Alimentarius Commission (CAC), an inter-

national intergovernmental body, was set up in the

early 1960s with the primary aim of protecting the

health of the consumer and to facilitate international

trade in food commodities. When CAC was formed,

it was decided that JECFA would provide expert

advice to Codex on matters relating to food additives.

0004While CAC is the ultimate specification and can

provide for approval throughout the world, each

country is free to adopt its own standards.

0005The international numbering system (INS) for

food additives is intended as an identification for food

additives for use in one or more countries. The

tbl0001 Table 1 Annual usage (tons) of gums in the various food industry sectors

Food sector Starches Carrageenan Alginates Gumarabic Guar gum Xanthan Gelatin Pectin CMC

Confectionery 8000 200 200 4800 13 000 900

Dairy and desserts 6000 1800 700 3900 250 4500 190

Pet food 3500 150 250 2000 150

Readymade meals 1500 1500 200 160

Meat products 350 5500 120

Bakery products 2000 400 2100 130

Sauces and dressings 700 200

Other 2000 1000 300 700 300 180 1500 2900

120

Total usage 23 000 3500 1850 5500 10 500 980 24 500 3800 720

Mainly jams.

Source: Giract based on utilization in the UK, France, and West Germany in 1988.

CMC, carboxymethyl cellulose.

GUMS/Food Uses 3001

criteria for INS inclusion are: the compound must be

approved by a country as a food additive, it must

be toxicologically cleared for use by a country, and

it must be identified on the final product label.

0006 In the European Union, gums accepted for food

use are classified by so-called E numbers. Where

both INS and E numbers are available they are inter-

changeable. INS and E numbers for gums used in

foods are given in Table 2, together with their func-

tional characteristics.

Food Applications

Condiments, Mayonnaise, and Dressings

0007 Gum tragacanth was traditionally used in thick

sauces, pickles, and relishes because of its ability to

maintain the desired rheological properties in the

acidic conditions normally associated with these

products. However, because of its uncertainty of

supply and increasing high cost, modified starches

are nowadays the thickeners of choice. Novel prod-

ucts are continually being introduced into the market-

place and some examples of sauces in which gums are

incorporated are shown in Figure 1. The choice of

gum is dependent on the nature of the product. The

tartare sauce, smokey barbecue sauce, and horserad-

ish relish, for example, contain xanthan gum and this

acts to thicken the sauces and is stable in the acid

conditions found in these products. The creamed

garlic sauce contains both xanthan gum and guar

gum and these are known to interact synergistically

to give enhanced rheological properties. The seafood

sauce has a higher oil content than the other sauces

and, therefore, propylene glycol alginate is included

with xanthan gum. The propylene glycol alginate

functions as an emulsifier, preventing droplet coales-

cence, while the xanthan gum enhances the viscosity

of the aqueous phase, thus preventing droplet

creaming. The apple sauce, cranberry sauce, and

mint jelly all contain pectin, which gives the products

gel-like characteristics.

0008Traditional mayonnaise is a concentrated, oil-in-

water emulsion containing about 65% vegetable oil,

acidifying ingredients (vinegar or lemon juice) and egg

yolk, which acts as an emulsifying agent. The semisolid

characteristics associated with this food product are

principally controlled by the concentration of oil and

the size of the emulsion droplets. Spoonable products

can be made at much lower oil content (30–50%) by

the incorporation of gums at concentrations as low as

0.5%. The gums used are xanthan gum (sometimes in

tbl0002 Table 2 International numbering system (INS) and E numbers for food gums

Hydrocolloid INS/Enumber

Function

Carrageenan (including furcelleran) 407 Thickener, gelling agent, stabilizer, emulsifier

Processed euchema seaweed 407a Thickener, gelling agent, stabilizer, emulsifier

Xanthan gum 415 Thickener, stabilizer, emulsifier, foaming agent

Gellan gum 418 Thickener, gelling agent, and stabilizer

Guar gum 412 Thickener, stabilizer, and emulsifier

Locust bean gum 410 Thickener, gelling agent

Gum arabic 414 Emulsifier, stabilizer, thickener

Pectin 440/E440 (i) Gelling agent, thickener, stabilizer

Amidated pectin E440 (ii) Gelling agent, thickener, stabilizer

Microcrystalline cellulose INS460 (i) Anticake, emulsifier, stabilizer, and dispersing agent

Powdered cellulose INS460 (ii) / E460 Anticake, emulsifier, stabilizer, and dispersing agent

Cellulose 460 Anticake, emulsifier, stabilizer, and dispersing agent

Tragacanth gum 413 Emulsifier, stabilizer, thickening agent

Karaya gum 416 Emulsifier, stabilizer, and thickening agent

Konjac mannan E425 Gelling agent, thickener, emulsifier, stabilizer

Propylene glycol alginate 405 Thickener, emulsifier

Sodium alginate 401 Thickening agent, stabilizer

Potassium alginate 402 Thickening agent, stabilizer

Alginic acid 400 Thickening agent, stabilizer

Calcium alginate 404 Thickening agent, stabilizer

Ammonium alginate 403 Thickening agent, stabilizer

Methyl cellulose 461 Thickening agent, emulsifier, stabilizer

Hydroxypropyl cellulose 463 Emulsifier, thickener, stabilizer, binder, suspension agent, film coating

Hydroxypropylmethyl cellulose 464 Emulsifier, thickening agent, stabilizer

Sodium carboxymethyl cellulose 466 Thickening agent, stabilizer, suspending agent

Agar 406 Thickening agent and stabilizer

Oat gum 411 Thickener, stabilizer

Where no distinction is made, the INS and E numbers are identical. When only an E number is given, there is no equivalent INS number. From Phillips

GO, Williams PA (2000) Handbook of Hydrocolloids. Cambridge: Woodhead.

3002 GUMS/Food Uses

combination with guar gum or locust bean gum),

which functions as a thickener, and propylene glycol

alginate, which aids emulsification.

0009 Xanthan gum is widely used nowadays in place of

gum tragacanth in pourable dressings because of its

stability at low pH, its ability to slow down the

separation of the oil-and-water phases, and suspend

particulate ingredients, and because of its pro-

nounced shear thinning characteristics.

0010 Coleslaws, potato pasta and Florida-style salads are

now commonly available ready-prepared and xanthan

gum, perhaps in conjunction with guar gum or locust

bean gum, is often incorporated as a thickener.

Icecream, Yogurt, and Other Dairy Products

0011 Icecream Icecream is a complex food system con-

sisting of a liquid phase incorporating fat particles, air

bubbles, ice crystals, milk proteins, sugars, and soluble

and insoluble salts. Gums are commonly used in com-

bination with emulsifiers in icecream formulations to

control the stability of the product. The level of gum

used depends on the type and overall composition but

is typically in the range of 0.1–0.35%. Even at these

very low levels, the gums can have a profound effect,

serving to enhance the viscosity of the icecream mix,

thus increasing the whipping properties and allowing

incorporation of a greater proportion of air

prior to freezing. The amount of air incorporated is

termed the overrun and it can be 100% or more by

volume. The use of gums also has a considerable

influence on the organoleptic properties of the prod-

uct, affecting the body, texture, and mouth feel. Ice-

creams made without gums also tend to melt much

faster. The major influence on texture comes from the

ability of gums to inhibit ice crystal growth, which

occurs as a result of the phenomenon known as

Ostwald’s ripening. This process arises from the fact

that ‘small’ ice crystals have a greater solubility than

‘large’ ice crystals. Hence, the continual melting and

freezing of the crystals as a consequence of the tem-

perature fluctuations experienced on prolonged stor-

age in a freezer result in the formation of increasingly

large ice crystals. It has been argued that the gums act

by binding water molecules, thus preventing them

from freezing. However, since they are used in such

small quantities, it is more likely that they act by

adsorbing on to the ice crystals, thus inhibiting crystal

growth. Gums can also reduce ‘sandiness’ which is

found in some icecreams as a result of lactose crystal-

lization.

0012For batch processing the gum can be added to the

cold or hot mix, but for high-temperature, short-time

(HTST) pasteurization the gum is dispersed in the mix

when cold and should be cold-water-soluble. The

gums are usually blended with a proportion of the

sugar before incorporation into the mix in order to

aid dispersibility.

0013Today the most widely used gums are alginates,

carboxymethyl cellulose, guar gum, and locust bean

gum. Serum separation can sometimes occur in the

mix before it is frozen and this is avoided by incorpor-

ation of kappa-carrageenan as a secondary stabilizer

(at, say, 10% of the total stabilizer content). It is

believed that the carrageenan interacts with the milk

constituents present, notably the kappa-casein, to

form a weak gel structure. Microcrystalline cellulose

has been shown to be particularly effective at redu-

cing ice crystal formation and enhancing the body,

and has application in reduced-fat icecreams.

0014Yogurt Yogurt is produced from milk following

lactose fermentation induced by the action of

fig0001 Figure 1 Typical sauces incorporating gums.

GUMS/Food Uses 3003

microflora. These include Lactobacillus acidophilus,

L. bulgaricus, and Streptococcus thermophilus. Bifi-

dobacterium longum is also used in the ‘bioyogurts’

which have now become popular. A culture contain-

ing the bacteria is added to the milk after it has been

homogenized and undergone heat treatment. The for-

mation of lactic acid causes the milk proteins to co-

agulate, forming a semisolid gel which entraps the fat

globules and the serum containing the dissolved com-

ponents. For ‘set’ yogurts, coagulation is carried out

directly in retail cartons, resulting in a gel-like prod-

uct. For ‘stirred’ yogurts, coagulation is carried out

when transferring through a cooler and then pack-

aging. A variety of gums are used in yogurt produc-

tion in order to reduce syneresis and enhance the

rheological and organoleptic properties. It should be

noted, however, that legislation in some countries

prohibits their use. It is important that the gums do

not mask the natural flavor of the yogurt and that

they are effective at the product pH of about 4.3.

Gums reportedly used are carboxymethyl cellulose,

guar gum, locust bean gum, pectin, alginate, agar,

carrageenan, and xanthan gum. However, the most

common are pectin, gelatin, and modified starch.

They are normally used at levels of 0.2–0.5%

depending on the gum and the milk solids content.

They are often added to the warm milk prior to

pasteurization in order to insure complete dissol-

ution. In some cases the gum is added to the coagulum

after incubation, in which case its microbiological

quality needs to be assured. Fruit-flavored yogurts

are produced by adding fruit pulp, consisting of fruit

pure

e( 50%), sugar (30%), and a suitable stabil-

izer to the yogurt prior to packaging. Low-ester

pectins (and low-ester amidated pectins) are particu-

larly effective stabilizers since they are able to provide

the optimum rheological properties at low pH and are

incorporated at typical concentrations of 0.6%.

0015 Cheese In cheese manufacture, lactic acid-producing

bacteria are added to milk and the mixture is stirred

at a constant temperature. When sufficient acidity has

developed, rennet, which is a natural enzyme, can be

added and this hydrolyzes the kappa-casein in the

milk, causing the casein micelles to coagulate and

form a gel. The gel is commonly referred to as curd

and is separated off from the liquid (known as whey)

and may be pressed, salted, and left to ripen

according to cheese type. Addition of gums such as

guar gum, locust bean gum, and carrageenan in-

creases the rate of coagulation and aids the recovery

process, thus increasing the yield of curd. In soft

cheeses, where there is a high water content (> 80%),

gums can lead to improvement in the body and tex-

ture of the product and are also reported to reduce

water loss. Blends of carrageenan and galactomannan

are particularly effective. Carrageenan is also used in

some processed cheeses, and this allows the cheese

content to be reduced whilst maintaining good mouth

feel and melting properties and improving grating

and slice integrity. The use of gums in cheese is,

however, subject to food additive regulations and

they are generally only allowed in composite cheese

products and spreads.

0016Whipped cream Whipping cream has a high milk

fat content (> 30%) and its functional requirements

include its ability to incorporate air (i.e., whippabil-

ity), foam stability, and resistance to serum separ-

ation. Sodium alginate, carrageenan, and modified

starches can be used to improve these characteristics.

Bakery Products

0017Bread In the process of bread making, flour, yeast,

salt, shortening, water, and so-called ‘improvers’ are

mixed together to form a homogeneous dough.

During the process the glutenin and gliadin proteins

present in the flour interact to form gluten, giving

the dough its elastic characteristics. On standing, the

yeast ferments the sugar components present in

the flour, producing carbon dioxide which distends

the dough, giving it a cellular structure. During

baking the starch granules dispersed within the gluten

matrix swell irreversibly (gelatinize), releasing amy-

lose and absorbing water, which adds to the structure.

The gluten is coagulated by the heat.

0018Although it is not common practice, gums such as

guar, locust bean gum, carboxymethyl cellulose, and

xanthan gum can be used in bread manufacture at

levels of up to 2%. They have been reported to speed

up the development of gluten during mixing, giving a

significant reduction in mixing time. In addition, it is

claimed that they enhance moisture retention, thus

retarding the staling process, which results from the

aggregation of amylopectin chains, a process referred

to as retrogradation.

0019Xanthan gum has been used in the preparation of

gluten-free bread. It is believed that the xanthan inter-

acts with the starch to form a matrix, allowing struc-

ture development comparable to normal bread to

occur during baking.

0020Cakes Gums such as xanthan gum, guar gum, and

carboxymethyl cellulose can be used in the produc-

tion of cakes and they have two major functions.

First, they can control the rheological properties of

the batter, which is important in large-scale manufac-

ture, where mixing, pumping, and filling stages are

encountered. Their shear thinning characteristics are

important since a low viscosity is preferable when

3004 GUMS/Food Uses

mixing and pumping, whereas a high viscosity is

required after filling the baking pans in order to pre-

vent splashing and to suspend any particles such as

fruit in the batter. The second function is to facilitate

more even hydration of the dry ingredients and to

control the moisture of the finished product. A more

even moisture distribution assists in the stabilization

of air cells formed during mixing and this gives rise to

a finer, more uniform cell structure, thus improving

the volume and texture of the finished cake. Control

of the moisture content is of utmost importance since

this will influence not only the texture and appear-

ance but also the shelf-life.

0021 Fruit pie fillings Fruit pie fillings usually contain

modified starches, which thicken the acidic juices

associated with the fruit. Gums such as carrageenan,

carboxymethyl cellulose, and low-methoxy pectin

and locust bean gum blends are sometimes used in

combination with the starch to improve heat stability,

to give increased clarity, and to reduce syneresis.

0022 Sodium alginate can be used to produce fruit

analogs for pie fillings utilizing the so-called ‘internal

setting procedure.’ In this process a sodium alginate

solution containing an insoluble calcium salt (e.g.,

calcium phosphate) is combined with a fruit pure

which contains a sequesterant (e.g., sodium citrate)

and acid (citric acid). On mixing, the insoluble cal-

cium salt begins to dissolve in the presence of the acid,

releasing calcium ions which initially interact with

the alginate, inducing gelation. The uniform gel

formed is then cut and a thickened fruit syrup is

added to give the finished pie filling.

0023 Sodium alginate can also be used to prepare struc-

tured fruits using a coextrusion technique and this is

particularly appropriate for fruits such as blackcur-

rants, which have an outer skin and liquid center. In

the process a sodium alginate solution and fruit pure

mix are fed separately through nozzles consisting of

coaxial tubes positioned above a bath containing a

solution of calcium salt (e.g., calcium lactate). The

flow of alginate solution is kept constant while that of

the fruit pure

e is intermittent. As each drop of pure

breaks away from the nozzle it is coated with a film of

the alginate solution which gels instantly, forming a

hardened skin on hitting the calcium bath below. The

fruit gels formed are then collected and a thickened

syrup is added to produce the pie filling.

0024 Gellan gum is now also finding some applications

as a gelling agent in fruit fillings for pies and cakes.

0025 Icings, Frostings, and Glazes The icings, frostings,

and glazes used for bakery products consist of a sat-

urated solution of sugar in water. Gums such as car-

boxymethyl cellulose and sodium alginate are used to

inhibit sugar crystal growth and to control the rheo-

logical and film-forming properties. Such coatings

show improved adhesion to the product, have less

tendency to crack, and have reduced stickiness.

0026Gum tragacanth is used in decorative icings for

wedding cakes.

0027Batter Coatings Thickeners such as guar gum,

locust bean gum, and xanthan gum are often used in

the large-scale production of batter coatings for sea-

food and poultry. They provide the required rheo-

logical properties to the batter and assist in its

adhesion to the product.

Desserts

0028Specialty desserts There is a vast assortment of des-

sert products available today for the consumer to

choose from, and gums are widely used to control

the characteristics of the various components, which

make up each product. Carrageenan, for example, is

often used in milk-based desserts since it interacts

with the milk proteins present, giving rise to the for-

mation of a weak gel structure and thus preventing

serum separation. Thickeners such as guar and locust

bean gum or gelling agents such as pectins are used to

control the viscous or gel-like characteristics of the

liquor associated with fruits, while sodium alginate is

often used to stabilize whipped-cream toppings.

Examples of typical dessert products, with details of

the additives incorporated into each, are given in

Figure 2.

0029Gums are also commonly used in frozen gateaux in

order to confer the desired properties on the individ-

ual components and, in particular, to enhance freeze–

thaw stability.

0030Table jellies Jellies are traditionally prepared using

gelatin. The material is dissolved in hot water and

gelation occurs on cooling in a refrigerator. The

gelatin molecules in solution undergo a coil-to-helix

transition, which occurs at about 25



C, and the heli-

ces aggregate to form a gel. The gels formed have high

clarity and on heating melt at 37



C, which corres-

ponds to body temperature. The jelly, therefore, melts

in the mouth, providing rapid flavor release and a

smooth texture, but they are prone to toughening on

storage.

0031Jellies can also be prepared using gums such as

carrageenan, alginate, and pectin. Iota-carrageenan

gives rise to compliant gels similar to those of gelatin.

However, they have a higher melting temperature and

hence do not have the same attractive organoleptic

properties but since they also have a higher gelling

temperature, the gels form without the need for

refrigeration. Kappa-carrageenan itself forms very

GUMS/Food Uses 3005

brittle gels but can be used in conjunction with

(purified) locust bean gum, which improves the clar-

ity and makes the gels more elastic (less brittle) and

less prone to syneresis. Jellies can also be prepared

using alginate with a high mannuronic acid content.

Soft-textured, nonbrittle gels can be produced with

calcium ions under controlled conditions.

0032 Low-acyl gellan gum can be used to prepare dessert

jellies with a firm brittle texture. Mixtures of low-

and high-acyl gellan gum can be used to produce

jellies with a range of textures. Low-acyl gellan can

also be used to modify the texture of gelatin gels. In

Japan, konjac mannan is commonly used to produce

dessert jellies.

0033 Syrups, toppings, and dry dessert mixes Gums are

commonly used to enhance the viscosity of syrups for

use on pancakes and icecream. They provide the ne-

cessary flow characteristics and cling and, in add-

ition, retard sugar crystallization. Xanthan gum and

carboxymethyl cellulose give products of higher clar-

ity than those prepared using guar gum or locust bean

gum. Propylene glycol alginate is used in some

buttered syrups because of its emulsifying character-

istics. Xanthan gum, guar gum, and locust bean gum

are often used in whipped nondairy dessert toppings

in order to control the viscosity of the system prior to

whipping. Methyl cellulose and hydroxypropylmethyl

cellulose can also be used in this application and they

have the added benefit of promoting emulsification of

the oil, although other emulsifiers can also be present.

Microcrystalline cellulose has been found to be par-

ticularly effective at stabilizing foams. The toppings

are normally sold frozen and the gums present inhibit

ice crystal formation.

0034Gums are often used in dry dessert mixes. Xanthan

gum, carboxymethyl cellulose, and guar gum are par-

ticularly effective since they are soluble in cold water.

Pectins and alginates are included in some dessert

mixes, such as mousses and cheesecakes, in order to

provide a gel structure. Xanthan gum is particularly

useful in dry sorbet mixes because of its good solubil-

ity and stability in acid conditions and also because it

can form a weak gel structure, which traps air

bubbles formed during mixing.

0035Carrageenan is widely used in dry milk pudding

mixes because it interacts with the casein present,

leading to the formation of a gel structure.

Jams, Jellies, and Marmalades

0036The formulations of jams, jellies, and marmalades in

Europe are controlled by a European Union directive

which dictates the minimum fruit and sugar solids

required for the various categories. Manufacture

consists of blending the ingredients, raising the

temperature, and evaporating to the correct soluble

solids content either at 100



C at atmospheric pres-

sure or at temperatures down to 60



C under vacuum.

Vacuum boiling avoids heat damage, caramelization,

and loss of fruit volatiles, but an additional pasteur-

ization step is required.

0037The primary characteristic of all preserves is that

they are gelled systems, and for conventional pre-

serves pectin is used as the gelling agent. For preserves

with a high total soluble solids (TSS) content (> 60%,

mainly sugar), one or more high-methoxyl pectins are

fig0002 Figure 2 (see color plate 80) Typical desserts incorporating gums. The additives contained in each dessert include the following:

chocolate delight: modified starch, carrageenan, sodium alginate; caramel dessert: modified starch, carrageenan, pectin; raspberry

royale: amidated pectin, sodium alginate; pineapple cheesecake: modified starch, gelatin, pectin, guar gum; strawberry fruit fool:

gelatin, sodium alginate.

3006 GUMS/Food Uses

used to control gelation. At TSS content of 20–55%,

either an amidated or a nonamidated low-methoxyl

pectin is used. Gelation of high-methoxyl pectins is

pH-dependent and a pH of < 3.5 is required for gel-

ation to occur. This may require the addition of fruit

acids to the recipe to reduce the pH, with most jams

having a final pH of 2.8–3.4. For low-methoxyl

pectins, gelation is controlled by the presence of cal-

cium ions and a high soluble solids content is not

required. Gelation is optimized at pH 3–4.5.

0038 In high-sugar preserves the sugar stabilizes the

structure and immobilizes the water, thus reducing

syneresis. This becomes much more of a problem in

low-sugar preserves.

0039 A number of reduced-sugar products are available

with TSS contents of < 25%. In these systems gelation

is achieved using carrageenan or carrageenan and

low-methoxyl pectin blends. Other gums such as

guar and locust bean gum may be added to modify

the texture and reduce syneresis.

Meat, Stews, Gravies, and Soups

0040 Gums, notably carrageenan and guar gum, are often

incorporated into meat products such as sausages,

cooked hams, and poultry products where they serve

as binders to control the texture and structural integ-

rity and to retain water.

0041 Methyl cellulose is used in fryable products since it

gels on heating and hence helps to retain the product’s

shape during frying.

0042 Gums such as modified starches, guar gum, and

carboxymethyl cellulose are used to thicken the gravies

for meat pies, canned meats, and stews and to reduce

fat migration and water separation during storage.

0043 Modified starches are used to thicken canned

soups, while guar gum is commonly used in instant

dry soup mixes to add body and aid dispersion of the

various ingredients.

Confectionery

0044 Gelatin, modified starch, gum arabic, and pectin are

the main gums used in confectionery products. Gum

arabic is the major component in traditional wine

gums and is present at concentrations of *50%. Pro-

duction involves dissolving the gum in water, keeping

the temperature as low as possible (< 60



C) in order to

avoid precipitation, and it is then added to a preboiled

sugar/glucose solution (70%) followed by flavorings

and colors. After standing the liquid is deposited into

starch trays and placed in a stoving room for 4–6 days.

The gums are then removed from the starch molds,

brushed to remove starch, and often glazed with oil or

wax. Softer gums or pastilles can be obtained by redu-

cing the stoving time. In view of shortages in gum

arabic and severe price fluctuations, considerable

efforts have been made to find alternative gums. Now-

adays pastilles are commonly made with gum arabic in

combination with other gums, notably, starch, malto-

dextrin, gelatin, pectin, and agar.

0045Slow-setting, high-methoxyl pectin is used in the

preparation of fruit-flavored acidic confectionery jel-

lies and is usually present at concentrations of less

than 2%. Some flavors, such as liquorice and vanilla,

are unstable in the acid conditions necessary for the

gelation of the pectin, and low-ester pectins which gel

in the presence of calcium are used instead. These

pectins are also used in the manufacture of Turkish

delight.

See also: Bread: Chemistry of Baking; Cakes: Nature of

Cakes; Cream: Types of Cream; Clotted Cream; Dairy

Products – Nutritional Contribution; Dressings and

Mayonnaise: Chemistry of the Products; Gums:

Properties of Individual Gums; Ice Cream: Methods of

Manufacture; Jams and Preserves: Methods of

Manufacture; Chemistry of Manufacture; Meat: Hygiene;

Sweets and Candies: Sugar Confectionery; Syrups;

Yogurt: The Product and its Manufacture