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and thus on the wheat, but it may also thriveon flour residues on the walls of the bakery or

on the equipment. When it finds its way intothe dough it survives baking and destroys thecrumb during storage of the bread. Warm,damp conditions promote the development of the micro-organisms, so its appearance ismore frequent in summer.The dough shows normal baking propertiesand the fresh bread has a normal appearance.But within a short time a fruity flavour developsin the bread, turns into sweet smell and finallybecomes disgusting. Meanwhile, degradation

of the bread crumb takes place, along with ayellowish-brownish discoloration. When thebread is broken, thin slimy strands are formed(Fig. 158).

The optimum growth conditions for B.mesentericus are 37 °C and pH 6. But it cangrow in the range of 10 - 45 °C and a pH of 4.9- 9.3. At 97 °C only 90% of the spores are inac-tivated within 2 h, and this temperature is farhigher than that reached in the bread crumb.

Thorough cleaning of the wheat reduces thechance of the bacterium to get into the bread,because it only adheres to the surface of thekernels. The baker can reduce its survival byproper cleaning of the bakery and equipment.If ropiness has occurred, the bakery andequipment should be disinfected, e.g. bywashing with vinegar solution. Acidification isa means of controlling the growth of Bacillus

mesentericus in the dough, for instance withsour dough or edible acids. Antimicrobial

substances such as acetic or propionic acidand their salts (acetates and propionates) arealso very effective in suppressing the growthof the organisms. Their effect is improved atlower pH values, i.e. in the presence of otheracidifying agents. Since they affect taste andyeast growth, their dosage should be limitedto a required minimum. The lack of volumeyield caused by the antimicrobial agents canbe compensated for by increased yeast levelsand with flour additives such as enzymes or

emulsifiers.

18.13 Flour Treatment forSpecific Applications

18.13.1 Steamed Bread

Introduction

Although they differ in details, steamed breadsfrom various regions have several propertiesin common, for instance the lack of stabilization

by a firm crust (in contrast to baked bread), avery fine crumb structure, and a mild, almostbland taste. This can be considered an advan-tage because of the absence of acrylamideand the possibility of combining the steamedbread with various fillings and dishes.

Since little or no salt is normally used, thedough is very extensible, but the stability of the finished, steamed product is also reduced.This is a special challenge to additives such

as enzymes, ascorbic acid and other flourimprovers.

In the laboratory, steamed bread can beprepared in the traditional way – in basketsplaced on woks containing boiling water (Fig.159), stainless steel pots placed on a fire orelectric hotplate, or in stainless steel steamchambers (Fig. 160). For the following investi-gations a steam chamber was used.

Furthermore, flour with normal propertieswithout any obvious quality problems wasused. It fell into the flour quality range usualfor steamed bread (Tab. 95).

18.13 Flour Treatment for Specific Applications

Fig. 158: Ropiness in wheat bread(Schünemann and Treu, 2002)


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265The course of the core temperature duringsteaming is significantly lower than duringbaking (Fig. 161). This has to be taken intoaccount if ingredients coated with fats oremulsifiers or pure fat or emulsifier powders

are used, and also if enzymes that have a highinactivation temperature, such as bacterialamylase, are included. Whereas the formerwould not dissolve readily, the latter wouldsurvive the curing process and cause damagein the final product.

Enzymes

AmylasesAmylases affect the volume yield and crumbsoftness of the steamed bread. Fig. 162 showsthe effect of adding pure fungal α-amylasewith 5,000 SKB/g. The volume yield increased

by almost 25%, displaying a maximum at 250ppm (equal to 1,250 SKB per kg of flour).


Fig. 159: Basket for traditional steaming(source: H. Moegenburg, Muehlenchemie Asia Pte. Ltd.)

Fig. 160: Stainless steel steaming chamber

0

20

40

60

80

100

0 5 10 15 20

Baking time (min)

Steamed bread

Baked buns

Fig. 161: Core temperature of baked buns and steamed bread

Tab. 95: Flour quality for steamed bread trials

Parameter Range

Wet gluten % 29 - 32

Gluten index 90 - 75

Ash % 0.45 - 0.55

Falling Number s 250 - 450

Farinogram

Water absorption % 55 - 62

Dough development min 1.5 - 3

Dough stability min min. 2

Dough softening FU max. 90

Extensogram (135 min)

Energy cm2 110 - 120

Extensibility mm 140 - 160

Dough resistance BU 380 - 410

Ratio 1.5 —1.7


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HemicellulasesNot unexpectedly, the positive properties of

hemicellulases, described in chapter 18.5.2,were also observed in the preparation of steamed bread.

For instance, a hemicellulase from Aspergillusniger (Alphamalt HCC) achieved a volume

increase similar to that of amylase (Fig. 163).At the same time the pore structure becamemuch finer (not shown).


Reference Alphamalt VC 5000, 125 ppm

Alphamalt VC 5000, 500 ppmAlphamalt VC 5000, 250 ppm

Fig. 162: Effect of α -amylase with 5,000 SKB/g (Alphamalt VC 5000) on the size of steamed bread.The volume yield per 100 g of flour was 300, 325, 369 and 351 mL respectively (from upper left to lower right).

Reference Alphamalt HCC, 5 ppm

Alphamalt HCC, 20 ppmAlphamalt HCC, 10 ppm

Fig. 163: Effect of hemicellulase on the size of steamed bread.The volume yield per 100 g of flour was 300, 382, 373 and 373 mL respectively (from upper left to lower right)


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Glucose OxidaseThe enzyme glucose oxidase (GOD) convertsglucose into gluconic acid while oxidizingwater into hydrogen peroxide, an oxidizingagent, as described in chapter 18.3.3. Thereaction requires oxygen, which is readilyconsumed by yeast and some chemical reac-tions at the very beginning of the dough pre-paration process. This means that the effectof GOD is often only perceptible on the surfaceof the dough or the baked product (dryerdough surface, stabilized structure), while thevolume yield is hardly affected. Most probably

due to the specific dough development processoften used in the preparation of steamedbread, the GOD has a better supply of oxygen.The effect on volume yield is thereforemeasurable. In our example the improvementwas about 10% (Fig. 164). One further effect isalways mentioned by the bakers: the doughshave better machinability because of reducedstickiness.

Lipase

Lipase is yet another miracle enzyme, under-estimated for a long time. The enzymeconverts lipids into di- and monoglycerides,

i.e. emulsifiers (chapter 18.5.4). Especiallyafter extensive kneading, lamination or longfermentation processes, a dramatic effect ondough stability and volume yield can benoted. In the example shown in Fig. 165, theincrease was a net 70%. Since it is highlydependent on processing conditions, thiseffect cannot be reproduced with all doughpreparation methods.

Development of the dough by sheetingpromotes the beneficial effect of lipase. Thisis probably due to a more extensive exposure

to atmospheric oxygen.Endogenous lipoxygenases prefer to react withfree unsaturated fatty acids rather than withunsaturated fatty acids bound to the glycerolbackbone. Lipolysis exposes the fatty acids tothe action of lipoxygenases which, in thepresence of sufficient oxygen, are convertedinto hydroperoxides; these in turn react withcomponents of the flour. In addition to doughstrengthening, a bleaching effect occurs due tothe oxidation of flour carotenoids. Since

lipases are specific to the type of fatty acidpresent in the triglyceride, not all lipases aresuitable for improving steamed bread.


Reference Alphamalt Gloxy, 20 ppm

Alphamalt Gloxy, 250 ppmAlphamalt Gloxy, 125 ppm

Fig. 164: Effect of glucose oxidase on the size of steamed bread.The volume yield per 100 g of flour was 300, 317, 334 and 321 mL respectively (from upper left to lower right).


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n t Fig. 166 and Fig. 167 summarize the effects of

various enzymes on volume yield. The dataare taken from two sets of trials, so there aretwo different references. Tigerzym 01 and LP12066 signify two different lipases; Gloxy

7082 stands for glucose oxidase from

Aspergillus niger ; VC 5000 is 5,000 SKB/gα-amylase from A. oryzae; HCC, HCE andHCH are hemicellulases from A. niger ,Thermomyces lanoginosus expressed in


Reference Tigerzym 01, 5 ppm

Tigerzym 01, 50 ppmTigerzym 01, 25 ppm

Fig. 165: Effect of a commercial enzyme preparation containing a specific lipase on the size of steamed bread.The volume yield per 100 g of flour was 300, 447, 477 and 512 mL respectively(from upper left to lower right; colour differences were due to a rising thunderstorm).

0

100

200

300

400

500

600

Dosage (ppm)

R e

f e r e

n c e

T i g

e r z y

m 0 1 ,

5

T i g e

r z y m

0 1 ,

2 5

T i g e

r z y m

0 1 ,

5 0

L P 1 2 0

6 6 , 2

0

L P 1 2 0

6 6 , 5

0

L P 1 2 0

6 6 , 1

0 0

G l o

x y 7 0 8

2 , 2 0

G l o

x y 7 0 8

2 , 1 2 5

G l o

x y 7 0 8

2 , 2 5 0

V C 5 0 0

0 , 1 2 5

V C 5 0 0

0 , 2 5 0

V C 5 0 0

0 , 5 0 0

H C C ,

5

H C C ,

1 0

H C C ,

2 0

V o l u m e y i e l d ( m

L / 1 0 0 g f l o u r )

Fig. 166: Effect of specific lipases (Tigerzym 01, LP 12066), glucose oxidase (Gloxy 7082),α -amylase (VC 5000) and hemicellulase (HCC) on the volume yield of steamed bread


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269 A. niger and from Bacillus subtilis respectively;C 132 is a cellulase from a Trichoderma species,

and BG 31 is a β-glucanase from A. niger .

By combining several enzymes, additiveeffects resulting in even larger volume yieldcan be achieved (Tigerzym 02). Pure lipase,Tigerzym 01, served as an internal standardfor both sets of trials.

OxidationAscorbic acid is known to improve dough

stability, crumb structure and volume yield inbaking. Would it have comparable effects insteamed bread? Fig. 168 answers part of thisquestion, showing the volume yield whenascorbic acid is combined with α-amylase in

normal and long fermentation (1 h and 2 hrespectively). A distinct maximum as a function


R e

f e r e n c

e

T i g e

r z y m

0 1 , 2 5

H C E , 2 0

H C E ,

4 0

H C E ,

6 0

H C H ,

2 0

H C H , 3 5

H C H ,

5 0

C 1 3 2 ,

1 0

C 1 3 2 ,

3 5

C 1 3 2 ,

5 0

B G 3 1 ,

3 5

B G 3 1 ,

5 0

T i

g e r z

y m 0 2 ,

1 0

T i g e

r z y m

0 2 , 5 0

T i

g e r z

y m 0 2 , 1

0 0

T i g e

r z y m

0 2 , 1 5 0

0

100

200

300

400

500

600

Dosage (ppm)

V o l u m e y i e l d ( m L / 1 0 0 g f l o u r )

Fig. 167: Effect of specific lipases (Tigerzym 01), hemicellulases (HCE, HCH), cellulase (C 132), β -glucanase (BG 31)and an enzyme combination (Tigerzym 02) on the volume yield of steamed bread

250

280

310

340

370

400

430

0 2 4 6 8 10

Ascorbic acid (g/100 kg)

V o l u m e y i e l d ( m L / 1 0 0 g )

Normalfermentation

Normal fermentationwith amylase

Longfermentation

Fig. 168: Effect of ascorbic acid on the volume yield of steamed bread


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of ascorbic acid concentration appeared in allthe trials. Amylase caused a shift towards higherconcentrations, which is analogous to baking.The exact amount necessary to achieve amaximum depends on various factors such asthe recipe, process, and flour quality.

EmulsifiersThe number of emulsifiers used in baking isstill increasing. In our investigations we usedthe most common ones, i.e. SSL, CSL, DATEMand mono/diglycerides. The dosage was inthe typical range for baking applications, i.e.

between 0.1 and 0.5% on flour. While DATEMhad the best volume yield (Fig. 169), the ap-pearance and pore structure of the buns werenot satisfactory. The best overall result wasachieved with SSL, which produced goodvolume, a regular shape, a fine, even andbright pore structure and prolonged crumbsoftness.

Trials with sucrose esters also resulted inimproved volume (not shown), but the overall

properties were inferior to SSL and the costwas much higher.

18.13.2 Rye and High-Fibre Flour

In Northern Europe high-fibre bread has a

long tradition. Rye flour contributes a largeproportion of the dietary fibre in all countriesaround the Baltic Sea. Rye per se does nothave a higher fibre content than wheat, butthe dark flours used for most types of rye ormixed flour bread provide up to 3 times asmuch fibre as standard wheat flour (Fig.170).

A large variety of breads are made with ryeflour (Fig. 171). Due to the lack of a gluten

network, the volume yield is comparativelylow if a large proportion of rye flour is used.

Acceptable processing conditions and suffi-cient dough stability can only be obtained byacidification, either through sour dough orwith acidifiers such as lactic acid, acetic acidor fumaric acid.

Ascorbic acid as a maturing agent is only usedin mixed flour bread. Sour dough fermentation

reduces the amount of available simple sugar,improving the glycemic index further.


R e f e

r e n c

e

S S L ,

0 . 1

S S L ,

0 . 3

S S L ,

0 . 5

C S L ,

0 . 1

C S L ,

0 . 3

C S L ,

0 . 5

D

A T E M

, 0 . 1

D

A T E M

, 0 . 3

D

A T E M

, 0 . 5

M

o n o /

D i , 0

. 1

M o n

o / D i

, 0 . 3

M

o n o /

D i , 0

. 30

100

200

300

400

500

600

700

800

Dosage (%)

V o l u m e y i e l d ( m L / 1 0 0 g f l o u r )

Fig. 169: Effect of emulsifiers on the volume yield of steamed bread


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0

20

40

60

80

100

815 997 1370 1800 Whole

Rye flour

C o n t e n t ( % d . b . )

0

20

40

60

80

100

550 812 1050 1700 Whole

Wheat flour

C o n t e n t ( % d . b . )

Protein (Nx5.8) Fat Available carbohydrates Dietary fibre Minerals

Type:

Type:

Fig. 170: Composition of wheat and rye and some typical flours (data from Souci et al., 2000)

Fig. 171: Selection of rye bread


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Enzymes for Wheat and Rye "Volume" Bread

AmylasesAlthough bread with a high fibre content already

has a lower staling rate due to the higher waterabsorption, amylolytic enzymes of microbialor cereal origin are able to improve this evenfurther, particularly if grains with low intrinsicenzyme activity (i.e. high Falling Numbers) areused (chapter 18.10.1, page 246).

HemicellulasesPentosanases and glucanases affect thehemicelluloses of wheat and rye (Fig. 172).Pentosans consist of two fractions, one of

which is water soluble, while the other is not.Hydrolysis of the water-insoluble fractionresults in smaller, water-soluble fragments(solubilized) which absorb more water. Whensoluble or solubilized pentosan is hydrolyzed,water is released from the gel. Some pento-sanases only act on one or the other pentosanfraction, while others are less specific.

Non-Specific PentosanaseSecabon, a standard wheat flour treatment

pentosanase from a Trichoderma species,acts on both soluble and insoluble pentosans.At a suitable concentration the water absorptionwill first rise, improving machinability. Later in

the process, water will be released from thepentosan gel through the continuing hydrolysisof soluble and solubilized pentosans (Fig. 173).This increases the availability of water and

thus softens the dough structure (bettervolume yield), retarding and reducing starchretrogradation.

Dough "Drying" with Specific PentosanasesIf the doughs are already quite slack, a veryspecific xylanase which acts almost solely onthe insoluble pentosans may be useful: itincreases water absorption and thus resultsin dryer and more stable dough. Fig. 31 showsthe effect of such a xylanase on a wheat flour

type 550 in the Farinograph. The effects maybe even stronger in rye and dark wheat flour.


Fig. 172: Effect of glucanase on the structure of rye kernels. Left: untreated, right: treated with β -glucanase.(Source: K. Autio, VTT, Helsinki, Finland)

90

100

110

120

130

0 10 20 30 40 50 60Fermentation time (min)

V i s c o s i t y ( % )

Fig. 173: Effect of Secabon on the viscosityof wheat pentosans


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ProteasesSome baking properties of rye flour and darkwheat flours, for instance the volume yield, canbe improved by adding vital wheat gluten. Itdoes not have exactly the same functionality asnative gluten (chapter 18.9). Some of its naturalbehaviour can be recovered by protease. It canbe used to improve the structure of the proteinif the bread-making process is well controlled,taking into account the time-dependent actionof the enzyme. Purified fungal proteases willbe preferable due to their comparatively mild(specific) action at acidic pH.

High-Extraction Wheat Flour In addition to rye, bread from dark wheat flour(high extraction) or whole wheat meal is alsofairly common, especially in Germany but alsoin some other northern European countries.Its specific volume is superior to that of ryebread. Sour dough or acidification is notnecessary but sometimes used, in particularfor dark varieties of bread. Flour treatment isnot unlike that for white wheat flour, i.e.

oxidation or ascorbic acid and enzymes(amylases, hemicellulases).

Crispbread Crispbread (Fig. 174) is a speciality fromScandinavia. Most types are made from a

rather liquid yeast sponge dough (doughyield about 190%) which is sheeted, or ratherspread, after 2 h fermentation into a layer 2.5mm thick. This is followed by another fermen-tation of 30 - 60 min. Major challenges are thesticky dough and the instability of the sensitivesheeted foam, as well as sufficient energysupply to the yeast without impairing thetaste and colour of the final bread. The energynecessary for dehydration is a further importantfactor, as the dough moisture has to be reducedfrom about 50% to below 6%.

The flour treatment for crispbread can besummarized as follows:• Ascorbic acid: little or none• Amylase: for browning and fermentation• Hemicellulases and cellulases: to decrease

water addition and avoid checking(hairline cracks)

• Protease to avoid checking.

Amylases are able to provide a constant supplyof energy to the yeast. While a given sugar

addition can result in vigorous fermentationat the beginning followed by a sudden stoppingof yeast activity once the sugar resources arefinished, the amylases continue to producefermentable sugar in the same measure asthe yeast continues its fermentation. Instead


Fig. 174: Examples of crispbread


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of collapsing dough due to over-fermentation,a constant volume increase can be achieved,with its maximum at the beginning of thebaking process.

Some pentosanases are able to increase theamount of bound water at the beginning of their action, while in the long run water will bereleased again. This is a property that can beexploited particularly for the crispbreadprocess. During pre-fermentation and doughprocessing, good stability with dry surfaces isrequired, whereas after a further fermenta-

tion time the water retention should be low toimprove the drying behaviour.

Oxidases mainly affect the surface of thedough. Only in a small mixer such as theFarinograph mixer do they have a visibleeffect on the dough rheology (Fig. 138, page248), because the surface to volume ratiois large enough to permit the access of sufficient oxygen to the system. In crispbreadproduction they reduce the stickiness of

the dough sheet, improving its processingbehaviour.

Biscuits and CrackersBiscuits and crackers offer yet another possi-bility of incorporating high-fibre flour.Whereas rye is not very common for crackersor biscuits, wholemeal is. In this case,distribution is not limited to Northern Europe.Typical examples are biscotti integrale (biscuits)or crackers integrale from Italy and granolabiscuits from England (Fig. 175). Here again,Secabon, a hemicellulase with broad activityon pentosans, is very useful. It improves thechewing properties, making the bite shorter,but it also improves the properties of the

return dough, since it counteracts the dryingout of the dough during processing.

18.13.3 Noodles and Pasta Flour

Improvers for noodle flour include:

• vital wheat gluten;• emulsifiers;• bleaching agents;• colorants, in particular ß-carotene;• ascorbic acid;

• hemicellulase and• lipases.


Fig. 175: Wholemeal and high-fibre biscuits (and crackers)

171

174


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Enzymes with xylanolytic, glucanolytic andparticularly lipolytic activities have provedextremely useful in the production of noodlesand instant noodles from soft and hardwheat. They offer many advantages, forinstance:• reduced tendency to bend;• increased firmness of the cooked noodles;• enhanced overcooking tolerance;• reduced oil uptake of fried instant noodles;• reduced drying time;• improved surface appearance and

mechanical stability of dried noodles,

• reduction of raw material costs.

The addition of a lipolytic and xylanolyticenzyme compound (Pastazym) improves thetolerance of noodles made from soft and hardwheat flour to overcooking, as shown in Fig.176. With 10 g of the compound per 100 kgflour, the resistance to compression increasesby almost 30% for over-cooking conditions(10 min).

The uncooked noodles already show improvedstability (Fig. 177). This results in improvedhandling properties such as better resistanceto mechanical stress (e.g. packaging) andreduced stickiness.

To create the optimum texture of instantnoodles is a major challenge: On the one handdry noodles have to rehydrate as quickly aspossible, and on the other they must have ahomogenous texture without overcooked

outer layers and hard cores. Furthermore,they should not become soggy through extendedexposure to hot water. As Fig. 178 shows,Pastazym improves the firmness of cookedinstant noodles while the rehydration propertiesremain constant. The result is a firm bitewithout a hard, dry core texture.

The colour of raw noodles tends to deterioraterather quickly. With the enzyme compoundthe darkening is reduced, and the noodles

show improved whiteness even after 24 h(Fig. 179). The difference in L* between thereference and the noodles with 10 g Pastazym isabout 3. The human eye can detect differences


0.0

0.2

0.4

0.6

0.81.0

1.2

1.4

0 2 4 6 8 10

Dosage (g/100 kg flour)

F o r c e ( N )

5 10

Cooking time

(min)

Fig. 176: Improvement of overcooking tolerance

100

105

110

115

120

125

130

0 5 10 15 20 25


F i r m n e s s ( % )

Fig. 177: Firmness of fresh, uncooked noodleswith the addition of a lipolytic and xylanolytic enzyme compound

100

101

102

103

104

105

106

107

0 5 10 15 20 25


F i r m n e s s ( % )

Fig. 178: Firmness of cooked instant noodles made from soft wheat with the addition of a lipolyticand xylanolytic enzyme compound

70

72

74

76

78

80

82

84

0 2 4 6 8 10


C o l o r ( L * )

1 24

Hours after

extrusion

Fig. 179: Colour of fresh, uncooked noodles with theaddition of a lipolytic and xylanolyticenzyme compound


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exceeding L* = 1. The colour difference persistsafter cooking (Fig. 180).

Other additivesTab. 96 is a summary of noodle extrusion trialswith soft wheat flour using various additives.Although hemicellulases have the potential toreduce the viscosity of the extruded noodle orpasta dough or to reduce the water addition if added in very large amounts, this did not

show at the chosen dosage. Surprisingly, theydid not modify the appearance or texture of thefinished products even at very high dosages.

In sheeted noodle production, hemicellulasesimprove sheetability because they soften thedough without weakening the protein.

Transglutaminase strengthens the protein,which should improve the cooking tolerance


Fig. 180: Effect of Pastazym on the colour of dry and rehydrated noodles made from wheat flour. A: Dry noodles, reference; B: with Pastazym; C: Cooked noodles, reference; D: with Pastazym

A B

Tab. 96: Soft wheat noodle extrusion trials (double spiral noodles) with various additives

Product Reference EMCEvit Plus Dry gluten Transglutaminase

Dosage g/100 kg 3000 3000 10

Water addition % 24 24 24 24

Dough moisture content % 30.4 29.8 30.3 30.4

Extrusion pressure bar 175 185 185 155

Vacuum cm Hg 55 52 55 52

Sensory evaluation

Cooking water milky milky milky milky

Appearance, raw bright beige brownish bright beige bright beige

Appearance, cooked a bit slimy, a little slimy, slimy, brownish-grey slime, instablewhite brownish-grey brownish-grey shape, white

Eating properties tough, tough, tough, irregular bite,a little sticky elastic elastic tougher


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of noodles. The bite was indeed firmer, butthe appearance of the cooked noodle did notimprove as compared to the reference.

The addition of vital wheat gluten achievedthe expected improvement in texture. A

phospholipid-protected gluten resulted inbetter visual ratings.

An emulsifier compound of mono- and digly-cerides and lecithin sprayed onto a carrier(Mulgaprot S1) was rated best. For manyyears Mulgaprot has been used successfully

as a flour improver in Central European countries.Its use in tropical and subtropical areas islimited by the negative effects of elevatedtemperatures on particle size distribution.

Oxidizing agents and ascorbic acid also

strengthen the protein, but they impair theprocessing properties of the dough. This mayresult in an irregular noodle structure with anincreased tendency to checking. Furthermore,this strengthening cannot be detected in thefinished product in the form of improvedcooking tolerance.


C D

Hemicellulase Guar gum Guar gum Mulgaprot S1 Mulgaprot S1

50 500 1000 30 500

24 25.8 26 25.8 26

30.2 30.1 29.6 30.1 30.1

175 153 158 160 180

52 52 52 55 55

milky milky less milky less milky less milky

bright beige bright beige bright beige smoother surface, smoother surface,darker darker

irregular, porous sur face, a little slimy, white a little slimy, white not slimy, white not slimy, whiteslimy, white

irregular bite, tougher, irregular bite, slimy tough, regular, tough, regular,slimy regular bite surface, off-taste pleasant pleasant


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18.13.4 Composite Flour

In most cases the use of non-wheat flours in

mixtures with wheat flour results in a noticeableloss of volume and changed appearance (Fig.181); the sensory attributes are also different.If the overall quality of goods baked fromcomposite flour (taste and smell, chewingproperties, appearance, shelf-life) is to approachthat of pure wheat products, the wheat flourcomponent of the composite flour must firstbe treated – although even then the amountof other flours that can be added is verylimited. The well-known flour improvers

potassium bromate and ascorbic acid haveproved useful for this purpose. The dosagehas to be adjusted to the particular wheat

flour quality. As a rule it is between 20 and 50ppm. To take the other flours into account

seems to make little difference. If lipasesare used in conjunction with soy flour, forexample, there is no noticeable improvementin volume (Fig. 182), although this would bethe case with wheat flour alone.

Modern enzyme preparations also help tocompensate for the loss of volume caused byusing composite flour instead of wheat flouralone. Besides amylases, hemicellulases andalso lipases can be used.

Fig. 183 shows the effect of treatment withascorbic acid and a baking enzyme on thestructure of bread made from wheat flour with


Fig. 181: Structure of bread made from untreated wheat flour, alone or mixed with tapioca starch,rye flour or soybean flour (70 / 30%; upper left to lower right)

158

159


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Fig. 183: Effect of flour treatment on bread made from composite flour with defatted soybean flour, (70:30). 60 ppmascorbic acid plus Powerzym 6000 (hemicellulase/amylase compound), 0, 75, 100 and 150 ppmon wheat flour (upper left to lower right)

Fig. 182: Bread made from composite flour (90/10) with defatted soybean flour (upper row) and toasted, full-fat soybean

flour (lower row), using a lipolytic enzyme (from left to right 0, 60 and 180 ppm Alphamalt LP 12066)


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the addition of soy flour (70:30). Other additi-ves commonly used in baking improvers, suchas emulsifiers, improve the results still further.Fig. 184 shows the effects of various flourimprovers on the volume of pan bread madefrom a composite flour consisting of CWRSand cassava flour in comparison with CWRSflour alone. In this case a combination of ascorbic acid, enzymes and emulsifiers madeit possible to restore the volume of the loavesalmost completely up to a wheat/cassavaratio of 85:15. If the wheat flour used is lessstrong it will be necessary to add wheat gluten

or reduce the proportion of non-wheat flour.The nature of the foreign cereal may also playan important role.

The effect of the emulsifiers GMS, CSL andlecithin, and also of pre-gelatinized starch, hasalready been described in chapter 16.

There are no rules for such flour treatment. Ithas to be optimized in each case, dependingon the composition of the flour and the baking

properties of the wheat flour used.

Reference has also been made to the use of potassium bromate and ascorbic acid as flourimprovers in chapter 16.

The wheat flour used should have optimumbaking properties, and these can be achievedby suitable treatment with enzymes and oxidi-zing agents along with emulsifiers and water-binding substances.

18.13.5 Flours for Biscuits, Crackersand Wafers

Whereas a high protein content and strong

gluten are desirable properties in many breadprocesses, flours with little and weak glutenare preferable for durable baked goods. Thetendency of dough to spring back after rollingand the undesirable formation of gluten lumpsin wafer batters are the reasons for this require-ment. Whether a flour with low and weakprotein is available or not, the use of elasticity-reducing agents (proteases, L-cysteine, gluta-thione, inactivated yeast, sodium metabisul-phite) will have benefits at all stages of the

process: the lamination will be more uniform;


0

20

40

60

80

100

120

W F + A A +

F A A

W F u n t r e

a t e d

C F u n t r e

a t e d

C F + A A

C F + A A +

E N Z

C F + A A +

E N Z +

E M U L

W F + b r e a

d i m p

r o v e r

R e l a t i v e

v o l u m e y i e l d ( % )

Fig. 184: Effect of flour treatment on pan loaves made from composite flour (CWRS flour/cassava flour 85:15)in comparison with wheat flour alone(WF = wheat flour, CF = composite flour, AA = ascorbic acid, FAA = fungal α -amylase,ENZ = enzyme compound, EMUL = emulsifier, DATEM)

47

50


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reduction of the thickness of the dough sheetcan be performed faster and more reproducibly;relaxing periods for the dough sheet can beshortened or even omitted; the dough pieceswill keep the shape given by cutting; shrinkageand bending in the oven and also the forma-tion of hairline cracks (checking) are avoided.With suitable amylases, expensive recipecomponents such as milk solids otherwisenecessary for sufficient browning can beomitted. Furthermore, the whole processwill be less dependent on flour quality.Emulsifiers, particularly lecithin (Fig. 185),

but also mono- and diglycerides or DATEM,improve the spread of cookies and the regularityof biscuits and crackers. They can also be usedto reduce fat in a recipe. Emulsifiers are usuallyapplied at the bakery itself.

Biscuit and Cracker ApplicationsTab. 97 shows the recipes for simple hardbiscuits made without and with bacterialprotease. The last row compares the dimen-sions of the biscuits. As the length/width ratio

shows (average of 25 biscuits), there is almost

no difference between the length and width of biscuits with enzyme addition, whereas thosewithout enzyme show shrinkage in one direction.

Since the protease takes away most of theinternal tension, the products are less inclinedto bend during baking: the first row of Fig. 186shows the underside of biscuits withoutprotease; colouring occurred mainly at themargins, which were still touching the oven

stone when the cookies became convex due to


Fig. 185: Effect of lecithin on the spread of cookies. left: reference; right: 1% liquid lecithin on flour (Courtesy of J. v. Wakeren, Caracas)

Tab. 97: Biscuits baked with and withoutbacterial protease

Component (kg) Reference With enzyme

Flour 100 100

Fat 50 50

Sugar 50 50

Salt 0.2 0.2

Water 10 10

Protease - 0.05

Length/width (mm) 62.3 / 59.6 63.6 / 63.3


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asymmetric protein shrinkage upon thermaldenaturation. Biscuits made with proteaseremained flat and showed uniform browning(bottom row). This, too, is a common problemthat can be observed with many commerciallyproduced hard biscuits.

Wafer ApplicationsBatters for wafer production contain a largeamount of water. A low viscosity and a uniform

dispersion of all the ingredients is essential foreven wafers with a homogeneous structure.Since the formation of gluten lumps duringmixing can result in standstill of the machinerydue to blocked tubes and sieves, or in unevenbrowning and reduced stability of the bakedgoods, the use of low protein flour is desirable,but may not be sufficient. Liquefying hydrolyticenzyme complexes are able to decompose anygluten present in a liquid batter, resulting in auniform mixture with optimum flow properties.The viscosity reduction enables less water tobe used in the recipe, and this in turnresults in lower energy consumption forbaking and a higher oven throughput. Such

enzymes are most suitable for semi-continuousprocesses with batch times of at least 10 min,because the enzyme reaction needs someminutes to take effect.

We used the Amylograph at a constant tempe-rature for a simple test to demonstrate theeffect of a "wafer enzyme" (bacterial protease,hemicellulase) on the rheological propertiesof a liquid dough system (Fig. 187). Standard

wheat flour for bread making was used in allthe tests; 250 g flour was premixed with 330mL of water in a Braun mixer for 1 min 45 sand then put into the reaction jar of theAmylograph, which was adjusted to a constant30 °C. The wafer enzyme was added to onesample at 20 g per 100 kg flour before the startof mixing.

Whereas the reference sample remained atalmost the same viscosity for about 40 min,the enzyme caused an immediate viscositydrop. Furthermore, all the gluten strands weredestroyed, which is evident from the definiteshape of the curve. By contrast, the reference


Fig. 186: Underside of hard biscuits baked without (top) and with bacterial protease (bottom)


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curve shows large fluctuations due to glutenlumps or strands adhering to the mixing toolof the Amylograph.

Similar results can be obtained with otherviscometric devices, e.g. the Brookfield visco-meter (Fig. 188), although only the rotatingrods of the Amylograph seem to be able toshow the development – and disappearance –of gluten lumps.

In baking trials with a pilot-scale plant it waspossible to control the water addition andthus the weight and density of the waferswith the help of the enzyme compound. Thisoffers great economic advantages (reducedenergy demand, higher throughput) andmore freedom for product development (Fig.189). Wafers of higher density are crisper andremain crisp longer because of reducedwater absorption.


0

500

1.000

1.500

2.000

2.500

3.000

3.500

0 15 30 45 60

Time (min)

No enzyme Enzyme A, 15 g Enzyme A, 40 g

Enzyme B, 15 g Enzyme B, 40 g

V i s c o s i t y ( c p s )

Fig. 187: Effect of a "wafer enzyme" on the viscometric behaviour of wheat flour batter (Amylograph, 30 °C)

no enzyme

Alphamalt LQ 4020

Fig. 188: Viscogram of wafer batter with different proteolytic enzyme compounds and dosages(Brookfield Rotovisco, 25 °C)

10

11

12

13

14

15

16

17

18

100 120 140 160

Initial water content (kg/100 kg flour) E

n e r g y c o s t s ( E U R / 1 0 0 k g f l o u r )

50

60

70

80

90

100

D e n s i t y ( g / w a f e r , 2 9 x 4 6 c m )

1 2

Fig. 189: Effect of water addition on evaporation costsand wafer density (energy costs: 0.15 e /kWh)➀ with wafer enzyme ② no enzyme


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Replacement of Sodium Metabisulphite (SMB)in Cracker and Wafer ProductionThis powerful reducing agent (chapter 18.4.3)splits the inter-chain and intra-chain disulphide

bonds of the gluten, causing an immediatefall in dough resistance (Fig. 115, page 228) orbatter viscosity. SMB is very cheap and easyto use.


Fig. 190: Farinographs with sodium metabisulphite (SMB)

or enzymes. A: proteolytic enzyme for liquid wafer batters;B: proteolytic biscuit and cracker enzyme;C: proteolytic, amylolytic and hemicellulolytic

enzyme complex.

Reference SMB 50 g/100 kg

Enzyme A, 50 g/100 kg Enzyme B, 50 g/100 kg

Enzyme C, 50 g/100 kg

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In many countries, therefore, SMB is still usedin wafer and cracker production although itcauses a sulphurous off-taste. Enzymes as analternative to SMB improve the taste andhave definite technical advantages, namelyconstant dough properties once the reactionis accomplished, including similar texture of return dough and fresh dough, the reductionof water addition to wafer batters and controlof wafer density and stability (Fig. 189).

When tested in the Farinograph, both SMBand enzymes show a decline in kneading

resistance (Fig. 190). The reaction of SMBoccurs much faster, but probably due to thepresence of atmospheric oxygen, some of theresistance is restored upon continued mixing,when disulphide bonds broken by SMB recover(upper right). The slower but persistentreaction of the enzymes results in minimumresistance, when all the substrate of theenzymes has been degraded.

18.14 References

• Ahrenholz SH and Neumeister CE, 1987.Development and use of a sampling and analyticalmethod for azodicarbonamide. Am Ind Hyg. Assoc. J. 48:442-446.

• Bauer N, Koehler P, Wieser H and Schieberle P,2003. Studies on the effects of microbial transglu-taminase on gluten proteins of wheat. In: Recent Advances in Enzymes in Grain Processing. CourtinCM, Veraverbeke WS and Delcour J, (eds.),Laboratory of Food Chemistry KatholiekeUniversiteit Leuven, Leuven, Belgium, p 107-113.

• Bechtel WG, Meisner DF and Bradley WB, 1953.The effect of the crust on the staling of bread.Cereal Chem. 30:160-168.

• Chung OK and Pomeranz Y, 1977. Wheat flour lipids, shortening and surfactants. Baker's Dig. 5:32-44; 153.

• Diderichsen BK and Christiansen L, 1986.Preparation of a maltogenic amylase enzyme. US Patent Application 4,598,048.

• Dirndorfer M, 2000. Personal communication.

• Freund W, 1995. Bäckerei Konditorei Manage-

ment 5 – Verfahrenstechnik Brot & Kleingebäck.Gildebuchverlag GmbH & Co. KG, Alfeld, Germany.

• Frisbæk J, 2003. Novel tailor-made xylanases:Their characteristics, performance in cereal proces-

sing and use as a tool to understand xylanase functionality in baking. In: Recent advances inenzymes in grain processing. Courtin CM,

Veraverbeke WS, Delcour JA (eds.), Lab. of Food Chem., Katholieke Univ. Leuven, Belgium. 241-245.

• Gebruers K, Courti, CM, Goesaert H, VanCampenhout S and Delcour JA, 2002. Endoxylanaseinhibition activity in different European wheat cul-tivars and milling fractions. Cereal Chem.79(5):613-616.

• Geissmann T and Neukom H, 1973. On the composition of the water soluble wheat flour pento-sans and their oxidative gelation. Lebensm.-Wiss.Technol. 6(2):59-61.

• Gonzalez P, 2001. Sunn Pest – Unlocking theMysteries of an Ancient Problem. Int. Center for Agric. Res.

• Gray JA and Bemiller JN, 2003. Bread staling:molecular basis and control. Compreh. Rev. Food Sci. Food Safety 2:1-21.

• Grosch W and Wieser H., 1999. Redox reactionsin wheat dough as affected by ascorbic acid. J.Cereal. Sci. 29:1-16.

• Hedwig A, 1996. Personal communication.

• Höfer M, Ghyczy M and Popper L, 1996. Yeast

interaction with lecithin fractions. Food Technol.Int. 86-88.

• Hoseney RC and Faubion JM, 1981. A mechanism for the oxidative gelation of wheat flour water-soluble pentosans. Cereal Chem. 58(5):421-424.

• Jörgensen H, 1935. Ein Beitrag zur Beleuchtungder hemmenden Wirkung von Oxidationsmittelnauf proteolytische Enzymaktivität: Über die Natur der Einwirkung von Kaliumbromat und analogenStoffen auf die Backfähigkeit der Weizenmehle.Biochem. Z. 280:1-37; 283:134-145.

• Kieffer R, 2003. Die Elastizität von Weizenteig –

ein häufig überschätztes Qualitätsmerkmal.Getreide Mehl Brot 57(6):335-339.

• Kieffer R, Kim JJ, Walther C, Laskawy G and Grosch W, 1990. Influence of glutathione and cysteine on the improver effect of ascorbic acid ste-reoisomers J. Cereal Sci. 11:143-152.

• Köhler P, 1999. Untersuchungen zur Backwirk-samkeit von DATEM und seinen Komponenten.Getreide Mehl Brot 53(4):224-233.

• Kragh KM, Larsen B, Rasmussen P, Duedahl-Olesen L and Zimmermann W, 1999. Non-maltoge-

nic exoamylase and their use in retarding retrogra-dation of starch. WO 99/50399.

• Krog N, 1971. Amylose complexing effects of food-grade emulsifiers. Staerke. 23:206-210.

18.14 References

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