determining baking quality of wheat

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A number of methods for determining thebaking quality of flours have been developedand standardized throughout the world. Inparticular they have been elaborated by thescientific bodies of the ICC (Vienna, Austria,www.icc.or.at) and AACC International (St.Paul, MN, USA, www.aaccnet.org). They areregularly checked and optimized in specialstudy groups. So when making comparisons itis important always to use the latest issues ofthe collections of methods.

The following chapter describes the methodsfor analyzing kernels and the products groundfrom wheat or rye. Before the procedure isdescribed (usually the ICC method) the stan-dards and principles of the ICC and AACCInternational are compared in the form of atable. For a discussion of the results it isimportant always to state the method bywhich the analysis was carried out.

12.1 Determining the Moisture Content of Flours

The water content or moisture of the flours isvery important not only for their shelf life butalso for determining the solids content. Formany tests it is necessary to know the dryweight of the material in order to determinethe amount of the substances it contains. Theweight of the flour sample therefore has to beadjusted to the moisture content of the flour.There are tables to show that at a moisture

12.1 Determining the Moisture Content of Flours

12 Determining the Baking Quality of Wheat and Rye Flour

W. Freund and M.-Y. Kim

Method No. Description

ICC Standard No. 110/1 Temperature: 130-133 °CTime: 90 min

ICC Recommendation No. 202 Determination by NIR spectroscopy

AACC Method 44-19 Temperature: 135 °CTime: 90 min

content of 15.5%, 305.3 g of flour have to beweighed into the Farinograph instead of 300 g,since the solids content decreases as themoisture content increases. Most analyticalmethods are designed for flour with a moisturecontent of 14%, so at 12.5% only 294.9 g offlour are needed. Bakers have to think on thesame lines, since they need flours with a highsolids content. With the exception of maize and brewer'sbarley it is possible to determine the watercontent of all cereals and cereal products bydrying them at 130 °C for 90 min (ICC Standard110/1). Fig 37 shows a device permitting virtual-ly continuous determination of the moisturecontent of several samples at the same time. By using NIR spectroscopy (ICC Recommen-dation 202) it is possible to obtain the resultwithin seconds (Fig. 38). This method makesuse of the fact that the light rays in the near-infrared (NIR) range are absorbed or reflectedby the sample at different wavelengths (seeSpectrometry). The calibration of the equip-ment enables the computer to determine thevalues for moisture and protein very quickly.The moisture content of whole kernels can bedetermined as well as that of flour. The near-

Fig. 37: Device for determining the moisture content(source: Brabender OHG)

12_Determining 20.10.2006 13:49 Uhr Seite 101

12.2 Determining the Mineral Content of Flours

In most regions, flours are traded accordingto their mineral content (which also used tobe called the ash content). Since the bakingproperties of the flours change with thedegree of extraction, the mineral contentshould be stated in concrete terms.

The mineral content is determined by ashing aflour sample in a muffle furnace (Fig. 39) at900 °C. The organic material initially burnsquite fiercely; after this it is necessary tocontinue heating the sample for up to 120minutes. Only pure white ash is then to beseen in the porcelain crucible. After cooling,the crucible is weighed and the quantity of ashstated as a percentage of the dry matter. InGermany the type designation is obtained bymultiplying this value by 1,000. The mineral content of flours may fluctuatebetween a minimum and a maximum, depen-ding on the regulations in individual countries.

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infrared transmission technology (NIT; Fig. 38)necessary for this is the more convenientmethod for mills, since the kernels do not haveto be crushed. The water content of flour depends to a largeextent on climatic conditions during harvestingand ambient moisture during storage.Moisture values well over 15% restrict theshelf life. Both storage time and storagetemperature have to be monitored to ensurethat the cereal products do not becomeinedible through enzyme or microbiologicaldegradation and that their processing pro-perties do not suffer. In wholemeal products,especially, a stale, mouldy taste can developvery quickly.

12.2 Determining the Mineral Content of Flours

Fig. 38: Determining the moisture content of whole kernels (left) and flour (right) using near-infrared transmission technology (NIT) or near-infrared reflection spectroscopy (NIR) (sources: Brabender OHG / Mühlenchemie GmbH)


ICC Standard No. 104/1 Temperature: 900 °CTime: 2 h

ICC Recommendation No. 202 Determination by NIR spectroscopy

AACC Method 08-03 Temperature: 600 °CTime: 2 h

AACC Method 08-21 Determination by NIR spectroscopy

Fig. 39: Muffle furnace for ashing flour, with porcelain crucibles (source: University of Hanover)


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In some cases the variability is very wide, andthis may result in differences in baking proper-ties. Especially in the production of bakedgoods with a high volume yield, e.g. breadrolls, it makes a difference whether the flourused has a mineral content of 0.51 or 0.63%. Ifthe level of extraction includes little more thanthe endosperm of the grain, the proteincontent increases considerably in addition tothe mineral content (Fig. 40), but at the sametime there is likely to be a sharp fall in thevolume yield.

In the case of the rye flour types, full use of theouter layers also changes the colour of theflour. This may result in bread with a noticeablydarker crumb in spite of using the same flourtype. The dough yield will also fluctuate if theflour has a mineral content of 1.11 g on oneoccasion and 1.30 g per 100 g of dry matter onthe next.

The ash content is determined according toICC Standard 104/1. A quick test is also possibleusing NIR.

12.3 Determining Acidity in Flours

The acidity of a flour is an important indicatorof its freshness. The fats and phosphatides(lecithin) are broken down enzymaticallyduring storage of the flour. This breakdown isaccelerated by a high water content, hightemperatures and a high degree of extraction.The lipases and phosphatases naturallypresent in the cereal cause an increase in thepercentage of free fatty acids and phosphate.

12.3 Determining Acidity in Flours

Fig. 40: Changes in the flour values when the flour yield is increased beyond the endosperm. red brown: aleuron cells; blue: cell walls; dark brown: starch granules (modified from Bolling, 1986 by L. Popper; wheat micrograph courtesy of VTT, Helsinki, Finland)


ICC Standard No. 145 Determination of acidity (according to Schulerud)

AACC Method 02-31 Titratable acidity

To a certain extent this breakdownis desirable as a maturing of theflour, but once the tolerances areexceeded the flours becomeinedible. By determining theacidity of the flour, taking thedegree of extraction into account,it is possible to monitor theprogress of maturing and thepossible start of deterioration. Since the changes in the flourduring storage consist mainly in anincrease in the free fatty acids, thesample is suspended in ethanol(67% alcohol) before filtration.The filtrate is then titrated withsodium hydroxide solution to apH of 8.5. The amount of 0.1 N(mol/L) of sodium hydroxidesolution required (multiplied bytwo) is a measure of the degreeof acidity. Titration is sometimescarried out using the indicatordye phenolphthalein, but thepoint at which the colour changesfrom yellow to pink is difficult todetermine precisely. It has there-fore become established practiceto use a pH meter.

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The gelatinization properties of the starchin wheat or rye dough depend greatly on theα-amylase activity. Since rye starch gelatinizesat low temperatures, it is more easily brokendown by this enzyme. It is therefore especiallyimportant to establish the gelatinizationproperties of rye flours. Determination of theFalling Number and the Amylogram haveestablished themselves as standard methods.The Amylogram is used mainly for testingrye, whereas the Falling Number serves as ameasure for both cereals.

To determine the Falling Number, 7 g of flour areheated with 25 mL of distilled water in a waterbath for one minute to approximately 95 °C(modified Falling Number: approx. 80 - 95 °C).The viscosity of the starch gel thus obtained isthen determined by measuring the time thestirring rod takes to sink through the gel to thebottom of the measuring cylinder. The FallingNumber is the sum of the stirring and sinkingtime. It is stated in seconds. The minimum FallingNumber is 60 s. When the flour is weighed, itsmoisture content is assumed to be 15%. If thewater content differs from this value, theamount weighed in must be corrected bycalculation or according to a special table.

Nowadays the test is performed with a FallingNumber device (Fig. 41) that carries out thestirring and measuring procedure automatically.If the enzymatic activity is high, the starch isbroken down very rapidly during gelatinization.The stirring rod falls through the relativelyliquid paste in a short time. The Falling Numberis low. If the activity of the amylases is low it

takes much longer for the rod to cover thedistance and trigger the signal for the end ofthe process.

This equipment can also be used to adjust theamylase activity of flour mixtures or determinethe amount of malt to be added. With the aidof a diagram it is easy to read off the mixingratios. Conversely, it is possible to make aprecise adjustment to the desired FallingNumber. But blending with other flours ispreferable, since enzyme-active malt flourscontain the whole spectrum of cereal enzymesas well as the starch-degrading enzymes. Inother words, they are able to break down theother constituents to an undesirable extent.

Determination of the Falling Number is aninternationally recognized method that haslong been used as ICC Standard No. 107.

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12.4 Determining the Falling Number as a Measure of α-Amylase Activity

12.4 Determining the Falling Number

Fig. 41: Equipment for determining the Falling Number (source: Mühlenchemie GmbH & Co. KG)


ICC Standard No. 107/1 Measurement of the degree ofα-amylase activity in grain and flour (according to Hagberg-Perten)

AACC Method 56-81B Identical

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12.5 Determining the Gelatinization Properties of Starch

Fig. 42: Amylograph(source: Brabender OHG)


ICC Standard No. 126/1 Measurement of the gelatinization properties of rye and wheat (Brabender OHG).- Gelatinization maximum (AU)- Gelatinization temperature (°C)Determination of enzyme activity.

AACC Method 22-10 Identical

12.5 Determining the Gelatinization Properties of Starch with the Amylograph

The Amylograph (Fig. 42) enables continuousmeasurement of the changes of viscosity in aflour-and-water suspension during heating.For heating, a temperature gradient is selectedthat corresponds to the rise in temperatureduring the baking process; this means that theAmylograph can be used to make importantpredictions about the baking properties of theflour. Besides the gelatinization characteristicsof the starch it also shows the effect of theamylases.

To obtain an Amylogram, flour (14% moisture)and water are transferred to the stirring bowl,ensuring that there are no lumps. The bowlcontains rods that project upwards with thesuspension between them. When the bowl hasbeen placed in the appropriate opening in thedevice, the sensor is inserted into it from thetop. The sensor is fitted with similar rods,projecting vertically downwards. During heating,the liquid has to flow between the rods projectinginto it from above and below, since the bowl isrotated continuously. The shear forces thatoccur between the rods as gelatinizationprogresses are recorded on a diagram aschanges in viscosity; this results in the typicalcurve of an Amylogram.

When gelatinization starts, the suspensionreaches the optimum temperature for α-amy-lase activity. The rise in viscosity to be seen onthe evaluation diagram is the product of theincrease caused by gelatinization and lique-faction by the amylases. Besides the maxi-

mum viscosity, the curve also shows thetemperature at the start of gelatinization andat its maximum. A viscosity of at least 200 AU(Amylogram units) alone is not enough for ryeto be classified as bread rye; a temperature ofat least 63 °C in the suspension must alsohave been reached at this time.

Testing of wheat and rye flours with theAmylograph conforms to ICC Standard 126/1.It is especially important for assessing ryeflour products. This method is also suitable forinvestigating the effects of enzyme-activeingredients.

A further measure of the breakdown of starchis the maltose content of the flour. Being adegradation product of starch, maltose – alsocalled malt sugar – may indicate increasedsprouting of the grain. The method is based onthe enzyme activity of the flours and measures


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the fermentable sugar formed within an hourat 27 °C. The amount of maltose measured isinfluenced chiefly by ß-amylase activity, butthe starch damaged during milling may alsocontribute to a high "maltose number". If avalue of 2.3% for rye or 1.8% for wheat isexceeded, it must be assumed that there is toomuch activity of starch-degrading enzymes ortoo much damage to the starch.

12.6 Quantitative Methods of Protein Determination

Quantitative methods are those tests in whichthe amount of a constituent is determined. Thetotal amount of protein has a very importantinfluence on the baking properties of wheatflour. Fig. 40 shows that the protein contentincreases with the degree of extraction, butthere is no increase in the gluten content thatenhances the properties of the dough and alsothe baking properties. The increase resultsfrom the protein contained in the aleuronlayer, which is especially protein-rich. This effect indicates that it is not just the proteincontent in absolute terms that matters. In wheatflour there are several protein fractions thatdiffer in respect of their solubility. It is the gluten-forming protein fractions of the endospermthat determine the baking properties of wheatflours. The amount of these present can onlybe established by testing for the wet glutencontent. The proteins from the outer layersand the germ have quite different properties.Although they are included in the determinationof the protein content, they are soluble inwater or brine and therefore have no influenceon the properties of a wheat dough.

12.6.1 Determining Total Protein

The total protein content of the wheat is deter-mined by the Kjeldahl method. The organicconstituents are oxidized in the presence of acatalyst. The ammonia formed after anotherstep is distilled and titrated. The amount ofnitrogen ascertained by titration is multipliedby a factor specified for each food. For wheatand rye and the products for human nutritionmade from these cereals the factor for con-

verting the nitrogen values found from theprotein is 5.7 (see also chapter 5.7.2 and5.8.2).

A more modern way of determining the nitrogencontent is the practically automatic "Dumascombustion method" (Fig. 43) in which thesample is incinerated under oxygen, the resul-ting nitric oxide converted into nitrogen andthe heat conductivity of helium and nitrogensubsequently measured against pure helium.This procedure is faster and less complicatedthan the Kjeldahl method usual in the past.



ICC Standard No. 105/2 Kjeldahl method

ICC Standard No. 159 NIR spectroscopy

ICC Standard No. 167 Dumas combustion principle

AACC Method 46-10 Improved Kjeldahl method

AACC Method 46-11A Improved Kjeldahl method, copper catalyst modification

AACC Method 46-12 Kjeldahl method, boric acid modification

AACC Method 46-13 Micro-Kjeldahl Method

AACC Method 46-15 5-minute Biuret method for wheat and other grains

AACC Method 46-16 Improved Kjeldahl method, copper-titanium dioxide catalyst modification

Fig. 43: Device for automatically determining the protein content by the Dumas combustion method (source: Elementar Analysensysteme GmbH)

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The method for determining the crude proteincontent of cereals and cereal products forhuman nutrition is specified in ICC Standard105/2. ICC Recommendation 202 favoursdetermining the protein content by near-infrared spectroscopy (NIR); see also thesection on determining the moisture content.

12.6.2 Determining the Wet Gluten Content

is the wet gluten content in percent by weight. The methods for washing the sample differgreatly. The gluten content can be determinedunder running water or in a gluten washer. Butreproducibility (repeatability of the results)can only be achieved with these methods ifthe test is carried out by very experiencedpersons. ICC Standard 106/2 uses a glutenwasher with an eccentric plate and a glutenpress. Mechanical determination of the wetgluten content of wheat flour (ICC Standard137) is carried out with the Glutomatic equip-ment. In this method the paste is prepared andwashed automatically in the machine (Fig.44). The washing vessel and the sieve onwhich the paste is processed are specified. Atthe end of the washing procedure the gluten isplaced in the centrifuge with tweezers and theadhering water removed.

Evaluation is carried out by weighing thepieces of gluten after centrifuging. The resulthas to be converted to correspond to a flourmoisture content of 14%. If a special sieve isused for certrifugation it is possible to deter-mine the Gluten Index. The centrifugal forcepresses some of the gluten through the sieve.The higher the proportion of gluten that hasnot passed through the sieve, the higher is theindex and the better the gluten.

The wet gluten content is a measure of theamount of swollen gluten in the wheat flourthat can be determined by forming a pastefrom a flour sample and washing it out. Theprinciple of the method is that a dough ismade with a buffered solution of common salt(for adjustment to a pH of 5.95) and thenwashed out to remove the starch and thewater-soluble constituents of the gluten. The gluten is then dried and subsequentlyweighed. The amount of gluten thus determined



ICC Standard No. 106/2 Method for the determination ofwet gluten in wheat flour

ICC Standard No. 137/1 Mechanical determination of the wet gluten content of wheat flour(Perten Glutomatic)

AACC Method 38-10 Gluten - hand washing method

AACC Method 38-12A Wet gluten, dry gluten, water-binding capacity and gluten index

Fig. 44: Perten gluten washer, with the Gluten Index centrifuge (source: Perten Instruments AB)


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12.6.3 Determining the Sedimentation Value

cylinder, the more suitable is the flour formaking bakery products that require strong-protein flours.

Determination of the sedimentation value iscarried out according to ICC Standard 116. Theresult may lie between 8 mL for an extremelylow protein content and 78 mL for a flour withvery strong gluten.

12.7 Methods for Testing the Quality of Wheat Gluten

As we already mentioned in connection withthe sedimentation value, the quality of thewheat gluten is extremely important. Since itis a genetic attribute, it is given great attentionin the breeding of new varieties. The quality ofthe gluten is the basis for assigning the wheatvarieties to quality groups. For investigating the dough properties depen-dent on the gluten it has become usual toemploy methods that show water absorptionand mixing stability and also record the exten-sibility of the dough. The changes to thedough during fermentation and baking canalso be detected with special instruments.Suitable devices for this purpose are theMaturograph and the Oven Rise Recorder.

The swelling properties of wheat flours aretested by determining the sedimentationvalue (sedimentation means the sinking of asolid in a liquid). Since gluten is insoluble inwater and comes from the floury kernel of thegrain, the method measures the volume of theswollen gluten proteins. On the one hand thisvolume of sediment (settled solids in a liquid)shows the amount of gluten, and on the otherit reflects the swelling properties of the gluten.Since the gluten-forming proteins of the wheatdiffer in their ability to bind water, the sedi-mentation volume is not solely a function ofthe quantity of protein. The sedimentationvalue combines qualitative and quantitativeelements of the measurement of the wheatgluten.

To carry out the test, small quantities of wheatflour (3.2 g, with 14% moisture content) areplaced in a sedimentation cylinder with 50 mLof bromophenol blue solution (sedimentationsolution I) and shaken first by hand for 5 s andthen with the mechanical shaker for 5 minutes.After this, 25 mL of sedimentation solution II(lactic acid and isopropyl alcohol with distilledwater) are added and the constituents mixedintensively for a further five minutes in theshaking device. The sedimentation cylinder isleft to stand without moving on a level table-top for another five minutes, then the amountof sediment is read off exactly at the end of thetime. The sedimentation value is stated in millilitres.It has proved possible to predict the restingtime of the dough, its gas retention capacityand the volume yield of the baked products bythe sedimentation value. The more millilitresof sediment that can be read off the measuring



ICC Standard No. 116/1 Determination of the sedimentation value (according to Zeleny) as an approximate measure of baking quality

AACC Method 56-60 Identical (for flour)

AACC Method 56-61A Identical (for wheat)

German Wheat Quality Groups:In the descriptive lists of varieties of theBundessortenamt (the German agencyresponsible for the protection of newplant varieties) the wheat varieties areassigned to baking quality groups.Besides the volume yield, which is themost important attribute, the FallingNumber, sedimentation value, dough pro-perties and milling properties are rated.Wheat with the highest volume yield (forbuns and toast) is classified as "elite"("E" wheat). The baked volume of "A"wheat is only slightly less. "B" wheat isquite suitable for ordinary breads, and"K" wheat with a low protein content isused for making biscuits. "C" wheatshould not be used for baking or forpasta production, since it is very difficultto process mechanically.


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12.7.1 Determining Water Absorptionand the Mixing Behaviour of Wheat Doughs with the Farinograph

development time permits conclusions on thespeed of swelling; the fall in consistency(degree of softening) shows whether the flouris strong (slight fall) or weak. The Farinogramcurves are characteristic of the gluten propertiesof a flour. Farinogram curves with a broad band (band-width) and only a slight fall over the mixingtime indicate elastic doughs that do not becomeweaker even when exposed to intensivemechanical stress. These flours are mostsuitable for bread rolls and toast slices. Inflours with very strong gluten the consistencymay even be found to increase during mixing.Subsequent swelling of the gluten causes thedough to become firmer. Narrow curves withvery obvious dough softening result fromweak flours (flours with weak gluten), whichshould preferably be used for making biscuits. Testing of wheat flours with the Farinographconforms to ICC Standard No. 115/1. Sincethere are other methods of evaluating the curves(e.g. according to Brabender), the methodused should be stated. Simple adaptation ofthe equipment and connection to a personalcomputer with the appropriate softwaremakes it possible to evaluate and store the

In the Farinograph (Fig. 45) a dough is prepa-red under standardized conditions from 50 or300 g of flour, depending on the size of themixer. While the dough is being made up, itsresistance to the mixing paddles is measuredand recorded continuously. In order to achieveuniform dough properties it is first necessary tomeasure the water absorption of the dough. Todo this, water is added to the flour, which hasa moisture content of 14%, from a burette untilthe dough reaches a consistency of 500 FU.This amount of water is a measure of the waterabsorption of the flour, since a consistency of500 FU corresponds to the average firmness ofa dough. It is often necessary to make severalattempts to determine the amount of waterneeded, as it is rarely possible to add theliquid to the mixer so quickly the first time thatno dough softening occurs. Once the amount of water has been determined,another dough is made from the same flour byadding all the necessary water at once. Thisdough is then mixed for 12 min. On the graphpaper or the VDU 15 there appears a mixingcurve from which it is possible to read off thedevelopment time, the stability and the softe-ning of the dough. These Farinograph data can be used forpreparing the dough. The water absorption –largely dependent on the quality of the gluten– indicates the dough yield; the dough



ICC Standard No. 115/1 Measurement of quality and processing characteristics of wheat flour (Brabender OHG).Measurement of the waterabsorption of the flour.Determination of the mixing behaviour of the dough- Dough development time (min)- Stability (min)- Dough softening (FU14)


Fig. 45: Farinograph - E (source: Brabender OHG)

14 FU = Farinograph Units; also referred to as Brabender Units (BU)

15 VDU = Visual display unit


clear indication of the results to be expectedwhen the flour tested is baked. If the resistanceto extension is low, i.e. the curve is rather flat,the dough has weak characteristics and thebaked volume will be small. If the curve of theExtensogram rises steeply and is quite pointedat the top, the dough may be assumed to haveshort characteristics; such doughs are alsosaid to be "bucky". In this case it is difficult toinfluence the structure of the dough; the gasformed by the yeast is not sufficient to achievethe necessary leavening. The bestExtensograms for making bread and rollsare those with a well-balanced curve. Thefollowing curve (Fig. 47) shows an exampleof a flour that is well suited for the mechanicalproduction of bread.

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measurements electronically. With the additionof a printer, the software can produce acomplete report on the results if required. The water absorption for certain standardbaking tests is also determined in theFarinograph. For the baking test for white panbread the measurement used should be 350FU, for the Rapid Mix Test and the wholemealwheat baking test it should be 500 FU. TheFarinograph can also be used for standardi-zing rye doughs. The dough consistency forthe sour dough baking test with rye floursshould be 300 FU. The dough for measuringstretching properties with the Extensograph isalso prepared in the Farinograph.

12.7.2 Determining the Stretching Properties of Wheat Doughs with the Extensograph

The Extensograph (Fig. 46) has proved to be auseful instrument for determining the stret-ching properties of wheat flour doughs. To dothis a dough is made up of flour, water and saltunder standard conditions in the Farinographand rolled out in the rounder and shaping unit.After 45, 90 and 135 min the piece of doughheld by clips is pulled by the stretching hookuntil it ruptures.The force exerted during stretching and thelength of the extension are recorded on graphpaper. Both resistance to extension, measuredas the force required for stretching, and exten-sibility (stretching length to rupture) areimportant variables for assessing wheat flourdoughs. The curves of an Extensogram give a



ICC Standard No. 114/1 Measurement of quality and processing characteristics of wheat flour (Brabender OHG).Determination of the stretching properties of the dough.- Area (energy, cm2)- Resistance to extension (EU16)- Extensibility (cm)


16 EU = Extensograph Units; also referred to as Brabender Units (BU)

Fig. 46: Extensograph (source: Brabender OHG)

Fig. 47: Extensogram with a "balanced" curve (source: Brabender OHG)

EU 700

500

400

300

200

100

0 20 40 60 80 100 120 140 160mm

ResistanceExtensibility = Ratio Number

Maximum

5 cm

Energy(Area in cm2)


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The Extensograph offers a simple method oftesting the effect of additives on the proper-ties of the gluten. For example, the amounts ofascorbic acid to be added to improve wheatflour should first be determined in theExtensograph. Too much ascorbic acid resultsin Extensogram curves characterized by highresistance to extension and rapid rupture ofthe dough. All substances acting on the gluten(cysteine, cystine, proteinases etc.) can betested in this way for their effects on thedough made from a flour.

Evaluation of the curve drawn on the graphpaper by the plotting device yields a numberof measurements. First, the resistance of thedough to extension and its extensibilityshould be established. Then the area belowthe curve can be determined as an indicator offermentation tolerance. The area is stated incm2 and referred to as energy. ICC Standard114 does not provide either for information onthe energy or for calculation of the RatioNumber, but this data should always be usedfor rating flours. The Ratio Number is calculatedby dividing resistance by extensibility. Thedifferent measuring units are disregarded.High Ratio Numbers indicate a gluten withshort dough properties and baked productswith a low volume. Flours with Ratio Numbersbelow 2 are not suitable for making breadrolls.

12.7.3 Determining the Extensibility of Wheat Doughs with the Alveograph

The Alveograph (Fig. 48) is used chiefly in theMediterranean countries, parts of SouthAmerica and the former French colonies inAfrica for testing the extensibility of dough. The principle is based on an extension test inwhich a disc of dough in a holder is blown upinto a bubble (alveolus). The aim is to investi-gate the stretching properties of the dough upto the point where the bubble bursts. Theprocess of extension and the volume achievedare recorded as a curve from which it is possibleto read off the baking properties of the wheatflour. Testing of flour with the Alveograph isdescribed in ICC Standard No. 121.



ICC Standard Measurement of resistance of the dough to No. 121 extension and extent to which it can be

stretched under the conditions of the method (Chopin Alveograph).- Tenacity (max. pressure reached when blowing the dough piece to rupture)- Extensibility (length of the curve)- Strength of the flour (area of the curve)- Configuration ratio of the curve- P200/P Elasticity (P200 = pressure after 200 mL blowing or 4 cm from origin of the curve)

AACC Method Identical54-30A

Fig. 48: Alveograph and Consistograph (source: Mühlenchemie GmbH, Ahrensburg)


Aggregation times up to 80 s indicate softgluten structures that go hand in hand withhigh water absorption and average bakingpotential. Samples with a higher proteincontent and corresponding gluten structureformation have aggregation times of about100 - 250 s. In this case very good bakingproperties can generally be expected. Theflour quality is less suitable if the aggregationtimes are longer than 300 s.

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12.7.4 Mixograph for Determining the Water Absorption and Mixing Times of Wheat Doughs

In the gluten aggregation test (Fig. 50) a slurryof wheat flour is tested for its suitability formaking flat wafers. The instrument measuresthe electric current consumed by the mixer.

For the test a thin wheat flour/water suspen-sion is beaten at high speed. The gluten thusformed increases the shear forces, and this inturn alters the power consumption of themixer. The aggregation time, recognizable bythe time of greatest power consumption, andthe aggregation area described by the curveare used in the evaluation, as are the maxi-mum, mean power consumption and the risein temperature.



AACC Method 54-40A The Mixograph provides a check for uniformity and allows for prediction of baking functionality(National Manufacturing Co.).- Water absorption - Dough tolerance- Gluten strength- Mixing time

Fig. 49 Mixograph with mechanical plotting of the measurements (source: Oregon State University )

Fig. 50: Equipment for performing the gluten aggregation test (source: Brabender OHG)


Determination with gluten aggregation test(Brabender OHG)

In the USA the Mixograph (Fig. 49) is oftenused for testing the baking properties ofwheat flours. In the newly developed compu-terized Mixograph it is possible to determinethe water absorption of flours with as little as10 g of flour.

The Mixograph curve also reveals the mixingtolerance (MT) of the dough. The dough deve-lopment time and a fall in the viscosity of thedough can be read off the curve with certainty.As with the Farinograph, the extent of the"tail" of the curve indicates the quality of theflour.

12.7.5 Method for Testing the Aggregation Behaviour of Wheat Gluten for the Production of Wafer Batters


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12.8 Equipment for Testing the Fermentation of Doughs (Maturograph) and the Increase in Volume During the Baking Process (Oven Rise Recorder)

The Maturograph (Fig. 51) has shown itself tobe a useful instrument for testing doughs inthe fermentation phase. The device measuresthe increase in volume of a piece of doughduring proving. The dough ferments in an air-conditioned chamber. An automatic sensordraws the "Maturogram" in the form of acurve throughout the proving time. This makesit possible to read off optimum proving or thefinal proving time, proving stability, elasticity

and the dough level. The proving time for thepiece of dough, which is normally determinedmanually by the baker, can be made moreobjective by this equipment. The advantage ofthe device is that a piece of the actual doughwith all its ingredients is tested. So theMaturogram can be regarded as a very practicalmeasurement.

The Oven Rise Recorder (Fig. 52) is a veryuseful instrument for documenting the increasein volume during baking. The dough is heatedin an oil bath from approximately 30 °C to100 °C at the core. The resulting curve showsthe rise of the dough during heating. Thediagram yields information on the develop-ment of dough volume, the baked volume, theincrease during heating and the times at whichgas escapes.

12.8 Equipment for Testing the Fermentation of Doughs

Fig. 51: Maturograph for measuring dough stability during proving (source: Brabender OHG)


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12.9 Baking Tests to Determine Baking Properties

All the procedures described so far are termedindirect methods of testing flours made frombread cereals. But only baking tests that showthe complex interaction of all the ingredientsgive real information on baking characteristics.Carefully conducted baking tests are the onlyreliable way to predict the properties of thedough and the baked products. Like theindirect methods, the baking tests should bestandardized, i.e. human influence on theresults should be excluded as far as possible.But standardization also means that theconditions under which the tests are carriedout must be reproducible, so that the result isthe same if the same flour sample is usedagain. As long as these requirements are met it doesnot matter whether a baking test for flour iscarried out as suggested in the standardmethods or whether a special baking procedure

is used to reflect the conditions at a particularplant. The main criterion is that it must bepossible to describe the properties of theflour. The structure of the baking test must be suitablefor the raw material and reflect the usualproduction process. In the case of wheatflours the mixing system used in productionmust also be taken into account. For rye floursthe company's own sour dough should beused. Only then is it possible to assess thequality of the flour accurately and make anychanges to the process to compensate forchanges in the raw materials.

12.9.1 Baking Tests to Determine the Quality of Wheat Flours

A method permitting comparability throug-hout the world is the baking test with wheatflour described in ICC Standard 131. For theEuropean region the baking tests for panbread and rolls and the test using wholemealflours for pan bread have proved very satisfac-tory. The following section describes examplesfrom Germany that can be modified for specificapplications in other countries.

12.9.2 Standard Baking Test for Pan BreadMade with Wheat Flours of the German Classified Types

This baking test is suitable for all wheat floursof the types classified according to their ashcontent. The method reveals the bakingproperties of the flours from the point of viewof bread-making. The results yield informationon the baked volume that can be achieved, thetexture, and the characteristics of the crumb.To permit comparability the score can becalculated.

Even more than with the indirect methods, it isimportant to check the raw materials andmechanical equipment before the baking testis performed to ensure that it takes placeunder standardized conditions.

Before the dough is prepared, the moisturecontent of the flour must be determined, theweight corrected to a level of 14% and thewater absorption determined in the


Fig. 52: Oven Rise Recorder for measuring the increase in the volume of dough pieces during the baking process (source: Brabender OHG)


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Farinograph at 350 FU. The amount of waterdetermined in this way, 3% fresh yeast and1.2% salt are made up into a dough with 500 gof flour in a laboratory mixer (arm mixer),taking the dough development time shown inthe Farinogram into account. After a restingtime of 30 min and 60 min the dough isworked with 15 strokes of the mixer in eachcase. When the fermentation gases have beenexpelled for the second time, the dough isdivided into two pieces of equal weight. Thisresults in dough pieces that contain 250 g offlour each.

After being made into a round shape in the ballhomogenizer the dough pieces are put in a spe-cial container to prove. The proving time isdetermined on the basis of the baker's expe-rience. The first piece of dough is placed in theoven with the container when the normal levelof proving has been reached. The secondpiece of dough is used to ascertain the effectsof over-proving, so the fermentation time isextended by 20%. After baking for 30 min at240 °C, the loaves are brushed with water andstored in such a way that they cannot dry out.The evaluation is made after 15 to 24 hours(Association of Cereal Research, 1994).

12.9.3 Standard Baking Test for Bread Rolls Made with Wheat Flour Type 550 – Rapid Mix Test

Bread rolls are made almost exclusively fromwheat flour of the type 550. The Rapid Mix Test(RMT) was developed to establish the suitabilityof flours of this type for making bread rolls. Thename is derived from the quick method ofmixing and making the baked product. Theprinciple of the method is to have as manyactivities as possible performed by machines inorder to limit human influence on the results. Using a portion of wheat flour of the type 550corrected in weight to a moisture content of14% a Farinogram is made in which the waterabsorption is determined at a consistency of500 FU. The flour must previously have beenadjusted to a Falling Number of 250 ±25 s byadding malt flour. No malt flour is added toflours with high enzyme activity (FallingNumbers below 200 s).

The dough is prepared from 1,000 g of flourwith 5% yeast, 1.5% salt, 1% each of sugar andpeanut fat and 0.002% ascorbic acid (only ifthe flour is untreated). The temperature of thedough should be between 26 and 27 °C. Thecalculation of the water temperature shouldbe based on the sum of the flour and roomtemperature. The water temperature is thedifference between this sum and key figuresstated in the comprehensive instructions forthe test. The temperature of the mixing bowlshould be adjusted before the dough is prepared.The doughs are made up in a rapid mixer witha special mixing paddle. The mixing time isonly 1 min; after 20 s the sides of the bowlshould be scraped.

When performing the test it must be ensuredthat the dough pieces are placed in the ovenno more than one hour after mixing is finished,so the dough has to be kneaded and shapedwithin the resting times. The dough pieces aredivided and rolled into balls in the divider. Theelongated shape is produced by a moulderafter brief intermediate proving. The machinesettings are prescribed.

The rolled dough portions are placed on tiltingtrays with the open side downwards and set ina precisely adjusted fermentation cabinet for25 min to prove. Before baking, the doughportions should be left to stiffen for 2 min atroom temperature, exposed to a fan. They arethen baked at 250 °C in a deck oven with theopen side upwards. The baking time is 20 min.

12.9.4 Standard Baking Test for Pan Bread Made with Wholemeal Wheat Flour

To test wholemeal flours a baking test can beused in which the consistency of the dough isset at 500 FU (14% moisture content). Thedoughs are made from 600 g of flour in alaboratory mixer. 10% of the flour is soured ina one-stage sour-dough process. To preparethe dough, ascorbic acid (60 mL of a 0.1%solution) is added besides sugar, fat, salt andyeast (1.5% each).

The mixing time is based on the dough deve-lopment time determined in the Farinograph.



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After a resting time of 30 min the whole of thedough is put in a rectangular loaf tin, thenplaced in the oven after the appropriateproving time. The oven temperature should be210 °C. Evaluation is carried out 15 to 20 hoursafter baking. The rating criteria are much thesame as those for the pan-loaf baking testwith classified white flours.

12.10 Baking Tests to Determine the Quality Attributes of Rye Flours

The following baking tests are not as widelyused as those for wheat flours, since theindirect methods yield more information onthe baking properties of rye than is the casewith wheat. Nevertheless, baking tests areperformed with and without acid, using classifiedrye flour and wholemeal rye flour.

12.10.1 Baking Tests for Hearth BreadMade from Classified Rye Flours

This standard baking test can be carried outwith yeast, lactic acid or sour dough. In allthree cases the rye loaves are made as hearthbread. The yeast baking test can provide infor-mation on the baking properties of the ryeflours without the effect of acidification. Iflactic acid is added, the rating is carried outat slight acidification. Product quality atoptimum acidification can be ascertained inthe baking test with sour dough.

For both doughs, 1,000 g of rye flour, 1% yeastand 1.5% salt are placed in the laboratorymixer (arm mixer). In these tests, too, theamount of flour naturally has to be adjusted inaccordance with the moisture content. In thelactic acid baking test, lactic acid is added too.The temperature of the dough should beadjusted to 29 °C; the prescribed mixing timeis a total of 3 min. This is followed by a restingtime of 30 min. The dough weight used is thewhole of the dough; proving takes place infermentation baskets. Readiness for the ovenis a matter of experience; baking starts at atemperature of 250 °C, falling to 200 °C. Butwith these small amounts of dough the

temperature of the oven is unlikely to changemuch, so at the end of the baking time a lowertemperature can also be achieved by movingthe dough portions into a different part of theoven.

For the test with sour dough the dough yield isdetermined with the Farinograph at 300 FU.The sour used is a "Berlin short sour dough"with 20% starter, a dough yield of 190, atemperature of 35 °C and a maturing time of3.5 hours. If these parameters are adhered to,this one-stage sour dough process is just asreproducible as the Detmold one-stage process.45% of the flour should be soured. The remainingprocedure is no different from that of the yeast orlactic acid baking test, but the pH and degreeof acidity of the sour dough, the bread doughand the bread crumb should be ascertained(Association of Cereal Research, 1994).

12.10.2 Baking Test for a Pan LoafMade from Wholemeal Rye Flour

For this test the wholemeal rye flour is bakedinto a pan loaf as in the sour dough bakingtest. The dough yield is set at 180. The oventemperature should be adjusted to a constant210 °C. The evaluation criteria are the sameagain.

12.11 References

• AACC International, 2004. International ApprovedMethods.

• Association of Cereal Research (Arbeitsgemein-schaft Getreideforschung, Detmold), 1994.Standard-Methoden für Getreide, Mehl und Brot.

• Bolling H, 1986. Personal Communication.

• Cauvain SP (ed.), 2003. Bread making, Improvingquality, Cambridge 2003.

• Freund W, 1995. Verfahrenstechnik Brot undKleingebäck; Alfeld 1995.

• Freund W and Löns M, 2003. Methoden zurUntersuchung von Weizen- und Roggenmahler-zeugnissen. Handbuch Backwaren Technologie.Loose-leaf collection, Hamburg.

• International Association for Cereal Science andTechnology (ICC) (ed.), 2001. Standard Methods ofthe International Association for Cereal Science andTechnology, Detmold.

12.10 Baking Tests to Determine the Quality Attributes of Rye Flours


determining baking quality of wheat

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