Mixolab - Tecnica Molitoria Int 2008

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2 - Tecnica Molitoria International - Yearly issue 2008

Technologies to arrive at the current de-vice (Dubat, 2004).The Mixolab clearly stands out due to the geometry of its mixer blades and the ability to vary the temperature when conducting a test. The operator is thus able to heat the dough up to 90°C, and then to re-cool it if desired. This function makes the Mixolab unique, by allowing the user, through a single test, to obtain information on water absorp-tion capacity and kneading stability, as well as gelatinisation temperature, amylase activity or starch retrograda-tion. This information will then be used in industry for a better understanding of the potential of flours (storage time for white sandwich bread depending on the speed of retrogradation, for exam-ple). The device offers extensive meas-urement functions, for various cereals (Tulbek et al., 2006; Tulbek and Hall, 2007; Manthey et al., 2007; Piguel et al., 2007), for assessment of flours to be used in various products such as ba-guettes (Boizeau et al., 2007), noodles (Cato, 2006; Cato and Gianibelli, 2006) or cakes (Koksel et al., 2007). It can also be used to measure the effect of different ingredients (Collar et al., 2007; Bollain and Collar, 2005) or additives such as hydrocolloids (Rosell et al., 2007; Bonet et al., 2006). In addition, the Mixolab has been designed to en-able analysis both of flours and integral grists, meaning that it can be used in all areas of the wheat industry (Sinnaeve, 2000; Lenartz et al., 2006).The principle of the Mixolab device

involves measuring the torque exerted by the dough between two blades turn-ing in opposite directions. This dough consistency measurement enables tra-ditional measurement of the water ab-sorption capacity of flours as well as their behaviour during kneading. These applications make the Mixolab compa-rable to Brabender’s Farinograph. Due to the specific technical characteristics of the Mixolab, and in particular its unique mixer, a direct comparison be-tween the results provided by the two devices cannot be made. It is entirely possible, however, using a simplified protocol and mathematical models, to obtain values comparable to those of the Farinograph.This study, jointly conducted by the Arvalis-Institut du végétal, the Centre Wallon de Recherches Agronomiques de Gembloux, and Chopin Technologies, seeks to assess, through a collaborative scheme, the level of reliability of the method using the Mixolab (repeatabil-ity, reproducibility) on the one hand, and its accuracy on the other hand. To achieve this, the study was carried out with reference samples on the Farinograph using the intercomparison approach of Bipea (Bureau interprofes-sionnel d’études analytiques – Inter-Professional Analytical Studies Office). For each of the parameters: hydration, development time, weakening and sta-bility, the reference values communi-cated by Bipea represent true values which can be used for comparison purposes.

Tecnica Molitoria International - Yearly issue 2008 - 3

the MiXolab

Fig. 1 - The Mixolab.

- A PC interface including specific soft-ware: the operator can choose either to work on one of the fixed protocols, or on his own protocols, by modifying, for example, tray temperatures, heating and cooling speeds, cycle time and kneading speed. The device is illustrated in fig. 1. The mixer can be fully dismantled, enabling fast and easy cleaning (fig. 2).

The Chopin+ protocol

The test is carried out in two separate stages.a) Determination of water absorption potentialThe operator prepares the test on the PC interface, indicating:- the protocol used;- the water content of the sample (de-termined in advance in accordance with Afnor standard V03-707);- the hydration level at which the test

Fig. 2 - The mixer.

The device

The Mixolab is a device comprising:- A dough consistency assessment sys-tem: a torque sensor measures the consistency of the dough between the blades at any moment, in Nm, an inter-national unit.- A mixer temperature control system: heating resistors enable the temperature to be increased (up to 90°C), cooling be-ing carried out by the circulation of water (using a closed or open circuit). The tem-perature of the mixer can be measured at any moment, as can the temperature of the dough (patented system), allowing enhanced assessment of the quality of a tested product.- An automatic hydration water injection system: the water is measured out and automatically injected by the device in accordance with the test configuration set by the user, and its temperature is monitored.

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is to be conducted (by default, 55% is indicated, based on 14% water con-tent).- the software then indicates the quantity of flour to be weighed out for the test. The operator starts the test and ob-serves the behaviour of the dough. If it is visually observed that the C1 torque is within the limits of 1.1 ± 0.07 Nm, the operator leaves the test to run its course. If the C1 torque is outside these limits (as most often happens), the oper-ator stops the test, notes the C1 torque level reached, and cleans the bowl.b) Determination of rheological charac-teristics

Based on the test previously carried out, the operator then indicates:- the protocol used;- the water content of the sample;- the hydration level at which the test is to be conducted. This operation is carried out by means of an integrated calculation sys-tem which takes account of the data from the first test (hydration level used and C1 torque reached) in order to calculate the potential hydration of the test sample;- the software then indicates the quantity of flour to be weighed out for the test. The operator starts the test.The graph (fig. 3) obtained when apply-ing the Chopin+ protocol enables as-

Fig. 3 - Example of graph obtained for a Chopin + test on the Mixolab.


sessment of the rheological characteris-tics associated with the behaviour of the proteins and starch.- The green curve corresponds to the torque recorded by the sensor, in Nm.- The red curve indicates the tempera-ture of the mixer, in °C.- The pink curve indicates the tempera-ture of the dough in °C.- The horizontal purple line represents the target consistency, and the dotted lines delimit the acceptable tolerance (1.1 ± 0.07 Nm) during hydration determination.

Table 1 - Description of the phases of the Mixolab and the associated parameters. Phase 1 Initial kneading

Phase 2 Weakening

Phase 3 Gelatinisation

Phase 4 Cooking stability

Phase 5 Retrogradation

This graph involves 5 separate phases, described in tab. 1.

The simplified protocolIn order to emulate the operating condi-tions of the Farinograph, it was decided, for this study, not to use the heating section of the Mixolab and to extend the kneading time at 30°C.This simplified protocol (called Chopin S) is equivalent to the following settings:- kneading speed: 80 rpm;- target torque: 1.1 Nm;

The mixer is kept at a temperature of 30°C for 8 minutes. The kneading procedure specific to the Mixolab ensures that the dough is prepared and weakening takes place during this phase. The usual data concerning dough behaviour during the kneading process are measured.

A drop in consistency can be observed when the dough temperature rises. This fall, whose extent varies depending on the samples in-volved describes the weakening of the pro-teins under the dual effect of the mechanical constraint and the heat. It provides an indica-tion in respect of protein quality.

The starch granules break when a certain tem-perature is reached. This gelatinisation phase is measured on the dough, at hydration levels close to real conditions in which flour is used. The C3 level is dependent on the starch char-acteristics and amylase activity.

The drop in consistency between C3 and C4 indicates the stability of the starch gel when hot. It can be observed that this fall is greater when the amylase activity is high.

The increase in consistency between C4 and C5 indicates the way that the starch retrogrades when dough temperature is reduced. Studies cur-rently taking place have shown that this retrogra-dation measurement can be correlated with the staling phenomenon when the bread is in a tin.

- C1 in Nm: maximum consistency during phase 1- WA as a %: water adsorption- T1 in min: time elapsed before C1- Stability in min: time during which torque exceeds the C1-11% value- D1 in °C: dough temperature at C1

- C2: minimum consistency during phase 2- D2: dough temperature at C2

- C3: maximum consistency during phase 3- D3: dough temperature at C3

- C4: minimum consistency during phase 4- D4: dough temperature at C4

- C5: maximum consistency during phase 5- D5: dough temperature at C5

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- dough weight: 75 g;- mixer temperature: 30°C;- hydration water temperature: 30°C;- kneading time: 30 mins.The test is carried out in two stages (a and b) in the same manner as previously described.Following the tests, the curves (fig. 4) are mathematically processed in order to acquire data close to that obtained on the Farinograph for the following set-tings: hydration (%), development time (mins), weakening (Nm and UF equiva-lent) and stability (mins). The transforma-tion equations were implemented using a set of 125 calibration points and 20 validation points. The statistical analysis was carried out using Minitab software (Minitab 15.1.0.0).To assess the performance of the cali-

brations obtained by modelling, a series of measurements was carried out on the Bipea Farinograph Circuit no. 25 samples.Fig. 5 shows the position of the four set-tings obtained from 30 samples resulting from 4 years of different harvests in rela-tion to the reference value including the tolerance set on the Bipea. It is observed that:- the difference between the hydration levels is always less than 1%;- development time and stability remain within the acceptable tolerance for the circuit;- weakening, measured in Nm, and con-verted here into UF on the basis of 1.1 Nm = 500 UF, remains within the ac-ceptable tolerances for the circuit except for two points.

Fig. 4 - Examples of graphs obtained for a Chopin S test on the Mixolab.

coMparatiVe stUDY

A comparative study of results obtained on the Brabender Farinograph and on

the Chopin Mixolab using the simplified protocol is here reported.


Fig. 5 - Difference

between the calibration cal-culated based

on the result obtained by

each sample on the Mixolab

and its Bipea reference value

(in blue) and range of toler-

ances of the circuit (in red).

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Reliability assessment

Organisation of the inter-laboratory studyThe study was conducted in accordance with the provisions of ISO Standard 5725, parts 1, 2 and 6:- 12 laboratories took part in the col-laborative test, representing 6 countries (tab. 2);- 8 flour samples, including 6 external (Bipea) reference materials, and a sam-ple tested using the “blind duplicates” method were subjected to tests, cover-ing a value range from: 54.3 to 62.9% for hydration; 1.5 to over 4 mins for develop-ment time; 0.03 to 0.23 Nm (or from 15 to 105 in UF equivalent) for weakening; 2 to 14.5 mins for stability;- each laboratory was asked to repeat the simplified protocol twice after determin-ing water content.

ResultsTypical differences in repeatability and reproducibility were determined using

Table 2 - List of participants in the ring test.

Laboratory CountryArvalis-Institut du végétal FranceCRA Gembloux BelgiumChoPIN Technologies 1 FranceChoPIN Technologies 2 FranceChoPIN Technologies 3 FranceNDSU USAAWB AustraliaGranotec Argentine ArgentinaRheotec BelgiumIATA-CSIC Spainhorizon milling-Cargill USAEurogerm France

a one factor variance analysis, after elimination of aberrant averages (Dixon test) and variances (Cochran test). Tab. 3 shows, for each parameter and each sample, its average (M) as well as its typical differences in repeatability (Sr) and reproducibility (SR) and its coeffi-cients of variation for repeatability (CVr) and for reproducibility (CVR).For each parameter, it has been estab-lished (fig. 6) that the reliability values (typical differences in repeatability and reproducibility) are independent of the average, since the coefficients for deter-mination of the relations (R2) are adjusted by 1.The following limits for repeatability (r) and for reproducibility (R) were calcu-lated:• hydration level: r = 0.8% and R = 2.1%;• development time: r = 0.6 mins and R = 0.8 mins;• weakening: r = 0.02 Nm (equivalent to 11 UF); and R = 0.04 Nm (equivalent to 20 UF)• stability: r = 1.5 mins and R = 2 mins.The typical differences in repeatability obtained in this study with 12 labora-tories were compared to the typical differences in the control population of Bipea Farinograph circuit no. 25, i.e. 27 laboratories. These typical differences (tab. 4) illustrate inter-laboratory vari-ation.Comparison of the typical differences in repeatability of the study with those of the Bipea control population show greater variability for the hydration pa-


Table 3 - Statistical analysis of the parameters of the samples.

Flour A B C D E F G H

Hydration rate (%)Nb 10 12 11 10 10 11 12 12M (%) 62.8 58.8 61.8 56.0 56.9 53.8 51.7 51.7Sr (%) 0.28 0.38 0.27 0.27 0.19 0.35 0.26 0.33CVr (%) 0.4 0.6 0.4 0.5 0.3 0.7 0.5 0.6r (%) 0.8 1.1 0.7 0.7 0.5 1.0 0.7 0.9SR (%) 0.65 0.92 0.76 0.5 0.51 0.79 0.89 0.95CVR (%) 1.0 1.6 1.2 0.9 0.9 1.5 1.7 1.8R (%) 1.8 2.5 2.1 1.4 1.4 2.2 2.5 2.6Development time (min)Nb 10 12 11 11 12 12 12 12M (min) 4.4 1.7 2.9 1.7 1.7 1.4 1.0 1.1Sr (min) 0.25 0.17 0.43 0.24 0.19 0.33 0.00 0.13CVr (%) 5.7 9.8 14.8 14.3 11.2 23.6 0.0 11.6r (min) 0.7 0.5 1.2 0.7 0.5 0.9 0.0 0.4SR (min) 0.58 0.3 0.5 0.26 0.21 0.31 0 0.25CVR (%) 13.2 17.2 17.2 15.5 12.4 22.1 0.0 22.3R (min) 1.6 0.8 1.4 0.7 0.6 0.9 0.0 0.7Weakening (UF equivalent)Nb 10 12 11 11 12 12 12 12M (UF) 19 74 41 72 66 92 100 98Sr (UF) 4.87 3.72 3.92 3.23 2.76 3.97 4.02 4.52CVr (%) 0.256 0.050 0.097 0.045 0.042 0.043 0.040 0.046r (UF) 13.5 10.3 10.9 8.9 7.6 11.0 11.1 12.5SR (UF) 6.88 6.40 7.30 4.96 9.55 7.01 8.29 8.2CVR (%) 0.362 0.086 0.180 0.069 0.144 0.076 0.083 0.084R (UF) 19.1 17.7 20.2 13.7 26.5 19.4 23.0 22.7Stability (min)Nb 10 12 11 11 12 12 12 12M (min) 16.4 3.1 11.1 3.1 3.0 3.1 2.2 2.2Sr (min) 0.67 0.37 1.67 0.35 0.44 0.25 0.19 0.45CVr (%) 4.1 12.1 15.1 11.5 14.5 8.1 8.7 20.3r (min) 1.9 1.0 4.6 1.0 1.2 0.7 0.5 1.2SR (min) 0.76 0.51 2.49 0.49 0.46 0.42 0.31 0.43CVR (%) 4.6 16.7 22.5 16.1 15.2 13.6 14.2 19.4R (min) 2.1 1.4 6.9 1.4 1.3 1.2 0.9 1.2

Nb is the number of laboratories or tests; M is the average of the parameter; Sr and SR are the typical differences in repeatability and reproducibility; CVr and CVR are the coefficients of variation (CVr = 100 x Sr/M and CVR = 100 x SR/M); r and R are the limits of repeatability and reproducibility (r = 2.77 x Sr and R = 2.77 x SR).

rameter. However, this is explained by the accepted tolerances (±0.07 Nm) for the centring of the curve. This variability may be improved by the ap-plication of more restrictive tolerances

(±0.05 Nm). For all other parameters, the typical differences in repeatability are lower and comparable to those observed on the Bipea for each of the circuits.

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Fig. 6 - Correlation between the aver-

age obtained by each sample on

the Mixolab and its typical differences in repeatability and re-

producibility.


analysisFig. 7 -

Differences between the

average obtained by each sample on the Mixolab

and its Bipea reference value

(the samples are classed in

ascending order according to their reference value).


Fig. 8 - Correlation

between the average obtained by

each sam-ple on the

Mixolab and its Bipea ref-

erence value.

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conclUsions

The tests on the Mixolab led to the same classification for the four parameters studied. The reliability levels obtained are comparable to those of standard NF ISO 5530.1.Comparison of the typical differences in repeatability of the study with those of the Bipea control population show greater variability for the hydration pa-rameter. However, this is explained by the accepted tolerances (± 0.07 Nm) for the centring of the curve. This variability may be improved by the application of lower tolerances (± 0.05 Nm). For all other parameters, the typical differences

in repeatability are lower and comparable to those observed on the Bipea for each of the circuits.Finally, the statistical analysis of ac-curacy showed, for all parameters, that the Chopin Technologies Mixolab (using the Chopin S protocol) and Brabender Farinograph methods were similar.Therefore, the Mixolab is a measuring device suitable for determination of the level of water absorption in flours and the rheological characteristics (development time, weakening, sta-bility) of dough during the kneading process.

bibliographY

Boizeau S., Jollet S., Dubat A., Le Brun O., 2007. Utilisation du Mixolab Chopin Technologies pour caractériser les blés 2006 et certains in-grédients dans la filière blé-farine-pain. Indus-tries des Céréales, 153, 17.

Bollain C., Collar C., 2005. Innovative evaluation of the rheological behaviour of bread dough con-trolling mixing energy and temperature. In: Proceedings Intrafood, innovation in tradition-al foods, Volume II, p. 37-40, Fito P., Toldra F. (Eds). Elsevier, London.

Bonet A., Blaszczak W., Rosell C.M. Formation of homopolymers and heteropolymers between wheat flour and several protein sources by transglutaminase catalyzed crosslinking. Cere-al Chem., 83, 655-662.

Cato L., 2006. Processing & assessment of Udon noodles. Poster session AACC, San Francisco.

Cato L., Gianibelli M.C., 2006. Mixolab assess-ment of AWB noodle wheat. Poster session AACC, San Francisco.

Collar C., Bollain C., Rosell C.M., 2007. Innova-

tive assessment of the rheological behav-iour of formulated bread doughs during mix-ing and heating. Food Sci. Technol. Int., vol. 13, 2, 99-107.

Dubat A., 2004. Le Multigraphe: un appareil pour la détermination de la qualité des céréales. In-dustries des Céréales, 139, 5-10.

Koksel H., Kahraman K., Sakiyan O., Ozturk S., Sumnu G., Dubat A., 2007. Utilization of Mix-olab to predict the suitability of flours in terms of cake quality. In press.

Lenartz J., Sinnaeve G., Dardenne P., 2006. Éval-uation du Mixolab Chopin: comparaison avec d’autres méthodes d’appréciation de la qual-ité technologique des farines de blé tendre. In-dustries des Céréales, 147, 30.

Manthey F., Tulbek M.C., Sorenson B., 2007. Évaluation des blés durs américains à l’aide du Mixolab. Industries des Céréales, 153, 18-19.

Piguel P., Pernot A.G., Dubois M., Coste C., 2007. Effets du Procédé Oxygreen sur la


rhéologie des pâtes: étude de farines de sar-rasin par le Mixolab. Industries des Céréales, 152, 22-24.

Rosell C.M., Collar C., Haros M., 2007. Assess-ment of hydrocolloid effects on the thermo-mechanical properties of wheat using the Mix-olab. Food Hydrocolloid, 21, 452-462.

Sinnaeve G., 2000. Évaluation du multigraphe FFC pour l’appréciation de la qualité des blés et des farines. Journée d’étude “Waardebeoordeling

van tarwe en bloem: new opportunities met de multigraph FFC”, Gent, Belgium.

Tulbek M.C., Hall III C., 2007. Évaluation à l’aide du Mixolab de l’influence des farines de lin sur le comportement rhéologique des pâtes. Indus-tries des céréales, 153, 20-21.

Tulbek M.C., Manthey F., Simsek S., Dubat A., Mergoum M., Hareland G., 2006. Evaluation of hard red spring wheat quality with Mixolab. Poster session AACC, San Francisco.

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Mixolab - Tecnica Molitoria Int 2008

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