B. Nuestra posición respecto de la legitimación de los particulares para accionar en inconstitucionalidad
B.2 El constituyente de 2010 excluyó expresamente la “acción popular”
The most important wheat flour functionality tests are the ones that determine the dough’s rheological properties. These assays study the rheological properties of a dough optimally hydrated and mixed. They are of upmost importance because they are strongly associated with processing (optimum water absorption and mixing time) and end-product quality.
Among the various instruments used to test the dough’s rheological properties, most measure directly or indirectly the force or gluten strength and the dough extensibility or elasticity. The results obtained after analyzing the graphs are used by all segments of the wheat industry. In grain eleva-tors, rheological tests are used to classify incoming wheats, whereas in the milling industry, these tests are used to make important decisions related to blending different types of wheats for the production of certain types of flours. In addi-tion, the instruments are used to determine the amount of dough strengtheners and other additives needed to standard-ize the flour. In the baking, cookie, cracker, and even in the pasta industries, these rheological tests are considered the most critical to determine important processing parameters (water absorption, mixing time, and dough stability) and pre-dict product quality.
5.3.4.1 determination of dough Properties with the Farinograph (Method 54-21) This method was previously described in AACC (2000).
The farinograph has been the method most commonly used to evaluate rheological properties of dough. The popu-larity of the instrument resides in its ease of operation and in the fact that measurements are empirical and thus do not require the user to have an in-depth knowledge of rheological mathematics to interpret results (D’Appolonia and Kunerth 1984). The apparatus is a dynamic, physical dough testing instrument that records the torque applied during dough mixing. The resistance the dough offers to the mixing blades during mixing is transmitted to a dynamometer hooked to a recording device (D’Appolonia and Kunerth 1984). The instrument has eight basic parts: mixing bowl, dynamometer, level system, scale system, recording mechanism, dashpot, thermostat, and a buret. There are instruments that process either 50 g or 300 g of flour. The assay is based first on the determination of the optimum amount of water to achieve a maximum consistency of 500 farinograph units (FU).
Several prefarinograms are run to center the curve on the 500 FU. The amount of water required to produce this con-sistency is the flour–water absorption. Then, the flour with its optimum water absorption is run again for up to 20 min-utes to determine optimum mixing time and the behavior of the flour before and after attaining maximum consistency.
The analysis of the typical farinograph curve yields impor-tant parameters such as arrival time to first achieve 500 FU, optimum mix time also called dough development time (time required to achieve maximum consistency), departure time or last time in which the dough had a 500 FU consistency and dough stability (calculated by time difference between depar-ture and arrival times). Another important parameter is the mixing tolerance index calculated as the drop in consistency, 5 minutes after achieving dough development time. Both dough stability and mixing tolerance index are important factors, especially for bakers, because they are closely related to gluten strength and the dough tolerance to overmixning (AACC 2000; Bloksma and Bushuk 1988; D’Appolonia and Kunerth 1984). The preferred flours for yeast-leavened prod-ucts have high water absorption (62–64%), 4 to 6 minutes dough development time, 8 to 12 minutes dough stability and a mixing tolerance index of approximately 40 FU.
A. Samples, Ingredients, and Reagents
• Test wheat flour
• Distilled water
• Ink
B. Materials and Equipment
• Farinograph with all accessories including graph paper
147 Dry-Milling Processes and Quality of Dry-Milled Products
C. Procedure (Constant Flour Weight)
1. Turn on the thermostat and circulating pump at least 1 hour before analysis. Make sure the tem-perature of the mixing bowl is 30°C ± 0.2°C, the chart paper runs properly, and put a few drops of ink in the recording pen.
2. Determine flour moisture content and adjust flour weight according to the original mois-ture content. Allow flour to equilibrate at room temperature especially if it was frozen or refrigerated.
3. Place 300 g ± 0.1 g or 50 g ± 0.1 g flour (14% mb) for the large or small farinograph bowls, respec-tively. Make sure to adjust weight according to the moisture content according to the following equations: for the 300 g farinograph accurately weigh [258 g/(100 − % flour moisture)] × 100 and for the 50 g farinograph weigh [43 g/(100 −
% flour moisture)] × 100 (Figure 5.12).
4. Fill buret with water at room temperature. Make sure that the tip is full and the automatic zero adjustment is working properly.
5. Put a few drops of ink in a pen and place in con-tact at the 9-minute position on the chart.
6. Turn on the machine to high speed and run for 1 minute until the zero minute line is reached.
At this instant start adding water to the right front corner of bowl to the exact predetermined absorption volume value.
7. When the dough begins to form scrape down sides of bowl with plastic scraper, starting on the right side, front, left side and back. Cover immediately with the glass plate to prevent water losses.
8. If the farinograph curve levels off at a value higher than 500 FU cautiously add more water.
For every 20 FU add 0.6% to 0.8% more water.
Make sure to cover bowl with glass plate to pre-vent water evaporation.
9. If the farinograph curve levels off at a value lower than 500 FU register the maximum con-sistency and stop the instrument.
10. After cleaning the equipment, repeat the pro-cedure adjusting the water absorption until the 500 FU consistency varies less than 20 FU. Make sure to deliver corrected water absorption within 25 seconds after opening the buret. Remember that when the correct absorption is achieved, the curve at maximum dough development is centered on the 500 FU line.
11. Allow the machine to run until an adequate curve is obtained (generally 20 minutes after water addition).
12. Report absorption values to nearest 0.1%.
Adjust water absorption on 14% mb using the following equations: Absorption % for 300 g farinograph = (x + y − 300)/3, where x = mL water to produce curve with optimum consis-tency (500 FU) and y = g flour used. Absorption
% for 50 g farinograph = (x + y − 50)*2 where x = mL water to produce curve with optimum consistency (500 FU) and y = g flour used.
13. Determine the following properties of the opti-mized farinograph curve (Figure 5.12):
a. Arrival time: time is required for the top of the curve to first reach the 500 FU line after the mixer has been started and the water introduced.
b. Dough development time. The time to the nearest half minute between the first addi-tion of water and the dough’s maximum consistency. This value is also referred as
“peak time.” If two peaks are observed the second should be considered as the develop-ment time.
700 600 500 400 300
200 100
00 5 10 15
A B
C Mixing tolerance index (5 min after peak)
Time (minutes)
Consistency (Barbender units)
A=Arrival time B=Development time C=Departure time C - A=Dough stability time
(a)
(b)
FIgure 5.12 Farinograph used to determine the rheological prop-erties of wheat dough with its characteristic curve. (a) Farinograph;
(b) farinograph curve.
148 Cereal Grains: Laboratory Reference and Procedures Manual c. Departure time. The time to the nearest half
minute from the first addition of the water until the top of the curve leaves the 500 FU line.
d. Stability. Defined as the difference in time to the nearest half minute between arrival and departure times.
e. Mixing tolerance index (MTI). The MTI is the difference in farinograph units between the top of the curve at peak (development time) and the top of the curve measured exactly 5 minutes afterwards.
14. Classify the tested flour according to either of the following values:
a. Very strong flour for baking or suited to blend with weaker flours. Water absorption
>63%, dough development time >10 min-utes, and MTI < 10 FU.
b. Strong flour. Water absorption >58%, dough development times between 4 and 8 min-utes, and MTI between 15 and 50 FU.
c. Medium strength flour. Water absorption 54% to 60%, dough development times between 2.5 and 4 minutes, and MTI between 60 and 100 FU.
d. Weak flour. Water absorption <55%, dough development time <2.5 minutes and MTI
>100 FU.
5.3.4.2 determination of dough Properties with the extensograph (Method 54-10)
This method was previously described in AACC (2000).
The extensograph is an instrument that measures rheo-logical properties of optimally mixed and formed dough (optimum water absorption and mixing time) obtained with the farinograph. The dough is prepared from flour, 2% salt, and the optimum water based on the farinograph.
Pieces of dough (150 g) are formed into a cylinder that is proofed under controlled temperatures (30°C ± 2°C) and relative humidity. The dough cylinder is then cramped to the extensograph arms and then subjected to a constant
Extensibility (mm)
Soft flour All-purpose flour R50=Force of the mass when
extends 50 mm
Rm=Maximum resistance Rm
Rm R50
R50 Force (Brabender units)
(a)
(b)
FIgure 5.13 Extensigraph used to determine the rheological properties of wheat dough with its characteristic curve. (a) Extensigraph;
(b) extensigraph curve.
149 Dry-Milling Processes and Quality of Dry-Milled Products
displacement until rupture (AACC 2000, Method 54-10;
Rasper and Preston 1991; Bloksma and Bushuk 1988.).
The dough resistance to stretching is graphed in the typi-cal extensograph curve shown in Figure 5.13. The instru-ment records the resistance R on the y axis (R50 mm when the dough was stretched 50 mm and Rmax when reaches the maximum height) and the extensibility (E) in the x axis.
The ratio R/E is an important parameter because it relates gluten strength and dough extensibility and therefore flour functionality. The integration of the area under the curve is proportional to the energy (W) that is required to bring about rupture of the test piece and is also highly related to gluten strength. The assay is usually repeated after fixed amounts of times (45, 90, and 135 minutes) so the dough behavior throughout different proofing times can be determined.
A. Samples, Ingredients, and Reagents
• Test wheat flours
• Salt
• Distilled water
• Cooking oil
B. Materials and Equipment
• Extensograph with all accessories including graph paper
• Digital scale
• Planimeter
• Ink
• Convection oven
• Desiccator
• Aluminum dishes
• Tweezers
• Brush C. Procedure
Dough Preparation
1. Prepare a dough following the 300-g farino-graph procedure described before. The differ-ences are that the flour is supplemented with 6 g salt, the addition of 2% less water due to salt addition, and that the farinograph mixes the dough for 1 minute and stops for 5-minute intervals until maximum consistency or dough development time is achieved.
2. Before dough resting, make sure to fill the humidified chamber containers with distilled water and to slightly grease the metal forms where the center of the dough cylinders will rest.
3. After dough mixing, cut and weigh 150 g ± 0.1 g of dough and place it in the special device that mechanically rounds the dough. Shape the dough ball into a cylinder using the special forming device. Then, place clamps at the ends of the cylinder and store the dough in the exten-sograph chamber with strict temperature (30°C) and relative humidity controls.
Dough Testing
1. Dough can be tested at 30, 60, and 90 min-utes or after 45, 90, and 135 minmin-utes. Remove dough cylinder with clamps from the humidi-fied chamber and place it under the stretching hook arm. Adjust recording pen to zero in the extensograph paper.
2. Start the dough-stretching action until the dough ruptures. The instrument should graph the typical extensogram (Figure 5.13).
3. Remove dough and repeat the dough ball form-ing and restform-ing procedures after 30- or 45-min-ute intervals. The same reshaped dough should be tested at least three times.
Determination of Extensogram Parameters 1. Determine the following properties of the
extensograms (Figure 5.13):
a. Resistance to stretching (Rmax and R50 mm).
Obtained as the maximum curve height (EU) and after 50 mm dough stretching.
Values are measured on the y axis.
b. Extensibility (E). Obtained after measuring the length (cm) of the curve on the x axis.
c. Work (W) or energy calculating the area under the curve. It is calculated using a pla-nimeter and represents the work required to stretch the dough.
d. Calculate the Rmax/E ratio values.
2. Classify the tested flour according to either of the Rmax/E values:
a. Very strong flour for baking or suited to blend with other flours
Rmax/E 0.5–1 b. Strong flour
Rmax/E > 0.35 c. Intermediate flour
Rmax/E > 0.10 d. Weak flour
Rmax/E < 0.1
5.3.4.3 determination of dough Properties with the Mixograph (Method 54-40) This method was previously described in AACC (2000).
The mixograph is an instrument that works with the same principles as the farinograph. The interpretation of the char-acteristic mixograph curve yields important parameters such
150 Cereal Grains: Laboratory Reference and Procedures Manual as optimum dough mixing or peak time, stability, the height
of the curve, the angle and curve thickness especially before and after the optimum dough development time, and the area under the curve. However, the analysis of the curve is not as extensive as the farinograph curve but is the preferred method by plant breeders because it only requires a 10- or 35-g sample and the assays only lasts 7 to 8 minutes (AACC 2000, Method 54-40; Finney and Shogren 1972; Rath et al.
1990; Walker et al. 1997). The wheat quality laboratories use the mixograph extensively to evaluate thousands of early generation wheat lines. Mixogram curves will be evaluated for peak times and tolerance scores. Wheat breeders can then make decisions about discarding lines with no end-use qual-ity potential. The amount of water and sample weight varies according to protein and moisture, respectively. The instru-ment graphs a curve that shows a time point of maximum consistency (dough development time).
A. Samples, Ingredients, and Reagents
• Test wheat flour
• Distilled water B. Materials
• Mixograph with all accessories including graph paper
• Scale
• Buret (10 mL or 25 mL)
• Ink
• Convection drying oven
• Desiccator
• Aluminum dishes
• Tweezers
• Thermometer
• Laboratory clock C. Procedure
1. Check the speed of the mixing head (85–90 rpm) and the arm (AACC 2000, Method 54-40).
2. Adjust the range and sensibility of the instru-ment according to the official method (AACC 2000, Method 54-40).
3. Place ink in the pen and adjust mixograph paper so the test starts at zero.
4. Determine beforehand the flour moisture and protein content. The first parameter value will affect sample weight and the second will affect water absorption. After analysis, keep samples in sealed containers to avoid moisture gain or loss.
5. Before the test, temper the test flour, water, and mixing bowl to 25°C.
6. Calculate the sample weight according to the following equations. For the 35 g mixo-graph, accurately weigh [30.1 g/(100 − % flour moisture)] × 100, and for the 10 g mixograph, weigh [8.6 g/(100 − % flour moisture)] × 100.
Accurately weigh the predetermined sample (±0.05 g).
7. Carefully place flour in the tempered mixing bowl (Figure 5.14).
8. Calculate the desired water absorption which usually relates to the protein content. Add 50%
to the flour protein to estimate percentage of water absorption. For instance, for 9%, 10.5%, 12%, and 14% protein flours add 59%, 60.5%, 62%, and 64% distilled water, respectively.
Convert the percentage of water absorption for the 35 g or 10 g mixograph using the following equations:
(a)
(b)
A = Water addition B = Peak height C = Dvelopment time
A=Water addition B=Peak height C=Dvelopment time B
B
C
A
0 1 2 3 4 5 6 7 8
Time (minutes) Bread flour
Soft flour
0 1 2 3 4 5 6 7 8
Time (minutes) C
A
FIgure 5.14 Mixograph used to determine the rheological prop-erties of wheat dough with its characteristic curve. (a) Mixograph;
(b) mixograph curve.
151 Dry-Milling Processes and Quality of Dry-Milled Products
Water (mL) for 35 g mixograph = (% water absorption/100
× 35) + (35 − sample weight)
Water (mL) for 10 g mixograph = (% water absorption/100
× 10) + (10 − sample weight)
9. Fill burette with water tempered to 25°C. With a 25- or 10-mL buret, carefully deliver the prede-termined amount of water to the mixing bowl.
10. Place mixing bowl with flour sample and water, making sure to secure bowl with the two pegs.
Then, lower the mixing head.
11. Make sure the graph paper and pen are properly set and placed.
12. When the marking pen reaches the vertical line, turn on the mixing head and allow dough to mix for 8 minutes (Figure 5.14). If a laboratory clock is used, the 8-minute mixing can be automati-cally controlled.
13. Turn off mixing head. Immediately check and register the dough temperature.
14. Determine the following properties of the mixo-graph curve: the height of the curve, the angle and curve thickness especially before and after the optimum dough development time, and the area under the curve:
a. Area under the curve. Calculate the area under the 8-minute curve considering the center of the curve width.
b. Time to reach maximum curve height (peak time). Calculate the time (nearest half min-ute) and height (cm) of the mixogram. These parameters are related to optimum dough development time and flour strength.
c. Ascending and descending angle rays from the peak point. The center of the peak curve point is taken as the vertex of the angle whereas the ascending and descending rays should be drawn before the estimation of the angle.
d. Mixing tolerance index. The width of the mixogram curve and the angle of descent indicate the tolerance of the dough to over-mixing. Well-defined curves with wide bands and low angles of descent indicate strong tolerance to overmixing and superior protein quality.
5.3.4.4 determination of dough Properties with the alveograph (Method 54-30)
According to Faridi et al. (1987), in the 1920s, Marcel Chopin devised several prototypes to test the physical condi-tion of developed dough and related the tests to the bread-baking process. The key and most noteworthy design was the injection of air to a developed round disc of dough to form a bubble until it burst. During its inflation, the dough piece
is extended in two directions: along a parallel and along a meridian of the bubble. This mode of deformation is called biaxial extension. The final design was named the alveo-graph. This apparatus differs from other dough rheological instruments because it is the only one that measures biaxial extension. This simulates gas retention during fermentation.
The characteristic alveograph curve yields important dough rheological parameters that are closely related to wheat qual-ity and type. The main evaluated parameters are maximum overpressure (P), index of swelling, average abscissa at rup-ture (L), deformation energy (W), and the P/L ratio. The P/L ratio is an excellent indicator of flour functionality. Strong gluten flours usually yield curves with high P and W val-ues. The assay consists of mixing 250 g of flour for 8 min-utes with a 2.5% salt solution (AACC 2000, Method 54-30;
Dubois et al. 2008; Rasper and Walker 2000). The amount of water is adjusted according to the flour moisture content.
The resulting dough is divided into four equal parts that are rolled on a sheet to obtain a fixed thickness (12 mm). The dough sheets are cut into discs with a given diameter and then rested in an isothermic box. The alveograph curves are generally obtained 20 minutes after dough cutting. The disc of dough is placed in the equipment in preparation for air injection. The air is injected at a constant pressure until the dough bubble bursts. Strong gluten flours usually have high P and W values.
A. Samples, Ingredients, and Reagents
• Test wheat flour
• Distilled water
• Sodium chloride (reagent grade) solution (2.5%)
• Paraffin or vegetable oil B. Materials and Equipment
• Alveograph with all accessories
• Digital scale
• Graduated cylinder (100 mL)
• Plastic spatula
• Convection drying oven
• Volumetric flask (1 L)
• Desiccator
• Aluminum dishes
• Tweezers
• Brush
• Laboratory clock or chronometer
• Eye dropper C. Procedure
1. Prepare the following reagent:
a. Sodium chloride solution. Dissolve 25 g of sodium chloride in distilled water and make up to the 1000 mL mark.
2. Determine beforehand the flour moisture con-tent because this value will affect sample weight.
After analysis, keep samples in sealed containers to avoid moisture gain or loss.
3. Turn on alveograph and verify that the tempera-ture of the mixer and proof chamber is 24°C and 25°C, respectively. The optimum temperature
152 Cereal Grains: Laboratory Reference and Procedures Manual
and relative humidity ranges of the laboratory should be between 18°C and 22°C and 55% and 70% relative humidity.
4. Temper the test flour and salt water solution to
4. Temper the test flour and salt water solution to