Dough and Gluten Strength Tests

Flourpedia.com - Equipment below is to measure the resistance and extensibility of dough mixing. The glutomatic test measures the amount of gluten protein in wheat or flour. The farinograph test measures the resistance of a dough against the mixing action of paddles (blades). The extensograph test measures the resistance of dough to stretching. The alveograph test measures the resistance of a bubble of dough to expansion.

Glutomatic

Wet gluten content is determined by washing the flour or ground wheat sample with a salt solution to remove the starch and other solubles from the sample. The residue remaining after washing is the wet gluten. 

During centrifugation, the gluten is forced through a sieve. The percentage of gluten remaining on the sieve is defined as the Gluten Index, which is an indication of gluten strength. A high gluten index indicates strong gluten. 

Wet gluten content results are expressed as a percentage on a 14% moisture basis; for example, 35% for high protein, strong gluten wheat or 23% for low protein, weak gluten wheat.

The wet gluten test provides information on the quantity and estimates the quality of gluten in wheat or flour samples. 

Gluten is responsible for the elasticity and extensibility characteristics of flour dough. Wet gluten reflects protein content and is a common flour specification required by end-users in the food industry.

Farinograph

The farinograph determines dough and gluten properties of a flour sample by measuring the resistance of a dough against the mixing action of paddles (blades). Farinograph results include absorption, arrival time, stability time, peak time, departure time, and mixing tolerance index. Farinograph curves are described below :

Weak gluten Flour

Strong Gluten Flour

The Farinograph Test is one of the most commonly used flour quality tests in the world. The results are used as parameters in formulation to estimate the amount of water required to make a dough, to evaluate the effects of ingredients on mixing properties, to evaluate flour blending requirements, and to check flour uniformity. The results are also used to predict processing effects, including mixing requirements for dough development, tolerance to over mixing, and dough consistency during production. Farinograph results are also useful for predicting finished product texture characteristics. For example, strong dough mixing properties are related to firm product texture.

The Farinograph Test measures and records the resistance of a dough to mixing with paddles.

• Absorption is the amount of water required to center the farinograph curve on the 500-Brabender Unit (BU) line. This relates to the amount of water needed for a flour to be optimally processed into end products. Absorption is expressed as a percentage.
• Peak Time indicates dough development time, beginning the moment water is added until the dough reaches maximum consistency. This gives an indication of optimum mixing time under standardized conditions. Peak time is expressed in minutes.
• Arrival Time is the time when the top of the curve touches the 500-BU line. This indicates the rate of flour hydration (the rate at which the water is taken up by the flour). Arrival time is expressed in minutes.
• Departure Time is the time when the top of the curve leaves the 500-BU line This indicates the time when the dough is beginning to break down and is an indication of dough consistency during processing. Departure time is expressed in minutes.
• Stability Time is the difference in time between arrival time and departure time. This indicates the time the dough maintains maximum consistency and is a good indication of dough strength. Stability time is expressed in minutes
• Mixing Tolerance Index (MTI) is the difference in BU value at the top of the curve at peak time and the value at the top of the curve 5 minutes after the peak. This indicates the degree of softening during mixing. Mixing tolerance index is expressed in minutes Weak gluten flour has a lower water absorption and shorter stability time than strong gluten flour.

Extensograph

The extensograph determines the resistance and extensibility of a dough by measuring the force required to stretch the dough with a hook until it breaks. Extensograph results include resistance to extension, extensibility, and area under the curve. 

Resistance to extension is a measure of dough strength. A higher resistance to extension requires more force to stretch the dough. Extensibility indicates the amount of elasticity in the dough and its ability to stretch without breaking. Extensograph curves are described  below :

Weak Gluten Flour

Strong Gluten Flour

Results from the Extensograph Test are useful in determining the gluten strength and bread-making characteristics of flour. The effect of fermentation time and additives on dough performance can also be evaluated.

The Extensigraph Test measures and records the resistance of a dough to stretching.

• Resistance to Extension is the R value and is indicated by the maximum height of the curve. It is expressed in centimeters (cc), Brabender units (BU), or Extensigraph units (EU).
• Extensibility is the E value and is indicated by the length of the curve. It is expressed in millimeters (mm) or centimeters (cm).
• R/E Ratio indicates the balance between dough strength (resistance to extension) and the extent to which the dough can be stretched before breaking (extensibility).
• Area Under the Curve is a combination of resistance and extensibility. It is expressed in square centimeters (cm2). Weak gluten flour has a lower resistance to extension (R value) than strong
• gluten flour.

Alveograph

The alveograph determines the gluten strength of a dough by measuring the force required to blow and break a bubble of dough. The results include P Value, L Value, and W Value. A stronger dough requires more force to blow and break the bubble (higher P value). 

A bigger bubble means the dough can stretch to a very thin membrane before breaking. A bigger bubble indicates the dough has higher extensibility, that is, its ability to stretch before breaking (L value). A bigger bubble requires more force and will have a greater area under the curve (W value). Alveograph curves are described below :

Weak Gluten Flour

Strong Gluten Flour

The Alveograph Test provides results that are common specifications used by flour millers and processors to ensure a more consistent process and product. The alveograph is well suited for measuring the dough characteristics of weak gluten wheats.

Weak gluten flour with low P value (strength of gluten) and long L value (extensibility) is preferred for cakes and other confectionery products. Strong gluten flour will have high P values and is preferred for breads.

The Alveograph Test measures and records the force required to blow and break a bubble of dough.

• P Value is the force required to blow the bubble of dough. It is indicated by the maximum height of the curve and is expressed in millimeters (mm).
• L Value is the extensibility of the dough before the bubble breaks. It is indicated by the length of the curve and is expressed in millimeters (mm).
• P/L Ratio is the balance between dough strength and extensibility.
• W Value is the area under the curve. It is a combination of dough strength (P value) and extensibility (L value) and is expressed in joules. Weak gluten flour has lower P values than strong gluten flour.

Mixograph

The mixograph determines dough and gluten properties of a flour by measuring the resistance of a dough against the mixing action of pins. Mixograph results include water absorption, peak time, and mixing tolerance. The mixograph curve indicates gluten strength, optimum dough development time, mixing tolerance (tolerance to over-mixing), and other dough characteristics. The amount of water added (absorption) affects the position of the curve on the graph paper. Less water increases dough consistency and moves the curve upward. Mixograph curves are described below :

Weak Gluten Flour

Strong Gluten Flour

The Mixograph Test quickly analyzes small quantities of flour for dough gluten strength.Wheat breeders use mixograph results to screen early generation lines for dough gluten strength. Flour water absorption measured by the mixograph often serves as bake absorption in bread baking tests.

The Mixograph Test measures and records the resistance of a dough to mixing with pins.

• Peak Time is the dough development time, beginning the moment the mixer and the recorder are started and continuing until the dough reaches maximum consistency. This indicates optimum mixing time and is expressed in minutes.
• Mixing Tolerance is the resistance of the dough to breakdown during continued mixing and affects the shape of the curve. This indicates tolerance to overmixing and is expressed as a numerical score based

on comparison to a control. Weak gluten flour has a shorter peak time and less mixing tolerance than strong gluten flour.