Wheat Classification with Sedimentation Analysis: Gluten Quality

Wheat is one of the most widely used cereal products worldwide and is the primary raw material especially in bread production. The processability of wheat and the quality of the final product largely depend on protein structure and gluten quality. Whether the gluten structure is strong or weak directly affects the dough’s elasticity, gas retention capacity, and therefore bread volume.

Among the analysis methods used to determine wheat quality, protein analysis, gluten index, falling number, and sedimentation test hold an important place. The sedimentation test is widely used among these methods because it provides quick information about gluten quality.

Principle of Sedimentation Analysis

The sedimentation test is based on the principle of swelling and settling of milled wheat or flour samples in a specific chemical solution. The most commonly used method is known as the Zeleny Sedimentation Analysis.

During the test, the flour or milled wheat sample is mixed with a lactic acid solution and bromophenol. As a result of shaking, gluten proteins swell and form a sediment by the end of the test period.

This sediment settles in the tube after 5 minutes, and the sediment volume is measured in milliliters (ml).

The sediment volume is directly related to the water absorption capacity and swelling properties of gluten proteins. Wheat with strong gluten structure forms higher sediment volume, while wheat with weak gluten structure produces lower sediment volume.

Classification of Wheat According to Sedimentation Analysis

The sedimentation value is an important parameter in evaluating the technological quality of wheat. In general, as the sedimentation value increases, gluten quality and bread-making properties also improve.

Table 1. Preferred usage areas according to sedimentation value ranges

The classification in Table 1 is an important indicator for millers and grain traders in determining which products the wheat can be used for.

Sedimentation Analysis Process

For the sedimentation analysis to produce accurate results, it must be carried out in accordance with specific standards. The general process consists of the following steps:

• The wheat sample is cleaned from foreign materials.
• The wheat is milled to a specific particle size in laboratory mills.
• 3.20 g of the sample is weighed and transferred into a sedimentation tube using a plastic funnel.
• 50 ml of bromophenol solution is added and shaken in the device for 5 minutes.
• After shaking, 25 ml of lactic acid solution is added and left for another 5 minutes.
• After the device completes the process, the tube is kept on a flat surface for 5 minutes.
• The sediment level at the bottom is read at the end of this period.

Factors Affecting Sedimentation Value

Since the sedimentation test reflects not only protein quantity but also protein quality, it can be influenced by many factors.

Figure 1. Factors affecting sedimentation value

1. Wheat Variety and Genetic Characteristics

The genetic structure of wheat determines the ratio of glutenin and gliadin subtypes, which directly affects the sedimentation value.

• Bread wheat (Triticum aestivum): Forms strong gluten due to high molecular weight glutenin subunits, increasing swelling capacity and sediment volume.
• Durum wheat (Triticum durum): Produces a tighter but less elastic gluten network, resulting in lower sedimentation values.
• Genetic variations: Combinations of HMW-GS (High Molecular Weight Glutenin Subunits) and LMW-GS (Low Molecular Weight Glutenin Subunits) determine results. For example, varieties with 5+10 subunits generally have higher sedimentation values than those with 2+12 combinations.

2. Protein Structure and Gluten Quality

The sedimentation test reflects not only protein quantity but also its structural quality.

• Glutenin/Gliadin ratio: Glutenin forms structure while gliadin provides elasticity. Imbalance lowers sedimentation value.
• Polymerization level: Longer polymer chains and cross-linking increase water absorption and sediment volume.
• Enzymatic degradation: Alpha-amylase and proteolytic enzymes weaken gluten structure, reducing sedimentation value.

3. Pre-Harvest Sprouting (PHS)

Rainfall and moisture before harvest can cause early sprouting:

• Increased alpha-amylase activity breaks down starch and protein matrix.
• Protein degradation weakens gluten network.
• Reduced swelling capacity lowers sediment volume.

Thus, sprouted wheat generally has lower sedimentation values and poorer bread-making quality.

4. Milling Fineness

The degree of milling affects sample behavior in the solution:

• Fine milling: Increases surface area, allowing uniform swelling and reliable results.
• Coarse milling: Causes irregular swelling and lower sediment values.
• Milling method: Laboratory mills ensure repeatability by controlling particle size.

5. Storage Conditions

Storage conditions also influence gluten structure:

• Moisture and temperature: Increase enzymatic activity and weaken gluten.
• Oxidation: Long-term storage alters protein structure and elasticity.
• Storage duration: 6 months–1 year is optimal; longer improper storage reduces sedimentation value.

Relationship Between Sedimentation Value and Bread Volume

Figure 2. Correlation between bread volume and sedimentation volume

Sedimentation values are an important indicator for predicting bread-making quality.

In one dataset (A), R² = 0.18 indicated a weak correlation between sedimentation volume and bread volume, suggesting other factors play a major role.

In another dataset (B), R² = 0.53 showed a moderate correlation, making sedimentation a more reliable parameter—though still not sufficient alone. It is typically evaluated alongside protein, gluten, and enzyme analyses.

In general:

Table 2. Relationship between sedimentation, gluten, and bread volume

Sedimentation Analysis in Modern Grain Laboratories

Today, sedimentation testing is a critical laboratory method for quickly, reliably, and reproducibly determining wheat and flour quality. It provides direct information about gluten quality and bread-making potential.

Figure 3. Bastak Sedimentation 3100

Bastak Sedimentation 3100

The Sedimentation 3100 device developed by Bastak Instruments is manufactured in a 7000 m² closed facility using advanced production technologies. It is used to determine the pasta and bread-making quality, as well as insect (bug) damage, of samples obtained from commercial flour, wheat flour, whole wheat flour, durum wheat flour, bulgur, vital gluten, noodles, and semolina according to international standards.

Key Advantages:

• 40 rpm rotation speed and 30° working angle compliant with ICC standards
• Measurement of 6 samples simultaneously within 15 minutes
• Physicochemical method for normal and modified sedimentation tests
• LCD display for monitoring speed, ambient temperature, and remaining time
• 13 function keys and 6 test time settings
• Automatic stop with visual and audible alerts
• CE and ISO compliant design
• Ergonomic structure and high repeatability

If gluten quality is high, flour particles swell more, increasing sedimentation value. The delayed (modified) test helps evaluate protease enzyme activity and insect damage.

With the Sedimentation 3100 device, laboratories can measure gluten quantity and quality reliably according to international standards, ensuring high accuracy in bread and pasta quality analysis.

CONCLUSION

Sedimentation analysis is a fast and reliable indicator of wheat and flour quality. It provides insight into gluten strength and bread-making potential. With devices such as the Bastak Sedimentation 3100, test results can be obtained with high accuracy and repeatability.

Therefore, sedimentation analysis is considered a fundamental quality control tool in both milling and grain trade industries.